InfraRed Measurement Considerations
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When taking IR measurements the meter automatically compensates for ambient
temperature changes. Note that it may take up to 30 minutes to adjust to extremely
wide ambient changes.
Low temperature measurements quickly followed by high temperature measurements
may require several minutes to stabilize as a result of the IR sensor cooling process.
If the surface of the object under test is covered with frost, oil, grime, etc., clean before
taking measurements.
If an object's surface is highly reflective apply masking tape or flat black paint before
measuring.
Steam, dust, smoke, etc. can obstruct measurements.
To find a hot spot, aim the meter outside the area of interest then scan across (in an up
and down motion) until the hot spot is located.
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IR Theory
IR thermometers measure the surface temperature of an object. The meter’s optics sense
emitted, reflected, & transmitted energy that is collected and focused onto the meter’s
detector. The meter’s circuitry translates this information into an LCD reading.
IR Field of View
Ensure that the desired target is larger than the spot size as shown in the diagram below.
As the distance from an object increases, the spot size of the area measured by the meter
becomes larger. The meter’s field of view ratio is 8:1, meaning that if the meter is 8 inches
from the target, the diameter (spot) of the object under test must be at least 1 inch. Other
distances are shown below in the field of view diagram.
Distance to Object in inches
10”
8”
12”
6”
0.75”
1”
1.25”
Diameter of Spot in inches
1.5”
Emissivity
Most organic materials and painted or oxidized surfaces have an emissivity of 0.95 (fixed
setting in the model RH101). Inaccurate readings will result when measuring shiny or
polished surfaces. To compensate, cover the surface under test with masking tape or flat
black paint. Allow time for the tape to reach the same temperature as the material
underneath then measure the temperature of the tape or the painted surface.
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RH101 V2.1 8/07
EXTECH [ EXTECH INSTRUMENTS CORPORATION. ]
