HD500 Datasheet, PDF (6/10 Pages) Extech Instruments Corporation. – Heavy Duty Psychrometer + IR Thermometer

InfraRed Measurement Considerations
• 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.
• IR measurements cannot be made through glass.
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 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 30:1, meaning that if the meter is 30 inches (cm) from the target, the
diameter (spot) of the object under test must be at least 1 inch (cm). Refer below to the
field of view diagram.
Emissivity
Most organic materials and painted or oxidized surfaces have an emissivity of 0.95.
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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HD500 V3.1 12/07