PIR Motion Detector

This is the second kind of motion detector that can be bought. They're PIR, or Passive Infra Red motion detectors and are the standard type of motion detector used in security equipment. PIR detects motion when an infra-red emitting source with one temperature, such as a human body, passes in front of a different source with another temperature, such as a wall. Since the PIR motion detectors detect this infra red in the same way that an Infra-Red Thermal Imaging determines what is being recorded, it can be assumed that the mere movement of a small, localised source of heat or cold can trigger the alarm. Again, these motion detectors, when used on previous investigations, have had relative success in this context. Another use for them is that they can also be used when a trigger object has been set up so that it would make it impossible for any individual to be able to go and unscrupulously move something.