Fixed thermometers mainly fall into the following categories:
① Broadband thermometer, or broadband thermometer, its spectral response range is limited by the optical system. It is mainly used to measure low temperature and is equipped with a detector with a wide spectral response range.
② Select a band thermometer. Its response wavelength is limited by the optical filter. The response band of the detector can be selected according to the needs of the application.
③ Shortwave thermometer can reduce measurement errors when the emissivity changes. The short wave mentioned here is relative, it can be a wavelength of 0.6μm at a temperature of 1500K, or a wavelength of 3μm at a temperature of 300K.
④ Colorimetric thermometer, also known as two-color thermometer, has better measurement results when used in "very dirty atmosphere".
When selecting a thermometer, in addition to the temperature requirement range, the two parameters of the thermometer, "temperature change percentage" and "radiance change percentage", are also very important for accurate selection of the thermometer:
① The temperature change percentage of the thermometer refers to the change in the output value of the object due to temperature changes. For infrared thermometers, the greater the temperature change percentage, the higher its sensitivity.
② The percentage change in radiation rate refers to the change in the output value of the instrument when the radiation rate of the measured target changes. Since during the steel rolling process, the emissivity of the steel plate changes randomly within a certain range at a certain wavelength and temperature, the change in the thermometer output value caused by the change in the emissivity is not the true temperature change of the target. Therefore, it is also necessary to adjust the radiation rate change percentage.
