Reduced uncertainty radiation thermometer calibration serviceNew fixed points offer improved temperature measurementThe National Physical Laboratory (NPL) is a world leader of research into high temperature fixed points based on eutectic alloys of metal and carbon that extend the temperature range for practical and stable references up to 2750 °C. These references have been shown to agree to within 0.1 °C, even at the highest temperatures.
NPL now uniquely offer a UKAS-accredited radiation thermometer calibration service based on these references with traceability to national standards. For suitable radiation thermometers this has the potential for much reduced calibration uncertainties. Comparison has shown that calibration laboratories can achieve a level of uncertainty in scale realisation comparable to using a standard calibrated as a primary ITS-90 realisation.
Novel fixed point materials have expanded the options for high temperature calibration
© Q
ueen
’s Pr
inte
r and
Con
trol
ler o
f HM
SO, 2
013.
107
11/1
113/
REP
NPL has been extensively involved in researching high temperature fixed points (HTFPs). We maintain a set of standard HTFPs with very precisely known ITS-90 temperatures. These can be used to calibrate a suitable radiation thermometer†, readily achieving a calibration uncertainty of 0.05 % (k = 2)*(1.25 °C at 2500 °C) traceable to national standards. In practice this has been shown to make it possible for a calibration laboratory using such a secondary standard to achieve scale realisation uncertainties previously requiring a primary realisation of ITS-90** Any temperature range can be covered using a combination of ITS-90 defined fixed points and ITS-90 traceable high temperature fixed points, but the biggest benefit is expected to be from 1200 °C to 2800 °C.
This is a specialised service intended to give the lowest possible uncertainties in a cost effective manner. Please contact NPL to discuss details.
For further reading1. ** Reducing uncertainty in practical radiation thermometer
calibration based on proposed changes to the mise en pratique of the definition of the kelvin, David Lowe, Mick Broughton, Jon R Willmott, International Congress of Metrology 15010 (2013). http://dx.doi.org/10.1051 metrology/201315010
2. D Lowe 2013 Meas. Sci. Technol. 24 01590 http://doi:10.1088/0957-0233/24/1/015901
Contact details Further information
National Physical LaboratoryHampton RoadTeddingtonMiddlesexUnited KingdomTW11 0LW
Switchboard: 020 8977 3222Website: www.npl.co.uk
For further information please contact: David Lowe [email protected]
The National Physical Laboratory is operated on behalf of the National Measurement Office by NPL Management Limited, a wholly owned subsidiary of Serco Group plc
Fixed point metal-carbon Nominal temperature / °CIron 1153
Cobalt 1324
Platinum 1738
Ruthenium 1954
Rhenium 2474
Tungsten carbide 2748
Example of the possible reduction in uncertainty in assigning a temperature to a blackbody source when changing to a radiation thermometer calibrated with HTFPs
† The requirements for a suitable thermometer are: target size < 1.5 mm, low size-of-source effect and non-linearised output. NPL can supply a suitable radiation thermometer with UKAS accredited calibration certificate.
* subject to the performance of the instrument being calibrated
0478