Measure the apparent temperature of the aluminum foil and write it down.
10727003;a2
Figure 20.4 Measuring the apparent temperature of the aluminum foil
5
20.2.1.2 Step 2: Determining the emissivity
Select a place to put the sample.1
Determine and set reflected apparent temperature according to the previous procedure.2
Put a piece of electrical tape with known high emissivity on the sample.3
Heat the sample at least 20 K above room temperature. Heating must be reasonably even.4
Focus and auto-adjust the camera, and freeze the image.5
Adjust Level and Span for best image brightness and contrast.6
Set emissivity to that of the tape (usually 0.97).7
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).
8
Write down the temperature.9
Move your measurement function to the sample surface.10
Change the emissivity setting until you read the same temperature as your previous measure-
ment.
11
Write down the emissivity.12
Note:
Publ. No. T559580 Rev. a486 – ENGLISH (EN) – November 17, 2010 127
20 – Thermographic measurement techniques
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