How to manually calibrate a Thermal Sensor

1. Are there any parasitic drags?

Make sure that there are no parasitic drags close to the object you are trying to measure. Be aware that objects reflect radiation from other heat sources, especially metals and glasses.

Hint: Before installation check with the thermal camera the surrounding area for parasitic drags, such as:

  • Heating or cooling systems

  • Objects between the thermal sensor and the object to be measured

  • Water vapor etc.

2. Determine the emissivity of your object

The emissivity of a body is determined by:

  • Its material

  • The kind of surface

  • Its temperature

  • The wave length

  • The angle of measurement

Please find attached the emissivity values of different materials. Thermal sensors can measure accurately the temperature of objects with an emissity of > 0.5. A possible solution for objects < 0.5 is to put a label with a high and known emissivity on the material to be measured. One can measure this spot in particular and receive an accurate measurement.

Example: Fill up a metal mug with boiling water and put a standard fiber tape on a surface. The surface of the tape displays the correct temperature of the mug.


The picture above is showing that different surfaces have different emissivity values.

3. What is the atmospheric temperature?

Figure out the temperature between the sensor and the target. In the best case the temperature stays the same throughout the day. If not, set the average temperature. Please be aware that the accuracy of
measurement will be affected by setting an average value.

4. Transmissity of the air between the thermal sensor and the object to be measured?

The transmissity is determined by two parameters: The distance and the structure of the atmosphere. In most applications the distance is fixed.

For adjustment of the the parameter atmospheric transmission the following is recommended:

  • Put a black-body or another object of which you know the the exact temperature
    (e.g. a person) next to the object you want to measure.

  • Adjust the parameter until the correct temperature is shown by the sensor.

5. Make test measurements under extreme conditions

Make test measurements once in a while to check if the parameters are set correctly.

-For example: Hot/Colddays, Day/Night, etc. Adjust if necessary.

Table of Emissivity values of Different Materials