Discussion on How to Determine the Verification Distance of Infrared Thermometer
1 Infrared thermometer verification distance
In the actual verification process, even within the range of the verification distance allowed by the manufacturer, the distance of the verification distance will affect the verification results, causing the verification data to differ by a few degrees. The basic error stipulated in the current JJG (Railway) 149-2005 Verification Regulations for Portable Infrared Thermometers for Railways 3.1 is that within the range of 30-95 °C, the basic error of any verification point is not greater than ±2 °C, and at 95-150 °C Within the range of ℃, the basic error of any test point is not more than ±3℃. The error of the verification distance will change an infrared thermometer from qualified to unqualified. It seems that how to determine the verification distance of the infrared thermometer is particularly important.
2 Determine the verification distance of the infrared thermometer
How to solve this problem in the verification process, it is recommended that the target diameter be ≥ 1.5S. According to the above relationship, assuming that the diameter of the surface source blackbody radiation source used is 100 mm, then S should be 66.67 mm. Assuming that D:S=6:1 (according to the instruction manual of the infrared thermometer provided by the manufacturer), then D=400 mm. By discussing this issue with experts, manufacturers and verification personnel, coupled with years of practical experience, it is suggested that during the verification process, the verification distance of the infrared thermometer should be set at D≤300 mm. The products that are certified as qualified when D≤300 mm are taken to the site to detect the temperature of the axle are consistent with the temperature test results of the axle detected by other methods. At the same time, it is also recommended to mark the verification distance during the verification process on the back of the verification certificate when verifying the infrared thermometer for reference by users.
