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Testo 635-1 Thermohygrometer

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Dual Probe Measurement 

Measurement of air moisture,
material equilibrium moisture, pressure dew point

U - Value probe connection 

Protection class IP54

Availability: In stock

Only 1 left
Exc. GST

Product Description

The Testo 635-1 temperature and humidity measuring instrument is ideally equipped for checking the air humidity, temperature and dew point in living areas, in production, storage and server areas and in museums and art galleries. Measurements of the ambient absolute pressure and dew point in compressed air can be quickly and efficiently carried out with the testo 635-1.

Attachable probes, which are available as an option, mean the measuring instrument can record the following values:

  • Air humidity
  • Material moisture
  • Pressure dew point in compressed air
  • Air temperature
  • Surface temperature
  • Core temperature
  • U-value
  • Absolute pressure

The Testo 635-1 temperature and humidity measuring instrument has two probe inputs for plug-in probes with cables. 

Robust, practical and easy to handle

In addition to readings, the Testo 635-1 temperature and humidity measuring instrument also displays min., max. and mean values.

When the pressure dew point probe is attached, it can measure the pressure dew point in compressed air. If a humidity probe is attached to the measuring instrument, it can also measure the dew point and water content of indoor air along with the psychrometric temperature, in addition to air humidity and air temperature.

The measuring instrument also calculates the dew point distance between indoor air and wall surface. In the event of mould in the home, this means you get an initial indication of whether mould has been caused by incorrect use of ventilation or by moisture ingress. You can find out more about the measurement of mould in the home with the testo 635-1 in the “Applications” tab.

The temperature and humidity measuring instrument is really easy to use and the menu guidance is user-friendly. The display with its illumination function means the readings are easily legible even when visibility is poor. A solid housing reliably protects the measuring instrument from impacts.

Documentation of measurement data with the Testo 635-1 temperature and humidity measuring instrument

Would you like to document your readings quickly and in a verifiable way? The optional Testo fast printer enables you to print out measurement data such as air humidity or temperature really easily at any time.

Use the practical cyclical printing function on the Testo 635-1. It not only enables the printout of individual readings, but also of whole series of measurements on the Testo fast printer at freely adjustable intervals (for example once a minute).


Technical Data

Storage Temperature -20 to + 50°C
Operating temperature -50 to + 45 °C
Battery Type  AA Alkaline 
Housing  ABS/TPE/Metal
Dimensions 220 x 74 x 46 mm


Instrument Sensor  

Sensor  Measuring range Accuracy Resolution
Type K (NiCr-Ni) -200 to +1370 °C ±0.5 °C (-60 to +60 °C) 
±(0.2 °C + 0.3% of mv) (remaining range)
0.1 °C
NTC (humidity probe) -40 to +150 °C ±0.2 °C (-25 to +74.9 °C)
±0.4 °C (-40 to -25.1 °C) 
±0.4 °C (+75 to +99.9 °C)
±0.5% of mv (remaining range)
0.1 °C
 Testo humid. sensor, cap. 0 to +100 %RH Please See Probe Data In Accessories 0.1 %RH
Absolute Pressure  0 to 2000 hPa Please See Probe Data In Accessories 0.1 hPa


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