Infrared Thermometer Determination of Distance Factor
The distance coefficient is determined by the ratio of D:S, that is, the ratio of the distance D between the probe of the thermometer to the target and the diameter of the target to be measured. If the thermometer must be installed far away from the target due to environmental conditions, and a small target must be measured, a thermometer with high optical resolution should be selected. The higher the optical resolution, i.e. increasing the D:S ratio, the higher the cost of the pyrometer. Raytek Infrared Thermometers D:S range from 2:1 (low distance factor) to over 300:1 (high distance factor). If the thermometer is far away from the target and the target is small, a thermometer with a high distance coefficient should be selected. For a pyrometer with a fixed focal length, the focal point of the optical system is the minimum position of the spot, and the spot near and far from the focal point will increase. There are two distance factors. Therefore, in order to accurately measure temperature at a distance close to and far from the focus, the size of the measured target should be larger than the spot size at the focus. The zoom thermometer has a minimum focus position, which can be adjusted according to the distance to the target. If D:S is increased, the received energy will decrease. If the receiving aperture is not increased, the distance coefficient D:S will be difficult to increase, which will increase the cost of the instrument.
