What method does a PIR use to detect?

What method does a PIR use to detect?

• A. Change of climate
• B. Infrared radiation changes
• C. Sound waves
• D. Magnetic field

Answer: (A)

A PIR detects changes in infrared radiation. It uses a pyroelectric sensor to sense IR energy emitted by objects in its view. When a warm body moves, the pattern of infrared energy reaching the sensor changes, producing a signal that triggers the alarm. It’s passive, meaning it doesn’t emit energy itself; it only senses what’s already radiated by people or objects. Change in climate isn’t what it measures, heat from moving bodies is detected as a changing IR pattern, not a general climate change. Sound waves require a microphone or acoustic sensor, and magnetic fields are detected by a magnetometer, not a PIR.

A PIR detects changes in infrared radiation. It uses a pyroelectric sensor to sense IR energy emitted by objects in its view. When a warm body moves, the pattern of infrared energy reaching the sensor changes, producing a signal that triggers the alarm. It’s passive, meaning it doesn’t emit energy itself; it only senses what’s already radiated by people or objects.

Change in climate isn’t what it measures, heat from moving bodies is detected as a changing IR pattern, not a general climate change. Sound waves require a microphone or acoustic sensor, and magnetic fields are detected by a magnetometer, not a PIR.