Ensuring the emissivity setting is correct is particularly crucial where there are large differences in temperature between the measuring object and the measuring environment.
Setting emissivity
When the temperature of the measurement object is higher than the ambient temperature:
- emissivities set too high result in too low temperatures in the thermal image.
- emissivities set too low result in too high temperatures in the thermal image.
When the temperature of the measurement object is lower than the ambient temperature:
- emissivities set too high result in too high temperatures in the thermal image.
- emissivities set too low result in too low temperatures in the thermal image.
Tips on emissivity
- The greater the difference between the temperature of the measuring object and ambient temperature and the lower emissivity is, the greater the measurement errors. These errors increase if the emissivity setting is incorrect.
- Many materials which are transparent for the human eye, such as glass, are not permeable for long-wave infrared radiation.
- Among the few transmissive materials are, for example, thin plastic sheets and Germanium, the material from which the lens and the protective glass of a Testo thermal imager are made.
- If necessary remove any covering over the measurement object, otherwise the thermal imager will measure only the surface temperature of the covering.
- Always observe the operating regulations of the measurement object.
- If elements which lie under the surface influence the temperature distribution of the measurement object's surface through heat conduction, one can often identify structures from the interior of the measurement object in the thermal image. Nevertheless, the thermal imager only ever measures the surface temperature. An exact statement about the temperature values of elements within the measuring object is not possible.
Practical thermography
Find out in our compact tutorial how to turn theoretical basics and the right thermal imager into meaningful thermal images in practice.
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