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Climate measurement improved to the maximum.

The universal air velocity & IAQ measuring instrument testo 400

The universal air velocity & IAQ measuring instrument testo 400

One measuring instrument for all climate-related parameters

  • The right probe to hand for every application: Flexible, mutually compatible Bluetooth and cable probes for measuring all climate-relevant parameters

  • Intelligent calibration concept: Calibration of the probes or probe heads independent of the measuring instrument

Individual applications

What would you like to measure? Find out about your individual application area here.

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testo 400 – the multitasker for IAQ professionals

  • Measures all IAQ-related parameters: Flow, temperature, humidity, pressure, illuminance, radiant heat, turbulence, CO2 and CO

  • High-precision, location-independent and integrated differential pressure sensor

  • High-quality digital probes and an intelligent calibration concept

Smart support

Stored measurement menus and evaluation of measurement values according to the traffic light principle – for error-free measurements.

  • VAC grid measurement as per EN ISO 12599

  • PMV/PPD in accordance with EN ISO 7730

  • Draught and degree of turbulence in accordance with EN ISO 55

  • WBGT measurement in line with DIN 33403 and EN ISO 7243

  • NET measurement in accordance with DIN 33403

Determination of volume flow in ducts using grid measurement in accordance with EN 12599

  • For all flow velocity probes (hot wire, vane) and Pitot tubes

  • Input of duct geometry and duct apertures

  • Single-point or timed measurement

  • Automatic display of insertion depths for traversing duct

  • Duct distribution for rectangular ducts according to the trivial method, and for circular ducts according to the centroidal axis method

  • Calculation of measurement uncertainty according to EN 12599

Work efficiently on site – no workarounds, just on to the next job

  • Manage and save all relevant customer data including measurement locations directly in the instrument

  • Complete and send measuring values with full documentation, including photos, comments and your own logo directly on site – and get to the next job faster

Customer testimonials for testo 400

For us as a technical service provider for air conditioning and ventilation systems, testo 400 is our preferred instrument with its versatility and convenient data management functionalities. It's very easy to use and, most importantly, provides reliable readings.

Jean-Marie Leroy



We use testo 400 to determine reliable results of the indoor climate. Here the measuring programs for PMV/PPD and draught rate are already stored in the instrument. The flexible attachment of various probes is another plus point of the testo 400 for me. If my applications expand in the future, I can simply purchase additional probes. If a probe breaks or needs calibration, I can send it to the service department separately and continue to use the measuring instrument in the meantime.

Wolfgang Lochner



The IAQ measuring instrument testo 400 makes you a measurement data billionaire. Because with its huge memory, we don't have any more headaches about data management and documentation.

Omar El Masry



The wireless probes, simply designed touch display and magnetic mount for attaching to ducts make it quite easy to use. In addition, the calibratability of the instrument and accessories as well as the high accuracy are crucial for the pharmaceutical customers we support as a service provider for technical facility management.

Annette Groth



Product video

The universal air velocity & IAQ measuring instrument testo 400 with smart touch technology.

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testo 400 brochure

All information on the measuring instrument, probes and accessories compactly summarized.

More information about air velocity & IAQ measuring

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