Thermographic measurement techniques15
Note
• Avoid forced convection
• Look for a thermally stable surrounding that will not generate spot reflections
• Use high quality tape that you know is not transparent, and has a high emissivity you
are certain of
• This method assumes that the temperature of your tape and the sample surface are the
same. If they are not, your emissivity measurement will be wrong.
15.3 Reflected apparent temperature
This parameter is used to compensate for the radiation reflected in the object. If the emis-
sivity is low and the object temperature relatively far from that of the reflected it will be im-
portant to set and compensate for the reflected apparent temperature correctly.
15.4 Distance
The distance is the distance between the object and the front lens of the camera. This pa-
rameter is used to compensate for the following two facts:
• That radiation from the target is absorbed by the atmosphere between the object and
the camera.
• That radiation from the atmosphere itself is detected by the camera.
15.5 Relative humidity
The camera can also compensate for the fact that the transmittance is also dependent on
the relative humidity of the atmosphere. To do this set the relative humidity to the correct
value. For short distances and normal humidity the relative humidity can normally be left at
a default value of 50%.
15.6 Other parameters
In addition, some cameras and analysis programs from FLIR Systems allow you to com-
pensate for the following parameters:
• Atmospheric temperature – i.e. the temperature of the atmosphere between the camera
and the target
• External optics temperature – i.e. the temperature of any external lenses or windows
used in front of the camera
• External optics transmittance – i.e. the transmission of any external lenses or windows
used in front of the camera
#T559918; r. AN/42281/42281; en-US
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