The Ridgid HM-100 Micro Humidity and Temperature Meter is a professional and easy to use device for accurately measuring air humidity and temperature. Both measured values (%RH and deg;C or deg;F) are instantly and simultaneously displayed on the dual backlit LCD. The HM-100 also automatically calculates the Dew Point and Wet Bulb temperature, while its Capacitance Sensor easily withstands the effects of condensation and high temperatures, making it perfectly suitable for any HVAC environment. Supplied with a soft carrying case, and 9V battery. Specifications: Power Source: 9V battery (supplied).Measurements: Humidity, temperature, dew point, wet-bulb.Humidity Range: 0% to 100% RH.Humidity Accuracy: plusmn;2% RH.Temp. Range: -30deg;C - 100deg;C.Temp. Accuracy: plusmn;0.5deg;C.Response Time: 30 seconds.Data Hold: Yes.Auto Power-Off: Yes, after 15 minutes (can be disabled).