Short Answer:

A potentiometric displacement sensor works by changing electrical resistance based on the position of a sliding contact (called a wiper) on a resistive track. As the object moves, the wiper slides along the resistor, and the resistance changes according to the position.

This changing resistance is converted into a voltage output, which represents the displacement of the object. Potentiometric sensors are simple, low-cost, and suitable for measuring both linear and rotary displacement in machines, robotics, and control systems.

Detailed Explanation:

Working of potentiometric displacement sensor

A potentiometric displacement sensor, also known as a position potentiometer, is a contact-type sensor used to measure the linear or rotary displacement of an object. It operates on the principle of variable resistance and is commonly used due to its simplicity, low cost, and ease of use.

Construction:

A typical potentiometric displacement sensor consists of the following parts:

Resistive Element: A fixed resistor made from materials like carbon, wire, or conductive plastic, shaped either as a straight line (for linear motion) or a circle (for rotary motion).
Wiper or Sliding Contact: A movable contact that touches the resistive surface and moves along with the object being measured.
Housing and Terminals: The sensor is enclosed in a casing with three terminals—two at the ends of the resistive element and one connected to the wiper.

Working Principle:

The potentiometric sensor works by dividing the voltage across the resistive element based on the wiper position.

Voltage Supply: A constant voltage is applied between the two fixed terminals at the ends of the resistive element.
Object Movement: As the object moves, it pushes or rotates the wiper along the resistive track.
Resistance Change: The position of the wiper determines how much of the resistor lies between the wiper and each end terminal. This changes the resistance value in the circuit.
Output Voltage: The sensor outputs a voltage from the wiper terminal. This output voltage is proportional to the displacement:
- When the wiper is near one end, the voltage is low.
- As the wiper moves, the voltage increases linearly or as per design.
Signal Interpretation: This output voltage is then read by a controller or monitoring system to determine how far the object has moved.

Features and Advantages:

Simple and Cost-Effective: Very easy to use and affordable.
Linear Output: Provides a direct voltage signal proportional to position.
No Need for Signal Conversion: Works directly with analog input systems.
Suitable for Linear and Rotary Displacement: Available in both forms.
Good Accuracy for General Applications

Limitations:

Wear and Tear: Due to physical contact, the wiper and resistive element may wear out over time.
Limited Lifespan: Not ideal for continuous or high-speed motion.
Environmental Sensitivity: Dust, moisture, or vibration may affect accuracy.
Lower Precision Compared to Non-contact Sensors

Applications:

Control levers in joysticks or game controllers
Volume knobs and sliders in audio systems
Position detection in automation systems
Robotics arm positioning
Feedback in servo motors and actuators

Conclusion:

A potentiometric displacement sensor works by moving a wiper over a resistive surface to change the output voltage based on position. This voltage change is used to measure how far an object has moved. It is a simple, effective, and low-cost method widely used in basic position-sensing applications, though it has limitations related to wear and environmental conditions.