Multiple choiceQuestion 1 · Recall
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By the end you can choose the right sensor for a monitoring or control job, and say what an actuator does in a control system.
A processor in a box knows nothing about the room it's in. Sensors are its senses: they measure the world and turn it into signals.
Actuators are its muscles. They turn the processor's signals back into movement in the real world.
Sensor
An input device that measures a physical quantity (such as temperature or pressure) and sends the measurement to the computer as a signal. Most sensors give an analogue signal, so an ADC converts it to digital.
| Sensor | Measures | Example uses |
|---|---|---|
| temperature | how hot or cold something is | central heating, greenhouse, fridge, car engine |
| pressure | the force pressing on it, or the pressure of a gas or liquid | burglar alarm pressure pad, car tyre warning, water level in a washing machine |
| infra-red | infra-red radiation: body heat moving, or a beam being broken | burglar alarm motion detector, automatic doors, counting people through a gate |
| sound | sound level (a microphone) | noise monitoring near an airport, detecting breaking glass, voice-activated devices |
Others you may meet: light (street lights), humidity or moisture (greenhouses, watering), pH (river pollution).
Worked example: Easy first: pick the sensor
A home security system must notice three things. Choose a sensor for each.