The AN310 is a Large Vane CFM/CMM Anemometer/Psychrometer. This meter measures Air Velocity, Air Flow, Relative Humidity, Wet Bulb and Dew Point. Extech's Large Vane Thermo-Anemometer series allows for more precise readings on larger size ducts. With Min/Max, Data Hold, and Auto power off functions. Complete with 4 AAA batteries and hard carrying case.