What is the distance to spot (D:S) ratio?

The distance to spot (D:S) ratio is the ratio of the size of the area where the temperature is being measured in relation to the distance from the target. For instance, if the IRT has an 8:1 distance-spot (D:S) ratio, that means that at 8ft away from the target, the target area is a circle with a 1ft diameter with the laser pointer as the center. The lower the D:S ratio, the closer you have to get to target to make an accurate reading. The minimum distance can become a safety issue when measuring very hot (or cold) surfaces and objects.

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