Traceability toward industry: from TRIRAT to ILART

Abstract

The impact of thermal radiation and its associated radiance temperature on nearly all facets of technology and society is tremendous. Reliable temperature measurements are in that context of vital importance in many areas in science, technology, industry and environmental protection. This implies the use of a sound traceability framework, involving accurate reference standards to begin with and a calibration procedure for radiation thermometers that incorporates all sources of measurement errors (uncertainties). Latter procedure should be two-fold; first a traceable comparison is made against a blackbody radiator, then the instrument is evaluated and/or calibrated in its application.In this paper all three traceability steps will be addressed, that is, the dissemination of the international temperature scale of 1990 (ITS-90) and the initial and on-site calibration of radiation thermometers. First two steps were investigated in detail and improved on European level in the TRIRAT program that was funded by the European Community. This included international intercomparisons for radiation thermometer calibrations and recommendations for the standardization and testing of infrared radiation thermometers as transfer standards. An other project, ILART, bridges the gap in traceability between initial calibrated radiation thermometers and their industrial application. It involves realization of a portable calibration facility, intrinsically insensitive for surface emissivity and reflection error using active two-color thermometry.

ITS-90 Scale Realization on the New Radiation Thermometer Calibration Facility at NMi VSL

“…Stirred-oil bath and heat-pipe BBRs are used from −50 • C to 1,050 • C. These BBRs are fully characterized in order to unambiguously link the calibrated contact thermometer reading to the derived radiance temperature. The uncertainties of t 90 , as shown in Table 1, include components for stabilization, equilibration, short-term stability, calibration of contact thermometers, immersion effects, temperature drop across the cavity wall, temperature distribution along the cavity wall, wall emissivity, and uncertainty of the cavity emissivity [5,6]. Between 1,000 • C and 3,000 • C, two graphite-tube radiators are used.…”

“…Corrections for background and ambient temperature should therefore be taken into account [5]. A facility for measuring the size-of-source effect of LT-RTs was realized by successively aligning water-cooled flanges at ambient temperature with increasing clear apertures, a hot disk with a 25 mm aperture, a highly-polished metal baffle, and a flat-plate ammonia heat-pipe radiator.…”

“…The latter system is used to determine correction factors that apply to the daily measurements taken with conventional RTs [4]. To further reduce the uncertainties of on-site calibrations, an active two-color pyrometer [5] is being developed. To increase awareness of size-of-source-induced uncertainties by industry, a calibration facility has been designed to measure the size-of-source of MT/HT RTs.…”