The process of infrared (IR) temperature measurement relies on determining the amount of invisible light given off by objects in the form of infrared radiation. In order to obtain the most accurate IR temperature measurement, there are a few general tips that can be followed. When using a non-contact IR thermometer, it is important for both the lens and the object that is being measured to be clean, dry and free of any obstructions. It can also be important to properly calibrate the thermometer, if that is possible. If a thermometer cannot be calibrated, it is often possible to modify an object by applying black paint or even tape to achieve the necessary characteristics.
Accurate infrared temperature measurement relies on a principle known as emissivity. This term refers to the ability of an object to emit infrared radiation in comparison to a black body. The lower the emissivity of an object, the worse it is at emitting infrared radiation. This means that if two objects have the same temperature, the one with a lower emissivity will emit less infrared radiation. In order to obtain the most accurate IR temperature measurement, this must be taken into account.
In order to get the best results out of IR temperature measurement, a number of different techniques can be used. One tip to obtaining an accurate IR temperature measurement involves making sure the thermometer is in good condition. The batteries should be in a good state of charge, and the lens must be clean and unobstructed. If the thermometer has any manual adjustment settings, it is important for those to be set properly as well. Many high-end, non-contact IR thermometers allow an operator to input the emissivity value of an object, which can allow for the most accurate reading possible.
If an object has an unknown emissivity, or a thermometer is not adjustable, it is still sometimes possible to obtain an accurate IR temperature measurement. In the case of an object with an unknown emissivity, it is sometimes possible to alter the surface with something that has a known emissivity value. If a thermometer is not adjustable, then the surface should be modified to fall within its designated emissivity range. In many cases, this can be accomplished by painting the object with a flat black paint or attaching a piece of black tape.
Other factors, such as wind, can also affect IR temperature measurement. Wind can cause convective heat transfer, in effect cooling warm objects and heating cold ones. This effect cannot easily be accounted for by a non-contact thermometer, but there are a few ways to obtain a more accurate measurement. If the object can be shielded from the wind, then measuring the part of the surface that is protected can provide a higher level of accuracy. Large objects can also be measured on the downwind side to provide a somewhat more accurate result.