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Navigating Precision: Common Types of Feedback Devices in Servo Systems


In the intricate world of servo systems, achieving precise motion control hinges on the utilization of feedback devices. These devices serve as the eyes and ears of the system, providing real-time information about the position, velocity, and acceleration of the actuator. By continuously monitoring these parameters, feedback devices enable servo systems to maintain accuracy, responsiveness, and stability in diverse applications. Let's explore some of the common types of feedback devices used in servo systems and their significance in achieving optimal performance.


Encoders are one of the most widely used feedback devices in servo systems, prized for their accuracy and versatility. These devices convert mechanical motion into digital signals, providing precise position feedback to the controller. Encoders come in two main types: incremental encoders and absolute encoders.

- Incremental Encoders: Incremental encoders generate pulses as the shaft rotates, allowing the controller to track the position and velocity of the actuator. They provide relative position information but do not retain absolute position after power-off.

- Absolute Encoders: Absolute encoders provide absolute position information, allowing the controller to determine the actuator's position even after power-off. They use a unique code to represent each position, ensuring accurate positioning without the need for homing routines.


Resolvers are rugged and reliable feedback devices commonly used in harsh environments or applications that require high durability. These devices operate on the principle of electromagnetic induction, generating sinusoidal signals that represent the actuator's position. Resolvers offer excellent accuracy and immunity to electromagnetic interference, making them suitable for demanding industrial applications.

Hall Effect Sensors:

Hall effect sensors are semiconductor devices that detect changes in magnetic fields and convert them into electrical signals. In servo systems, Hall effect sensors are often used to provide feedback on the position and speed of the actuator. They offer fast response times and can operate in extreme temperatures and harsh environments, making them ideal for applications with stringent performance requirements.


Potentiometers, or pots, are simple yet effective feedback devices that measure the rotational position of the actuator. They consist of a resistive track and a wiper that moves along the track as the shaft rotates. By measuring the resistance between the wiper and the ends of the track, potentiometers provide analog feedback on the actuator's position. While potentiometers are less accurate and durable compared to encoders and resolvers, they are often used in cost-sensitive applications or as secondary feedback devices for redundancy.

Linear Variable Differential Transformers (LVDTs) and Linear Potentiometers:

For linear motion applications, feedback devices such as LVDTs and linear potentiometers are used to measure the linear displacement of the actuator. LVDTs are electromechanical devices that generate an electrical signal proportional to the linear displacement of a core within a coil assembly. Linear potentiometers operate on a similar principle to rotary potentiometers but measure linear displacement instead of rotational position.


In conclusion, feedback devices are indispensable components of servo systems, enabling precise motion control and ensuring optimal performance in diverse applications. Whether it's encoders, resolvers, Hall effect sensors, potentiometers, or linear displacement sensors, each type of feedback device offers unique advantages and capabilities to meet the demands of specific applications. By selecting the appropriate feedback device and integrating it effectively into the servo system, engineers can harness the full potential of servo technology to drive innovation and efficiency across industries.

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