Abstract
In this paper, a characteristic equation to show the characteristics of narrow-band radiation thermometers in the wide temperature range is investigated.
The characteristic equation is written as follows
V=Cexp(-c2/AT+B)
where V is the output signal voltage of the radiation thermometer, T is the temperature to be measured, c2=0.014388m·K and A, B and C are coeffcients intrinsic to the radiation thermometer. The equation can be transformed as follows
T=c2/A/lnC-lnV-B/A
or
aT·lnV+b·lnV+c=T,
A=ac2/(b/a+c), B=bA/a, C=exp(l/a),
The coefficients A, B and C can easily be calculated from the measured values by the least square meathod and then the temperature can directly be obtained from the output signal voltage.
When the radiation thermometer with the measuring wavelength of 0.9μm is calibrated by blackbodies at three freezing points Al, Ag and Cu with high accuracy, and when the detector sensitivity is linear, a temperature scale with accuracy of ±0.1K shall be given by the equation. In this case, the measuring wavelength width of the radiation thermometer as wide as 90nm is permitted. Such goodness of fit of the characteristic equation are discussed to three radiation thermometers of measuring wavelengths 4, 0.9 and 0.65μm.
