Infrared motion sensor IP65, PIR MB-115

The passive infrared motion sensors (PIR) are sensing the shift of heat emitted by creatures and in case of appropriate value of shift the relay inside of sensor switch. Because of this operational method the sensor have to see the moving object otherwise the relay will not switch.
The sensitivity of device for transverse movements is higher, for opposite movements is smaller so the devices including one sensor are recommended to install parallel with the expected direction of motion.