The Amprobe TH-3 Relative Humidity and Temperature Meter 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 a long shaft extending from the top surface of the unit, making probing into duct work and hard to reach areas more easy.