The Fieldpiece SIP2 is a handy and accurate Shirt Pocket Thermometer. The SIP2 uses a sensor that is more accurate than most. Accuracy is +/- 1.8°F. When used to measure ambient air temperature, the 1:1 cone of view enables the technician to easily get an average temperature of a large area. With narrower cones of view, a "hot spot" or "cold spot" can significantly affect the readings. For registers and grills, you need to get close.