AFRIMETS.T-S5 Supplementary comparison Liquid-in-glass thermometers -35 °C to 250 °C Final report (16 August 2017) Page 1 of 18 Final report on AFRIMETS comparison of Liquid in Glass thermometer calibrations from -35 °C to 250 °C (Final report) 16 August 2017 1. Introduction ..................................................................................................................................................... 1 2. Participants ..................................................................................................................................................... 1 3. Detailed description of the devices ................................................................................................................. 2 4. Procedure for measurement ........................................................................................................................... 2 5. Comparison reference value (RV) .................................................................................................................. 2 6. Results ............................................................................................................................................................ 2 7. Evaluation of results ....................................................................................................................................... 8 8. Conclusions and recommendations ............................................................................................................... 8 9. Appendix: Uncertainty budgets .....................................................................................................................10 1 Introduction The purpose of this interlaboratory comparison (ILC) is to test the proficiency / evaluate the measurement capabilities of the participant National Metrology Institutes (NMIs), in the field of calibration of liquid-in-glass thermometers (LIGTs), in order to support their submissions of Calibration and Measurement Capabilities (CMCs) in the field of Thermometry to the BIPM Key Comparison Database (KCDB). The comparison forms part of the project “Strengthening Quality Infrastructure for Trade Enhancement and Consumer Protection in the SADC Region in accordance with the TBT Annex to the SADC Trade protocol” (Project No.: PN 2012.2297.5 – 95088). In accordance with the terms of the project, participation in the ILC was restricted to those members of the SADCMET sub-RMO (Regional Metrology Organisation) who are signatories of the CIPM Mutual Recognition Arrangement (MRA), namely, Botswana, Mauritius, Namibia, Seychelles, South Africa, Zambia and Zimbabwe. 2 Participants Institute Contact person Email Measuremen t period National Metrology Institute of South Africa (NMISA) Dr Efrem Ejigu [email protected]13 Jan 2016
Transcript
AFRIMETS.T-S5 Supplementary comparison Liquid-in-glass thermometers -35 °C to 250 °C Final report (16 August 2017)
Page 1 of 18
Final report on AFRIMETS comparison of Liquid in Gl ass
thermometer calibrations from -35 °C to 250 °C (Final report)
3. Detailed description of the devices ................................................................................................................. 2
4. Procedure for measurement ........................................................................................................................... 2
5. Comparison reference value (RV) .................................................................................................................. 2
Note: Owing to logistical reasons, no closing measurement could be made to confirm artefact stability after
measurement at SBS - however, the results obtained by SBS suggest that the artefact was in good condition
at the time of measurement, and that SBS results may reasonably be compared to the Reference Values.
7 Evaluation of results
NMISA's 26 Feb and 20 June verification checks agree with their initial measurements within 0.02 °C,
-50 0 50 100 150 200 250-0.8
-0.4
0.0
0.4
0.8
AFRIMETS.T-S5: LIGT (Hg, total immersion), 2016
SBS U(RSS) U(RSS)
Temperature (°C)
LV -
RV
(°C
)
AFRIMETS.T-S5 Supplementary comparison Liquid-in-glass thermometers -35 °C to 250 °C Final report (16 August 2017)
Page 10 of 18
indicating that the artefacts were stable during the ILC. U(RV)/U(LV) ≤ 1 at all points (indeed,
U(RV)/U(LV) ≤ 0.5 at all points except MSB's 0 °C and 50 °C), indicating that RV is sufficiently accurate to
test most participants' measurement capabilities rigorously.
8 Conclusions and recommendations
The artefacts were hand-carried from South Africa to the first four participants. (Hand-carriage to Mauritius
and Seychelles was not possible, as mercury-in-glass thermometers may not be carried in passengers'
luggage on aero planes.) The comparison coordinator visited each of these four institutes for two days,
performing an on-site peer review of the evidence supporting the laboratory's Thermometry measurement
capabilities. During that time, laboratory staff completed their ILC measurements, calculated uncertainties
and handed their results to the coordinator.
This method of artefact circulation had significant advantages, namely:
i. The risk of damage to the artefacts was greatly reduced. (This risk is otherwise significant, as shown
by damage to one artefact on the return flight from Mauritius, and destruction of a second artefact
during shipment by courier from South Africa to Seychelles. The latter incident made it impractical for
Seychelles Bureau of Standards to participate in the present ILC.)
ii. The time required for shipment (particularly, Customs clearance) was shortened from approximately
one month (as experienced during past regional ILCs) to two days per journey.
iii. Delays in the transmission and analysis of results were avoided.
The present ILC has largely avoided the delays and damage that affected the 2001 LIGT ILC SADC.T-P1,
while covering a much larger temperature range than the 0 °C to 50 °C of that ILC. It should be of significant
value to participants, both in support of Thermometry CMC submissions to the AFRIMETS TC/WG-T, and to
satisfy the proficiency testing requirements of accreditation bodies.
As a guide to participants, the smallest CMC which can be supported by this interlaboratory comparison, for
a particular participant, at a particular point, is the larger of U (LV) and |LV-RV| at that point.
9 Appendix: Uncertainty budgets
Note: As the values of dominant uncertainty components estimated by a participant are often similar at the various comparison temperatures, a typical uncertainty
budget for each participant (the one for 100 °C) is reproduced below, rather than all their budgets.
Vertical Temperature Uniformity 0.515 ° C RECTANGULAR 1.7320508076 1 0.2973 20
E f fe c t iv e d e g r e e s o f f r e e d o m 2 2 .5 4 8 5 7 1 6 9
S t u d e n t t 's e f fe c t iv e d e g r e e s o f f r e e d o m 2 .1
Combined uncertainty (k=1): 0.3064
Expanded Uncertainty (k=2) 0.6128
D e g r e e s o f
f r e e d o m
ZABS:
100.00°C UncertaintySource of uncertainty Value Unit Probability Divisor Sensitivity contribution
distribution (k=1) REFERENCE STANDARDCalibration of standard thermometer 0.002000 °C Normal 2.00 1.E+00 0.0010000Repeatability of standard thermometer 0.003569 °C Normal 1.00 1.E+00 0.0035690Drift of standard thermometer 0.006000 °C Rectangular 1.73 1.E+00 0.0034641Resolution of standard thermometer 0.000050 °C Rectangular 1.73 1.E+00 0.0000289Uncertainty of Electrical Measuring Equipment 0.010000 °C Rectangular 1.73 1.E+00 0.0057735HEAT SOURCEBath Stability 0.004000 °C Rectangular 1.73 1.E+00 0.0023094Temperature gradient of bath 0.005000 °C Rectangular 1.73 1.E+00 0.0028868UNIT UNDER TEST (UUT)Resolution of test thermometer 0.050000 °C Rectangular 1.73 1.E+00 0.0288675Repeatability of test thermometer 0.000000 °C Normal 1.00 1.E+00 0.0000000Emergent Stem Temperature Correction 0.000000 °C Rectangular 1.73 1.E+00 0.0000000
Combined uncertainty (k=1): 0.0301010
2.0Expanded uncertainty U(k=2): 0.0602021
BOBS:
NSI:
MSB:
U n it Va lu e D is trib u tio D iv is or S e n s itiv ity C on trib u ti
c a lib ra tion of s td °C 0 .0 1 5 n orm a l 2 1 0.0075 9 5 2 0 0 1 .5 8 E -1 1
drift of standard °C 0 .0 1 5 rec ta n g u la 1 .7 3 2 0 5 1 1 0.008660254 9 5 2 0 0 2 .8 1 E -1 1
Resolution UUT °C 0.01 rec ta n g u la 1 .7 3 2 0 5 1 1 0.005773503 9 5 2 0 0 5 .5 6 E -1 2
Repeatability UUT °C 0 rec ta n g u la 1 .7 3 2 0 5 1 1 0 9 5 2 0 0 0
Temp Gradient bath °C 0 .0 5 rec ta n g u la 1 .7 3 2 0 5 1 1 0.028867513 9 5 2 0 0 3 .4 7 E -0 9
Stability of bath °C 0 .0 0 1 2 2 4 rec ta n g u la 1 .7 3 2 0 5 1 1 0.000706677 9 5 2 0 0 1 .2 5 E -1 5
Job c od e MT/2016/14/0374Ite m MIG Thermometer 100 °C c om b in e d u n c e rta in t 0.031597722 °C ex p a n d e d u0.063195445
C lie n t LMC Solutions 2 8 3 .0 5 3
Relia b ility
(% )
D e g re e s
of
fre e d om u i4(y )/v i
e f fe c tiv e
d e g re e of
fre e d om
SBS:
Uncertainty Budget at 100 ºC
DescriptionDivisor Unit Unit Comments
B Normal 0.018 2 0.0090000 ºC 1 ºC 0.009 1E^10
B Rectangular 0.0005 1.732 0.0002887 ºC 1 ºC 0.0002886836 1E^10
A Normal 0.00012 1 0.0001225 ºC 1 ºC 0.0001224745 4A Normal 0 1 0.0000000 ºC 1 ºC 0 4
B Rectangular 0.02 1.732 0.0115470 ºC 1 ºC 0.0115470054 1E^10
B Rectangular 0.01 1.732 0.0057735 ºC 1 ºC 0.0057735027 1E^10 obtained from manufacturer
B Rectangular 0.009 1.732 0.0051962 ºC 1 ºC 0.0051961524 50
B Rectangular 0 1.732 0 ºC 1 ºC 0 1E^10
B Rectangular 0.01 1.732 0.0057735 ºC 1 ºC 0.0057735027 1E^11 obtained from manufacturerStdard Therm Therm UT Combined Standard Uncertainty 0.0175527302
1 100.001 100.020 Effective Degrees of freedom veff 6510.58
