The Extech DV40 can quickly check for the presence of live wires before testing. Suitable for outlets or against wire insulation testing. Model DV40 combines a CAT III-1000V Voltage Detector (with a wide range from 50 to 1000 Volt) with an Infrared Thermometer which measures and displays non-contact surface temperatures on the built-in LCD screen using a from -20 to 445°F (-30 to 230°C). 1:1 distance to target ratio.