Electronic – Sensors that are also actuators


this is more of a theoretical question, and I do not know if this is suited for this QA site at all, but at school I was asked to provide 3 examples of sensors (in the narrow sense) that are also actuators.
I cannot find any information for the life of me. The only example I can find are piezoelectric sensors, but I am not sure if this is correct.

A sensor in the narrow sense is a device which reacts to a signal/stimulus from a electrical signal.

Best Answer


  • (As you said) a piezoelectric transducer. It can produce sounds, or work as a microphone.
  • An electromechanical speaker. The same device can act as a speaker, or as a microphone (old walkie-talkie toys use that fact).
  • Even an LED. If you apply forward current through an LED, it produces light, and it is an actuator. If you bias it with a reverse voltage, and measure the reverse current (very low), you can measure light with it, and it will be a sensor.
  • An antenna. It can transmit and receive (even simultaneously, at different frequencies, or using other discrimination schemes).
  • An electric motor. You can use it to produce and to detect (and measure) movement.
  • Even an NTC/PTC resistor (which is supposed to be "only" a sensor), could also work as an actuator, if I inject enough current so as to modify its temperature, and that of its surroundings. I could use it to keep a (very) small mass at a constant temperature, in a low ambient temperature environment, and a single device would suffice as a sensor and actuator.