testo 400 – Universal IAQ instrument

  • Smart, intuitive measurement programs including HVAC grid measurement as per EN ISO 12599 and ASHRAE 111, PMV/PPD and turbulence as per EN ISO 7730 and ASHRAE 55
  • High-precision, location-independent and integrated differential pressure sensor
  • Measure all IAQ-related parameters – with our wide range of probes for all IAQ measurements
  • Document measuring values directly on the customer’s site and send them by e-mail, or further analyze them using the testo DataControl PC software


The testo 400 is the universal measuring instrument for all IAQ professionals. Measure, analyze and document all IAQ and comfort level parameters using just one instrument – simply, conveniently and in compliance with the standards. High-quality measuring technology, intuitive measurement assistants, versatile documentation options and a comprehensive selection of IAQ probes make the testo 400 the perfect partner for your day-to-day work.


Product Description

As an expert in the field of air conditioning and ventilation, you will find the testo 400 universal IAQ measuring instrument ideal. The IAQ measuring instrument with a built-in measurement assistant provides optimum support for carrying out air flow and comfort level measurements in accordance with the standards, as well as for adjusting and inspecting air conditioning and ventilation systems.

testo 400 universal IAQ instrument – features

Impressive IAQ measurement technology

  • High-precision, location-independent, built-in differential pressure sensor
  • Integrated absolute pressure sensor
  • Measures all IAQ-related parameters: Flow velocity, temperature, humidity, pressure, illuminance, radiant heat, turbulence, CO2 and CO
  • Numerous connection options for probes: 2 x cable probes (TUC), 4 x Bluetooth® probes, 2 x type K thermocouple probes
  • Compatible with a wide range of available Bluetooth® and cable probes – so you’ll be equipped for any measuring task
  • Compatible with the testo 420 volume flow hood: Simply connect to the testo 400 via Bluetooth, measure volume flow at larger air inlets and outlets and manage all customer and measuring site data on site using one measuring instrument
  • For high-precision measurements and less downtime: Adjustment function at up to six measuring points for zero-error display, probe heads can be replaced without restarting the IAQ measuring instrument, high-quality probes with an intelligent calibration concept (probe calibration independent of the measuring instrument)
  • Long-term monitoring of the indoor air quality: Order the IAQ data logger for carrying out long-term measurements with the testo 400 IAQ measuring instrument. While the stand-alone data logger is carrying out the IAQ measurement, you can use the IAQ measuring instrument for measurements elsewhere

Smart, intuitive, practical: Measurement programs, measurement data management and operation

  • For error-free measurements in accordance with the standards: Smart, intuitive measurement menus and evaluation of readings provide optimum support for your measuring task. Use the measurement programs for standard-compliant measurements: HVAC grid measurement as per EN ISO 12599 and ASHRAE 111, PMV/PPD as per EN ISO 7730 and ASHRAE 55, draught and turbulence as per EN ISO 7730 and ASHRAE 55, WBGT measurement as per DIN 33403 and EN ISO 7243, NET measurement as per DIN 33403
  • Complete the measurement along with full documentation including photos, comments and your own logo at the customer’s premises, and send by e-mail (via WLAN)
  • Customer and measuring point management is carried out on the measuring instrument itself – for efficient work on site.
  • Smart-touch display for intuitive operation of the IAQ measuring instrument
  • testo DataControl PC software for further analysis, archiving and documentation of measurement data on your computer
  • Built-in WLAN and Bluetooth® interfaces: Send measurement reports directly on site or print them out with a suitable printer

Delivery Scope

1 x testo 400 universal IAQ instrument, including transport case for air flow measurements, connection hose, mains unit with USB cable, calibration protocol and instruction manual.

Technical Data

Temperature – NTC
Measuring range -40 to +150 °C
Accuracy ±0.2 °C ±1 Digit (-25 to +74.9 °C)

±0.4 °C ±1 Digit (-40 to -25.1 °C)

±0.4 °C ±1 Digit (+75 to +99.9 °C)

±0.5 % of mv ±1 Digit (Remaining Range)

Resolution 0.1 °C
Temperature – TC Type K (NiCr-Ni)
Measuring range -200 to +1370 °C
Accuracy ±(0.3 °C + 0.1 % of mv) ±1 Digit
Resolution 0.1 °C
Differential pressure (internal sensor) – Piezoresistive
Measuring range 0 to +200 hPa
Accuracy ±(0.3 Pa + 1 % of mv) ±1 Digit (0 to 25 hPa)

±(0.1 hPa + 1.5 % of mv) ±1 Digit (25.001 to 200 hPa)

Resolution 0.001 hPa
Absolute Pressure (internal sensor and external probe)
Measuring range 700 to 1100 hPa
Accuracy ±3 hPa
Resolution 0.1 hPa
General technical data
Weight 510 g (instrument)
Dimensions 210 x 95 x 39 mm ((LxWxH))
Operating temperature -5 to +45 °C
Product-/housing material Plastic
Protection class IP40
Connectable probes 4 x digital Bluetooth® probe or testo Smart Probe; 2 x digital probe with fixed cable or temperature probe NTC with fixed cable (via Testo Universal Connector – TUC); 2 x temperature probe TC type K with fixed cable
Product colour black/orange
Camera image size Main camera: 8.0 MP; Front camera: 5.0 MP
Battery life approx. 10 hrs continuous operation
Display type 5.0″ touch display, HD 1280*720 pixels, IPS (160 k)
Power supply Rechargeable li-ion battery (5550 mAh)
Interface Bluetooth®; USB; WLAN
Memory 2 GB; 1,000,000 measuring values
Storage temperature -20 to +60 °C