Middle Temperature Scale for Infrared Radiation Thermometer Calibrated Against Multiple Fixed Points

Abstract

The NMIJ has established a temperature scale for infrared radiation thermometry from 100 to 420 • C consisting of three fixed-point blackbodies at the In, Sn, and Zn points and an InSb detector thermometer at a wavelength of 4.7 µm. The blackbody cavities have large openings of 15 mm diameter. The expanded uncertainties (k = 2) of the In, Sn, and Zn fixed-point radiance temperatures are estimated to be 0.03, 0.03, and 0.05 K, respectively. The expanded uncertainties (k = 2) for the calibration of the infrared radiation thermometer are estimated to be 0.04 K at 157 • C (In point), 0.04 K at 232 • C (Sn point), and 0.07 K at 420 • C (Zn point).

Calibration of Radiation Thermometers and Blackbodies in the Temperature Range from 160 °C to 420 °C

“…A graphite aperture of 5 mm diameter is placed at the opening of the cavity, resulting in an effective emissivity of 0.99989. The graphite cells are placed in threezone furnaces [3]. The uniformity of temperature from the opening to the bottom of the cavity is kept within 1 • C at the In and Sn points, and 1.5 • C at the Zn point.…”

“…The uncertainty in the thermometer output S/S is transferred to the uncertainty in the blackbody temperature T by using the equation in [3] of…”

“…The propagated uncertainty is calculated for each of the three fixed-point temperatures by evaluating changes in the interpolated temperatures caused by a shift of any one of these base temperatures by an amount of its uncertainty [3]. First, the temperature T is calculated using primary values of the parameters A, B, and C in Eq.…”

“…The former consists of fixed-point blackbodies and 0.65 µm and 0.9 µm radiation thermometers using Si photodiodes, and the latter consists of a variable-temperature blackbody (VTBB) with a reference platinum resistance thermometer (PRT) sensor traceable to the ITS-90 and an infrared radiation thermometer with a cryogenically cooled InSb photodiode. To bridge the gap in the temperature scale between 160 • C and 400 • C, we constructed the InSb radiation thermometer working at the wavelength of 4.7 µm calibrated against three fixed-point blackbodies [3]. We chose the longer wavelength detector, because we considered that the NMIJ should have the standard thermometer working in the thermal infrared region to calibrate any thermometers working over the wavelength range of 8 µm to 14 µm, which are widely used in industry.…”

Evaluation of a wireless infrared thermometer with a narrow field of view

“…The degree to which an IRT is sensitive to reflected and internal radiation is affected by the FOV (Brewster, 1992). Uncertainties associated with infrared thermometer signals are a combination of the effects of ambient temperature, the alignment of the thermometer, detector noise and non-linearity (Shimizu and Ishii, 2008), calibration shifts, the inability to eliminate or properly account for the influence of detector temperature on the measurement (Baker et al, 2001), true target emissivity values, and background radiation.…”