Distance-To-Spot Ratio - Craftsman 81998 Owner's Manual

Distance-to-spot ratio

The meter's distance-to-spot ratio is 13:1. For example, if the
meter is 13 inches from the target (spot), the diameter of the
target must greater than 1 inch. Other distances are shown in
the field of view diagram. Measurements should normally be
made as close as possible to the device under test. The meter
can measure from moderate distances but the measurement
may be affected by external sources of light. In addition, the spot
size may be so large that it encompasses surface areas not
intended to be measured.
Diameter of Spot
4"
3"
2"
1"
13"
26"
39"
52"
Distance to Object
14