ESA Certified Alarm Technician Practice Exam

A PIR sensor is designed to detect which of the following environmental factors?

1. Changes in Sound

2. Changes in Light

3. Changes in Infrared Energy

4. Changes in Pressure

The correct answer is: Changes in Infrared Energy

A Passive Infrared (PIR) sensor is specifically designed to detect changes in infrared energy. These sensors operate based on the principle of detecting the heat emitted by objects, particularly living beings. When a person or animal moves in the detection area, the PIR sensor registers the change in infrared radiation in that zone, allowing it to trigger an alarm or alert system. The functioning of a PIR sensor is centered around the detection of infrared signals that vary with the temperature of the surrounding environment. When a warm body, such as a human or an animal, enters the sensor's field of view, it causes a shift in the infrared energy detected by the sensor, which then activates the device. In contrast, the other listed factors—sound, light, and pressure—are not the primary functions of a PIR sensor. Sound detection would require microphones or acoustic sensing devices, light changes would pertain more to photoelectric sensors, and pressure changes would require pressure transducers. Thus, the focus of PIR technology on infrared energy distinguishes it from these other types of environmental detection methods.