# Potentiometer

Rotary or linear-travel potentiometer controlled by physical signal

**Library:**Simscape / Electrical / Passive

## Description

The Potentiometer block represents a rotary or linear-travel potentiometer, with the wiper position controlled by the input physical signal.

If the potentiometer resistance changes linearly based on wiper position, then the
resistance between the wiper position and port **L** is:

$${R}_{WL}=\frac{{R}_{0}-2r}{{x}_{\mathrm{max}}-{x}_{\mathrm{min}}}\left(x-{x}_{\mathrm{min}}\right)+r$$

where

*R*is the resistance between the wiper position and port_{WL}**L**.*R*is the total resistance between ports_{0}**L**and**R**.*x*is the wiper position.*x*is the value of the wiper position when the wiper is at port_{min}**L**.*x*is the value of the wiper position when the wiper is at port_{max}**R**.*r*is the residual resistance. This is the resistance between the wiper and port**L**when*x*is equal to*x*. This is also the resistance between the wiper and port_{min}**R**when*x*is equal to*x*._{max}

If you specify `Logarithmic`

for the
potentiometer resistance **Taper** parameter, then the resistance
between the wiper position and port **L** is:

$${R}_{WL}=\{\begin{array}{ll}A\left({e}^{\lambda \left(x-{x}_{\mathrm{min}}\right)}-1\right)+r\hfill & \text{ifresistancegradientishigheratR}\hfill \\ {R}_{0}-A\left({e}^{\lambda \left(x-{x}_{\mathrm{min}}\right)}-1\right)-r\hfill & \text{ifresistancegradientishigheratL}\hfill \end{array}$$

where *A* and λ are chosen such that
*R _{WL}* at

*x*is

_{max}*R*, and

_{0}- r*R*at

_{WL}*x*= (

*x*+

_{max}*x*) / 2 is equal to

_{min}*R*, the resistance when the wiper is centered.

_{av}**Note**

Potentiometers widely described as LOG or logarithmic taper are, in fact, exponential taper. That is, the gradient of the resistance between wiper and left-hand port increases as the resistance increases. The Potentiometer block implements this behavior.

For both linear and logarithmic tapers, the resistance between the wiper position and
port **R** is:

$${R}_{WR}={R}_{0}-{R}_{WL}$$

where

*R*is the resistance between the wiper position and port_{WR}**R**.*R*is the total resistance between ports_{0}**L**and**R**.*R*is the resistance between the wiper position and port_{WL}**L**.

## Ports

### Input

### Conserving

## Parameters

## Model Examples

## Extended Capabilities

## Version History

**Introduced in R2010a**