Technical article about the measuring distance of pyrometers, infrared thermometers and infrared temperature sensors. One question we are often asked is:
How far in distance can I measure with a pyrometer, infrared thermometer or infrared temperature sensor?

This depends on several influencing factors:
• Size and material of the measurement object
• Surface texture of the measurement object
• Surface temperature of the measurement object
• Ambient temperature around the sensor or the measurement object
• Heat sources around the measurement object
• Measuring distance of the pyrometer to the measurement object

On the device side:
• Optical resolution

Example:
A very hot and large measurement object has a higher thermal radiation and can be measured from a greater distance (with a pyrometer, which has the appropriate wavelength for metal measurements) than a very small measurement object, which only has a surface temperature of 30°C.
The further the measuring distance from the measuring object to the pyrometer, the lower the heat radiation that can still be detected by the sensor electronics.

In order to achieve a precise measurement result, it is recommended to position the sensor as close as possible to the object to be measured when the measuring object has a low surface temperature.
The measurement object should completely fill the measurement spot of the sensor optics.
See also our Wiki/Glossary article here https://www.novasens.de/en/optical-resolution/

The optical resolution (distance to spot ratio) of the sensor optics should be suitable for the desired measuring distance and target size.

Our IR402 and IR702 pyrometers and the HighTemp 530 infrared thermometer are suitable for further measuring distances. Information on the optical resolutions can be found in the respective data sheets.
To be on the safe side, the pyrometer should be tested for the application beforehand.