The AN320 is a Large Vane CFM/CMM Anemometer/Psychrometer plus CO2. This meter measures Air Velocity, Air Flow, Relative Humidity, Wet Bulb, Dew Point and Carbon Dioxide. Extech’s Large Vane Thermo-Anemometer series allows for more precise readings on larger size ducts. Min/Max, Data Hold, and Auto power off functions. Complete with 4 AAA batteries and hard carrying case.