MEMS and sensors

Which sensor, widely used in motion sensors that turn on lights when a person approaches, uses a material that generates charge when its temperature changes?

  1. APyroelectric infrared sensor
  2. BHall element
  3. CStrain gauge
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Answer: A. Pyroelectric infrared sensor

A pyroelectric infrared sensor uses a pyroelectric material whose surface develops charge when its temperature changes, detecting changes in the infrared radiation emitted by the human body. Because it responds only to changes, it produces a signal when a person moves. Combined with a Fresnel lens, it is used in motion sensors for lighting and security.

  • A. Correct. It detects changes in infrared via the pyroelectric effect.
  • B. A Hall element detects magnetic fields.
  • C. A strain gauge measures the resistance change caused by deformation.
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