The desired spot size on the target will determine the maximum measurement distance. To avoid erroneous readings, the target spot size must completely fill the entire field of view of the sensor. Consequently, the sensor must be positioned so the field of view is the same as or smaller than the desired target size. For a list indicating the available optics, see section 3.2 Optical Charts, page 15.
The actual spot size for any distance can be calculated by using the following formula. Divide the distance D by your model’s D:S number. For example, for a unit with D:S = 10:1, if the sensor is 400 mm (15.7 in.) from the target, divide 400 by 10 (15.7 by 10), which gives you a target spot size of approximately 40 mm (1.57 in.).