Motion sensors detect the movement and, in some special cases, the presence of objects. These are usually people or animals, but objects can also be detected. This must be distinguished from inertial sensors which detect the movement of the sensor itself, i.e. its linear acceleration or rotation. The motion sensors in our portfolio are based on different principles: Pyrosensors (passive infrared or PIR for short) detect people based on the heat radiation emitted by them. Radar sensors use harmless high-frequency radiation to measure the speed or distance of objects. Thermopile arrays can be used to generate two-dimensional images that can be used to identify objects against a generally colder background and track their movement.