Amprobe thwd 3 relative humidity and temperature meter amprobe thwd 3 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 the sensor is mounted on a long shaft extending from the top surface of the unit making probing into ductwork and hard to reach areas more easy br br