Passive and active sensors
What is the difference between passive and active sensors? Professor Richard Mitchell explains more.
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A passive sensor is one which just ‘listens’ to what is happening. Examples include:
- A light sensor which detects if a light is shining on it
- An infra-red sensor which detects the temperature of an object
An active sensor is one which transmits a signal into the environment and then measures the response that comes back.
One example is an ultrasonic system:
- A pulse of ultrasound is emitted
- If an object is in the way, the pulse is reflected back
- The sensor detects it
- The time taken between emission and detection gives an indication of the distance of the object.
Hence an active sensor has an actuator and a sensor. In the next step you can find out more about this in Richard’s demonstration on echo location.
© University of Reading
