This application is designed to connect any occupancy sensor with dry contact outputs. Usually, PIR (Passive Infrared) sensors are used for this purpose. The PIR sensors are commonly called simply “PIR”, or sometimes “PID”, for “passive infrared detector”. The term passive refers to the fact that PIR devices do not radiate energy for detection purposes. They work entirely by detecting the changes of infrared radiation (radiant heat) emitted by or reflected from objects in their field of view. The PIR sensors are commonly used in security alarms and automatic lighting applications to detect general movement. These sensors are usually readily available, inexpensive, and come in a variety of designs, directional characteristics, etc.
Since detectors differ in sensitivity, viewing angle, distance, location, etc., one universal sensor cannot be designed to cover all types of rooms and installations.
Because conventional cheap sensors mainly detect the movement of people in the room, it limits their ability to detect the mere presence of people in the room. If people sit at tables and act or watch a presentation, it may happen that the detectors do not record any movement after some time and therefore evaluate the room as empty. For these reasons, it is possible to set the time during which the room is marked as busy after motion detection, even if the sensors do not detect any movement. When sensors are used to automatically confirm meetings in a room, mere motion detection is in most cases sufficient because people in the room usually come, leave, and move at the beginning of the meeting. However, if the sensors are to be used to detect a room exit during a meeting and to cancel a meeting in the room calendar, we recommend using more sophisticated (and more expensive) sensors that use technologies other than PIR to evaluate the presence of people, such as those based on temperature changes, active IR technology, microwave radar, evaluation of camera images, etc. Such sensors are called “Presence Sensor”, “True Presence” etc.