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Bilateral comparison of radiation thermometers

Project Description

Objective  is to perform bilateral intercomparison of radiation thermometers of MIRS/UL-FE/LMK and NSAI NML in the range from -30 °C to 250 °C. Results will be used to form and support the uncertainty budget of NSAI NML.

Final Report 2016-07-01

First set of measurements in both institutions were performed in 2014 and the first half of 2015 but due to inconsistency in results at temperatures higher than 50 °C the NSAI NML investigated the cause of inconsistency and proposed another date for measurements. Further measurements were performed in the second half 2015 in NSAI NML and MIRS/UL-FE/LMK after the upgrade of equipment at NSAI NML. In 2016 additional measurements were performed at NSAI NML. The results were analysed and presented at TEMPMEKO 2016. Additionally the article was accepted on 8th March 2017 for publication in Measurement, title: Development and Characterisation of a Bath-Based Vertical Blackbody Cavity Calibration Source for the Range -30 °C to 150 °C.
Industrial use of Radiation Thermometers (RTs) is becoming increasingly common due to the perceived advantages and wide market availability. Blackbody Cavity Radiation Sources (BBCRSs) are typically used for calibration of these instruments, and these cavities are oriented horizontally in most cases. The project partners analysed a unique design of bath-based vertical BBCRS and the method, results and analysis of an international comparison of this and other BBCRSs designed for both horizontal and vertical use. The comparison was conducted through a collaboration between LMK and NSAI with the intention of evaluating the suitability of the vertical orientation for calibration work. A transfer pyrometer and Standard Platinum Resistance Thermometers (SPRTs) were used as comparison standards. The transfer pyrometer used has spectral sensitivity from 8 µm to 14 µm in this temperature range.
In summary, a vertical cavity was constructed and evaluated. The cavity was found to offer a flexible, low-cost alternative to purpose-built horizontal cavities. The design was also found to be an improvement over the LMK vertical cavity. It is expected that such vertical cavities could be of use to other calibration laboratories wishing to extend the temperature range of their non-contact capabilities, prototype cavities with different dimensions or add additional cavities for use as reserves or for cross-checks.
The evaluated expanded uncertainties ranged from 0.65 °C when the cavity was immersed in the oil bath to 0.22 °C when immersed in the water bath. The key outcome is that the use of vertically oriented cavities is a valid method for achieving repeatable measurement traceable to ITS-90. 

Progress Report 2016-01-29

Measurements were performed in both institutions in 2015 in the range from 600 °C to 1500 °C. After the analysis of results the measurements in the range from 600 °C to 1000 °C at NA heat pipe were inconsistent de to different distance of a transfer radiation thermometer from the blackbody aperture. After repeated measurements at the same distance the results were consistent. The analysis of result will be presented at TEMPMEKO 2016.

Progress Report 2015-02-20

First set of measurements in both institutions were performed but due to inconsistency in results at temperatures higher than 50 °C the NSAI NML will investigate the cause of inconsistency and propose another date for complete the measurements.


Thermometry (T)
Igor Pušnik, MIRS/UL-FE/LMK (Slovenia)
Phone: +386 1 4768 224
Coordinating Institute
MIRS/UL-FE/LMK (Slovenia)
Participating Partners
NPL (United Kingdom)


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