I am using camera traps a with passive infrared sensor for my research and last week I decided to test their detection zones. I expected to find detection zone looking like this:
with a certain angle and range in which the sensor would operate, but instead I kept finding that the camera would only detect within a more 'rounded' zone:
Is this normal for passive infrared sensors? Or is it a consistent measurement error? Someone mentioned directivity to me but I have not been able to understand how that applies here. I hope this is the right place to ask, otherwise please point me in the right direction.
Best Answer
PIR sensors work by focusing several narrow "zones" within the field of view onto a pyroelectric sensor. When a warm body moves into and out of these zones, it is the amplitude of the AC signal produced by the sensor that triggers a detection.
The effective sensitivity of the detector across its field of view depends on many factors in addition to an object's distance from the sensor, such as the size and temperature of the moving body, its speed and direction, etc.