Greenlee TG-150 Manual Del Usuario página 11

Distance from Target
Temperature guns measure the surface temperature of an object by sensing its emitted,
reflected and transmitted energy. The sensor collects this energy from the area being
measured (spot size). The spot size varies as the distance to the target changes. The farther
the distance from the area being targeted, the larger the spot size.
When determining the appropriate distance from the object, the spot size must be somewhat
smaller than the target area. When accuracy is critical, the spot size should be half as large as
the target. If the spot size is larger than the target size, the thermometer will pick up the
temperature of the background, resulting in inaccurate readings.
Object 1 is the correct distance from the unit. Note the
target is slightly larger than the spot size being
measured.
Object 2 is too far away. The thermometer also
measures the background because the target is smaller
than the instrument's spot size. This can result in an
inaccurate reading.
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