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Temperature compensation of the motion sensors

Motion sensors track the movement of the thermal object. The person and other objects for the sensor are perceived as thermal spots. The sensor tracks these heat spots, and if they move, the sensor will give an alarm.

The motion sensor reacts to the motion of bodies with the temperature close to the temperature of the human body. In the case when the room temperature is approximately equal to the body temperature of the person (for example, in the Summer), in this case, the correct operation of the sensor is not guaranteed unless temperature compensation is introduced.

The temperature compensation technique is used in the following Ajax sensors:

  • Motion Protect
  • Motion Protect Plus
  • Combi Protect

Temperature compensation is used to allow the sensor to recognize human movement, even if the room/object temperature is approximately equal to the human body. This is implemented programmatically, at the level of the sensor. The sensor periodically measures the temperature for the correction. The sensor uses a table of correction factors, these coefficients depend on the temperature measured by the processor of the sensor. Correction factors are used at temperatures from 14 to 42 degrees. These correction factors help the sensor to adequately detect and detect the human movement at a close to human temperature environment.

For example, the temperature of the room is 36 degrees Celsius, in this case, a person with a temperature comparable to the room temperature moves in the room.

Changes in the picture (signal) from the sensor will be insignificant since the person for the sensor almost merges with the background due to a small difference in temperature. Using correction factors, the base signal from the sensor at the software level is processed and when the warm body moves the signal changes will be much larger, which will allow detecting movement even in the case of a very small temperature difference between the human body and the background/room.

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