General Tools and Instruments IRT105 - Manual (Page 16)

To eliminate measurement error, the IRT must be moved close
enough so the motor is the only object in the target area (see
Fig. 5, bottom). For a motor with an area of 1 ft
2 and using the
IRT105, with a D:S ratio of 6:1, the optimum measurement
distance would be 6 ft.
Fig. 5. Measuring a motor’s temperature from the wrong
(top) and right (bottom) distance.
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