Amprobe THWD-5 [3311803] Relative Humidity and Temperature Meter with Wet Bulb and Dew Point. The Amprobe THWD-5 Relative Humidity and Temperature Meter with wet bulb and dew point is a microprocessor-based psychrometer. The THWD5 is designed for HVAC and plant maintenance engineers and technicians.The Amprobe THWD-5 allows easy and quick access to wet bulb and dew point values as well as relative humidity and temperature. The THWD-5 is equipped with an extended probe for easy target access, a large dual LCD display, and is tripod mountable.