Testo 420 Volume Flow Hood



  • Volume flow hood for larger swirl outlets for measuring volume flow, temperature and relative humidity
  • Impressively light with a weight of 2.9 kg
  • Precise measurement even at swirl outlets thanks to integrated volume flow straightener
  • Fast set-up, convenient usability and practical functions such as measurement data management and on-site report creation via testo Smart App


+ Temperature – NTC:

Measuring range: -20 to +60 °C


±0.5 °C (0 to +60 °C)

±0.8 °C (-20 to +0 °C)

Resolution: 0.1 °C

Reaction time: 45 s (t₉₀)

+ Humidity – Capacitive

Measuring range: 0 to 100 %RH


±1.8 %RH + 3 % of mv at +25 °C

(5 to 80 %RH)

Resolution: 0.1 %RH

+ Differential Pressure – Piezoresistive

Measuring range: -120 to +120 Pa

Accuracy: ±2 % of mv + 0.5 Pa at +22 °C, 1013 hPa

Resolution: 0.001 Pa

Reaction time: 1 s (t₉₀)

+ Absolute Pressure

Measuring range: 700 to 1100 hPa

Accuracy: ±3 hPa

Resolution: 0.1 hPa

Reaction time: 1 s

+ Volume flow

Measuring range: 50 to 4000 m³/h


±3 % of mv + 12 m³/h at +22 °C

1013 hPa (85 to 3500 m³/h)

Reaction time: 1 s (t₉₀)

Resolution: 1 m³/h

+ General technical data

Weight: 2900 g

Dimensions: 610 x 610 mm (Standard hood)

Operating temperature: -5 to +50 °C

System requirements: requires iOS 12.0 or newer; requires Android 6.0 or newer; requires mobile end device with Bluetooth 4.0

EU-/EG-guidelines: EU-guideline 2014/30/EU

Battery type: Alkali manganese, mignon, type AA

Battery life: 40 h

Display size: 3.5″

Display function: Dot matrix

Display ligthing: with illumination

Interface: Micro-USB; Bluetooth® 4.0 wireless technology

Data transfer: Bluetooth®

Radio range: 10 m

Memory: 2 GB (internal)

Storage temperature: -20 to +60 °C

Introduction Testo 420 Volume Flow Hood

The testo 420 volume flow hood is designed for larger air inlets and outlets, ensuring rapid and accurate adherence to hygiene guidelines and room air quality requirements. It offers dependable assistance in calculating the total volume flow in HVAC systems, making it particularly valuable in environments such as hospitals, office buildings, and commercial facilities.

Máy đo vận tốc lưu lượng gió Testo 420 (8)

Features Testo 420

1. High measuring accuracy at swirl outlets thanks to volume flow straightener

Measurement of volume flow is commonly conducted at swirl outlets, where turbulent air can often lead to inaccurate readings.

By utilizing the testo 420 volume flow hood, these measurement inaccuracies can be greatly minimized. The built-in volume flow straightener effectively reduces turbulence and transforms it into a more uniform airflow. This enables precise calculation of volume flow within the range of 80 to 3,500 m3/h.

2. Exceptionally light volume flow hood with fast set-up

The volume flow hood is equipped with ergonomic handles and a tiltable display, making it lightweight at under 2.9 kg. This allows for reliable and comfortable volume flow calculations in large rooms and measurements above head height. The hood features a large measuring button for easy recording of readings.

With dimensions of 610 x 610 mm, the hood can be supplemented with additional hoods for ceiling outlets. For air inlets and outlets located at great heights, our optional tripod arm provides valuable assistance, extending up to 4 meters.

Setting up the volume flow hood is quick and easy, thanks to tension rods. The included trolley ensures safe transport.

3. Create protocols directly on site and mail them using the App connection

Make the most of additional convenient features by downloading our free App. By connecting the App to the volume flow hood via Bluetooth, you can utilize mobile devices like smartphones and tablets as secondary displays and remote controls. This is particularly useful when using a tripod arm for high ceilings.

The App allows for live measurements on HVAC systems, offering start and stop functions, as well as the ability to save measurement data in txt format. On-site, you can create measurement protocols directly within the App. Measurement results, such as overall volume flow and air exchange rate, can be directly assigned to customized protocol templates for specific customers. You can then easily send your readings and protocols via the email function, saving significant time and increasing efficiency.

4. Volume flow hood with removable measuring instrument – performance overview

The volume flow hood designed for HVAC systems is equipped with a user-friendly measuring instrument that displays measurement data. The instrument can be tilted and removed for easy reading of measured values.

With the testo 420 measuring instrument, you can measure flow velocity, volume flow, absolute pressure, temperature, and relative humidity. The automatic zeroing feature ensures higher accuracy for low pressures.

All measurement values are clearly displayed on the large illuminated screen. For analysis and documentation purposes, measurement data can be saved and measurement protocols can be created directly on-site using the App connection. Managing measurement data is simple on a PC without the need for additional software, thanks to the plug & play function.

The testo 420 volume flow hood, with its integrated measuring instrument, is not only designed for volume flow measurement at larger ceiling outlets. The measuring instrument can also be detached from the hood and used for pressure, flow, and volume flow measurements in the duct. This eliminates the need for purchasing an additional measuring instrument.

To conduct measurements in ducts, simply attach a Pitot tube and optional connection hoses. Timed and multi-point mean calculation, as well as their combination, along with easy input of duct geometry, provide support for accurate measurements in ducts.



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