10
Infrared K-Thermometer Model CA876
CHAPTER 4
OPERATION
4.1
Infrared Measurement Considerations
MEASUREMENT THEORY
Every object emits infrared (IR) energy proportional to its temperature. By
measuring the amount of this radiant energy, it is possible to determine
the temperature of the emitting object. Infrared radiation is invisible light
(electromagnetic radiation), which easily travels through air and is easily
absorbed by solid matter. An IR thermometer, which operates by detecting
infrared radiation, can accurately measure an object surface temperature
without touching it and independently of the air temperature or the mea-
surement distance.
Infrared radiation, which is emitted from the object, is focused into an infra
-
red radiation sensor through an optical system. This system includes an
optical lens, which is transparent to infrared radiation, and a 5.3μm cut
off filter. The output signal from the infrared radiation sensor is input to an
electronic circuit, along with the output signal from a standard temperature
sensor, to calculate the temperature and display it on the meter display.
EMISSIVITY
All objects emit invisible infrared energy. The amount of IR energy emitted
is proportional to the object’s temperature and its natural ability to emit IR
energy. This ability, called emissivity, is based upon the object material
type and its surface finish. Emissivity values range from 0.10 for a very
reflective object to 1.00 for a black body. Factory set emissivity value of
0.95 will cover 90-95% of typical applications.
If frost or other material/substance covers the measured surface, clean it
to expose the surface. If the surface to be measured is highly reflective,
apply dull masking tape or matte black paint over the surface. If the ther-
mometer seems to be giving incorrect readings, check the front sensor.
There may be condensation or debris obstructing the sensor. Only clean
per instructions.
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