How to Select Linear Potentiomters
Image Credits: Novotechnik US Inc., OMEGA Engineering Co., Spectrum Sensors & Controls
Linear potentiometers produce a resistance output that varies according to the displacement or position of a slider or wiper.
How Linear Potentiometers Work
Linear potentiometers are variable resistors with three leads. Two leads connect to the ends of the resistor, so the resistance between them is fixed. The third lead connects to a slider that travels along the resistor varying the resistance between it and the other two connections. The resistance element is excited by either DC or AC voltage. This video discusses potentiometers in general and compares linear and logarithmic tapers.
Video Credit: Planet Z
Types of Linear Potentiometers
"Linear" can refer to the motion of the slider. Such a device is also known as a slide potentiometer. By contrast, a rotary potentiometer slider twists.
"Linear" can refer to the taper (law)-how the output voltage varies with the motion of the slider. A linear taper means that resistance increases in direct proportion to the distance traveled along the resistive element. This contrasts with a change in resistance via a logarithmic scale (a log or audio taper).
Specifications and Features
Sensors vary in dimension (length, width, height, diameter, weight).
Electrical working range is the length of the stroke (e.g., less than 1" to 29" or more).
Total resistancevaries (e.g., less than 2 to more than 74 kiloohms).
Minimum accuracy ranges (better than 15% to better than 0.02%).
Electrical output signals can be analog (current, voltage, or frequency), digital (serial, parallel, or other), an alarm, or a change in state of switches.
Sliders can be housed in rectangular or cylindrical body types, sealed against environmental contamination, and/or free to rotate.
Resistive element types can be carbon (inexpensive), cermet (relatively limited life), conductive plastic (long life), wire wound (current drawn during use).
Devices can tolerate certain operating temperatures (e.g., -13 to 165 F).
Packaging can be a raw sensor element or a housed transducer. Self-contained instruments or meters display output at or near the device. Gauges/indicators have an analog display and no electronic output.
Linear potentiometers are used in test/lab, marine, medical, and farm equipment, as well as heavy industry, industrial processing, and robotics.
Related Products & Services
Capacitive Linear Position Sensors
Capacitive linear position sensors are devices that sense position / displacement using capacitance technology.
Eddy Current Linear Encoders
Eddy current linear encoders detect the distance from a target by using magnetic fields generated by a reference and sensing coils.
Linear Variable Differential Transformers (LVDT)
Linear variable differential transformer (LVDT) linear position sensors have a series of inductors in a hollow cylindrical shaft and a solid cylindrical core. These devices produce an electrical output proportional to the position of the core
Optical Linear Encoders
Optical linear encoders use fiber optic technology to sense position and displacement.
Optical Triangulation Position Sensors
Optical triangulation position sensors use reflected waves to pinpoint position and displacement. The source of these waves may be a light emitting diode (LED), infrared (IR) light, or laser.
String Potentiometers are used to measure the movement and displacement of objects. A cable or wire is attached to an object, and as the object moves, the transducer produces an electrical signal proportional to the wire's linear extension.
Ultrasonic Linear Position Sensors and Switches
Ultrasonic linear position sensors and switches use ultrasonic waves in combination with light and frequency readings for position and displacement sensing.