8.3. Locating a hot Spot
To find a hot spot aim the thermometer outside the area of interest,
then scan across with an up and down motion until you locate hot
spot.
Reminders
1. The unit cannot measure through transparent surfaces such as
glass. It will measure the surface temperature of the glass
instead.
2. Steam, dust, smoke, etc. can prevent accurate measurement by
obstructing the unit´s optics.
8.4 Emissivity
Most (90 % of typical applications) organic materials and painted or
oxidised surfaces have an emissivity of 0,95. Inaccurate readings
will result from measuring shiny or polished metal surfaces. To
compensate, cove the surface to be measured with masking tape or
flat black paint. Allow time for the tape to reach the same
temperature as the material underneath it. Measure the temperature
of the tape or painted surface.
Material
Condition
Temperature-
Range
Emissivity-
factor (ɛ)
Aluminium
polished
50°C … 100°C
0.04 ... 0.06
Raw surface
20°C … 50°C
0.06 ... 0.07
oxidized
50°C ... 500°C
0.2 ... 0.3
Aluminium oxide,
Aluminium
powder
normal
Temperature
0.16
Brass
matt
20°C ... 350°C
0.22
oxidized at 600°C 200°C ... 600°C
0.59 ... 0.61
Polished
200°C
0.03
Wrought with
sandpaper
20°C
0.2
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