Laina Ma

Calibration Facilities for High Temperature Radiation Thermometers at NMIJ

National Metrology Institute of Japan (NMIJ/AIST) realizes and disseminates standard temperature scale at high temperature for radiation thermometry. The calibration facilities consist of fixed-point blackbodies, spectral responsivity measurement system and so on. The characterization facilities consist of the size-of-source effect measuring system and distance effect measuring system. Their specifications and measurement methods are described

Calibration and characterization of Chino 900 nm silicon narrow-band radiation thermometer

This paper describes the calibration and characterization of the Chino 900 nm standard radiation thermometer, IR-RST-90 W. The gain ratio, fixed-point calibrations, spectral responsivity, nonlinearity, size-of-source effect, distance effect, zero-offset stability and temperature drift were measured. Some problems were found for this thermometer regarding the out-of-band suppression, the size-of-source effect and the temperature drifts. A new type radiation thermometer was manufactured for improving the quality to use as a standard radiation thermometer.This paper describes the calibration and characterization of the 650 nm standard radiation thermometers used in the traceability system of radiation thermometers in Japan. NMIJ started in 2001 a new calibration service including the copper-point calibration. spectral responsivity and nonlinearity measurement. Characterization covers the size of source effect, distance effect, ambient temperature dependence, zero offset drift and long term stability.

Intercomparison of radiation temperature scales between PTB and NMIJ from 1000/spl deg/C to 2500/spl deg/C

The intercomparison of radiation temperature scales between PTB and NMIJ was carried out in September 2001. PTB sent their radiation thermometer LP3 to Japan and NMIJ made the comparison between the LP3 and NMIJs Topcon radiation thermometers with a comparison blackbody from 1000/spl deg/C to 2500/spl deg/C. Both scales agreed within /spl plusmn/0.8/spl deg/C in the whole range.

Development of InGaAs radiation thermometers

In 1996 an InGaAs radiation thermometer was developed for the temperature range from 150degC to 1100degC. The quality was good except for the size of source effect (SSE). NMIJ and Chino jointly developed a technique for reducing the SSE by using a ray trace method in the design of the objective lens of 0.65 mum and 0.9 mum radiation thermometers. We applied this technique to develop new InGaAs radiation thermometers with the measuring wavelength of 1.6 mum and 2 mum and their SSEs were much improved. The detector temperature of the 2 mum thermometer should be cooled down to -15degC to obtain a good signal to noise ratio at the indium point. These thermometers can be used as standard thermometers from 150degC to 1100degC for 1.6 mum and from 100degC to 660degC for 2 mum, respectively.

Improvement of size of source effect measurement of standard radiation thermometers

The size of source effect (SSE) influences the calibration uncertainty of the radiation thermometer. For each standard thermometer, the SSE must be measured. If the size of the radiance source is different, the output of the radiation thermometer must be corrected using its SSE. The SSE was measured in indirect technique since 1995 at National Metrology Institute of Japan. The SSE was measured by using an integrating sphere of 400 mm in inner diameter and 140 mm in exit opening diameter. The radiation thermometer was focused onto a black spot and a uniform bright area. The definition of the SSE is the ratio between the signal at the black spot and that of the bright area. The qualities of the black spots are the important factors that influence the uncertainty of the SSE. The uniformity and stability of the radiance source are other factors. To make the size of the black spot more precise, we renewed the black spot in 2005. Although the transmittances for the wavelengths of 650 nm and 900 nm were smaller than 0.001%, we found that the transmittances were 0.01% to 0.06%, 0.06% to 0.4%, and 0.1% to 0.5% for the wavelengths of 1600 nm, 2000 nm and 2200 nm, respectively. The SSE results were corrected using their transmittances of the black spots. The effect of the reflectance of the black spot was also a problem.

Range ratio of topcon radiation thermometers

Topcon 0.65 mum and 0.9 mum radiation thermometers are used as the standard thermometers at high temperatures. These radiation thermometers employ three to five ranges to cover their whole temperature ranges. The range ratios of these thermometers influence largely on the calibration uncertainty. The measurement method, measured results and the long term stability of the range ratios are shown.

Method to determine temperature distribution and intrinsic emissivity of a cavity

A method is presented to determine simultaneously the temperature distribution and the intrinsic emissivities of a cavity surface when radiance distributions along the cavity wall for two wavelengths are given. The intrinsic emissivity and reflection characteristics are assumed not to depend on position on the cavity wall. The intrinsic emissivity and reflection characteristics giving the smallest difference between calculated temperature distributions for the two wavelengths are found. The values found and thus the temperature distributions are verified to be close to the true ones. The method is examined on a cylindrocone by a simulation and applied to radiance temperature distributions measured on a commercially available double cone.