Determine wavelength range: The emissivity and surface characteristics of the target material determine the spectral response or wavelength of the thermometer. For high reflectivity alloy materials, there is a low or varying emissivity. In high-temperature areas, the optimal wavelength for measuring metal materials is near-infrared, with wavelengths ranging from 0.18 to 1.0 μ m. Wavelengths of 1.6 μ m, 2.2 μ m, and 3.9 μ m can be selected for other temperature ranges. Due to some materials being transparent at a certain wavelength, infrared energy can penetrate these materials, and special wavelengths should be selected for this type of material. If measuring the internal temperature of glass, select wavelengths of 1.0 μ m, 2.2 μ m, and 3.9 μ m (the measured glass must be very thick, otherwise it will pass through); Measure the internal temperature of the glass using a wavelength of 5.0 μ m; It is advisable to choose a wavelength of {{20}} μ m for low measurement areas; For example, for measuring polyethylene plastic films, a wavelength of 3.43 μ m is selected, while for polyester films, a wavelength of 4.3 μ m or 7.9 μ m is selected. When the thickness exceeds 0.4mm, choose a wavelength of 8-14 μ m; For example, CO2 in flames is measured at a narrowband wavelength of 4.24-4.3 μ m, CO in flames is measured at a narrowband wavelength of 4.64 μ m, and NO2 in flames is measured at a wavelength of 4.47 μ m.
Determine response time: The response time represents the reaction rate of the infrared thermometer to changes in the measured temperature, defined as the time required to reach 95% energy of the reading after *, and is related to the time constant of the photodetector, signal processing circuit, and display system. The response time of Raytek's new infrared thermometer can reach 1ms. This is much faster than the contact temperature measurement method. If the target's movement speed is very fast or when measuring rapidly heated targets, a fast response infrared thermometer should be selected, otherwise it cannot achieve sufficient signal response and will reduce measurement accuracy. However, not all applications require fast responsive infrared thermometers. When there is thermal inertia in a stationary or target thermal process, the response time of the thermometer can be relaxed. Therefore, the selection of response time for infrared thermometers should be adapted to the situation of the target being measured.
In sealed or hazardous material applications (such as containers or vacuum boxes), the thermometer is observed through a window. The material must have sufficient strength and be able to pass through the working wavelength range of the thermometer used. It is also necessary to determine whether the operator needs to observe through the window, so appropriate installation positions and window materials should be selected to avoid mutual interference. In low-temperature measurement applications, Ge or Si materials are usually used as windows, which are opaque to visible light and cannot be observed by the human eye through the window. If the operator needs to pass through the window target, optical materials that transmit both infrared radiation and visible light should be used. For example, optical materials that transmit both infrared radiation and visible light, such as ZnSe or BaF2, should be used as window materials.
