Infrared Non-Contact Digital Thermometers. ... IR831 Mid-Range Infrared Thermometer - Circle Dot Laser. Manual Data Sheet. Range: -30°C to +1350°C; Accuracy: ±2% rdg. ±2°C; Resolution: 0.1°C up to 999.9 ...Infrared thermometers have a lens that focuses infrared radiation onto a detector which converts it into a readable electronic signal. Because of this, it is possible for nearby objects emitting their own thermal radiation to interfere with the measurement- even the thermal body temperature emitted by the user.