Testboy TV 322 Operating Instructions Manual page 17

Distance & Spot Size
As the distance (D) from the object increases, the spot size (S) of the
area measured by unit becomes larger. The relationship between dis-
tance and spot size for each unit is listed below.
Locating a Hot Spot
To find a hot spot, aim the thermometer outside the area of interest, and
then scan across with an up and down motion until you located hot
spot.
Emissivity
Emissivity is a term used to describe the energy-emitting characteristics
of materials. Most (90 % of typical applications) organic materials and
painted or oxidized surfaces have an emissivity of 0.95 (pre-set in the
unit). Inaccurate readings will result from measuring shiny or polished
metal surfaces. To compensate, cover 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 tempera-
ture of the tape or painted surface.
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