Sensor vs Actuator: What is the Difference Between Sensor and Actuator?

In any automation or control system, two components are fundamental: sensors and actuators. Although they are often mentioned together, their functions are opposite. Sensors supply the input data needed for decision-making, while actuators generate the output actions that change the state of the system.

Technical Definition of a Sensor

A sensor is a transducer that detects a physical quantity (e.g., temperature, pressure, light, displacement) and converts it into an electrical signal. The output is typically voltage, current, resistance, or a digital value, which can be processed by a microcontroller, PLC, or computer.

Function: Measurement and signal conversion.
Energy flow: Environment → Signal → Controller.
Examples: Thermocouples (temperature), LVDTs (position), strain gauges (force), IMUs (motion).

In short, a sensor is the eyes and ears of a control system.

Technical Definition of an Actuator

An actuator is a device that transforms an energy source (electrical, hydraulic, pneumatic, or thermal) into mechanical motion. It acts as the final control element by executing commands from the controller and influencing the physical process.

Function: Energy conversion and physical action
Energy flow: Controller → Actuator → Environment
Examples: Electric motors (rotary/linear motion), hydraulic cylinders (linear force), pneumatic valves (flow control), piezoelectric elements (micro-movement).

In short, an actuator is the hands and muscles of a control system.

How They Interact in Control Loops

A typical closed-loop control system (feedback control) integrates both sensors and actuators:

Sensor measures process variable (e.g., fluid temperature).
Controller compares measurement to desired setpoint and computes an output.
Actuator executes the corrective action (e.g., opening a valve to adjust flow).

This cycle enables precision, automation, and self-regulation in mechatronic and industrial systems.

Difference Between Sensor and Actuator – Technical Comparison

Aspect

Sensor (Input Device)

Actuator (Output Device)

Role in Control Loop

Measures and provides feedback (input)

Executes control action (output)

Energy Flow

Physical phenomenon → Electrical signal → Controller

Control signal + energy → Mechanical action → Environment

Primary Function

Sensing, monitoring, signal conversion

Motion generation, force application, process regulation

Signal Direction

Unidirectional: environment → system

Unidirectional: system → environment

Examples

Temperature sensors, optical encoders, pressure transducers

Motors, solenoids, hydraulic cylinders, pneumatic pistons

Real-World Example: Industrial Process Control

Sensor: A pressure transducer monitors fluid pressure in a pipeline.
Controller: A PID controller compares measured pressure to setpoint.
Actuator: A pneumatic control valve opens or closes to regulate flow.

This loop ensures stable operation, compensates for disturbances, and maintains system safety.

Summary – Key Difference Between Sensor and Actuator

A sensor provides information by converting physical conditions into measurable signals.
An actuator produces action by converting energy into controlled motion.
Together, they form the input and output layers of automation, enabling machines to not only sense the environment but also modify it.

The chain — Sensor → Controller → Actuator → Process defines how every mechatronic and industrial automation system operates.

Author

Mariana Butkovská

Mariana is the Marketing & Communications Director at RVmagnetics and RVactuators, where she leads the company’s global brand strategy and corporate communications. She is responsible for shaping the company’s narrative, strengthening partnerships, and positioning RVmagnetics as a leader in micro-wire based sensor and actuator technologies.

ID:	14051877
TAX number:	CZ14051877
VAT number:	VAT non-payer
IBAN:	CZ6727000000001459693001
SWIFT:	BACXCZPP
DUNS number:	496910270