The THWD-3 uses a precision capacitance sensor to deliver accurate performance with long term stability. This high accuracy instrument measures the full range of relative humidity from 0% to 100% and features an exceptionally wide ambient temperature measurement range from -4 °F to 140 °F. The sensor is mounted on along shaft extending from the top surface of the unit, making probing into ductwork and hard to reach areas more easy. The large LCD displays two measurements simultaneously with a full range of display options including hold, min, max, dew point (DP) and wet bulb (WB).