Calibration Services - VTT · 2020. 6. 14. · Email: [email protected] . : Finland has a...

Calibration Services International competitiveness and reliability VTT MIKES

2 — VTT MIKES METROLOGY Calibration services

Copyright © VTT MIKES 2020 VTT Technical Research Centre of Finland Ltd P.O. Box 1000 (Vuorimiehentie 3, Espoo), FI-02044 VTT Tel. +358 20 722 111, fax +358 722 7001 www.vttresearch.com

http://www.vttresearch.com/

VTT MIKES Calibration services 2020 — 3

VTT MIKES

Mass, pressure, flow Calibration of weights ............................................................................... 6 Calibration of pressure measuring devices .............................................. 8 Calibration of force and torque .............................................................. 10 Water flow meter calibrations ................................................................ 12 Calibration of gas flows and density of liquids ........................................ 14 Acceleration of free fall ........................................................................... 16

Humidity, temperature Calibration of hygrometers .................................................................... 18 Calibration of radiation thermometers ...... Error! Bookmark not defined. Fixed point calibration of platinum resistance thermometers .................. 22

Electricity, acoustics Calibration of direct voltage and current ................................................. 24 Calibration of alternating voltage and current ......................................... 26 Calibration of capacitance and inductance standards ............................ 28 Calibration of resistance ......................................................................... 30 Calibration of power and energy at line frequency ................................. 32 RF and microwave calibrations ............................................................... 34 High voltage and high current................................................................ 36 Acoustic calibrations ............................................................................... 38

Time Calibration of time, time interval and frequency...................................... 40

Length, geometry Quantitative Microscopy – Atomic Force Microscope ............................. 42 Characterization of nanoparticles .......................................................... 44 Calibration of laser interferometers ....................................................... 46 Interferometric calibration of gauge blocks ............................................. 48 Calibration of gauge blocks by mechanical comparison ......................... 50 2D and 3D measurement of form and surface roughness ...................... 52 Optical measurement of surface microstructures ................................... 54 Calibration of tachymeters ..................................................................... 56 Angle and perpendicularity measurements ............................................ 58 Measurements of accurate inner and outer dimensions ......................... 60 Coordinate measurement ....................................................................... 62 Optical coordinate measuring – vision measuring .................................. 64 Calibration of line scales and distance meters ....................................... 66 Interferometric measurement of flatness and form ................................. 68 Machine tool measurements ................................................................. 70 Measurement of roundness ................................................................... 72 Calibration of microscopes and calibration standards ............................. 74 Length in geodesy .................................................................................. 76

Optics (Aalto University) Optical quantities .................................................................................... 78

Chemistry (SYKE) Water quality .......................................................................................... 80

4 — VTT MIKES Calibration services 2020

VTT MIKES VTT MIKES Tekniikantie 1 FI-02150 ESPOO

VTT MIKES-Kajaani, Tehdaskatu 15, Puristamo 9P19 FI-87100 KAJAANI

Tel. +358 20 722 111 (call centre) Email: [email protected] www.mikes.fi

Finland has a slightly distributed metrology infrastructure. VTT MIKES is the National Metrology Institute and it acts as the National Standards Laboratory for most of the quantities. MIKES designates the other National Standards Laboratories and Contract Laboratories.

VTT MIKES is a specialised research institute for measure-ment science and technology. As the National Metrology In-stitute of Finland, MIKES is responsible for the implemen-tation and development of the national measurement stand-ards system and realisation of the SI units in Finland.

The number of staff is 65 supported by VTT ltd. administra-tion.

The MIKES building is situated in the city of Espoo and its branch office in Kajaani is the northernmost National Stand-ards Laboratory in the world. The high-quality laboratories provide the most accurate measurements and calibrations – close to 1600 certificates per year – in Finland.

MIKES also performs high-level metrological research and develops measuring applications in partnership with indus-try. The activities of MIKES aim to improve industrial com-petitiveness, the national innovative environment, and pub-lic safety.

MIKES is a signatory to CIPM MRA (International Commit-tee for Weights and Measures, Mutual Recognition Ar-rangement) and a member of EURAMET (European Asso-ciation of National Metrology Institutes). Through interna-tional collaboration, MIKES is linked to the international measurement system and to the European and interna-tional metrology research community. MIKES takes actively part in the European Metrology Research Programme (EMRP and EMPIR).

• We realize SI-system of units in Finland

• We do high level research in the field of metrology

• We develop measurement methods for industry and society

• We offer high level calibration service, expert service and training

http://www.mikes.fi/


The Metre Convention

The National Measurement Standards System

VTT MIKES

Electricity, acoustics, time, frequency, length, tempera-ture, humidity, pressure, mass, force, torque and flow

Water quality Air quality Ionising radiation Length in geodesy and acceleration of free fall

Photometry and radiometry

Figure 1. National measurement standards system in Finland. Aalto = MIKES Aalto Metrology Institute, SYKE = Finnish Environment Institute, FMI = Finnish Meteorological Institute, STUK = Radiation and Nuclear Safety Authority, NLS = National Land Survey of Finland, and FGI = Finnish Geospatial Research Institute.

Calibration and Measurement Capa-bilities (CMCs) recorded in the BIPMkey comparison database, KCDB

Acoustics: 30 Length: 59 Time and frequency: 11 Thermometry: 44 Optics: 53 Mass and related quantities: 28 Electricity: 99 Ionising radiation: 30 Chemistry: 5

Total Finland 359 / total 24031 entries Source :BIPM July 1, 2015, kcdb.bipm.org

Voluntary peer review project

MIKES is a coordinator in the EURAMET TC-Q pro-ject Peer reviews of Quality Management Systems (QMSs). The other partners in the project are CMI (CZ), GUM (PL) and SMU (SK). The project supports the evaluation and improvement of QMS processes and procedures of the participating institutes. Learn-ing from each other and sharing the best practice for QMS implementation are other goals of the project. The QMSs of the institutes are based on ISO/IEC 17025. A programme with on-site visits by peers is planned on an annual basis and one or two fields in each institute are reviewed every year. In 2012, the QMS of MIKES in the field of length metrology was peer reviewed by an expert from GUM, and vice versa. In addition, the humidity laboratory of MIKES was peer reviewed by a GUM expert.

Figure 2. CIPM MRA logo tells us, that our measurement results are accepted globally.


Mass, pressure and flow

Temperature and humidity

Electricity, time and acoustics Optics

Length and geometry

Chemistry

Calibration of weights Heikki Kajastie, Researcher Tel. +358 50 410 5511(Espoo) [email protected]

Kari Kyllönen, Research Technician Tel. +358 50 4434180 (Kajaani) [email protected]

MIKES, Tekniikantie 1, FI-02150 Espoo MIKES-Kajaani, Tehdaskatu 15, Puristamo 9P19, FI-87100 Kajaani Tel. +358 20 722 111, www.mikes.fi

Traceability The weight standards of MIKES mass laboratory are traceable via the Pt-Ir prototype number 23 of kilo-gram to the international prototype of kilogram kept at the BIPM. The comparability of measurement stand-ards of mass laboratory is maintained by international comparisons (e.g. EURAMET key comparisons). We carry out research and development related to scales and weights and offer expert services on the usage of scales and weights. Our mass laboratories are of high quality and we have scales equipped with automatic weight handlers. Our laboratories are located in Es-poo and Kajaani.

Measurement methods The measurement range of mass at MIKES is 1 mg ... 2000 kg. The calibrations of weights are performed by using generally accepted weighing methods: the direct comparison method and the subdivision method. In the first method, the weight is directly com-pared to a standard and in the latter, a set of weights is calibrated by using one or several weight stand-ards.

mailto:[email protected]



Massa, paine ja virtaus

Lämpötila ja kosteus

Sähkö, aika ja akustiikka Optiikka

Pituus ja geometria Kemia

Calibration of weights


Calibration services MIKES is capable to calibrate weights of OIML clas-ses E1, E2, and F1, whose nominal masses are at most 20 kg (E1), 50 kg (E2) and 2000 kg (F1). In ad-dition, MIKES offers calibration services for weights of lower OIML classes, whose masses are between 10 kg and 2000 kg. MIKES also calibrates other weights such as weights of pressure balances. In the calibration certificate, the masses are given as con-ventional masses or as true masses. The smallest achievable measurement uncertainties in mass cali-brations are presented in table 1. Weights whose nominal mass is 50 kg or bigger are calibrated at MIKES Kajaani.

Calibration of volume of weights When calibrating a weight, a correction due to the air buoyancy has to be made to the weighing result. The magnitude of the correction depends on the volume of the weight and on the density of air. In order to be able to make the correction accurately enough, the volumes of the most accurate weights have to be known. Mass laboratory calibrates volumes and den-sities of solid artefacts. The density standard is either distilled water or silicon. The measurement methods is hydrostatic weighing. The measuring equipment is suitable for volume calibration of 2-kg weights or lighter. If needed, volumes of bigger weights can be determined by using e.g. dimensional measurements. The measurement uncertainties of volume calibra-tions of weights are presented in table 2.

Table 1. Measurement uncertainties of weight calibrations.

Mass Measurement uncertainty (k=2)

2000 kg *) 3000 mg 1000 kg *) 1500 mg 500 kg *) 750 mg 200 kg *) 300 mg 100 kg *) 200 mg 50 kg *) 30 mg

20 kg 3.0 mg 10 kg 1.5 mg 5 kg 1.0 mg 2 kg 0.3 mg 1 kg 0.05 mg

500 g 0.03 mg 200 g 0.02 mg 100 g 0.015 mg 50 g 0.010 mg 20 g 0.008 mg 10 g 0.007 mg 5 g 0.005 mg 2 g 0.004 mg 1 g 0.003 mg

500 mg 0.003 mg 200 mg 0.002 mg 100 mg 0.0015 mg 50 mg 0.0015 mg 20 mg 0.0010 mg 10 mg 0.0008 mg 5 mg 0.0008 mg 2 mg 0.0008 mg 1 mg 0.0008 mg

*) Calibration in MIKES-Kajaani.

Table 2. Measurement uncertainties of calibrations of weight volumes.

Mass Volume Uncertainty (k=2)

1 g – 2 kg 0.1 – 255 cm3 0.000 3 – 0.008 cm3





Length and geometry

Chemistry

Calibration of pressure measuring devices Monika Lecklin, Research Technician Tel. +358 50 410 5516 [email protected]

Sari Saxholm, Senior Scientist Tel. +358 50 410 5499 [email protected]

MIKES, Tekniikantie 1, FI-02150 Espoo Tel. +358 20 722 111 www.mikes.fi

Figure 1. Pressure balance is used for the traceable reali-zation of pressure unit.

MIKES has good capabilities to calibrate different measuring devices of pressure. The measuring range for gauge pressure is 0 ... 500 MPa and for absolute pressure 0.0005 Pa ... 1.75 MPa. The best measure-ment standards at MIKES are pressure balances, which are used to realise pressure according to its

definition p = F / A, i.e. pressure is force divided by area. The force is produced by the mass of the piston of the pressure balance and by the masses of weights loaded over the piston. The local value for the accel-eration of free fall must be known. The area A is the effective area of the piston cylinder assembly of the pressure balance.

Pressure balances are used for gauge and negative gauge pressure measurements and for absolute pressure measurements. To cover a wide range of pressures, several piston cylinder assemblies of dif-ferent sizes are needed in order to be able to realise different pressures and to keep the number of weights still easy to handle.

In pressure ranges below the range of pressure bal-ances, capacitive sensors and spinning rotor gauges are used as measurement standards. The lowest pressures (absolute pressures 0.0005 Pa ... 2 Pa) are calibrated by using spinning rotor gauges. These measurements are demanding, as they require long stabilisation and measurement times.

Measurement methods and devices used for pres-sure depend on the pressure range.

Figure 2. Pressure measurements are made in a very broad pressure range, for instance from 10-9 Pascals required in particle accelerators to over 109 Pascals, i.e. 1 GPa, pressures used in powder metallurgy. Measuring devices and their operational principles are very different in different pressure ranges. The measurement range in MIKES is from 0.5 mPa to 500 MPa and is marked with blue bar in the figure.








Calibration of pressure measuring devices


Figure 3. In practice, measurement of pressure is always measuring differential pressure. Depending on the refer-ence point various names are used for pressure and diverse devices used.

Absolute pressure The ideal vacuum as reference point (vacuum gauges).

Atmospheric pressure Atmospheric pressure is the absolute pressure caused by the atmosphere so the reference is the ideal vacuum (barometers).

Gauge pressure The reference point is the atmospheric pressure. E.g., the tyre pressure of a car is gauge pressure. Any gauge pressure can be converted to an absolute pressure by adding the momentary atmospheric pressure.

Negative gauge pressure The reference point is the atmospheric pressure. When converted to absolute pressures, negative gauge pressure is thereby lower than the atmos-pheric pressure. Thus, negative gauge pressure means that the objects pressure is lower than the pressure in its environment.

Differential pressure Pressure is called as differential pressure especially when the reference pressure is other than the vac-uum or the atmospheric pressure. The reference pressure is then usually called as a line pressure.

Absolute pressure gaseous medium

Pressure range (Pa)

Relative measurement uncertainty k = 2 (%)

Gauge pressure gaseous medium

Pressure range (Pa)


0.0005 9 100 0.03 0.001 6 1000 0.01

0.01 3 10 000 0.004 0.1 3 100 000 (0,1 MPa) 0.003

1 2 1 000 000 (1 MPa) 0.002

10 0.5 10 000 000 (10 MPa) 0.004 100 0.1 16 000 000 (16 MPa) 0.004

1000 0.01

Figure 4. Piston cylinder assemblies of different size for pressure balances.

10 000 0.005 100 000 (0.1 MPa) 0.004 1 000 000 (1 MPa) 0.004

1 750 000 (1.75 MPa) 0.003

Negative gauge pressure

gaseous medium Pressure range (Pa)


Gauge pressure, in oil medium

Pressure range (Pa)


–100 0.03 500 000 (0.5 MPa) 0.005 –1000 0.01 1 000 000 (1 MPa) 0.004

–10 000 0.005 10 000 000 (10 MPa) 0.003 –100 000 (–0.1 MPa) 0.004 100 000 000 (100 MPa) 0.003

500 000 000 (500 MPa) 0.01

Absolute pressure

Gauge pressure Differential pressure

Atmospheric pressure

Absolute pressure P = 0





Length and geometry

Chemistry

Calibration of force and torque Sauli Kilponen, Research Technician Tel. +358 50 443 4178 [email protected]

Jani Korhonen, Research Engineer Tel. +358 50 443 4206 [email protected]

MIKES, Tehdaskatu 15, Puristamo 9P19, FI-87100 Kajaani, Tel. +358 50 443 4213, www.mikes.fi

Traceability and calibration of force

VTT MIKES-Kajaani performs force calibrations from 1 N to 1.1 MN. Calibrated measurement devices are usually force transducers, force measurement de-vices, balances (e.g. hook, wheel weight and airplane) and pull force testers. The smallest measurement un-certainty is 2×10-5.

The calibration of force is based on the ISO 376 stand-ard. The force calibration from 1 N to 110 kN is carried out in dead weight force standard machines. A dead weight machine is a mechanical structure that gener-ates force by subjecting dead weights to the local grav-itational field. Hydraulic force standard can be used in the calibrations from 20 kN to 1.1 MN.

The masses that are used in VTT MIKES-Kajaani are traceable to the national standard of mass, which is in turn traceable to the international prototype of the kil-ogram held in the BIPM. Force traceability is realised from mass calibrations and international comparisons.

Figure 1. A 1-MN hydraulic force standard and a 100-kN direct load force standard. The total equipment height is eight meters, including the load masses below floor level.

Table 1. Measurement ranges for force.

Load method Measurement range Measurement uncertainty (k=2)

Direct load Compression / pulling: 10 N ... 10 kN 2 ⋅ 10–5

Direct load Compression / pulling: 10 kN ... 100 kN 5 ⋅ 10–5

Hydraulic load Compression / pulling: 20 kN ... 1 MN 1 ⋅ 10–4

Field calibration of force 1 N ... 1 MN 5 ⋅ 10–4








Calibration of force and torque


Traceability and calibration of torque

MIKES-Kajaani performs calibrations of torque in the range 0.1 Nm ... 20 kNm, the smallest uncertainty be-ing 5×10–4. The calibration of torque is carried out us-ing reference standards for torque or standards based on reference sensors.

The need for torque calibrations can be classified in three groups of different types of devices. The most stringent accuracy requirement (< 0.05 % ... 0.5 %) is for calibration of torque sensors that are used e.g. in measurement of torque in research of rotating ma-chines such as pumps and motors. The second group is devices used for calibration of torque-controlled as-sembly tools. In calibration of these devices, the un-certainty of the torque standard should not exceed 0.5 %. The third group is calibration of torque-controlled assembly tools for industries that do not have their own calibration devices. The calibration uncertainty for torque-controlled assembly tools is typically from 1 % to 10 %.

There exist only a few standards for torque calibra-tions. For torque-controlled assembly tools is the standard ISO 6789, which however mainly describes test methods but also defines a calibration procedure. There is no standard for devices used for calibration of torque-controlled assembly tools. For torque sen-sors, there exists the recommendation Euramet/cg-14.

Torque is a derived quantity that consists of known masses and a known length of a lever arm. Even though traceability for masses and length can be achieved separately, verifying the consistency of torque in entity is mainly verifying the consistency of torque in entity is mainly based on interlaboratory comparisons

Figure 2. A 2-kNm torque standard used for comparison measurements in the range 100 Nm – 2 kNm and for calibration of torque sensors.

Figure 3. A 20-kNm torque standard based on a reference sensor.

Torque standard Measurement range Measurement uncertainty (k=2) Lever - mass 0.1 ... 10 Nm right / left 5 . 10–4

Lever - mass 10 ... 2000 Nm right / left 5 . 10–4

Reference standard 2 ... 20 kNm right / left 5 . 10–4





Length and geometry

Chemistry

Water flow meter calibrations Mika Huovinen, Researcher Tel. +358 50 415 5974 [email protected]

MIKES, Tehdaskatu 15, Puristamo 9P19, FI-87100 Kajaani, Tel. +358 50 443 4213 www.mikes.fi

Calibration provides reliability Accurate liquid flow measurements are needed in many areas of industry, such as process, mining and energy industry. To maintain global competitiveness and high quality of the end products, accurate liquid flow measurements make it possible to optimise dif-ferent industrial processes and in this way reduce raw material consumption and emissions to environment. Regular calibration and stability tracking of liquid flow meters are essential part of measurement reliability, regardless of the application.

Figure 1. Graphical user interface of the D200 liquid flow calibration rig.







Water flow meter calibrations


Traceability The most important activities of MIKES Kajaani are to implement the traceability of the flow measurements in Finland, maintain liquid flow measurement stand-ards, and provide calibration and expert services. These are achieved by participating in international and domestic research and intercomparison projects. The MIKES’s liquid flow calibration laboratory’s qual-ity management system is based on the ISO/IEC 17025 standard.

Calibration services MIKES Kajaani has three different calibration rigs for liquid flow calibrations. One of the rigs is the national measurement standard of flow. In this rig, the meas-uring principle is gravimetric and the measurements carried out are traceable to the national standards of mass, temperature and time.

The gravimetric reference standard of water flow is based on weighing the water. In the measurements, water is first continuously pumped up to a constant head tank located 20 m above ground level. The wa-ter level is held constant in the tank by sufficient over-flow and by adjusting the water flow in a measuring pipe section, where the flow meters under test are placed. The calibration is done by comparing the re-sults of the balance and the meter under test reading.

In the closed loop type calibration rigs, the reference meters are usually magnetic or Coriolis mass flow meters. In these rigs, the source of traceability up to DN200 is based on the national flow standard. For pipe sizes DN200 >, the source of traceability is a for-eign NMI, typically PTB from Germany.

The measuring principles, ranges, and reachable measurement uncertainties are shown in Table 1.

Table 1. Measuring ranges of the liquid flow calibration rigs and the measurement uncertainty.

Equipment Measuring principle

Pipe sizes Volume flow Pressure Measurement uncertainty (k=2)

D100 reference meter DN 15 DN 50

0.3 l/s … 20 l/s <0.7 MPa 0.3 %

D500 reference meter DN 150 DN 500

7 l/s … 750 l/s <0.5 MPa 0.3 %

D200 gravimetric DN 10 DN 50 DN 100 DN 200

0.1 l/s … 200 l/s 0.2 MPa 0.03 %

For pulp and paper industry, MIKES Kajaani has a mass circulating rig applied with a cooling system. Con-sistency area 0–12 % and flow speed 0.5–3 m/s.

Figure 2. Part of the D500 liquid flow calibration rig.





Length and geometry

Chemistry

Calibration of gas flows and density of liquids Richard Högström, Research Team Leader Tel. +358 50 303 9341 [email protected]

Heikki Kajastie, Researcher Tel. +358 50 410 5511 [email protected]


Calibration gives reliability Nowadays, measurement of small gas flows is needed in various applications. For instance, in health care and medical industry is very important to assure the safety of customers. In order to maintain interna-tional competiveness and to guarantee the high qual-ity of products, the accuracy of gas flow measure-ments in process industry has to be reliably verified. No matter what the application is, the regular calibra-tion and stability monitoring of gas flowmeters is an essential part of quality control. MIKES calibrates gas flowmeters in the flow range 5 ml/min ... 110 l/min and offers research and expert services in the field of gas flow measurements and their reliability.

Traceability MIKES provides circumstances for traceable gas flow measurements in Finland by developing and main-taining standards for gas flows and offers calibration and expert services.

The traceability of gas flows at MIKES is based on a dynamic weighing system, DWS developed at the flow laboratory of MIKES. The measurements per-formed using this system are traceable to the national standards of mass and time. The DWS equipment is used to calibrate measurement standards based on laminar flow elements (LFE) and customers’ devices whose relative accuracy level is better than 1 %.

The high level of our gas flow measurement activities is maintained by actively participating in international research projects and comparisons and by carrying out own research projects in this field.








Calibration of gas flows and density of liquids


Calibration services

If the relative accuracy level of a gas flowmeter is bet-ter than 1 %, the DWS equipment will be used in the calibration. Typical examples of such flowmeters are high-quality laminar flow elements and some piston-cylinder volume flowmeters.

Most of our customers’ flowmeters are calibrated at MIKES using the LFE calibration equipment. It is much more convenient to use than the DWS equip-ment and it does not have such a strict tolerances for environmental conditions. Performing of calibrations are thus more flexible and faster. The equipment has proven to be well suited for calibration of gas flowme-ters having relative accuracy above 1 %. Such meters include thermal mass flowmeters and controllers.

Furthermore, MIKES performs liquid density meas-urements. We calibrate for instance areometers and density meters based on vibrations and determine densities of customers own liquid samples in the den-sity range 600 kg/m3 ... 2000 kg/m3.

Table 1. Measurement ranges and best achievable calibration uncertainties at MIKES.

Quantity Measurement range Measurement uncertainty (k=2)

Mass flow (DWS) 0.1 mg/s ... 625 mg/s 0.3 % ... 0.8 %

Mass flow (LFE) 0.1 mg/s ... 625 mg/s 0.4 % ... 0.9 %

Volume flow (LFE) 5 ml/min ... 30 l/min 0.4 % ... 0.9 %

Density of liquid (LDCS) 600 kg/m3 ... 2000 kg/m3 15 ppm

Calibration of areometers (HCS) 600 kg/m3 ... 2000 kg/m3 0.05 %

DWS = Dynamic weighing system, LFE = Laminar flow element LDCS = Liquid density calibration system HCS = Hydrometer calibration system





Length and geometry

Chemistry

Acceleration of free fall Markku Poutanen, Prof. Tel. +358 29 531 4867 [email protected]

Mirjam Bilker-Koivula Senior Research Scientist Tel. +358 29 531 4696 [email protected]

Hannu Ruotsalainen Senior Research Scientist Tel. +358 29 531 4976 [email protected]

Finnish Geospatial Research Institute, FGI, Geodeetinrinne 2, FI-02430 Masala, Tel. +358 29 530 1100, www.fgi.fi

Finnish Geospatial Research Institute, FGI The Finnish Geospatial Research Institute, FGI, of the National Land Survey of Finland maintains meas-urement standards for geodetic and photogrammetric measurements and is the National Standards Labor-atory of acceleration of free fall and length. The FGI takes care of the fundamental measurements in Finn-ish cartography and of geographical information me-trology and carries out scientific research in geodesy, geographic information sciences, positioning, naviga-tion, photogrammetry and remote sensing.

Methods and traceability The national measurement standard is the absolute gravimeter FG5-221. Its results are directly traceable to length and time standards. We have participated in all international comparisons since the year 1989. At a customer’s site, the measurements are usually per-formed with a relative gravimeter, measuring the gravity difference with respect to a point with known gravity.

Acceleration of freefall and gravity The acceleration of free fall depends on location and time. The time dependence originates from tidal forces (variation in Finland 3 μm s–2) and from mass variations of groundwater and atmosphere (at least an order of magnitude smaller). When the most im-portant time variations are removed from the acceler-ation of free fall by using agreed methods, the result is the acceleration due to gravity, which can be treated as a time independent quantity.

Figure 1. Acceleration of free fall in Finland, unit ms–2.




http://www.fgi.fi/





Acceleration of free fall


Calibration services and uncertainty We measure gravity at requested sites and report the value for the acceleration of free fall. The time varia-tion is included in the uncertainty of 4 μm s–2 (k=2). If needed, we supply an accurate value for gravity (the smallest uncertainty is 0.008 μm s–2) and methods to predict the time variation (the smallest uncertainty 0.10 μm s–2). We maintain an open calibration line where customers can verify their gravimeters.

Research, development and reporting We carry out research and develop national infra-structure for measurements of gravity and accelera-tion of free fall for all applications (e.g. geodesy, geo-physics and geology). With the help of the 30 000 points in the national gravity grid, the acceleration of free fall can be estimated with an accuracy of 0.1 mm s–2 without any new measurements. We have performed measurements using absolute gravime-ters in 20 countries.

Figure 2. A measurement using Figure 3. The absolute gravimeter FG5X-221 is based on a relative gravimeter. a free fall experiment.

Figure 4. Superconducting gravimeter (Metsähovi, Kirkkonummi) registers even 0.1 nm s–2 variations in the acceleration of free fall.





Length and geometry

Chemistry

Calibration of hygrometers Richard Högström, Research Team Leader Tel. +358 50 303 9341 [email protected]

Heikki Kajastie, Researcher Tel. +358 50 410 5511 [email protected]


Reliability from calibrations Reliability of humidity measurements is important, e.g. in storage of wood, paper, food, etc. in aviation and environmental monitoring as well as in diverse fields of industry and research. Calibration of hygro-meters at regular intervals and monitoring their stabil-ity is an essential part of verification of measurements.

MIKES provides high-quality calibration services for instruments measuring humidity of gases and expert services on research and development related to hu-midity measurements and their reliability.

Traceability to humidity measurements MIKES creates conditions for traceable humidity measurements in Finland by developing and main-taining measurement standards for humidity and by offering calibration and expert services.

The high quality of the humidity laboratory is main-tained by taking part in international research and comparison projects and by carrying out own re-search projects.








Calibration of hygrometers


Traceability Traceability of humidity measurements is based on a dew-point temperature scale. The scale is realised by using a humidity generator, which is the national measurement standard in Finland.

The core of a dew-point generator is a saturator in which total saturation of air with respect to water or ice is reached. The dew point temperature of the air com-ing out of the generator is calculated from the satura-tor temperature and from the pressure difference be-tween the saturator and the device under calibration. When saturated air is led into the measurement cham-ber of the generator, the equipment is also suitable for calibration of relative humidity sensors.

Figure 1. Calibration of chilled mirror hygrometers.

The dew-point meter under calibration is directly con-nected to the dew-point generator. In calibration of a relative humidity sensor, the sensor is placed in the measurement chamber system. The reading of the sensor is compared to the value of relative humidity that is calculated from the dew-point temperature and the air temperature inside the chamber.

Calibration services Most dew-point meters are calibrated using a dew-point generator. The measurement standards of hu-midity laboratory at MIKES cover the dew-point tem-perature range –80 °C to +84 °C. Dew-point calibra-tions are also carried out as comparison calibrations in calibrators, for instance for capacitive dew-point meters.

Most relative humidity sensors are calibrated in a cli-matic chamber. The dew-point temperature and the air temperature in the chamber are measured by us-ing a chilled mirror hygrometer and a digital thermom-eter, respectively. The relative humidity is calculated from measured temperature and dew-point tempera-ture. If the achievable uncertainty is not sufficient or the temperature range extends to below +10 °C, the calibration is performed using a humidity generator. Relative humidity sensors are calibrated in the range 10 %rh to 95 %rh at temperatures between –20 °C and +85 °C.

In cases of other humidity quantities, calibrations are performed with the same equipment the relative humidity calibration systems. The values of these quantities are calculated from measured dew point temperature, temperature, and pressure.

Quantity Measurement range Measurement uncertainty (k=2)

Dew-point temperature –80 °C ... –60 °C –60 °C ... +84 °C

0.2 °C ... 0.1 °C 0.05 °C ... 0.06 °C

Relative humidity 10 %rh ... 95 %rh (–20 °C ... +85 °C)

0.1 %rh ... 1.0 %rh (generator)

Relative humidity 10 %rh ... 95 %rh (+10 °C ... +85 °C)

0.4 %rh ... 2.0 %rh (climate chamber)





Length and geometry

Chemistry

Calibration of radiation thermometers Richard Högström, Research Team Leader Tel. +358 50 303 9341 [email protected]


Measurement methods Blackbody radiators are used in calibration of radia-tion thermometers. The operation range of MIKES ra-diators is –40 °C ... 1500 °C.

The temperature of a blackbody radiator can be measured using e.g. a temperature sensor that is em-bedded in the radiator wall. When calculating the ra-diation temperature from the measured temperature, the emissivity of the wall and bottom materials of the radiating cavity and the geometry of the blackbody ra-diator as well as the temperature gradients are taken

into account. The radiation temperature measured by a radiation thermometer is often lower than the sur-face temperature of the measured object, since the surface emissivity is usually lower than the emissivity of an ideal blackbody (the emissivity of a blackbody is 1 but the emissivity of a glossy copper surface is 0.1).

In MIKES, radiation thermometers are calibrated by using either a calibrated reference pyrometer or refe-rence radiators.








Traceability The international temperature scale ITS-90 is realised above the temperature of 962 °C with a reference py-rometer and fixed-point radiators (962 °C, 1064 °C and 1085 °C). Of these fixed-points MIKES has the first and the last one, which are the freezing points of silver (figure 1) and copper. Below the temperature of 962 °C, ITS-90 is realised by using resistance ther-mometers instead of a pyrometer. The reference equipment for radiation temperatures between –40 °C … 962 °C at MIKES are based on resistance ther-mometers calibrated according to the ITS-90.

Size-of-source-effect The size of the radiation source (size-of-source-ef-fect, SSE) affects the calibration results of a radiation thermometer. A radiation thermometer detects ther-mal radiation also outside the blackbody radiator or the object to be measured. The significance of this additional thermal radiation depends on the construc-tion of the optics (figure 2). On demand, the size-of-source-effect is measured at MIKES.

Figure 1. A silver cell that is used in the cali-bration of a reference pyrometer.

Figure 2. SSE: In this example, a pyrometer detects lower temperatures when the aperture of the radiator is less than 15 mm and the temperature of the radiator is higher than ambient temperature.

Vocabulary • reference meter: measurement standard • pyrometer: radiation thermometer (infrared thermometer) • a black-body radiator does not reflect at all radiation coming from the outside. The temperature of an object depends only from the heat energy brought to the object and hence its radiation intensity is proportional to the temperature of the object.

Outer cover graphite

Inner cover graphite

Silver

Aperture diameter of the radiator (mm)





Length and geometry

Chemistry

Fixed point calibration of plati-num resistance thermometers Richard Högström, Research Team Leader Tel. +358 50 303 9341 [email protected]


Calibration objects and methods

Standard platinum resistance thermometers (SPRT) of good quality (i.e. stable) are calibrated at the fixed points of the ITS-90 temperature scale. A fixed-point cell (Figure 1) usually contains pure metal, e.g. tin, zinc, aluminium or silver (Table 1) sealed in a crucible f purified graphite. The purity of the metal is typically ca. 99.99995 %. The graphite crucible is enclosed in a fused quartz tube.

The fixed-point cell is placed in a vertical tube furnace and the temperature is slowly raised until the melting is complete. At this stage, the furnace temperature is reduced to a value slightly below the melt tempera-ture in order to start solidification. When the metal is in a supercooled state, the thermometer to be cali-brated is carefully inserted into the cell. The thermom-eter is coupled to a resistance bridge using four-wire coupling. The solidification state can be maintained up to 10 hours (Figure 2) and the temperature of the fixed point cell stays within ±0.5 mK.

The resistance bridge is used to measure the electri-cal resistance of the thermometer during the solidifi-cation state. The thermometers are usually calibrated using three or five different fixed points.

Figure 1. Pt25-sensor (SPRT) in a fixed-point cell.







Fixed point calibration of platinum resistance thermometers


Calculation of calibration coefficients The temperature T90 is determined according to the ITS-90 temperature scale. First a resistance ratio W(T90) = R(T90) / R(T0.01°C) is calculated by dividing the sensor resistance at a given fixed point by the re-sistance value at the water triple point. A deviation function of the resistance ratio and calibration con-stants (a, b) are determined for each sensor under calibration. The deviation function can be e.g.

W(T90) – Wr(T90) = a[W(T90) – 1] + b[W(T90) – 1]2

where Wr(T90) is a reference function given in the ITS-90 scale. The deviation function to be used and the number of calibration constants depend on the tem-perature range and the used fixed points.

The deviation function can also be used to determine any temperature between the fixed points when the constants a and b are known. In this case, W(T90) is first determined at the unknown temperature and the resulting Wr is used to calculate T90.

Uncertainty in fixed point calibration The uncertainties of the fixed points at MIKES are be-tween 0.0002 ... 0.010 °C. The lower limit is reached at the triple point of water and the upper limit at the fixed points of aluminium and silver. The uncertainty of the resistance thermometer calibrations is larger since it includes also uncertainties of the calibration equipment (resistance bridge, reference resistor) and the stability of the thermometer during the calibration.

Other fixed point calibrations Noble metal thermocouples of B-, R- and S-type are also calibrated at fixed points. The highest fixed-point temperature is the freezing point of copper at 1084.62 °C.

Traceability The MIKES fixed points are part of the realisation of the international ITS-90 temperature scale. The sta-bility of the fixed-point cells are monitored and the temperatures they provide are compared to the tem-peratures from similar cells at our own and foreign la-boratories.

Table 1. MIKES fixed points for resistance thermometers.

Subtance Temperature (°C) State *

Argon (Ar) –189.3442 t Mercury (Hg) –38.8344 t Water (H2O) 0.01 t Gallium (Ga) 29.7646 m Indium (In) 156.5985 f Tin (Sn) 231.928 f Zinc (Zn) 419.527 f Aluminium (Al) 660.323 f Silver (Ag) 961.78 f

* t = triple point, m = melting point, f = freezing point

Figure 2. Freezing curve of zinc.

Abbreviations: Pt25 = 25-ohm platinum resistance thermometer HTPRT = high temperature platinum resistance ther-mometer

Time (h)

Tem

pera

ture

(°C

)





Length and geometry

Chemistry

Calibration of direct voltage and current Pekka Immonen, Researcher Tel. +358 50 410 5520 [email protected]

Ilkka Iisakka, Researcher Tel. +358 50 410 5519 [email protected]

MIKES, Tekniikantie 1, FI-02150 Espoo, Tel. +358 20 722 111, www.mikes.fi

Accuracy of almost all electrical measuring instru-ments is based on traceability of direct voltage and resistance. MIKES maintains the national standard of direct voltage and direct current in Finland. The unit of direct voltage, volt, is determined very accurately (repeatability even 10–10) by using Josephson voltage standard. The volt is transferred from the Josephson standard to Zener working standards and further to calibrators and multimeters. The measurement range is extended above 10 V by using resistive voltage di-viders. In practice, traceability of direct current comes from voltage and resistance using Ohm’s law. Trace-ability of currents smaller than 100 pA can be realized also by charging a capacitor by a linearly increasing voltage. One research topic is the development of a quantum standard for direct current based on single-electron phenomena in nanostructures. The methods and measuring instruments developed at MIKES are of high international level. One demon-stration of this is the excellent success in international comparison measurements with other national me-trology institutes. Moreover, MIKES research on di-rect current metrology is in the international front line. Most important research topics are development of voltage standards based on microelectromechanical systems (MEMS) and closing the so-called quantum metrological triangle to prove by Ohm’s law that there is a mutual agreement between the quantum stand-ards of electric current, voltage, and resistance.

Figure 1. The traceability of direct current is based on a Josephson standard cooled in liquid helium.






Calibration of direct voltage and current


Calibration services In addition to accredited calibration laboratories, MIKES provides services to all customers requiring low measurement uncertainty. The most important calibration subjects in the field of direct current are solid-state voltage standards, dc- and multifunction calibrators as well as precision multimeters. Zener standards are calibrated usually by comparison to MIKES working standards. A relay scanner connects the voltage difference of the standards to a nano-volt-meter and the results are recorded at regular intervals for a couple of weeks. Routine calibrations of direct voltage and current ranges of calibrators and multi-meters are carried out using a reference multi-meter and a multifunction calibrator. The measuring ranges and uncertainties of calibrations for voltages up to 1 kV are presented in table 1.

Direct current calibrations are usually performed for currents between 0.1 mA and 1 A with relative uncer-tainty of 10 μA/A and for 100 fA – 100 μA with uncer-tainties varying from 600 μA/A to 20 μA/A.

When lower uncertainties are needed, calibrations can be performed by using directly the MIKES Jo-sephson standard. On special order, calibrations of multimeters and calibrators can be carried out using directly the Josephson and Zener standards and a re-sistive voltage divider. Direct current calibrations re-quiring lower than 10 μA/A uncertainties and meas-urements above 1 A current levels can be performed by measuring the voltage across a resistance stand-ard. The lowest achievable uncertainties of these measurements are listed in table 2. Resistive voltage dividers are calibrated by comparison to the MIKES reference divider or with the Josephson standard. The value of voltage or current together with its un-certainty is given in the calibration certificate.

Stability or temperature dependence measurements can be carried out on customer’s request. MIKES fol-lows the long-term stability of customers’ voltage standards and can attach follow-up results to the cal-ibration certificate if needed.

In addition to the calibration, we carry out special as-signments related to voltage and current measure-ments and actively participate in research and devel-opment projects in these fields.

Figure 2. A Zener direct voltage standard.

Table 1. The smallest measurement uncertainties for the most common direct voltage calibrations. By using special tech-niques, even much lower calibration uncertainties can be achieved.

Device Zener-standard Calibrator or multimeter Voltage (V) 1 1.018 10 0 ... 10 10 ... 100 100 ... 1000 Uncertainty (μV) 0.2 0.2 2 0.3 ... 20 70 ... 610 1000 ... 10000

Table 2. The smallest uncertainties of direct current calibrations for currents less than 20 A.

Device Zener-standard Calibrator or multimeter Current < 0.1 pA (0.1 ... 100) pA (1 ... 100) nA (0.1 ... 100) μA (0.1 ... 100) mA (0.1 ... 20) A Uncertainty 0.1 fA (1 ... 0.6) mA/A (0.1 ... 2) pA 20 μA/A 5 μA/A (5 ... 20) μA/A





Length and geometry

Chemistry

Calibration of alternat-ing voltage and current Ilkka Iisakka, Researcher Tel. +358 50 410 5519 [email protected]


In society, many important functions such as the measurement of electrical energy, which is supplied by electrical power networks to consumers, are based on the accurate measurement of alternating voltage and current. MIKES is responsible for the traceability of alternating voltage and current in Finland. The traceability of the most accurate measurements of AC voltage is based on thermal converters and range re-sistors acting as secondary standards. The traceabil-ity of AC voltage and AC current ranges of multifunc-tional calibrators and precision multimeters comes from AC voltage standards calibrated at MIKES or at other national metrology institutes and from their cal-ibrated range and shunt resistors. The reliability of re-sults is verified by taking part in international compar-isons. MIKES performs also high-level research on AC volt-age metrology. Especially, MIKES is at the top of in-ternational metrology research in development work of two different types of AC voltage standards in do-mestic collaboration with VTT: a primary standard for AC voltage based on Josephson effect and an AC voltage working standard based on micromechanical sensors (MEMS).

Figure 1. Equipment of the national metrology laboratory for alternating voltage and current.






Calibration of alternating voltage and current standards


Calibration services MIKES has accurate AC voltage meters and calibra-tors as working standards. We calibrate voltages from 1 mV to 1000 V in a frequency range from 10 Hz to 1 MHz and currents from 100 μA to 20 A in a fre-quency range from 50 Hz to 10 kHz (up to 8000 A in the frequency range 45 Hz …. 65 Hz). Typical devices that we calibrate include thermal converters, precision multimeters and calibrators, and current sources and sensors. In addition, other devices can be calibrated in agreement with a customer. Usually customer’s AC voltage and current devices are calibrated by compar-ing their AC/DC difference to the AC/DC difference of a Fluke 5790A working standard and Fluke A40 AC/DC current shunts or by comparing the rms values directly to the rms value of a MIKES device. The measuring ranges and smallest achievable uncertain-ties for these calibrations are shown in the tables be-low.

Figure 2. AC-DC-relay and two thermal converters.

Table 1. Measurement ranges and smallest relative uncertainties in parts per millions from measurement results (μV/V) for the alternating voltage range of a multifunctional calibrator.

Frequency

10 Hz 20 Hz 40 Hz 53 Hz 400 Hz 1 kHz 10 kHz 20 kHz 50 kHz 100 kHz 500 kHz 1 MHz

1 mV 1200 1200 1200 – 1200 1200 1200 1200 1200 1400 3300 5000 2 mV 590 590 590 – 590 590 590 590 590 680 1600 4600 20 mV 130 120 120 – 120 120 120 120 120 140 350 580 100 mV 50 50 30 – 30 30 30 30 35 60 220 450 1 V 40 40 20 – 15 15 15 15 30 50 110 440 10 V 40 40 20 – 20 20 20 20 30 45 140 400 100 V 40 40 30 – 20 20 20 20 35 40 – – 1000 V – – 50 50 50 – – – – – – –

Table 2. Measurement ranges and smallest relative uncertainties in parts per million of measurement result (μA/A) for the alternating current range of a multifunctional calibrator.

Frequency

40 Hz 400 Hz 1 kHz 5 kHz 10 kHz

100 µA 80 80 80 90 110

1 mA 35 35 35 35 40

10 mA 35 35 35 35 50

100 mA 35 35 35 35 60 1 A 35 35 35 50 110 10 A 110 110 110 150 210 20 A 110 110 110 180 260

Cur

rent

(rm

s va

lue)

Vo

ltage

(rm

s va

lue)





Length and geometry

Chemistry

Calibration of capacitance and inductance standards Ilkka Iisakka, Researcher Tel. +358 50 410 5519 [email protected]


Capacitors and inductors are essential components in electronics. Moreover, capacitive sensors are used in many high-precision measurements: e.g. in meas-urements of position, distance and level. For calibra-tion of precision LCR meters, inductance and capaci-tance standards are needed. Therefore, traceable measurements of capacitance and inductance are of utmost importance. In Finland, MIKES is responsible for the traceability of capacitance and inductance.

In MIKES, ac coaxial bridges are used to provide traceability of the decade capacitance standards in the range 10 pF – 1 μF to resistance and frequency

Figure 1. Traceability to capacitance from resistance and frequency in MIKES impedance laboratory.

— quantities which are maintained at MIKES. The re-liability of the results is verified by international com-parisons and by taking advantage of capacitance measurement services at the BIPM. The capacitance values between calibration points are interpolated by using measuring bridges based on inductive dividers.

Inductance standards in the range 100 μH – 100 mH are traceable to the MIKES capacitance and resistan-ce standards.

Calibration services MIKES calibrates capacitance standards in the range 0 pF … 1 μF using a very stable capacitance bridge and reference capacitance standards. The measure-ments are usually carried out at 1 kHz but other meas-urement frequencies are also possible. The calibra-tion is performed using either two-terminal or three-terminal method by connecting the calibrated capaci-tance standard through a 16-channel coaxial relay to the capacitance bridge and by measuring automati-cally for about two or three days. The device under calibration is placed together with a Pt-100 sensor into a volume having a constant temperature. Temper-ature is varied during the measurement by about one or two degrees in order to measure the temperature coefficient of the device under calibration. The results are corrected to the temperature of 23 °C.

Traceability of inductance standards at MIKES is ba-sed on the link to the capacitance (100 pF) standards, which are calibrated at BIPM and the resistance standards, calibrated from the Quantum Hall Re-sistance in MIKES. The 100 mH inductance is linked to capacitance standards at 1 kHz and 1.59 kHz with the use of series resonance method, where 253 nF and 100 nF capacitors are used as references.






Calibration of capacitance and inductance standards


Sampling method, which is based on the use of two DVMs is used to define the values of inductance stand-ards in the range 100 μH – 10 mH. Impedance of the calibrated inductors is compared with the impedance of the reference resistor, by measurements of the volt-age ratios at frequencies below 1 kHz.

In addition to the calibration of capacitance and induct-ance standards, we carry out special assignments re-lated to impedance measurements and actively partic-ipate

Figure 2. AH2500A measuring bridge and a 1-nF capaci-tance standard under calibration.

Table 1. Measuring ranges and smallest calibration uncertainties at MIKES for calibration of capacitive standards at 1 kHz frequency. The expanded relative uncertainty (k = 2) is expressed as parts per million of measured capacitance.

Capasitance value 10 pF 100 pF 1 nF 10 nF 100 nF

Relative uncertainty (µF/F)

5 5 10 30 100

Table 2. Measuring ranges and smallest calibration uncertainties at MIKES for calibration of capacitive standards that have capacitance values smaller than 10 pF or larger than 100 nF or whose value is not even decade. The expanded relative uncertainty (k = 2) is expressed as parts per million of measured capacitance. For capacitances lower than 10 pF a base capacitance of 5 aF is added to the uncertainty.

Capasitance value 0 pF – 10 pF 10 pF – 1 nF 1 nF – 10 nF 10 nF – 100 nF 100 nF – 1 μF

Relative uncertainty (µF/F)

10 (+ 5 aF) 10 30 200 400

Table 3. Measurement methods, inductance values, and reference standards used in calibration of inductance standards at 1 kHz.

Method Inductance Impedance 1 kHz Reference Uncertainty 2σ

Relative uncertainty (µF/F) 5 5 10 30

2 DVM 0.1 mH 1 Ω 1 Ω 50

2 DVM 1 mH 10 Ω 10 Ω 50

2 DVM / SR 10 mH 100 Ω 100 Ω 20

SR / 2 DVM 100 mH 1 kΩ 253 nF / 100 Ω 20





Length and geometry

Chemistry

Calibration of resistance Ilkka Iisakka, Researcher Tel. +358 50 410 5519 [email protected]


Resistance is the most important quantity of electrical measurements together with direct voltage. In addi-tion to resistance calibrations, resistance standards are needed for providing traceability to other electrical quantities. MIKES is the national standards laboratory of resistance. The traceability of resistance standards at MIKES is based on its own quantum Hall standard, which connects the unit of resistance to the values of physical constants with a relative uncertainty of 10–8. The dissemination to secondary and working stand-ards, which are stored in oil or air baths, is performed by using a cryogenic current comparator or a direct current comparator resistance bridge. Traceability of resistance standards with value above 1 GΩ is real-ized by using a modified Wheatstone bridge.

The accuracy of MIKES’s resistance standard calibra-tions is at high international level, confirmed by good results in international resistance comparisons. MIKES has also participated in coordination of inter-national key comparisons, in which the accurate re-sistance transfer standards developed at MIKES have been used.







Calibration of resistance


Calibration services In addition to accredited calibration laboratories, MIKES provides services to all customers requiring very low measurement uncertainty. In resistance cal-ibration, the resistance of the device under calibration is measured and the uncertainty of the measurement result is calculated. On demand, temperature, power, or voltage dependence of resistance standards can be determined, too. MIKES follows the long-term sta-bility of customer’s resistance standards and when re-quested attaches the results to the calibration certifi-cates. In addition to resistance standards, other cali-bration services for calibration of precision multime-ters and multifunction calibrators are offered.

In the range 0.0001 Ω ... 100 MΩ, the resistance stan-dards are calibrated by comparing them to the prima-

ry and working standards of MIKES by using a MI 6242B resistance bridge. When special accuracy is needed, the measurements can be carried out by us-ing a cryogenic current comparator. In the range 1 MΩ ... 100 TΩ, a modified Wheatstone bridge is used. During the calibration, the resistance standards are placed in a thermal bath. Either two point or four point measurements are used and when needed a guarded measurement is carried out. The resistance ranges of multimeters are calibrated by using MIKES multimeters.

In addition to calibrations, we provide special assign-ments related to resistance measurements and ac-tively participate in research and development pro-jects in this field.

Figure 1. Measurement ranges and measurement uncertainties for resistance standards.

Unc

erta

inty

ppm

Resistance to be calibrated/ Ω

Resistance standards by cryogenic current comparator Resistance standards by direct current resistance bridges Multimeters by resistance standards Calibrators by direct current resistance bridges





Length and geometry

Chemistry

Calibration of power and energy at line frequency Esa-Pekka Suomalainen Senior Scientist, Tel. +358 50 382 2463 [email protected]

Tapio Lehtonen, Researcher Tel. +358 50 511 0037 [email protected]

Pekka Immonen, Researcher Tel. +358 50 410 5520 [email protected]

MIKES, Tekniikantie 1, FI-02150 Espoo, Tel. +358 20 722 111, www.mikes.fi

The measurement of electric energy consumption has a huge economic importance. Through the de-velopment of electric energy market, the importance of measurement accuracy and traceability is further emphasised. Accurate electric power standards are required in the calibration of energy meters. At MI-KES, measurements of electric power at 50 Hz are traceable to SI units through a sampling power standard. Calibrations are performed using either single-phase or three-phase measurements. Typi-cal devices that we calibrate are electric power me-ters and converters.

At MIKES power laboratory, the traceability of elec-tric power at 50 Hz is based on direct voltage from a Josephson standard and resistance realised by a quantum Hall equipment. The sampling power stan-dard consists of two 8½ digit voltmeters, which are accurately synchronised. Currents smaller than 20 A are converted to voltages using specially con-structed shunt resistors, whose resistance values are traceable to the quantum Hall resistance stand-ard. Because of the construction of the shunts, their frequency dependence is very small. Measurement results of voltage meters are based on fast sampling and are traceable to the Josephson voltage stand-ard. The same measurement equipment with a cur-rent sensor based on a Rogowski coil is used to measure currents and current ratios up to 8000 A. The measurement uncertainty of the MIKES power reference equipment is 0.005 % at its best.

Figure 1. In power and energy measurements, traceability for large currents is also needed. Parts of 8000 A meas-uring setup based on a Rogowski coil

The methods and equipment of MIKES power labora-tory represent international top quality. The high quality of measurements is verified by taking part in interna-tional comparison measurements together with na-tional metrology laboratories from other countries. MIKES is also an active member in different expert working groups at international level and takes part in national as well as international joint research projects. Several projects are in the European Metrology Re-search Programmes EMRP and EMPIR.









Calibration of power and energy at line frequency


Calibration services MIKES calibrates especially reference standards of customers who need the best available measuring accuracy. Typical instruments are power comparators and converters. The calibrations are performed by connecting the same current and voltage to the cus-tomer’s device and the reference meter of MIKES. If necessary, effect of the power source used in the cal-ibrations is minimized by accurately synchronising the meters. The reference meter used in the calibrations is either a single-phase sampling power standard or a three-phase power comparator.

In addition to power standards, we calibrate current and voltage transformers and transducers up to 200 kV voltage and 8 kA current. We carry out special assignments related to the measurement of electric power and energy and take part in research and de-velopment cooperation projects in this field. More-over, we organise educational opportunities in this field and custom tailored training.

Figure 2. A coaxial shunt resistor of the sampling power standard.

Table 1. Measuring ranges and calibration uncertainties at MIKES for calibrations of power and energy at line frequency.

Measured quantity Expanded relative uncertainty (k = 2) Single phase, 30 V – 500 V, 5 mA – 10 A Active power 50 μW/VA Reactive power 100 μvar/VA 3-phase, 50 V – 350 V, 5 mA – 12 A Active power 120 μW/VA Reactive power 250 μvar/VA Active power 120 μWh/VAh Reactive power 250 μvarh/VAh





Length and geometry

Chemistry

RF- and microwave calibrations Kari Ojasalo, Researcher Tel. +358 50 410 5557 [email protected]

Jari Hällström, Senior Scientist Tel. +358 50 382 2127 [email protected]


The importance of measurement reliability is empha-sized along with the continuously increasing amount of applications in RF- and microwave ranges. MIKES is the national metrology institute in this field and of-fers traceability with low uncertainty to internationally accepted measurement standards in RF and micro-wave power measurements and measurements of S parameter (reflection and attenuation). We calibrate power sensors and attenuators for instance.

Our calibration equipment is equipped with precision type N connectors, thus our measurement range ex-tends to 18 GHz. The measurements and the analysis of results are mainly automated. The measurements are carried out in a controlled 23 °C temperature in an electromagnetically shielded room.

The high standard of the measurements is verified by actively taking part in international comparisons to-gether with other national metrology institutes. The traceability is based on power and attenuation cali-brations at NPL (National Physical Laboratory) in U.K. and on the primary standards at MIKES.

Figure 1. Measurement of power sensors.








RF- and microwave calibrations


Calibration services Power The calibration coefficients of sensors are determined with measurement equipment based on a power di-vider. Measurement of reflection coefficient by using a vector network analyser is included in the sensor calibration. Typically, calibration takes five workdays. The calibration of the absolute power of a power ref-erence in a power meter is performed for thermocou-ple and diode power sensors. The reflection coeffi-cient of the power source is determined at the same time.

Attenuation Attenuation calibrations are carried out by traceable vector network analyser measurements. Determina-tion of reflection coefficient by is included in the cali-bration. We calibrate fixed value attenuators as well as step attenuators. The step attenuators can be con-trolled by using a GPIB bus, RS-232 connection or directly using the step attenuator controller Agilent 11713A.

Reflection coefficient Traceable measurements of reflection coefficient are performed using a vector network analyser. The im-pedance of the impedance standards used in the measurements is determined at MIKES with accurate dimensional measurements. Dimensional measure-ment services for N-type airlines are offered for cus-tomers, also.

Figure 2. Measurement set-up for power sensors.

Figure 3. Measurement of reference step attenuator.

Table 1. Measurement ranges and uncertainties.

Quantity Measurement range

Measurement frequency range Uncertainty

Calibration coefficient of power sensors 1 mW 10 MHz – 18 GHz(1) 0.4 % – 1.1 % (k=2)(2)

Absolute power 1 mW 10 MHz – 18 GHz(1) 4 mW/W – 11 mW/W (k=2) Attenuation 0 dB – 80 dB 300 kHz – 6 GHz 0.02 dB – 0.17 dB (k=2) Attenuation 0 dB – 60 dB 6 GHz – 18 GHz 0.05 dB – 0.18 dB (k=2) Reflection coefficient (real and imaginary parts)

between –1 and 1 10 MHz – 18 GHz 0.013 – 0.024 (k=2.45) (3)

1) Frequencies for power calibrations: 10 MHz, 30 MHz, 50 MHz, 100 MHz, 300 MHz, 500 MHz, 1 GHz, 1,5 GHz, 2 GHz – 18 GHz in 1 GHz steps.

2) Absolute value of reflection coefficient ≤ 0,08 3) A 95 % coverage for the complex uncertainty of a complex variable is obtained when k=2.45.





Length and geometry

Chemistry

High voltage and high current Esa-Pekka Suomalainen, Senior Scientist Tel. +358 50 382 2463 [email protected]

Jussi Havunen, Researcher Tel. +358 50 590 6536 [email protected]


High voltage quantities The importance of high voltage measurements has been emphasized with the opening of electricity mar-kets. The quality of electricity, transmission losses and the sale of electricity for industry and for private households have become more important measuring and monitoring subjects. In addition to electricity, electronics and information industries, high voltage users can be found, in almost every industrial sector. High voltage metrology at MIKES is internationally re-spected and provides services on traceability also at customers premises in Finland and globally.

Traceability The high voltage measurements at MIKES are trace-able to capacitance, resistance and voltage, which in turn are based on quantum primary standards: quan-tum Hall resistance standard and Josephson voltage standard. We have performed well and also acted as a coordinator in international comparisons in high voltage metrology. As an example of this is the coor-dination of broad European and worldwide compari-sons of lightning impulse voltage measuring systems.








High voltage and high current


Calibration services MIKES offers calibration services for almost all high voltage quantities and measuring systems up to 200 kV voltage. The range of alternating current calibra-tions extends to 6 kA. The measuring range for pulse quantities covers a voltage range from millivolts up to megavolts and currents up to tens of kiloamperes. Our expert services cover different aspects of calibra-tion of measuring systems. If wanted, we evaluate customer’s measuring systems and modify them to be more accurate and stable if needed. In future, our area of qualification will be extended to calibrations related to measurements on the quality of electricity. The best calibration uncertain y is achieved, when calibrations are performed in a laboratory at MIKES but calibrations can be carried out at customer’s premises, also. Measuring systems can be calibrated on-site when the voltage level, the size of the system, grounding conditions or proximity effects necessitate it.

Calibration subjects Devices that we calibrate include.

• voltage dividers • voltage and current transformers • measuring probes, voltage and current sensors

and current shunts • high voltage inductors and capacitors • transient recorders, peak voltage meters • surge-, EFT- and ESD- test devices • voltage testers • pulse calibrators • partial discharge calibrators

Table 1. Calibration services of high voltage.

Quantity Measurement range Uncertainty (k=2)

Direct current 1 kV – 1000 kV 0.0005 – 0.01 % Alternating voltage, voltage ratio 1 kV – 200 kV 0.002 – 0.01 % – angle error 0 – 100 mrad 0.02 mrad

Alternating current, current ratio 1 A – 6 kA 0.0025 – 0.02 % – angle error 0 – 100 mrad 0.2 – 0.4 mrad

Capacitance 1 – 100 kV / 10 pF – 200 µF 0.002 – 0.05 % – loss coefficient tan δ 1.10–5 – 2 1 % (1.10–5 abs) Inductance / losses 1 µH – 10 H 0.03 % / 0.2 mrad Lightning impulse 50 mV – 400 kV 0.1 – 0.5 % Switching impulse 1 V – 200 kV 0.1 – 0.2 % Other voltage impulses (e.g. surge) 1 V – 400 kV 0.1 – 0.5 % Current impulses 1 A – 10 kA 3 % ESD-pulse 1 A – 50 A 5 % Time parameters of pulses 0.7 ns – 100 ms 0.5 – 5 % Apparent charge of a pulse (partial discharge) 1 pC – 1 nC 2 % (0,2 pC abs)





Length and geometry

Chemistry

Acoustic calibrations Kari Ojasalo, Researcher Tel. +358 50 410 5557 [email protected]

Jussi Hämäläinen, Researcher Tel. +358 50 410 5518 [email protected]


The need of accurate acoustic measurements is growing for instance due to regulations and legisla-tions concerning noise emissions and exposure to vi-brations. A good measurement accuracy requires, in addition to high-quality measurement devices, regu-lar and traceable calibrations. In Finland, MIKES is responsible for the traceability of the acoustic quanti-ties: sound pressure and acceleration.

Sound pressure is transformed into an electrical sig-nal by using accurate condenser microphones, whose primary calibration equipment is in use at MIKES. Sound level calibrators are calibrated using these condenser microphones. The traceability chain of sound pressure level starts from the calibration of laboratory grade microphones by using a so-called reciprocity calibration system. This calibration gives the voltage-pressure sensitivities of the microphones. The method is described in the standard IEC 61094- 2 (1992-03) and it is in use in several other national metrology institutes.

A vibration transducer produces a signal, typically a voltage or a charge, which is proportional to the ac-celeration of mechanical motion. Therefore, in the cal-ibration of a vibration transducer, the sensitivity (typi-cally mV/(m/s2) or pC/(m/s2) of the sensor is deter-mined as a function of frequency. MIKES calibrates vibration transducers by comparing their readings to a known vibration produced with a vibration exciter. The real amplitude of acceleration and frequency is simultaneously measured by using a reference sen-sor. The method is described in the standard ISO 16063-21:2003.

Figure 1. A reciprocity calibra-tion of microphones is starting in the soundproof laboratory at MIKES.








Acoustic calibrations


Calibration services Microphones We calibrate ½ (LS2P) and 1 (LS1P) inch condenser microphones described in the standard IEC 61094-1 (Table 1). The calibration method depends on the ac-curacy required by the customer. The smallest cali-bration uncertainties can be achieved by using the reciprocity method. In many cases, a comparison with a reference microphone by a sound level calibrator is adequate.

Table 1. Uncertainties of calibration for microphones.

Type of microphone

Frequency [kHz]

Uncertainty [dB]

LS 1

0.0315 0.06 0.063 ... 2 0.04 4 0.05 5 0.06 8 0.08 10 0.10

LS 2

0.0315 0.08 0.063 0.06 0.125 ... 8 0.05 10 0.06 12.5 0.08 16 0.10 20 0.14

Sound level calibrators

Sound level calibrators and pistonphones are the most common devices calibrated at MIKES acoustics laboratory. We calibrate the sound pressure levels at fixed frequency points. At the same time, the distor-tion and frequency of the sound source is measured.

Vibration transducers and loggers We calibrate vibration transducers, loggers and vibra-tion measurement devices in the frequency range 1 Hz – 10 kHz. Typical nominal acceleration is 10 m/s2. The calibration gives the magnitude and the phase of the sensitivity of the vibration transducer. The uncertainty of the calibration depends on the transducer under calibration. Typical uncertainties for the magnitude are 1–3 % and for the phase 1–2° de-pending on the frequency (Figure 2).

Figure 2: The measurement ranges and uncertainties of calibration of vibration transducers.

Table 2. Calibration ranges and uncertainties for sound level calibrators. The type of the measurement.

Type of calibrator Frequency (Hz) Sound level [dB re 20 µPa] Uncertainty [dB]

Single-frequency 125 – 1000 70 – 130 0.08

Multi-frequency 31.5 94 – 114 0.15

63 – 4000 94 – 114 0.15 8000 – 12500 94 – 114 0.15

relative uncertainty Am

plitu

de /

m

Freq. range f =

Cal. range





Length and geometry

Chemistry

Calibration of time, time interval and frequency Ilkka Iisakka, Researcher Tel. +358 50 410 5519 [email protected]

Anders Wallin, Senior Scientist Tel. +358 50 415 5975 [email protected]


Measurements of frequency and time interval are needed in various direct and indirect measurements, e.g., in telecommunication; therefore, precise and traceable frequency and time interval measurements are important nationally. The importance of absolute time is increasing, too (e.g. time stamps).

MIKES is responsible for the traceability of time, time interval, and frequency in Finland. MIKES time labor-atory maintains the official time in Finland with an un-certainty of 10 ns in relation to the coordinated univer-sal time (UTC) and national frequency with a 1•10–13 relative uncertainty. The reference standards for time and frequency are one caesium atomic clock, four hy-drogen masers and several GPS receivers. Finland participates in maintaining of the UTC with its five ref-erence standards through GPS based time compari-son.

Figure 1. The traceability of time and fre-quency is based on hydrogen masers (in the figure left) and on caesium atomic clocks, which are located in enclosures having with a special climate control.








Calibration of time, time interval and frequency


Calibration services We calibrate e.g. GPS receivers (frequency), oscilla-tors, time interval counters, stopwatches, strobo-scopes, and optical tachometers. The frequency range is 1 mHz to 5 GHz. We make time interval measurements according to customer’s need, with a lower limit of approximately one nanosecond. Fur-thermore, MIKES has a transmitter for time code and precise 25 MHz frequency for those near the Helsinki metropolitan area who need precise time and fre-quency.

In addition to calibration, we carry out special assign-ments related to time and frequency measurements and participate in research and development collabo-ration projects in this field.

NTP - network time service Computer clocks can be synchronised with the na-tional time in Finland maintained by MIKES by using Network Time Protocol, NTP. The achievable uncer-tainty depends on network connections but it is around one millisecond at its best. MIKES maintains NTP servers subject to charge for institutions and companies. We have four servers of the highest level (stratum-1): two of them are synchronised directly to MIKES atomic clocks and two to GPS receivers. Moreover, we control two public NTP servers that are locked to MIKES servers. These servers are available free of charge for public use.

Figure 2. MIKES participates in maintaining of the UTC through GPS-based time comparison.





Length and geometry

Chemistry

Quantitative Microscopy – Atomic Force Microscope Virpi Korpelainen, Senior Scientist Tel. +358 50 410 5504 [email protected]


Development and research in nanotechnology has in-creased the need for accurate measurements in re-search institutes and industry. Different kinds of Scan-ning Probe Microscope (SPM) measurements are commonly used in many institutes and companies. In order to guarantee accurate and reliable dimensional measurements at nanometre range, MIKES has a traceably calibrated Atomic Force Microscope (AFM). Thus, MIKES can provide customers with traceable measurements also at nanometre range.

MIKES provides accurate AFM measurement ser-vices to match the needs of customers. In addition, we calibrate SPM transfer standards.

Figure 1. Alignment of laser beams for interferometric calib-ration of y-axis of the AFM.







Quantitative Microscopy – Atomic Force Microscope


MIKES has a PSIA XE-100 AFM, which is calibrated interferometrically and with grating calibrated by la-ser diffraction at MIKES. The AFM is traceable to the definition of the metre. The xy-movements of the AFM are mechanically separated from the z-move-ments. This increases the linearity of the move-ments, decreases out of plane movements and elim-inates crosstalk. The structure of the device allows rather large samples to be measured. Measure-ments can also be done using the most usual meas-urement modes: contact, non-contact, tapping and lateral force. The measurement results can be ana-lysed using SPIP software 1.

Scale errors of uncalibrated SPMs typically range from 2 % to 20 %. In addition, measurement errors may cause distortions in the measured figure, which might be difficult to detect from the figure. Therefore, the device has to be calibrated. New, more advan-ced SPMs have increased measurement precision, but the development does not remove need for cali-bration. Especially in all quantitative form measure-ments, the measurements should be traceable to the definition of the metre. Usually SPMs are calibrated by using calibrated transfer standards. 1 The Scanning Probe Image Processor SPIPTM

http://www.imagemet.com

Property Data Sample size <100 mm × 100 mm Sample thickness <20 mm Sample mass <500 g Measurement range (xy) 100 µm × 100 µm Measurement range (z) 12 µm

Resolution (xy) 0.15 nm 0.02 nm (low voltage mode*)

Resolution (z) 0.05 nm 0.01 nm (low voltage mode*)

Uncertainty (k=2), x and y directions Q [3; 2 L/µm] nm

Uncertainty (k=2), z direction Q [3; 2 L/µm] nm

Q [x; y] = (x2 + y2)1/2

Figure 2. 2-D grid standard.

Figure 3. AFM image of Seeman tile type DNA nano-origami structures.

DEFINITION OF THE SI-UNIT METRE

Laser frequency calibration

Realisation of the metre • Frequency comb (links the metre to the second) • Iodine-stabilised lasers

Interferometrically traceable AFM

Calibration of a SPM

Traceable SPM measurements

Calibration of physical transfer standards for scanning probe microscopes (SPMs) 1D and 2D gratings, flatness & step height standards

Laser diffractometer

At M

IKES

http://www.imagemet.com/





Length and geometry

Chemistry

Characterization of nanoparticles Virpi Korpelainen, Senior Scientist Tel. +358 50 410 5504 [email protected]


Nanoparticles are widely used in many applications. Accurate characterization of the nanoparticles is im-portant in research, production and applications in several fields including industry, health, safety and re-lated regulation. At VTT MIKES, the particles can be characterized using two different methods: Dynamic Light Scattering (DLS) and atomic force microscopy (AFM). The measurements are traceable to the defi-nition of the metre via MIKES interferometrically traceable metrological atomic force microscope (IT-MAFM). Both methods have advantages and lim-itations. DLS is fast method and the results are statis-tically representative. In DSL measurements, even a small number of large particles can prevent detection of small particles. AFM can be used to measure both size and shape of single particles. The disadvantage of AFM measurements is that only limited number of particles can be measured which leads to poor statis-tics. Tip sample interaction is important especially when measuring small particles. In addition, sample preparation might be challenging.

Figure 1. AFM image of 100 nm nanoparticles.

Figure 2. DLS measurements.

Table 1. VTT MIKES has two instruments suitable for nano-particle measurements.

Instrument Zetasizer Nano PSiA XE-100

Measurement method DLS AFM

Measurands Size distribution Zeta potential

Size Shape

Measurement range 0.3 nm – 10 µm 5 nm – 5 µm Measurement uncertainty 2 % from 1 nm







Characterization of nanoparticles


Zetasizer Nano Dynamic Light Scattering is used to measure particle and molecule sizes. This technique measures the dif-fusion of particles moving under Brownian motion, and converts this to size and a size distribution using the Stokes-Einstein relationship.

Laser Doppler Micro-electrophoresis is used to meas-ure zeta potential. An electric field is applied to a so-lution of molecules or a dispersion of particles, which then move with a velocity related to their zeta poten-tial.

Services for nanoparticle characterization

• Nanoparticle size and shape measurements us-ing AFM

• Nanoparticle size distribution in solution using DLS

• Nanoparticle surface charge (Zeta-potential) measurements in solution

Atomic force microscopy (AFM) An AFM uses a cantilever with a very sharp tip to scan over a sample surface. As the tip approaches the sur-face, the close-range, attractive force between the surface and the tip cause the cantilever to deflect to-wards the surface. However, as the cantilever is brought even closer to the surface, such that the tip makes contact with it, increasingly repulsive force takes over and causes the cantilever to deflect away from the surface.

In AFM images the topography of a sample surface by scanning the cantilever over a region of interest. The raised and lowered features on the sample sur-face influence the deflection of the cantilever, which is monitored by a position-sensitive photo diode (PSPD). By using a feedback loop to control the height of the tip above the surface the AFM can gen-erate an accurate topographic map of the surface fea-tures.

Figure 3. DLS results of ~100 nm nanoparticles.





Length and geometry

Chemistry

Calibration of laser interferometers Jeremias Seppä, Senior Scientist Tel. +358 50 410 5503 [email protected]

Veli-Pekka Esala, Senior Scientist Tel. +358 40 866 7636 [email protected]


Laser interferometers together with gauge blocks are the most important measurement standards in mod-ern length metrology. At 1980s a common under-standing was that laser interferometers are accurate and hence do not need any calibration. However, ever-increasing demand for accuracy and long expe-rience on usage of laser interferometers have shown that it is necessary to calibrate laser interferometers, also. At MIKES, we have traceable procedures to cal-ibrate laser interferometers. The calibration of laser interferometers improves their reliability and accuracy essentially.

Figure 1. Functional testing of a laser interferometer.

Figure 2. An iodine-sta-bile HeNe-laser used for the practical realisation of the metre.








Calibration of laser interferometers


Calibration procedure Calibration of laser frequency

The vacuum wavelength of lasers used in laser inter-ferometers is calibrated using iodine-stabilised lasers. Traceability to the definition of the metre is guaranteed as frequencies (vacuum wavelength) of the iodine-sta-bilised lasers are determined by an optical frequency comb referenced to an atomic clock.

MIKES maintains the following lasers that are locked to iodine absorption lines according to international recommendations: He-Ne lasers at wavelengths: 633 nm (Figure 2) and 543.5 nm and a Nd:YAG-laser at 532 nm. These laser have a relative frequency uncer-tainty better than 10-10 (expanded uncertainty, k=2).

The frequency of the laser under calibration is com-pared to the frequency of an iodine-stabilized laser. The calibration includes a long-term frequency (vac-uum wavelength) calibration and repeatability meas-urements. Moreover, the frequency difference of the horizontally and vertically polarised lights is deter-mined and the separation of the polarisation planes in-spected. Together these measurements provide good indication of the frequency stability of the laser under calibration. Lasers that operate at wavelengths not reachable by iodine-stabilized lasers can be calibrated using a frequency comb.

Figure 3. Errors in environmental sensors can have remark-able effects on the readings of a laser interferometer.

Table 1. Uncertainty of calibration.

Quantity Measuring range Uncertainty (k=2)

Wavelength 633 nm; 543.5 nm; 532 nm

~10–9 (relative)

Air pressure 970…1050 hPa (730 … 790 mmHg)

40 Pa

Air temperature 17…25 °C 0.10 °C Material temperature

15…25 °C 0.050 °C

Calibration and functional testing of environmental sensors

In addition to laser vacuum wavelength calibration, the environmental sensors are calibrated and their operation tested. These measurements are neces-sary to achieve the naturally good measurement ac-curacy of a laser interferometer. Especially, by cali-brating the environmental sensors order of magni-tude better measurement accuracy can be achieved for a laser interferometer.

The calibration of environmental sensors includes the calibration of air temperature sensors, atmos-pheric pressure sensors and material temperature sensors. The functional testing is performed in a temperature-stabilised laboratory room by measur-ing the locations of a moving carriage equipped with a retroreflector with the laser interferometer under calibration and with a reference laser interferometer (Figure 1). In these measurements, both laser beams travel through the same optical components and data is collected with and without the environ-mental sensors operating. In addition, the angle scale is tested using a reference laser. If necessary, the quality of the optical components is tested with a flatness interferometer.

If the readings of the environmental sensors deviate remarkably from readings of the reference instru-ments, they should be adjusted. By adjusting, the accuracy of the laser interferometer can easily be improved (Figure 3), e.g., the adjustment is relatively easy to perform in Agilent laser interferometers.

Traceability The frequencies of the iodine-stabilised lasers that are the national measurement standards of length are determined using an optical frequency comb ref-erenced to MIKES atomic clocks. The instruments used in the calibration of environmental sensors are calibrated in the corresponding national standards laboratories. Thus, the measurements are traceable to the corresponding definitions of the units.

Position / mm

Cor

rect

ion

/ µm

Correction of scale





Length and geometry

Chemistry

Interferometric calibra-tion of gauge blocks Pasi Laukkanen, Research Engineer Tel. +358 50 382 9674 [email protected]

Antti Lassila, Research Team Leader Tel. +358 40 767 8584 [email protected]


Calibration of gauge blocks Gauge blocks are the most important measurement standards of length in industry. Interferometric meas-urement of gauge blocks provides an absolute cali-bration method. By using interferometers, the practi-cal realisation of the metre is transferred to a gauge block via the calibrated wavelength of the frequency-stabilised laser used in the interferometer. Gauge blocks calibrated by comparison must be traceable to gauge blocks calibrated by interferometry. The length of a gauge block is defined in an ISO standard as the distance from the centre of the gauge face to an aux-iliary reference plane wrung to the other end of the gauge block at 20 °C temperature and at 1013.25 hPa barometric pressure. Gauge block sets calibrated by interferometry give a lower uncertainty for mechanical calibrations e.g. in accredited calibration laboratories.

Interferometers at MIKES MIKES have gauge block interferometers for short (0…300 mm) and for long (100…1000 mm) gauge blocks and end standards. The interferometers are lo-cated in a laboratory room having well stabilised en-vironmental conditions and they are equipped with temperature, humidity and pressure sensors. Low un-certainties for refractive index of air and for thermal expansion compensation can be achieved with a pre-cise control and monitoring of the environmental con-ditions. Difference in surface roughness between the gauge block face and the reference plane is meas-ured and corrected for in results. The parallelism and flatness of the surfaces can be measured, also.

The MIKES PSIGB interferometer for short gauge blocks (Fig. 1) uses stabilised He-Ne lasers at 633 nm and 543.5 nm. The interferometer is equipped with a large wringing bed, which enables fast and auto-mated calibration of even 14 gauge blocks in se-quence. In the Tesa interferometer, the gauge blocks are positioned vertically.

Figure 1. Tesa-NPL gauge block interferometer.

The long gauge block interferometer (Fig. 2) utilises white light and 633-nm laser light interference pat-terns. By using white light, beforehand knowledge of the length of the end standard is not required. The end standards and gauge blocks are positioned hori-zontally and supported at the Bessel points in such a way that the weight of the reference plane is compen-sated for.








Interferometric calibration of gauge blocks


Traceability The regular calibration of length standards and length measuring equipment is a necessary part of meas-urement quality control. Traceable calibrations and knowledge on the measurement uncertainty are basic demands for good and constant quality. The tracea-bility to gauge block calibrations is achieved by cali-brating the wavelengths of lasers used in the interfer-ometers against national measurement standards of length, iodine-stabilised He-Ne lasers. Measuring de-vices for temperature, humidity and pressure used in the interferometers are calibrated in corresponding MIKES laboratories. The reliability of calibrations are verified by taking regularly part in international com-parisons.

Calibration services Gauge block interferometers can be used to measure even other artefacts whose surfaces are flat and smooth enough; for instance to determine the thermal expansion coefficient of ceramic sealings and to measure the air gap between two parallel glass plates. Interferometric calibration sets also demands for gauge blocks: their end surfaces must be parallel, flat and without scratches. MIKES calibrates gauge blocks of grades K (00) and 0 and end standards, e.g. quartz metres, according to the following table.

Figure 2. MIKES length bar interferometer for calibration of long gauge blocks.

Table 1. Calibration subjects and measurement uncertainties.

Device Measurement range Uncertainty (k=2)

Gauge blocks, small 0.5 mm ... 300 mm Q[20; 0.3L] nm

Gauge blocks, long 100 mm ... 1000 mm Q[30; 0.11L] nm

Quartz meters 1000 mm 72 nm





Length and geometry

Chemistry

Calibration of gauge blocks by mechanical comparison Arttu Ollikainen, Research Assistant Tel. +358 50 395 2816 [email protected]



Mechanical comparison measurement is the most common way to determine the length of a gauge block. In this method, the length of the gauge block under calibration is compared to the length of a cali-brated gauge block with same nominal length by us-ing a specific comparator, Figure 1.

Gauge block measurement Comparison measurements of gauge blocks that have the same nominal length and that are of the same material are simple, reliable, fast and inexpen-sive. The method is also applicable to gauge blocks whose surfaces have been worn-out in use. MIKES calibrates steel, hard metal, and ceramic gauge blocks in lengths 0.1 ... 1000 mm (Table 1). In calibra-tion, we check the flatness of the surfaces and re-move splatters that could prevent reliable use of the gauge blocks. A regular inspection of gauge blocks prevents a possible damage to affect the whole set. The use of uncalibrated gauge blocks in production quality control and in calibration of measurement equipment causes extra risks and costs

Figure 1. The sensor of the gauge block comparator identi-fies the location of the surface by using 0.6 Nm measure-ment force.

Table 1. Calibration of gauge blocks by mechanical comparison.

Measurement device Measurement range Uncertainty

Tesa gauge block comparator 0.1 mm …100 mm Q[0.050; 0.00087L] µm

MIKES comparator for long gauge blocks 100 mm …1000 mm Q[0.20; 0.00087L] µm

L is the nominal length in millimetres








Calibration of gauge blocks by mechanical comparison


Traceability The reference gauge blocks used in mechanical com-parison measurements are regularly calibrated using MIKES gauge block interferometers. The wavelengths of lasers used in these interferometers are calibrated by national measurement standard of length, iodine-stabilised He-Ne lasers

Table 2. Accuracy grades of ISO 3650:1998 standard.

Nominal length range mm

Calibration grade K

mm

Grade 0

mm

Grade 1

mm

Grade 2

mm Lower length

Upper length ±te tv ±te tv ±te tv ±te tv

0.5 10 0.20 0.05 0.12 0.10 0.20 0.16 0.45 0.30

10 25 0.30 0.05 0.14 0.10 0.30 0.16 0.60 0.30

25 50 0.40 0.06 0.20 0.10 0.40 0.18 0.80 0.30

50 75 0.50 0.06 0.25 0.12 0.50 0.18 1.00 0.35

75 100 0.60 0.07 0.30 0.12 0.60 0.20 1.20 0.35

100 150 0.80 0.08 0.40 0.14 0.80 0.20 1.60 0.40

150 200 1.00 0.09 0.50 0.16 1.00 0.25 2.00 0.40

200 250 1.20 0.10 0.60 0.16 1.20 0.25 2.40 0.45

250 300 1.40 0.10 0.70 0.18 1.40 0.25 2.80 0.50

300 400 1.80 0.12 0.90 0.20 1.80 0.30 3.60 0.50

400 500 2.20 0.14 1.10 0.25 2.20 0.35 4.40 0.60

500 600 2.60 0.16 1.30 0.25 2.60 0.40 5.00 0.70

600 700 3.00 0.18 1.50 0.30 3.00 0.45 6.00 0.70

700 800 3.40 0.20 1.70 0.30 3.40 0.50 6.50 0.80

800 900 3.80 0.20 1.90 0.35 3.80 0.50 7.50 0.90

900 1000 4.20 0.25 2.00 0.40 4.20 0.60 8.00 1.00

Note: The calibration ISO grades 0, 1, and 2 correspond to accuracy classes A, B, and C in OIML standard no. 30, respectively

Abbreviations in the table 2: te = deviation of length from nominal length tv = variation in length





Length and geometry

Chemistry

2D and 3D measurement of form and surface roughness Björn Hemming, Senior Scientist Tel. +358 50 773 5744 [email protected]

Maksim Shpak, Researcher Tel. +358 50 415 5976 [email protected]


The manufacturing tolerances of modern products and the aim to high quality require the ability to meas-ure different form measurands of small artefacts hav-ing complicated shapes. Examples of such form measurands are straightness, parallelism, radius of curvature and surface roughness. MIKES measure-ment and calibration services using a computer con-trolled form and surface texture instrument provides one solution to these measurement problems. Form mesurement The form measurement instrument can detect form deviations even as small as 0.6 nm. Examples of typ-ical form measurements are accurate measurements of straightness, inner and outer determinations of ra-diation of curvatures and diverse dimensional meas-urements of small artefacts (Figure 1). These include determinations of grooves lengths and depths and in-ner and outer angle measurements. The most im-portant technical specifications of the Taylor Hobson Form Talysurf instrument are gathered in table 1.

Figure 1. Straightness measurement on a cylindrical sur-face.








2D- and 3D- measurement of form and surface roughness


Surface roughness measuremens In addition to calibration of surface roughness standards, the surface texture instrument at MIKES is used for tasks related to quality control and prod-uct development. The surface roughness measure-ments at MIKES are based on the following stand-ards: ISO 5436-1 and ISO 4287. Measurement subjects

• traceable calibration of surface roughness standards

• diverse measurements in development of prosthesis in health care industry

• measurement of tribological samples • profile measurements of blades of excavation

machinery • geometrical measurements in product devel-

opment and quality control of electronic com-ponents

• product development and quality control meas-urements of metal packings and components in hydraulics and pneumatics.

Traceability Traceability to the form measurement instrument comes from interferometrically calibrated gauge blocks, a line scale, an optical flat and a sphere.

Figure 2. Measurement of sideline.

Table 1. The most important technical specifications of the Taylor Hobson Form Talysurf instrument.

Property Information

Instrument and operational principle Taylor Hobson Form Talysurf Ser. 2, Type 112/2815-02, inductive

Measurement tips Diamond tip, radius 0.002 mm, Spherical sapphire tip, radius 0.397 mm.

Measurement forces 1.0 mN (using diamond tip), 15–20 mN (using sapphire tip)

Surface texture parameters R3y, R3z, Ra, Rc, Rda, Rdc, Rdq, RHSC, Rku, Rln, RLo, Rlq, Rmr, Rmr(c), Rp, RPc, Rq, RS, Rsk, RSm, Rt , Rv, RVo, Rz, Rz(JIS). In addition, a series of waviness parameters.

Longest measurement length 120 mm Maximum height of artefact 700 mm, maximum width in 3D measurement is 50 mm Largest allowed deviation 28 mm (120 mm arm) Measurement speed 1 mm/s Resolution 0.0006 µm Lowest uncertainty Q[10; 70P] nm, where P is the deviation from flatness in micrometers





Length and geometry

Chemistry

Optical measurement of surface microstructures Ville Heikkinen, Researcher Tel. +358 50 415 5980 [email protected]

Björn Hemming, Senior Scientist Tel. +358 50 773 5744 [email protected]


Micro to millimetre range structures can be measured at MIKES using scanning white light interference mi-croscope (SWLI).

The SWLI has sub-nm vertical and µm level horizon-tal resolution. It can measure square mm areas in a single scan. Benefit of SWLI compared to other in-struments with similar vertical resolution include large measurement area ability to measure high steps and ability to measure overlapping surfaces inside of transparent structures. See table 1 for more proper-ties of the instrument.

Real life measurement uncertainty is case dependent and depends on measurement environment, proper-ties of instrument and properties of measured sam-ple. At MIKES, we take care that the sample is clean, sample temperature is known and the sample is well attached and properly aligned. Measurements are done traceably under consistent conditions and re-sults are well documented.

Examples of potential measurement objects:

• Bearings, contact surfaces, surface topography and wear

• Semiconductors and MEMS • Medical instruments and implants • Optical components • Precision machined components

Figure 1. Bruker ContourGT-K scanning white light inter-ferometer.

We do different measurements using the SWLI

• Different type of objects o surface shape measurements o x,y,z dimensions of details on a surface o film thickness measurement, layer separa-

tion o surface roughness (2D and 3D ISO rough-

ness parameters), flatness, deviation from a shape

• Calibration of different instruments • Calibration of reference artefacts

o step heights, air gap artefacts, film thickness artefacts








Optical measurements of surface microstructures


Optimal measurement condition SWLI is in underground measurement room with (20 ± 0.1) °C temperature. Most heat sources in the room have been eliminated by venting warm air out.

Traceability SWLI is traceable to the SI-metre through MIKES’s own transfer standards such as step height stand-ards, gauge blocks and laser interferometer.

Table 1. Properties of SWLI Property Information Optical x-y resolution 3.8 – 0.7 µm Pixel size 7.2 – 0.2 µm Vertical resolution < 0.1 nm Step height measurement:

• repeatability < 0.1 % • accuracy < 0.75 %

Sample reflectivity: 0.05 % – 100 % Maximum surface tilt (smooth samples): 3° (2.5× objective), 18.9° (20× objective) Magnifications 2.5× and 20× objectives, 0.55×, 1× and 2× zoom lenses Measurement area (X × Y × Z mm3): smallest magnification

Measurement area (X × Y × Z mm3): 3.5 × 4.6 × 3.5

largest magnification 0.4 × 0.6 × 3.5 Measurement area in pixels 640 × 480 Programs Vision64 Analysis Software, MountainsMap, MatLab Maximum size of measured object 10 cm high × 20 cm wide, one dimension can be longer

Ability to measure overlapping surfaces 2 surfaces in single measurement Maximum depth is dependent on refractive index, geometry and magnification, e.g. it is possible to measure through 0.3 mm thick glass. 7 mm maximum depth limited by working distance.

Figure 2. Measurement of machined aluminium surface

Figure 3. Measurement of a groove on a glass surface.





Length and geometry

Chemistry

Calibration of tachymeters Jarkko Unkuri, Researcher Tel. +358 40 410 5506 [email protected]



MIKES calibrates angle and distance measurements functions of tacheometers.

Calibration of a distance metre in a 30-metre measuring rail Readings from a distance meter of a tachymeter is compared to readings from a laser interferometer of the 30-metre measuring rail. The measurement axis of the tachymeter and the laser interferometer are aligned to be parallel. The reading of the interferome-ter is set to zero at the beginning of the measuring rail. The observed reading of the distance meter at the zero point of the interferometer is subtracted from

the readings of the distance meter. In the calibration certificate, the deviations from the references dis-tances and the expanded measurement uncertainty are given for each target point. The target point can be a prism, a reflector tape or a target plate. The measurement uncertainty depends on the scatter of the measurement results and is typically between 0.05 – 0.25 mm for accurate distance meters.

Figure 1. MIKES 30-m measuring rail.








Calibration of tachymeters


Calibration of angle meas-urements by using a rotary table and collimation tubes The vertical and horizontal scales of a tachymeter are calibrated by using an Eimeldingen rotary table as a reference. The rotary table is calibrated using poly-gons and collimation tubes.

In the calibration of the horizontal scale, the tachym-eter is placed to the rotary table in such a way that the vertical axis is aligned to the rotational axis of the ta-ble (Figure 2). The table is rotated 360° in 30° steps and at each step the reading of the tachymeter that has been targeted to the collimation tube are rec-orded.

The vertical scale of the tachymeter is calibrated in the same way but now the rotary table is turned to vertical position by using optomechanics that have been designed especially for this purpose.

Figure 2. Calibration of the horizontal plane of a tachymeter in an Eimeldingen rotary table with a collimation tube as a target point.

Contents of tacheometer calibration Typical measurement uncertainty

Calibration of length scale

deviation from reference

precision target 0.15 mm spherical target 0.15 mm reflector tape 0.20 mm

without target

calibration of angle scale

scale error of the vertical circle 2" – 3" scale error of the horizontal circle 1" – 2" tilting axis error 1" – 2" index error of the vertical circle 0.5" – 1.5" line-of-sight error 0.5" – 1.5"

crosshair alignment and perpendicularity

influence of focussing

checking the readings of the environmental sensors

divergence test of automatic targeting





Length and geometry

Chemistry

Angle and perpendicu-larity measurements Pasi Laukkanen, Research Engineer Tel. +358 50 382 9674 [email protected]

Ville Heikkinen, Researcher Tel. +358 50 415 5980 [email protected]


Angle measurements are important in all mechanical engineering and construction industry. The signifi-cance of angle measurements is increased also in di-mensional measurements when dimensions in-crease. Perpendicularity that is related to right angles and square blocks is an important special case of an-gle measurement.

The SI-unit for angle is radian (rad) but depending on the branch of industry and the measurement subject other units are commonly used. In mechanical engi-neering angles are normally expressed in degrees [°], minutes ['] and seconds ["], in geodesy the most com-monly used unit is gon [gon] (also referred to as grade). In earth-moving work and for small angles the unit [mm/m] is generally used. The diverse group of units for angle include also the following ways to ex-press the angle: percent [%] and length ratios.

Perpendicularity according to the ISO1101 standard:

• As a result the width t of tolerance zone is given • One side is defined as the reference side and

only against this side the perpendicularity is de-termined.

Figure 1. Polygon attached to a rotary table. Errors from the rotary table and the poly-hedron can be separated by performing a measurement series using a Moller Wedel HPR autocollimator.








Angle and perpendicularity measurements


Instruments for measuring angle The most typical objects of calibration in mechanical workshops are rotary tables of machine tools and measuring machines, universal bevel proctractors, angle blocks, and different kinds of spirit (bubble) lev-els. Typical angle measurement instruments used in machine installation and in construction engineering are e.g. electronic levels, theodolites, levelling instru-ments, tacheometers, laser interferometers, autocol-limators and polygons.

Figure 2. Interferometric 2D small angle generator for cali-bration of autocollimators developed at VTT MIKES.

Measurement uncertainty All measurements are performed in a well-controlled laboratory room at temperature +20 °C ± 0.1 °C. The achievable measurement uncertainty depends criti-cally on the artefact under calibration and its proper-ties (e.g. form errors and surface roughness)

Figure 3. Preparation of angle measurements.

Table 1. Examples of lowest uncertainties for angle measurement instruments.

Instrument Measuring range

Measurement uncertainty (k=2) Limitations

Optical polygons 0° – 360° 0.2"

Rotary index table 0° – 360° 0.5" indexing angle n x 15°

Rotary table 0° – 360° 0.2"

Autocollimator 0° – 1° 0.02"

Electronic level 0° – 360° 0.2"

Theodolite 0° – 360° 0.2" instrument limits the vertical angle

Angle block 0° – 360° 0.2"

Steel or granite squares 90° 0.5" maximum length 1 m

Cylinder square 90° 0.5" maximum length 1 m

Optical right angle 90° 0.5"





Length and geometry

Chemistry

Measurements of accurate inner and outer dimensions Pasi Laukkanen, Research Engineer Tel. +358 50 382 9674 [email protected]



Measurements using SIP length measuring machine Precise measurements of inner and outer diameters are performed using SIP length measuring machine either by using its own scale or by referencing to a standard of equal length (Figure 2). In the measure-ment, a contact is made using a ceramic spherical measuring probe, a flat tip or in inner measurements a lever probe. If the measurement depth in inner measurements is over 15 mm, special hook-shaped jaws are used. The measuring force can be tuned be-tween 0.3…11 N. By measuring with several different forces, the deformations due to the measuring forces can be eliminated from calculations and the result given at so-called zero-force. This is essential when the reference and the artefact under calibration are made of different materials or have different shapes.

The accuracy of the length scale in SIP length meas-uring machine can be improved by using a laser in-terferometer (5528A) and a separate readout pro-gram. Measurements are performed in a well-con-trolled laboratory room at temperature +20 °C ± 0.1 °C. Different types of heat sources are eliminated by using vent pipes, heat shields, and when necessary with a separate laminar flow. In addition to the meas-urement length, the measurement uncertainty de-pends on the measured artefact (shape and surface texture), on measuring instrument, measurement conditions, and on the method used.

In addition to diameter measurements, the SIP length measuring machine is used for thread measurements and tolerance comparisons. The inner threads are measured using spherical probes and in outer thread measurements, three-wire method is used.

Figure 1. Measurement using SIP length measuring machine.








Measurements of accurate inner and outer dimensions


Measurements supplement-ing diameter measurements In order to get a precise picture of the features of an axially symmetrical artefact that is under measure-ment, one should also measure its roundness, sur-face roughness and straightness of sides using ap-propriate instruments.

Traceability Measurements made using the SIP length measuring machine are traceable to corresponding transfer standards that are calibrated at MIKES. The linear scale is calibrated using a laser interferometer, the reference gauge blocks are calibrated interferometri-cally, and the temperature sensors are calibrated in temperature baths against reference Pt25 thermo-couples.

Table 1. Measurement uncertainties achievable in diame-ter measurements.

Measurement artefact Measurement uncertainty (k=2)

Thread plug 0 – 550 mm Q[0.2; 0.87L] µm

Ring gauge 1 – 500 mm Q[0.2; 0.87L] µm

Sphere 0.2 mm … 200 mm Q[0.15; 0.7L] µm

L in metres

Figure 2. Mounting side by side the artefact under calibra-tion and the reference in a comparison measurement.

Figure 3. SIP 550M length measuring machine.





Length and geometry

Chemistry

Coordinate measurement Pasi Laukkanen, Research Engineer Tel. +358 50 382 9674 [email protected]



The coordinate measuring services at MIKES include measurements with an optical coordinate measuring machine and with a high-accuracy industrial size con-tact probe coordinate measuring machine.

Contacting coordinate measurement The basic properties of MIKES coordinate measuring machine are accuracy, flexibility, speed, and auto-matic calculation of results.

The MIKES 3D coordinate measuring machine is a Mitutoyo Legex 9106 with portal structure (Figure 1). Further information on this machine can be found in Table 1. The true measurement uncertainty is always case-specific and depends on the environmental con-ditions, on the machine, and on the properties of the work piece. We pay special attention in our working on surface cleanliness, temperature, mounting (Fig-ure 2), alignment, measuring system, and on the doc-umentation of results.

Figure 1. Mitutoyo Legex coordinate measuring machine.








Coordinate measurement


The coordinate measuring machine is used for: • custom measurements of 3D-workpieces

(figure 3) and difficult shapes – scanning – digitizing point clouds

• various calibration of measurement devices – rulers, surface plates, gauges, cones, squares

• calibration of transfer standards for coordinate machines – step gauges, ball cubes.

Optimal measurement conditions underground The coordinate measuring machine is located in a large volume underground laboratory room held at (20 ± 0.2) °C constant temperature. Most of the heat sources in the laboratory are eliminated using vent pipes. Moreover, the room is equipped with a 1000-kg load lifter on rails and a lift with 4000 kg maximum load capacity can be used to haul the goods into the laboratory.

Traceability In commissioning, various laser and gauge block measurement were carried out on the coordinate measuring machine. Furthermore, the machine is regularly calibrated using our own measurement standards: step gauges, ball plates, and a laser inter-ferometer. The measurement uncertainty and tracea-bility are verified in each case separately using so-called substitute method, i.e. results are corrected us-ing the results of a calibrated standard.

Figure 3. A typical artefact that can be measured using a coordinate measuring machine.

Figure 2. The proper mounting of work pieces is important.

Table 1. The main properties of the coordinate measuring machine.

Property Data Performance checked ac-cording to ISO 10360-2: • maximum error in

length measurements • maximum 3D contact

deviation • maximum error in scan-

ning measurement

MPEe = (0.35 + L /1000) µm, L = mm MPEP = 0.35 µm

MPEthp = 1.4 µm

Scales Mitutoyo Zerodur scales with floating mounting, resolution 0.01 μm.

Travelling length X-910 mm, Y-1010 mm and Z-610 mm

Contact probe Renishaw indexing head PH10MQ Renishaw SP25M contact and scanning probe

Software Mitutoyo COSMOS software • Geopak-Win geometry

program • Statpak-Win geostatistical

analysis for quality control • Scanpak-Win form

measurement • 3Dtol-Win/ MCAD300 com-

parison with CAD models and importing CAD data

Measuring force 0,03 N…0,09 N Max. workpiece mass 800 kg Diameter of probes 0.5 mm…30 mm





Length and geometry

Chemistry

Optical coordinate meas-uring – vision measuring Ville Byman, Researcher Tel. +358 50 386 9327 [email protected]

Björn Hemming, Senior Scientist Tel. +358 50 773 5744 [email protected]


The manufacturing tolerances of modern products and the aim for high quality require ability to make precise measurement of dimensional measurands on small artefacts of complicated shapes. The use of vi-sion measuring machines and machine vision is well established in non-contact high-precision measure-ment.

MIKES have a Mitutoyo Quickvision Hyper QV-350 vision measuring machine (optical CMM or video measuring machine) that is equipped with a CCD-camera as well as with a contact probe. In non-con-tact optical measurements, the machine takes ad-vantage of the measurement point location detected by the CCD camera and location information from the precise scales attached to mechanical guides.

Figure 1. The artefact under study can be illuminated with ring, coaxial or stage light.








Optical coordinate measuring – vision measuring


The machine is computer-controlled and measure-ments are fully automated. The machine is capable to measure length, diameter, angle, straightness, flat-ness, parallelism, and roundness.

The machine is especially suitable for measurements of circuit boards, thin-walled fragile plastic and metal-lic artefacts, and other artefacts that are inconvenient or impossible to measure with techniques using con-tact probes.

The artefact under study can be illuminated with ring, coaxial or stage light. There are four controllable seg-ments in the ring light and its height can be adjusted.

MIKES provides precise optical and contact dimen-sional measurements tailored according to custom-ers’ needs. Depending on the work order, a calibra-tion certificate or a field log is provided.

Table 1. Properties of the vision measuring machine.

Property Data

Measuring volume 350 mm x 350 mm x 150 mm

Size of the bench 490 mm x 550 mm Max. workpiece mass 15 kg

Lowest measurement uncertainty (k=2), optical mode

U1XY = (0.8 + 2 L/1000) µm * U2XY = (1.4 + 3 L/1000) µm * U1Z = (3 + 2 L/1000) µm *

Lowest measurement uncertainty (k=2), contact mode

U1XY = (1.8 + 2 L/1000) µm *

Max. speed (rapid travel) 100 mm/s

Maximum acceleration 490 mm/s2

* L is length in mm. U1 uncertainty along one axel, U2 along two axels.

Figure 2. A contact probe complements the vision measuring machine





Length and geometry

Chemistry

Calibration of line scales and distance meters Jarkko Unkuri, Researcher Tel. +358 40 410 5506 [email protected]



Calibration services at inter-ferometric measuring rails Line scale interferometer MIKES calibration equipment for precision line scales allows calibration of up to 1.12-m long line scales with best possible accuracy. The measuring instrument is located in an air-conditioned laboratory room in which the temperature is held at (20 ± 0.05) °C and the rel-ative humidity at (45 ± 5) %. The instrument performs computer-controlled measurements of distances be-tween the graduation lines using a microscope equipped with a CCD camera for line detection and a Michelson interferometer for position measurement of the microscope. The line scales are supported at Airy points which minimizes bendings. The refractive in-dex of air is calculated from the measured air temper-ature, pressure and humidity data by using updated Edlen’s equation. Thermal expansion is corrected to 20 °C using material temperature measured with four Pt100 sensors attached to the line scale. The gradu-ation line distances can be between 10 µm ... 1.12 m. The line scale interferometer is suitable for calibra-tions of metallic or glass graduated line scales.

Calibration of line scales and distance meters 30-m measuring rail MIKES 30-m measuring rail (Figure 2) offers good possibilities for calibration of precise length measur-ing devices. The temperature of the measurement room is kept at (20 ± 0.5) °C and the relative humidity

at (45 ± 5) %. The 30-m rail is realised using a high-quality linear motion guide and a movable measure-ment carriage. A microscope, a CCD camera and a monitor used in line scale measurements are mounted on the carriage, The position of the micro-scope is measured using a laser interferometer.

The temperature stability of the measurement room and precise gauges & sensors allow precise thermal expansion and refractive index of air compensation.

Figure 1. Line scale interferometer.








Calibration of line scales and distance meters


The rail is suitable for calibration of various length standards. The calibrated devices can be physical ar-tefacts like tapes and machinist scales or e.g. optical distance meters. Tapes and other flexible length standards are tensioned using a standardized force, a force given by the manufacturer or a force sepa-rately agreed with customer. Most commonly a 50-Nm force of is used for tapes.

For thermal expansion compensation, a measured temperature and a coefficient given by the manufac-turer or by the customer are used.

Figure 2. 30-m measuring rail.

Traceability The wavelengths of the lasers used in the line scale interferometer and in the 30-m measuring rail are cal-ibrated using national measurement standard of length, iodine-stabilized He-Ne laser. The tempera-ture, pressure, and humidity sensors used in the measuring rail are calibrated at MIKES.

Table 1. Line scales, measuring ranges and measurement uncertainties.

Device Measuring range

Uncertainty (k=2)

Precision line scales, micro-scope scales

10 µm ... 1 m Q[6.2; 82L] nm**

Tapes, wires 0.001 m ... 30 m, (60, 90 ...) m Q[35; 2L] µm

Machinist scales 0.001 m ... 5 m Q[4; 1L] mm**

Circometer 0.1 m ... 9,55 m (diameter) Q[7; 2D] mm**

Plumb tapes 1 m ... 30, (60, 90) m Q[250; 5L] mm**

Other devices 0 m ... 30 m (case dependent)

L, D = measured length or corresponding diameter in me-ters

*The uncertainty of calibration is usually larger than the aforementioned uncertainties due to the uncertainty resulting from the device to be calibrated.

**Calculation of uncertainty Q[x; y]=(x2+y2)1/2





Length and geometry

Chemistry

Interferometric measure-ment of flatness and form Björn Hemming, Senior Scientist Tel. +358 50 773 5744 [email protected]

Ville Byman, Researcher Tel. +358 50 386 9327 [email protected]


Flatness The surface structure and especially the flatness of the surface are important features of various compo-nents used in different areas of technology and phys-ics. Examples of these include silicon wafers in sem-iconductor industry, sealing faces, bearing areas, contact surfaces in contact measurement methods and surfaces of optical flats and lenses used for re-flecting and refracting light.

An optical flat is an easy to use transfer standard for flatness. In industry, optical flats are used, e.g. for

flatness measurements of gauge blocks and contact surfaces of micrometre gauges. In these cases, the quality of the surfaces of optical flats is of essential importance for successful measurements of subject surfaces. Moreover, optical flats are used to transfer flatness to interferometers measuring flatness and to other devices inspecting flatness in industry.

MIKES provides aforementioned measurements and metrological traceability with its equipment for flat-ness and form measurements (Figure 1).

Figure 1. Calibration of an optical flat.








Interferometric measurement of flatness and form


Measurement method The measurement device for flatness at MIKES is a Fizeau interferometer that uses a He-Ne laser at wavelength 633nm as a light source. Interference fringes are obtained by adjusting a small angle be-tween the reference plane and the plane to be meas-ured. The shapes of the interference fringes are ana-lysed by using a so-called phase stepping method. As a result, one receives deviations of the plane under inspection from the reference plane (Figure 2). The advantages of the method are speed, precision, and the fact that the entire measurement area is meas-ured at once.

Traceability The reference plane of the optical flat used in the in-terferometer is of high quality: deviations from a per-fect plane are less than 20 nm. The reference plane is calculated either by using an absolute three-point method or by comparing it to a liquid plane. Optical flats having different reflection coefficients are availa-ble which allows inspections of mirror surfaces as well as glass surfaces.

Measurement services The MIKES equipment (Zygo GPi) can be used for surface profile measurements of objects that have di-ameters below 150 mm, best available measurement precision being 45 nm. A prerequisite for such meas-urements is that the height variations of the artefact are less than 12 µm and slowly varying. As the method is based on interference of light and thus it is a non-contacting method, it is also applicable for frag-ile materials. Moreover, it is applicable for very de-manding measurement tasks due to its precision.

Figure 2. An example of measured surface profile of an op-tical flat.

Figure 2. An example of measured surface profile of an optical flat.





Length and geometry

Chemistry

Machine tool measurements Pasi Laukkanen, Research Engineer Tel. +358 50 382 9674 [email protected]



Demands of production and quality systems require knowledge on the precision of machine tools. Differ-ent measurement are performed on machine tools during acceptance inspection, in connection with transfers, and when striving for preventive mainte-nance. MIKES provides its wide experience on di-mensional and geometrical measurements, position-ing and repeatability accuracy measurements, and measurements on machine-tooled test work pieces.

The competent and experienced personnel of MIKES, modern equipment and continuous development of new measurement methods guarantee customers' precise measurements performed according to stand-ards.

Figure 1. Scale measurement for a machine tool.

Figure 2. Setup for machine tool measurements.








Machine tool measurements


Geometrical measurements Geometrical measurements are used for finding out the form defects in the most important organs of a machine tool and the mutual locations and positions of the organs. MIKES performs geometrical measure-ments according to ISO and DIN standards. The most important measurements subjects are measurement of spindle runout, the parallelism between the spindle and the machine, perpendicularity measurements, and straightness and perpendicularity measurements of machine movements.

Accurate positioning and repeatability measurements Spindle positioning and repeatability measurements reveal errors at different points of the spindle. Errors in spindle movement can be compensated for by giv-ing the compensation values to the control unit memory of the machine tool. The positioning meas-urement performed using MIKES laser interferometer is a fast and precise way to adjust the spindle move-ments of a machine (Figure 3); the measurement pre-cision is at its best below 0.001 mm/m.

Measurement of test workpieces Machine-tooling tests are used to find out the preci-sion of the machine in true machining circumstances. MIKES geometrical measurements and measure-ments on work pieces made in machine-tooling tests

complement each other. The work pieces are meas-ured in a temperature-controlled laboratory room us-ing versatile and modern measurement devices and methods. MIKES have a variety of the most common workshop measurement equipment and a selection of special tools (see Table 1).

Traceability All measurement standards used in machine tool measurements are calibrated using similar but more accurate MIKES transfer standards.

Table 1. Devices used in machine tool measurements.

Geometrical, positioning and repeatability meas-urements:

Measurements of test workpieces

– laser interferometers – surface structure, form,

roundness and length measuring machines

– autocollimators – inductive sensors

– electronic spirit level – common workshop measurement devices

– inductive sensors – coordinate measuring machine

– plumb

– other devices

Figure 3. X-axis errors of a broaching machine before laser measurement and adjustment and after.

Correction before adjustment (mm)

Correction before adjustment (mm)

Correction after adjustment (mm)

Correction after adjustment (mm)

Positioning accuracy x-axis

Devi

atio

n / m

m

Position / mm





Length and geometry

Chemistry

Measurement of roundness Björn Hemming, Senior Scientist Tel. +358 50 773 5744 [email protected]



Roundness in mechanical engineering industry Approximately 80 % of machined work pieces have elements with surfaces of revolution. Roundness has an important role for guaranteeing faultless operation of machines and devices. This is even emphasized when reliability, longevity, low operating costs, and friendliness to the environmental are required.

At MIKES, we perform measurements of roundness on ring gauges, screw-plug gauges, slide bearings, metallic packings and hydraulic and pneumatic com-ponents. We also measure runout eccentricity, coax-iality, parallelism and straightness (Figure 1).

Figure 1. Roundness measurement is an essential part of workshop manufacturing.








Measurement of roundness


Measurement potential Roundness is measured either by using a rotating spindle or by using a roundness measurement instru-ment equipped with a rotating table. Measurements can be performed using several different filters ac-cording to the ISO 1101 standard’s definition (MZ) or other computing methods (MC, MI, and LS). The use of two alternative machines guarantees the customer that the artefacts can be measured properly and cost effectively. More information on the machines can be found in table 1.

Cylindricity is measured using a machine equipped with a rotating table (Figure 2); with almost the same settings, the following measurement can be per-formed, also: coaxiality, runout eccentricity, parallel-ism and straightness. Cylindricity measurements are a part of the calibration of ring gauges and screw-plug gauges.

Traceability Traceability to the sensors in both machines comes from magnification standards that are calibrated using MIKES form measurement instrument which in turn gets it traceability from gauge blocks calibrated using an interferometer. The guide bars and shafts in the machines are calibrated using error separation.

Figure 2. Measurement instrument Talyrond 262 for round-ness and cylindricity.

Table 1. MIKES roundness and cylindricity measurement instruments.

Model Rotating part

Maximum height of

the artefact mm

Maximum inner/outer diameter of the artefact

mm

Maximum mass of

the artefact kg

Other Expanded uncertainty

(k=2)

Talyrond 73HR roundness

spindle 400 175 / 300 100 surface can be discontinuous or asymmet-rical

Q[0.01; 0.01R ] µm

Talyrond 262 cylindricity

table 500 – / 350 50 surface can be discontinuous

Q[0.1; 0.5L] µm

R is the deviation from roundness in micrometres; L is the height of the cylinder in metres; Q[x; y] = (x2+y2)1/2





Length and geometry

Chemistry

Calibration of microscopes and calibration standards Virpi Korpelainen, Senior Scientist Tel. +358 50 410 5504 [email protected]


Reliable measurement results in research, manufac-ture and quality control require knowledge of accu-racy of measurement instruments. Calibration is the best way to check the accuracy and stability of the instrument. The calibration can be done with cali-brated transfer standards. Official calibration certifi-cate guarantees traceability to the definition of the metre.

For optical microscopes MIKES provides calibration of high quality line scales.

Scanning probe microscopes (SPMs) can be cali-brated using several kinds of transfer standards [1,2], which can be calibrated at MIKES. 1-D and 2-D grat-ings are calibrated either by laser diffraction or by me-trology atomic force microscope (MAFM). Pitch and orthogonality of the grid can be measured. Step height standards or z scale of 1-D or 2-D gratings can be calibrated. [1] Guideline VDI/VDE 2656 Part 1 (Draft): Determination of geo-

metric quantities by Scanning Probe Microscopes - Calibration of Measurement Systems.

[2] V. Korpelainen and A. Lassila, Calibration of a commercial AFM: traceability for a coordinate system, Meas. Sci. Technol. 18 (2007) 395–403.

Figure 1. MIKES interferometrically traceable metrology AFM (MIKES IT-MAFM).







Calibration of microscopes and calibration standards


Calibration itself gives information about the accu-racy of the instrument. Accuracy of the measurement can be increased by corrections of the errors de-tected in the calibration either directly in the meas-urement software or after the measurement with sep-arate software.

The first step in the calibration is measurement of x and y scale errors by 1-D or 2-D gratings and z scale errors by step height standards. The calibration of the x and y scales gives also information about the linearity of the scales. The linearity of the z scale needs to be checked by several different step height

standards. Orthogonality errors can be detected by 2-D grids. Out-of-plane errors can be measured us-ing a flatness standard. In the most accurate calibra-tions also some other error types has to be measured and corrected; e.g. orthogonality of z-axis, rotational and other guiding errors. There are also other error sources, which should be taken into account, e.g. tip-sample interactions, vibrations, noise and thermal drift. Calibration period depends on the stability of the device, e.g. microscopes with open loop scanner need calibration before and after each measurement.

Figure 3. Some error types of SPMs.

Table 1. Calibration services for SPM standards. Range Uncertainty

1-D grid (diffraction measurement) Pitch 300 nm – 10 µm 50 – 100 pm 2-D grid (diffraction measurement)

Pitch 300 nm – 10 µm 50 – 100 pm Orthogonality

1-D grid (AFM measurement) Pitch, p 100 nm – 10 µm Q [3.4; 0.2 p/µm] nm Orthogonality 14 mrad Step height, h 10 nm – 2 µm Q [2; 0.2 h/µm] nm Flatness 100 µm × 100 µm 5 nm Step height standard 10 nm – 2 µm Q [2; 0.2 h/µm] nm Flatness standard 100 µm × 100 µm 5 nm

DEFINITION OF THE SI-UNIT METRE

Laser frequency calibration

Realisation of the metre • Frequency comb (links the metre to the second) • Iodine-stabilised lasers

Interferometrically traceable AFM

Calibration of a SPM

Traceable SPM measurements

Laser diffractometer

Calibration of physical transfer standards for scanning probe microscopes (SPMs) 1D and 2D gratings, flatness & step height standards

At M

IKES





Length and geometry

Chemistry

Length in geodesy Markku Poutanen, Prof. Tel. +358 29 531 4867 [email protected]

Paavo Rouhiainen, Senior Research Scientist Tel. +358 29 531 4875 [email protected]

Jorma Jokela Research Manager Tel. +358 29 531 4743 [email protected]

Finnish Geospatial Institute, FGI Geodeetinrinne 2, 02430 Masala, Tel. +358 29 530 1100, www.fgi.fi

Finnish Geospatial Research Instutute, FGI The Finnish Geospatial Research Institute, FGI, of the National Land Survey of Finland maintains meas-urement standards for geodetic and photogrammetric measurements and is the National Standards Labor-atory of acceleration of free fall and length. The FGI takes care of the fundamental measurements in Finn-ish cartography and of geographical information me-trology and carries out scientific research in geodesy, geographic information sciences, positioning, naviga-tion, photogrammetry and remote sensing.

Calibration services The FGI calibrates high precision electronic distance measurement (EDM) instruments, geodetic base-lines and photogrammetric test fields. Moreover, we calibrate precise levelling rods, digital and traditional, and system calibration of digital level instruments. The calibrations are performed in addition to the Ma-sala laboratories at Nummela Standard Baseline and at Metsähovi Fundamental station. Most of our work is carried out in field conditions or conditions analo-gous to operating situations.

Figure 1 and 2. The Nummela standard baseline measured by using the Väisälä comparator has been one of the most accurate and stable lengths over the past half decade.




http://www.fgi.fi/





Length in geodesy


Traceability and uncertainty National measurement standards for length at the FGI are a Väisälä interference comparator with a quartz meter system and a levelling rod comparator system with a laser interferometer. All the measure-ments are traceable with a known uncertainty. Base-lines (864 m and 432 m) measured with the Väisälä interference comparator have typically a measure-ment uncertainty ranging from 0.1 ppm to 0.2 ppm (k=2) and the measurement uncertainty for other baselines (1 m – 10 km) is at its best 0.2 ppm. The measurement uncertainty for calibration of levelling rods is 1 ppm and 5 ppm for calibration of levelling systems.

Figure 3. Calibration of the most accurate distance meters of the world can be done at the Nummela Standard Base-line. Nummela scale has been transferred also to several foreign baselines.

Research and development The FGI carries out research and development on methods and equipment for the measurements for geodesy and geospatial information science. In addi-tion to length measurements, we perform other preci-sion measurement in surveying, e.g. measurements of angle, azimuths, determination of coordinates and satellite positioning. We also participate in GNSS me-trology related projects. International cooperation is a central part of our work and we have measured base-lines in about 20 countries.

Figure 4. Calibration of a digital precise level instrument and system calibration of a barcode rod.

Figure 5. Research on the accuracy of GNSS antennas can be made at the test field of the Metsähovi obser-vatory.




Electricity, time and acoustics

Length and geometry Optics Chemistry

Optical quantities Farshid Manoocheri, Dr, Tel. +358 9 470 22337, [email protected]

Petri Kärhä, Dr, Tel. +358 9 470 22289 [email protected]

Metrology Research Institute, Otakaari 5A, FI-02150 Espoo http://metrology.tkk.fi

MIKES-Aalto Metrology Research Institute Metrology Research Institute (MIKES-Aalto Mittaus-tekniikka) is a joint laboratory of Aalto University and MIKES. It is the national standards laboratory of opti-cal quantities in Finland. The laboratory is a research and education unit belonging to the Department of Signal Processing and Acoustics at the Aalto Univer-sity. The laboratory carries out basic research on LED measurements, temperature measurements, optical properties of materials, measurement electronics and on various measurement methods of photometry and radiometry. In addition to calibration services, the la-boratory offers expert services and educates Diploma Engineers (M. Sc.) and Doctors of Technology for de-manding professional tasks in academy and industry.

Research activities Research activities and assignments of a national standards laboratory require continuous international cooperation. International comparisons have an es-sential role in creating traceability chains and verify-ing measurement uncertainties. The laboratory has an active role in, e.g. EURAMET, CCPR, and CIE or-ganisations and takes actively part in the EU research programs.

Figure 1. Integrating sphere is used as a light source in calibra-tion of luminance and radiance. The sphere has a uniform spa-tial distribution of the out coming light intensity.



http://metrology.tkk.fi/





Optical quantities


Calibration services Metrology Research Institute offers calibration ser-vices to the optical quantities listed in the following table. All measurements are traceable to national and international measurement standards. Meas-urement uncertainties are verified by international comparison measurements. We are pleased to give further information, e.g. on the contents of calibra-tion services and on the measurement uncertainty in different measurement and wavelength ranges. Calibration objects lnstruments that we calibrate include among others:

• illuminance meters • standard lamps • radiance and luminance meters • laser power meters • optical filters • reflectance references • UV-meters • fluorescent samples.

Figure 2. The spectral irradiance of a lamp is measured by positioning the lamp at an accurately determined distance from a radiometer, whose spectral responsivity and surface area are known.

Figure 3. Part of the calibrations can be car-ried out as field calibrations at customer’s la-boratory premises. A filter radiometer devel-oped in our laboratory for calibration of spec-tral irradiance or illuminance of standard lamps is shown in the figure.

Quantity Measurement range Wavelength range Uncertainty (k=2) Luminous intensity 1 – 10 000 cd – 0.5 % Illuminance Illuminance responsivity 0.1 – 5 000 lx – 0.5 % – 0.7 %

Luminance Luminance responsivity 1 – 40 000 cd/m2 – 0.8 % – 1.0 %

Luminous flux 10 – 10 000 lm – 1.0 %

Spectral irradiance 100 μW m–2 nm–1

– 500 W m–2 nm–1 290 – 900 nm 0.8 % – 2.9 %

Spectral radiance 100 μW m–2 sr –1 nm–1 – 1 W m–2 sr –1 nm–1

360 – 830 nm 1.4 % – 4.2 %

Colour coordinates (x, y) 0,1 – 0,9 – 0.0005 Colour temperature 2800 – 3250 K – 5 K Optical power 0.1 – 0.5 mW 325 – 920 nm 0.05 % – 1.0 %

Spectral responsivity 0.01 – 20 μW 0.05 – 5.0 mW

380 – 1700 nm 250 – 380 nm

0.5 % – 4.0 % 2.0 % – 5.0 %

Transmittance 0.0001 – 1 250 – 1700 nm 0.2 % – 5.0 % Absorbance 0 – 4 250 – 1700 nm 0.0009 – 0.022 Reflectance (5° – 85°) 0.01 – 1 250 – 1000 nm 1.0 % – 5.0 % Diffuse reflectance factor 0.1 – 1 360 – 830 nm 0.4 % – 1.0 % Fibre optic power 1 nW – 200 mW 1310 – 1550 nm 1.2 % – 2.0 %





Length and geometry

Chemistry

Water quality Teemu Näykki, PhD, Associate Professor Tel. +358 29 525 1471 [email protected]

Timo Sara-Aho, Researcher Tel. +358 29 525 1618 [email protected]

Finnish Environmental Institute Hakuninmaantie 6, FI-00430 Helsinki, Tel. +358 29 525 1000, www.syke.fi/envical/en

ENVICAL SYKE is focusing on the research and de-velopment of metrology in chemistry. Our activities in-clude development of accurate and traceable calibra-tion methods, testing the reliability of new measure-ment techniques and validation of methods of analy-sis and quality assurance.

Traceable calibrations The SYKE accredited calibration laboratory (K054: EN ISO/IEC 17025) produces calibration results with high accuracy and traceability and is responsible for developing methods based on primary techniques.

In general, Isotope Dilution Mass Spectrometry (IDMS) can be regarded as one of the main reference

methods for elemental analysis, and appropriately ap-plied it offers the highest accuracy and smallest measurement uncertainty.

This method is used to measure the elemental con-tent (usually mass fraction) of an unknown test sam-ple, which has natural isotopic composition. This sample is mixed with another sample (spike) contain-ing a known amount of the same element under in-vestigation. Isotopic composition of the spike sample is known and it is different from the isotopic composi-tion of the test sample; usually such a way that the rarer isotopes of the element are enriched. When the test sample and the spike are completely mixed, the resulting mixture (blend) has a new (isotope diluted)

Photo Timo Vänni



http://www.syke.fi/envical/en





Water quality


isotopic composition, where the isotope ratios are be-tween the test sample and the spike sample added. The isotope ratios of the mixture are measured and the result is directly proportional to the mass fraction or concentration of the element in the sample.

At present, the scope of SYKE’s calibration laboratory accreditation includes measurement of lead (Pb) in natural water and mercury (Hg) in natural and waste water. The methods are based on the isotope dilution inductively coupled plasma mass spectrometric (ICP-MS) technique. The range of measurements is being complemented with tests for dissolved oxygen and also nickel and cadmium, listed as priority substances in the Water Framework Directive. The isotope dilu-tion mass spectrometric technique is widely utilized by SYKE also for measurement of organic chemical contaminants.

Our customer base consists of public and private par-ties requiring accurate and reliable measurement re-sults for their environmental samples. For instance, we have produced traceable reference values for pro-ficiency tests (PTs).

Research activities The comparability of the measurement results is in-ternationally very important. Reliability and compara-bility of the measurement results can be improved with the realistic measurement uncertainty estima-tion, validation of the measurement methods, and en-suring the traceability of the measurement results.

ENVICAL SYKE is an experienced in research and development of the instrument’s reliability and proce-dures for measurement uncertainty estimation. We have constructed new tools for both laboratory meas-urements as well as for portable and continuous field water quality measuring devices to indicate and im-prove the reliability of the measurement results. Ex-amples of these tools are MUkit- and AutoMUkit- measurement uncertainty calculation software.

We also actively participate in organizing proficiency tests for water quality sensor measurements.

In addition to maintenance of measurement stand-ards’ international traceability, our activities include national and international communication, publica-tion, and training in the field of metrology. Upon re-quest, we arrange customized training in the estima-tion of measurement uncertainties in chemical meas-urements or validation of analytical methods.

Table 1. Calibration and measurement capabilities, CMCs.

Quantity / method /

object

Measurement range

CMC, Expressed as

expanded uncertainty

(k=2) Chemical analysis, amount of substance

Mass fraction of soluble total mer-cury (Hg) in syn-thetic water, fresh natural water (not sea water) and waste water

30–125 ng/kg >125–5000 ng/kg

6 % 3 %

Mass fraction of soluble total lead (Pb) in synthetic water and fresh natural water (not sea water)

0.200–1.00 μg/kg >1.00–100 μg/kg

0.030 μg/kg 3 %

Photo Timo Vänni

VTT MIKES Tekniikantie 1 FI-02150 Espoo

VTT MIKES-Kajaani Tehdaskatu 15, Puristamo 9P19 FI-87100 KAJAANI

Tel. +358 20 722 111 Email: [email protected] www.mikes.fi


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