The main factors affecting the measurement of infrared thermometers
1. Determine the temperature measurement range
Determining the temperature measurement range: The temperature measurement range is the most important performance indicator of a thermometer. Each model of thermometer has its own specific temperature measurement range.
If the coverage range is -50 ℃ -+3000 ℃, but this cannot be achieved by one type of infrared thermometer.
Therefore, the user's measured temperature range must be considered accurately and comprehensively, neither too narrow nor too wide.
According to the blackbody radiation law, the change in radiation energy caused by temperature in the short band of the spectrum will exceed the change in radiation energy caused by emissivity error. Therefore, short waves should be used as much as possible for temperature measurement.
Generally speaking, the narrower the temperature measurement range, the higher the resolution of the output signal for monitoring temperature, and the easier it is to solve the problem of accuracy and reliability.
If the temperature measurement range is too wide, it will reduce the temperature measurement accuracy. For example, if the measured target temperature is 1000 degrees Celsius, first determine whether it is online or portable, and if it is portable.
There are many models that meet this temperature requirement, such as 3iLR3, 3i2M, and 3i1M.
If measurement accuracy is the main concern, it is best to choose the 2M or 1M model, because if the 3iLR model is selected, its temperature measurement range is wide, and its high-temperature measurement performance is poorer;
If users need to take care of low-temperature targets in addition to measuring 1000 degrees Celsius, they can only choose 3iLR3.
2. Determine the target size
In order to obtain temperature readings from Jingque, the distance between the thermometer and the test target must be within an appropriate range, and the so-called "spot size" refers to the area of the measuring point of the thermometer. The farther you are from the target, the larger the size of the light spot.
Infrared thermometers can be divided into monochrome thermometers and two-color thermometers (radiation colorimetric thermometers) based on their principles.
For monochrome thermometers, the area of the measured target should fill the thermometer's field of view during temperature measurement. It is recommended that the size of the target being tested exceed 50% of the field of view size. 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 reading, causing errors.
On the contrary, if the target is larger than the field of view of the thermometer, the thermometer will not be affected by the background outside the measurement area.
For a colorimetric thermometer, its temperature is determined by the ratio of the radiated energy within two independent wavelength bands.
Therefore, when the target being measured is very small, does not fill the field of view, 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 energy attenuation of 95%, the required temperature measurement accuracy can still be guaranteed.
For small targets that are in motion or vibration, a colorimetric thermometer is the best choice.
This is due to the small diameter and flexibility of light rays, which can transmit optical radiation energy through curved, obstructed, and folded channels, making it possible to measure targets that are difficult to approach, have harsh conditions, or are close to electromagnetic fields.
3. Determine distance coefficient (optical resolution)
The distance coefficient is determined by the ratio of D: S, which is the ratio of the distance D between the thermometer probe and the target to the diameter of the measured target.
The higher the optical resolution, i.e. increasing the D: S ratio, the higher the cost of the thermometer. If the thermometer must be installed far away from the target due to environmental conditions and needs to measure small targets, a high optical resolution thermometer should be selected.
For a fixed focal length thermometer, the spot size is the smallest at the focal point of the optical system, and the spot size increases near and far from the focal point. There are two distance coefficients.
Therefore, in order to accurately measure temperature at distances close to and far from the focal point, the size of the measured target should be larger than the size of the light spot at the focal point. The zoom thermometer has a minimum focal point position that can be adjusted according to the distance to the target.
Increasing D: S reduces the received energy. Without increasing the receiving aperture, it is difficult to increase the distance coefficient D: S, which increases the instrument cost.
