The AN310 is a Large Vane CFM/CMM Anemometer and Psychrometer. This meter monitors air velocity, flow rate, relative humidity, wet bulb, and dew point. Extech's Large Vane Thermo-Anemometer series provides more precise readings for larger ducts. Includes Min/Max, Data Hold, and Auto Power Off capabilities. Comes with 4 AAA batteries and a sturdy carrying case.