Sensors collect data from the environment, actuators produce physical changes, and transducers convert energy or signals from one form into another. Together, they allow a control system to monitor conditions, process data, and control a physical process.
A sensor measures a physical property such as temperature, pressure, light intensity, or distance. It converts that property into a signal that a computer can process, so a sensor is a type of input transducer.
An actuator receives an output signal from the controller and causes a physical action. For example, a motor turns, a valve opens, or a heater increases temperature. Actuation normally involves output transduction, because an electrical control signal is converted into movement, heat, sound, or another physical effect.
A transducer is the broader category: any device that converts one form of energy or physical quantity into another.
| Component | Role in the control system | Example |
|---|---|---|
| Sensor | Collects environmental data as system input | A thermistor measures temperature |
| Transducer | Converts energy or a physical quantity into another form | A microphone converts sound into an electrical signal |
| Actuator | Converts a controller's output into physical action | A motor rotates a cooling fan |
In a closed-loop control system, the process is:
- A sensor measures the current condition.
- The signal may be converted by an analogue-to-digital converter.
- The processor compares the measured value with a set point.
- The processor sends an output signal to an actuator, sometimes through a digital-to-analogue converter or driver.
- The sensor measures the new condition, providing feedback.