Passive Infrared Sensors
PIR (Passive Infra-Red) sensor is a device that measures infrared light radiating from objects in its field of view. They are typically used in automatic lighting applications and security alarms.
Infrared radiation is electromagnetic radiation with longer wavelengths than those of visible light and is therefore generally not visible to the human eye. Thermal radiation, emitted by warm or hot objects is mostly infrared, therefore not only humans motion may trigger PIR sensor.
Plume Pod Installations with PIR
While operating, Plume Pods (in all variants) produce heat which radiates through the housing surface out. According to Plume lab tests, this radiation may be intensive enough to trigger PIR sensor when Pod is in the PIR sensor’s field of view and close enough to it. The distance between the Pod and the sensor which will trigger the sensor depends on current thermal radiation power emitted by Pod, sensitivity of the sensor (most of the sensors allows user to set level of sensitivity within certain range) and how large portion of the Pod’s radiation is within the sensor’s field of view.
As warmer the Pod is, higher its temperature is and more thermal radiation (heat) it emits. This depends on Pod’s activity which corresponds to its load - more (wireless) clients served means more load, low channel gains contribute to more load than high ones, also running speed test on the Pod increases its load, etc.
Pod installation Guidelines
Since thermal radiation from Pod is fact, and PIR sensors are triggered by thermal radiation is fact as well, we cannot avoid sensors false triggering under certain circumstances. Therefore we recommend positioning Pod 75 cm (2.5 ft) away from PIR sensor when the Pod is within the sensor’s field of view.
It is common that PIR sensors' field of view covers 180 degrees horizontally and 180 degrees vertically, meaning Pod plugged near the sensors built-in the wall (as the one in the figure below) will be within sensor's field of view.
Otherwise, if Pod is not within the sensor’s field of view, they can be closer, but being at least 10 cm (4 in) apart is strongly recommended.
As there are many various makes and models of PIR sensors, the above are recommendations only - some sensors may perform well with shorter distances, while others may require positioning Pods farther away from PIR sensors.