UNI-T UT305A, User Manual, Page: 12 / 26

12
Distance and Spot Size
As the distance (D) from the target being measured
increases, the spot size (S) of the area measured by
the unit becomes larger. The spot size indicates 90%
encircled energy. The maximum D:S is obtained when
the Thermometer is 600mm (60 in) form the target
resulting in a spot size of 20mm (2 in). See Figure 6.
Figure 6. Distance and Spot Size
Field of View
Make sure that the target is larger than the spot size.
The smaller the target, the closer you should be to it.
See Figure 7.
Figure 7. Field of View