Amprobe TMA-21HW [3730239] Hotwire Anemometer with Temperature. The Amprobe TMA-21HW Hot Wire anemometer technology eliminates the use of bearings and rotating parts. Because of this fact the meter is durable and provides good and stable accuracy of the measurements. The TMA21HW is used for indoor air quality and HVAC/R technicians measuring heating, ventilation, air-conditioning, refrigeration, wind flow and temperature in residential, commercial and industrial air conditioning systems. The Amprobe TMA-21HW is a highly accurate thermometer with 0.1% basic accuracy and is convenient for use in hard to reach places with its fast response telescopic probe. The TMA-20HW measures relative humidity and temperature and features a large backlit LCD display with 5 parameters.