Hand-held infrared “guns” are frequently used to measure heat in fusing machines. Usually these guns are aimed at the bottom or top conveyor belt as it comes out the exit end of the heat chamber. The back cover is often up and the instrument placed about 12” from the belt surface to measure any temperature differences across the width of the belt surface. This method is quick and easy, but is it accurate?
It is important to understand the limitations of these guns. When the rear cover is lifted (fusing machines should always be operated with all the covers closed and in place) the radiation that the gun “reads” is quickly compromised at the edges as it mixes with cool air from the side. This does not occur as quickly in the center because the heat rises there, in a steady, less compromised wave. Therefore, the readings will almost always read lower at the side, especially a side closest to an open door or air conditioning duct. In most instances, when reading across the belt on an AIT/Astex machine the side readings will be false.
The best way to read heat across the width of your fusing machine is to use temperature strips. These temperature strips actually make contact with the conveyor belt. We do recommend the use of these guns in diagnosing circuit and bearing problems where higher heat generally indicated excessive part wear. Contact us with further questions about heat measurement in your AIT/Astex fusing machine.