TESTO 420: Volume Flow Hood


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The testo 420 is used for volume flow measurements (main application), Pitot tube measurements and pressure measurements for air conditioning and ventilation systems. Thanks to its interchangeable flow hoods, the testo 420 can be used for air inlets and outlets of various sizes. With the additional App (Android/iOS), the readings can be conveniently displayed on a tablet or smartphone, and in addition a measurement can be started, stopped and saved via the App.

The testo 420 is the light, precise and convenient solution for regulating volume flows at larger air intakes and outlets. At swirl outlets in particular, the flow straightener significantly reduces the usual measurement errors. This allows users to fulfil hygienic Indoor Air Quality guidelines and stipulations in ventilation and air conditioning systems quickly and precisely, e.g. in industry, office rooms or in cleanrooms.

Handling is especially easy with a uniquely low weight of less than 2.9 kg and ergonomic handles. The measuring instrument can be tilted and removed for more comfortable readout of the measurement values. In addition to this, mobile devices can be used via Bluetooth App integration as a second display and remote control. This makes the use of a tripod for high ceilings especially secure and comfortable. Users can furthermore use the App to finalise and send the measurement report directly on site. The testo 420 App is completely free and is available for iOS from the App Store and Android via Google Play.


Rugged and toughflow hood that weighs less than 6.2 lbs. (2.9 kg.).
Large, easy to read, tiltable, backlit display (removable) makes it easy to see the readings.
Flow straightener for more precise measurement at turbulent outlets.
App integration via Bluetooth for fast and easy monitoring and reporting on site.

Testo 420 General Specifications:

  • Operating temperature: 23 to 140 °F (-5 to +60 °C).
  • Storage temperature: -20 to +60 °C.
  • Display: Dot matrix with illumination.
  • Memory: 2 GB internal.
  • Interface: Micro USB.
  • Power: 4 x 5 AA batteries.
  • Battery life: 40 h
  • Standard hood: 610 x 610 mm.
  • Weight: 2.9 kg.
  • Testo 420 Warranty: 2 years.


Includes: testo 420 flow hood base, 24″ x 24″ flow hood, USB cable, batteries, soft case w/ telescoping handle and wheels.

Additional information