testo 845 - Infrared temperature measuring instrument with integrated humidity module

Order-Nr.  0563 8451

  • Switchable optics for far-field (75:1) and close-focus (1 mm, distance 70 mm) measurements

  • Humidity module for determining surface moisture

  • Instrument memory for 90 measurement protocols

  • Visual and acoustic alarm if limit values exceeded

The testo 845 infrared thermometer enables non-contact measurement of the temperatures of a really wide range of surfaces. In addition, you can determine the ambient air humidity and the dew point distance with the integrated humidity module – and thus for instance detect mould at an early stage.


Product Description

The temperature measuring instrument is ideally suited for non-contact measurement of surface temperatures, both at short and long distances. And surface moisture can also be assessed using the infrared thermometer, thanks to the integrated humidity module.

Areas of application for the testo 845 infrared thermometer with humidity module

Applications for building services / air conditioning technology:
  • Early detection of mould: fast scanning of walls using non-contact measurement to assess the room and wall conditions, discover thermal bridges and detect mould
  • Checking the temperature on ventilation ducts
  • Determining heat profiles and thermal insulation in buildings

Industrial applications:
  • Temperature measurement on switching cabinets, refrigeration units, generators and drives, along with plastics in drying processes

Applications in heating engineering:
  • Surface measurement on radiators, painted heating pipes
  • Measurement of floor coverings to locate heating pipes

The advantages of the testo 845 temperature measuring instrument with integrated humidity module

The infrared thermometer calculates the surface moisture from the surface temperature and dew point of the air. This means that ceilings and walls that are at risk of developing mould can be more quickly located.

Far-field measurement means that surface temperatures can be measured very precisely at a great distance from the measurement object. At a distance of 1.2 m from the measurement object, the measuring spot diameter is only 16 mm. Bright cross-laser marking is used to indicate the real measuring spot.
For measurements a short distance from the measurement object, the close-focus optics provide a measuring spot diameter of only 1 mm at a distance of 70 mm. In the process, two laser points mark the measuring spot.
In order to switch from far-field to near-field (close-focus) measurements, simply move the slide switch on the infrared temperature measuring instrument to the appropriate position.

As an option, you can carry out additional measurements, such as determining the emission level, via attached temperature probes (the probe socket is located underneath the handle) for an even more accurate measurement result.

Delivery Scope

testo 845 infrared temperature measuring instrument with integrated humidity module, including case, calibration protocol, batteries, USB data cable and PC software.

Technical Data

General technical data


465 g


155 x 58 x 195 mm

Operating temperature

-20 to +50 °C

Product-/housing material

black/gray, metal screen

Measuring rate

t95: 150 ms; Scanning Max/Min/Alarm: 100 ms

Optical resolution far field

75:1 16 mm @ 1200 mm (90%)

Optical resolution close focus

1 mm @ 70 mm (90%)

Battery type

2 AA mignon batteries

Battery life

25 h (without laser), 10 h (with laser without light), 5 h (with laser and 50% light)

Storage temperature

-40 to +70 °C

Temperature - TC Type K (NiCr-Ni)

Measuring range

-35 to +950 °C


±0.75 °C (-35 to +75 °C)

±1 % of mv (+75.1 to +950 °C)


0.1 °C

Temperature - Infrared

Measuring range

-35 to +950 °C


±2.5 °C (-35 to -20.1 °C)

±1.5 °C (-20 to +19.9 °C)

±0.75 °C (+20 to +99.9 °C)

±0.75 % of mv (+100 to +950 °C)


0.1 °C

Attachable humidity module - Capacitive

Measuring range

0 to +100 %RH

0 to +50 °C

-20 to +50 °Ctd


±2 %RH (2 to 98 %RH)

±0.5 °C (+10 to +40 °C)

±1 °C (Remaining Range)


0.1 °Ctd / 0.1 %RH



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