The Testo 425 (0560 4251) Compact Thermal Anemometer with Fixed Velocity Probe is a compact anemometer with a fixed thermal flow velocity probe. It can measure cubic feet per minute (CFM) when conducting duct testing, as well as easily switch between flow and temperature readings. The telescoping handle of the thermal probe on this CFM meter makes it easy to reach ductwork above your head, extending to maximum length of 33 inches. The probe head has a diameter of 0.3 in. (7.5 mm). The 425 Anemometer also measures extremely accurately in the low flow velocity range. The volume flow is directly shown in the display. For the purposes of volume flow calculation, the duct area can be easily entered into the 425 Anemometer. Timed and point mean value calculation provide information on the average volume flow, flow velocity and temperature measurement value. The Hold function allows the current measurement value to be frozen in the display, min./max. values are also displayed at the press of a button.