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5. Environment Dust, gases, suspended water vaporand other particulate matter canaffectthe infrared sensor’s performance.These items can intercept, absorb orscatter infrared energy before it gets to the sensor. Therefore, it is best ifthe environment is kept fairly clean and free of contaminants. An airpurge collar is available to purge theoptics systems to prevent the accum-ulation of foreign material on the lens.

W A T L O W

Application Guide catalog - 7347 Application Guide

Temperature Sensors

exposed to a dramatically changingambient . The sensor output willstabilize when the ambienttemperature stabilizes. The sensor is accurate when maintained at aconstant ambient temperature.Air and/or water cooling jackets maybe available to help maintain thesensor at an appropriate operating ambient temperature.

Non-Contact Temperature Sensor Basics

Continued The sensor is “looking” at the objectas well as at background radiation;thus, it will average background en-ergy with the energy emitted by thetarget object. All background sur-faces around the target emit radiant energy according to the basic laws.Ifthe background radiation is withinthe spectral transmission (eight-14 microns) of the sensor, an error intheindicated temperature will occur.This background radiation can beenergy emitted from lamps, heaters,ovens, heat exchangers, motors, generators, steam pipes, etc. As ageneral rule of thumb, to minimizetheeffects of background radiation, the target size should be two timeslarger than the desired spot size. Forexample, if an object is 457 mm (18 in.) away and the spot size is rated for 51 mm (2 in.), the target should beat least 102 mm (4 in.) in size. 4.Sensor Placement Ideally, the temperature sensor should be placed at a right angle with respect to the target. This helpsreduce the effects of reflected energy.Not all applications will lend them- selves to perpendicular sensorplacement. In these situations, do not position the sensor at more than a 45°angle normal to the surface (see Reference 48).
Temperature Sensors 3. Ambient Temperature Check the operating ambienttemperature of the infrared sensor.Due to the thermal dynamics of theinfrared sensor, it is normal for theoutput to drift when the sensor is Ref. 48
Sensor 45 ° Product 59