• 0563 0425
  • Usually ships in 5-7 business days



  • -4 to 158°F temperature range
  • 0 to 5,905 fpm air velocity range
  • Timed and point mean value calculation
  • Fast in-app configuration and data memory
  • Durable, compact design with robust housing
  • °F, °C, fpm, m/s, cfm, and m3/h measuring units

What's in the Box

  • Testo 425 Thermal Anemometer
  • Carrying bag
  • 3 AAA batteries
  • Calibration protocol


The Testo 425 Thermal Anemometer with telescopic probe is designed for simple, fast and precise determination of flow velocity and volume flow in ventilation ducts of air conditioning and ventilation systems. The compact Testo 425 measures air velocity from 0 to 5,905 fpm and temperatures between -4 to 158°F. Additional calculations such as volume flow or time and point averages are performed automatically on the device.

The Testo 425 features more flexibility for duct measurements with the addition of the cable connected telescopic probe. The telescopic probe can be extended up to 32 inches, making it easier to work with overhead or large diameter ducts.

A connection to the testo Smart App enables convenient configuration, additional display, and storage as well as documentation of the measurement values directly in the App. Your smart phone becomes the secondary display with clear graphical presentation of readings, for quick interpretation of results and more flexibility on the job. Stored measurement data can then be converted to PDF or CSV files and shared via email.