Step 2: Determining The Emissivity - FLIR ix Series User Manual

18 – Thermographic measurement techniques
5 Measure the apparent temperature of the aluminum foil and write it down.
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Figure 18.4 Measuring the apparent temperature of the aluminum foil
18.2.1.2

Step 2: Determining the emissivity

1 Select a place to put the sample.
2 Determine and set reflected apparent temperature according to the previous procedure.
3 Put a piece of electrical tape with known high emissivity on the sample.
4 Heat the sample at least 20 K above room temperature. Heating must be reasonably even.
5 Focus and auto-adjust the camera, and freeze the image.
6 Adjust Level and Span for best image brightness and contrast.
7 Set emissivity to that of the tape (usually 0.97).
8 Measure the temperature of the tape using one of the following measurement functions:
Isotherm (helps you to determine both the temperature and how evenly you have heated
■
the sample)
Spot (simpler)
■
Box Avg (good for surfaces with varying emissivity).
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9 Write down the temperature.
10 Move your measurement function to the sample surface.
11 Change the emissivity setting until you read the same temperature as your previous measure-
ment.
12 Write down the emissivity.
Note:
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Publ. No. T559733_en-US Rev. a571 – ENGLISH (EN) – November 4, 2011