Quick answer: The testo 810 combines a non-contact infrared surface-temperature reading with an integrated air-temperature measurement. Select a suitable matte target, keep the measured area inside the 6:1 optical spot, allow the instrument to settle and compare air and surface readings. A laser marks the approximate aim; it does not measure temperature.
What is special about the testo 810?
The testo 810 (0560 0810) is not just an IR gun. It includes an NTC ambient-air temperature sensor and reports the difference between the surrounding air and a sampled surface, useful for HVAC grilles, radiators and windows. Testo specifies infrared measurement from −30 to +300 °C (−22 to 572 °F), air measurement from −10 to +50 °C (14 to 122 °F) and 6:1 optics. It is a spot instrument, not a thermal-imaging camera. For a comparable instrument-focused discussion, see testo 830-T1 infrared measurement guide.
Measure a surface without confusing the spot
- Check the instrument condition, lens and batteries. Confirm the target is within the specified IR temperature range.
- Choose a uniform, opaque, largely matte target. Be wary of polished metal, reflective foil and glass; emissivity and background reflections can dominate the apparent temperature.
- Estimate the spot: with 6:1 optics, a target approximately 60 mm across corresponds to about 360 mm measurement distance under ideal geometry. Leave a margin for alignment and the instrument’s real optical response.
- Aim with the laser, keep the entire field on the intended material and record the IR reading without aiming at eyes.
- Record the ambient-air value after the air sensor has equilibrated away from a hot hand, drafts or sunlight.
- For critical accuracy, cross-check with a suitable contact probe or manufacturer-approved emissivity treatment.
Worked example: surface-to-air temperature difference
Hypothetical check: air temperature is 21.5 °C (70.7 °F) and a painted wall reads 16.0 °C (60.8 °F). The difference is 16.0 − 21.5 = −5.5 °C: the surface is 5.5 °C cooler than the sampled air. This indicates a cooler apparent surface, not by itself a condensation event. Relative humidity and dew point must be measured separately to assess condensation risk. For a separate assessment of surface condensation risk, see condensation and dew-point risk.
Typical errors
| Error | Effect | Correction |
|---|---|---|
| Target smaller than spot | Background mixes into reading | Move closer within safe optical limits |
| Polished pipe or foil | Reflections/emissivity bias | Use suitable contact measurement or approved surface treatment |
| IR aimed through glass | Often measures glass-related radiation, not the remote surface | Measure accessible target directly |
| Air sensor near hand or heat source | Ambient comparison is not representative | Allow equilibration at representative location |
What the testo 810 cannot tell you
It cannot measure internal food temperatures, hidden leaks or the moisture content of a wall. Its optical measurement is a surface estimate affected by emissivity, reflections, distance and spot size. The 6:1 optics means it is better suited to larger targets at short distances than small components across a room. For a focused explanation of emissivity, reflections and target size, see IR reflective tape and spot size.
Official reference
See the testo 810 official product page and instrument manual for optical and environmental limits.