NALMCO Certified Apprentice Lighting Technician (CALT) Practice Exam

PIR occupancy sensors use technology that detects changes in which of the following?

1. Changes in reflected sound waves

2. Changes in heat radiation

3. Changes in availability of daylight

4. All of the above

The correct answer is: Changes in heat radiation

PIR (Passive Infrared) occupancy sensors operate by detecting changes in heat radiation, specifically the infrared radiation emitted by living beings such as humans and animals. These sensors are designed to recognize variations in thermal energy within their field of view. When a person enters an area, their body heat creates a change in the infrared radiation profile, triggering the sensor to activate the connected lighting system or other connected devices. The other options reference different types of sensors or technologies. For instance, changes in reflected sound waves pertain to ultrasonic sensors, which detect sound waves bouncing off objects to determine occupancy. Meanwhile, detecting changes in daylight relates to photo sensors, which respond to ambient light levels. Since PIR sensors specifically focus on thermal changes, the correct choice accurately reflects their operating principle.