The Extech 407123 Heavy Duty Hot Wire Thermo-Anemometer uses a telescoping probe (extends up to 2 ft) which is ideal for use in ducts and ventilating systems. It can accurately measure Air Velocity and Temperature and simultaneously displays them on the dual LCD. Additional functions include Data Hold and Min/Max measuring modes. A built-in RS-232 interface can be used with optional Data Acquisition software and cable for recording measurements directly to your PC.