optris CTratio Operator's Manual page 14

Sensor placement [1C mode]
The size of the measuring object and the optical resolution of the infrared thermometer determine the
maximum distance between sensing head and measuring object. In order to prevent measuring errors the
object should fill out the field of view of the optics completely. Consequently, the spot should at all times have
at least the same size like the object or should be smaller than that.
Sensor placement [2C mode]
In the 2-color-mode the sensing head can be placed under various conditions, like:
 Measurement through holes smaller than the spot size
 Measurement through dust, smoke or steam in the atmosphere
 Measurement of objects smaller than the measurement spot
 Measurement through a dirty lens or dirty sighting window
[► The Ratio Principle]
Please note that the sensor accuracy is not guaranteed for signal reductions of more than 95%.
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optris CTratio – E2013-04-A