Model rotary or linear-travel potentiometer controlled by physical signal

Passive Devices

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:

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

*R*is the resistance between the wiper position and port L._{WL}*R*is the total resistance between ports L and R._{0}*x*is the wiper position.*x*is the value of the wiper position when the wiper is at port L._{min}*x*is the value of the wiper position when the wiper is at port R._{max}

If you specify `LOG`

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

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

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:

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

*R*is the resistance between the wiper position and port R._{WR}*R*is the total resistance between ports L and R._{0}*R*is the resistance between the wiper position and port L._{WL}

**Total resistance**The resistance between port L and port R when port W is open-circuit. The default value is

`1000`

Ω.**Residual resistance**The lower limit placed on the resistance between the wiper and the two end ports. It must be greater than zero. A typical value is 5e-3 times the total resistance. The default value is

`1`

Ω.**Resistance when centered**This parameter is available only if you select

`LOG`

for the**Taper**parameter. If you select`Higher at R`

for the**Resistance gradient**parameter, then**Resistance when centered**is the resistance between port L and port W when the wiper is centered. Otherwise, if you select`Higher at R`

for the**Resistance gradient**parameter, then**Resistance when centered**is the resistance between port R and port W when the wiper is centered. Because the resistance taper is exponential in shape, the value of the**Resistance when centered**parameter must be less than half of the**Total resistance**parameter value. The default value is`200`

Ω.**PS input for wiper at L**The value of the input physical signal at port x that corresponds to the wiper being located at port L. The default value is

`0`

.**PS input for wiper at R**The value of the input physical signal at port x that corresponds to the wiper being located at port R. The default value is

`1`

.**Taper**Specifies the potentiometer resistance taper behavior:

`LIN`

(linear) or`LOG`

(logarithmic). The default value is`LIN`

.**Resistance gradient**Specifies whether the potentiometer resistance varies more rapidly at the left or the right end:

`Higher at L`

or`Higher at R`

. This parameter is available only if you select`LOG`

for the**Taper**parameter. The default value is`Higher at R`

.

The block has the following ports:

`L`

Electrical port representing the left pin

`R`

Electrical port representing the right pin

`W`

Electrical port representing the wiper pin

`x`

Physical signal input port controlling the wiper position

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