Target Size for Infrared Thermometers
Infrared thermometers can be divided into single-color thermometers and two-color thermometers (radiation colorimetric thermometers) according to the principle. For a monochromatic thermometer, when measuring temperature, the area of the target to be measured should fill the field of view of the thermometer. It is recommended that the measured target size exceed 50% of the field of view. If the target size is smaller than the field of view, the background radiation energy will enter the visual and acoustic symbols of the thermometer and interfere with the temperature measurement readings, causing errors. Conversely, if the target is larger than the pyrometer's field of view, the pyrometer will not be affected by background outside the measurement area.
For a two-color pyrometer, the temperature is determined by the ratio of radiant energy in two independent wavelength bands. Therefore, when the target to be measured is small, does not fill the site, and there is smoke, dust, or obstruction on the measurement path that attenuates the radiation energy, it will not affect the measurement results. Even in the case of 95% energy attenuation, the required temperature measurement accuracy can still be guaranteed. For targets that are small and moving or vibrating; sometimes moving in the field of view, or may partially move out of the field of view, under these conditions, the use of a two-color thermometer is the best choice. If it is impossible to aim directly between the pyrometer and the target, and the measurement channel is bent, narrow, obstructed, etc., the two-color fiber optic pyrometer is the best choice. This is due to their small diameter, flexibility, and the ability to transmit optical radiant energy over curved, blocked, and folded channels, thus enabling measurement of targets that are difficult to access, in harsh conditions, or near electromagnetic fields.
Response time of infrared thermometers
The response time indicates the reaction speed of the infrared thermometer to the measured temperature change, which is defined as the time required to reach 95% of the final reading (the two-color colorimetric optical fiber only needs 5% of the energy). It is related to the photodetector, signal processing circuit and Shows the time constant of the system involved. The response time of the new infrared thermometer can reach 1ms. This is much faster than the contact temperature measurement method. If the moving speed of the target is very fast or when measuring a rapidly heating target, a fast-response infrared thermometer should be selected, otherwise the sufficient signal response will not be achieved, and the measurement accuracy will be reduced. However, not all applications require a fast-response infrared thermometer. For static or target thermal processes where thermal inertia exists, the response time of the pyrometer can be relaxed. Therefore, the choice of the response time of the infrared thermometer should be adapted to the situation of the measured target.
