Differences Between Linear and Rotary Potentiometers

A potentiometer is a three-terminal variable resistor with a sliding or rotating contact that forms an adjustable voltage divider. Upon activation by turning a dial on the device, you can measure the amount of voltage running through different parts of a circuit. The way a potentiometer achieves this is through the use of an adjustable wiper that can be moved along the wire inside the device to control its resistance. Two of the three terminals are the input and output resistors of an internal conductive strip, while the third terminal is connected to the wiper. By adjusting the wiper and dividing the voltage between the two resistors, you can measure displacement in any direction. Though they both work to accomplish the same thing, potentiometers are split into two major design types to suit different applications. In this blog, we will be comparing these two types, linear and rotary, including some of the key benefits and potential drawbacks for each.

What Is a Linear Potentiometer? 

In a linear potentiometer, the electrical resistance is contained in the form of a straight section of track. This track may consist of a strip of resistive polymer or insulator with a coil of nichrome wire wrapped around it. The defining characteristic of linear potentiometers is that the wiper is slid linearly along the straight track to measure the range of voltage within the circuit. The advantages for this design are that it is simple, inexpensive, compact, and requires few components to operate. However, even with proper lubrication, the sliding motion of the wiper contact causes some wear over time, requiring that it be monitored for eventual repair or replacement. In particular, linear potentiometers contain an open slot that is vulnerable to outside contaminants. Therefore, you should take care to check for buildup of dust and other particles in the device.
 
What Is a Rotary Potentiometer?

Rotary potentiometers are virtually the same as linear potentiometers in every way, except that the wiper is instead turned to move across a circular track. These potentiometers can be further divided into arc-segment and multi-turn types. For an arc-segment type device, the resistive strip is in the shape of a simple arc. For higher-adjustment changes, multi-turn devices are used because their more complex design enables for greater voltages. Rotary potentiometers also typically contain a strip of resistive polymer or otherwise may consist of a coil of nichrome wire wrapped around an insulator. As the design difference does little to affect performance, rotary potentiometers are just as adept at measuring voltage and electrical potential. However, the circular design of rotary potentiometers makes them excellent options for smaller electronic devices because you only need enough space to turn the knob. In addition, rotary potentiometers do not have an open slot, so there is less need to check for contaminants that could interrupt or damage the track. Nevertheless, they do have the disadvantage of being generally harder to read, especially in very small electronic devices that will have no indicator markings whatsoever. For this reason, you will need to turn the knob to test the level for yourself.
 
Conclusion

In conclusion, rotary and linear potentiometers can both be used to control the flow of an electric current in its track to help you measure electrical potential or voltage. However, their varying design affects where the devices can be used. In general, rotary potentiometers are better-suited for smaller electronic applications, whereas linear potentiometers are easier to read, but require more space. If you are in need of high-quality sensors like potentiometers or other equipment, we at ASAP Parts Unlimited are well-equipped to help you meet all the part requirements and operational deadline for your next project. Panasonic Electronic Components and Bourns Inc. are the leading manufacturers of rotary and linear potentiometers, as well as entities in our trusted global supply network. Start the purchasing process today to receive knowledgeable solutions to all your procurement needs.