[TheForge] HF IR thermometer <$20!

[James Binnion]

IR thermometers are notorious for feeding the operator spurious information. They rely on the emission of IR light from surfaces to determine temperature.  Unfortunately almost every type of material has a different emission factor and in fact surface finish, oxidation and cleanliness can all affect the emissivity of an object. This means one needs to know what the temperature of an item is to calibrate the instrument to that particular item. The better ones are also thermocouple meters as well. This allows one to measure and calibrate the instrument for accurate readings by using the thermocouple to measure the surface you want to read to calibrate for the real emissivity of the object. The second issue is they average everything in the focal diameter of the lens. So if the object you are reading does not fill that circle you will get an erroneous reading. To avoid this one needs to know the diameter of the focus beam at the distance one is measuring from so you can assess if the object you are measuring is filling the beam at that range. Anyhow they are not the point and click devices that they are often portrayed as.


James Binnion
jbin at well.com