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 °C or °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 (included)Display: 4½ Dual Backlit LCDMeasurements: Humidity, Temperature, Dew Point, Wet-BulbHumidity Range: 0% to 100% RHHumidity Accuracy: ± 2% RHTemp. Range: -30°C – 100°CTemp. Accuracy:  ± 0.5 °CResponse Time: 30 SecondsSensor Type:  CapacitanceData Hold: YesMAX/MIN Values: YesAuto Power-Off: Yes, After 15 Minutes (can be disabled)   Ref: UTTK7531