Potentiometer
Rotary or linear potentiometer controlled by an external signal.
Description
The Potentiometer unit is a rotary or linear potentiometer with a movable contact that is controlled by an input signal.
If the resistance of the potentiometer varies linearly with the position of its stem, the resistance between the stem position and the L port is equal:
Where:
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- resistance between the position of the moving contact and the port L.
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- total resistance between ports L and R.
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- position of the moving contact.
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- is the value of the input signal at which the movable contact is at port L.
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- input signal value at which the movable contact is at the R port.
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- Residual resistance. This is the resistance between the movable contact and port L when is equal to . It is also the resistance between the movable contact and the port , when equals .
If Logarithmic is specified for the parameter Taper of the potentiometer resistance, the resistance between the moving contact position and port L will be:
where and are chosen so that in is and in is equal to the resistance Resistance when centred when the moving contact is at the centre.
| Potentiometers, often referred to as LOG potentiometers, or potentiometers with a logarithmic taper, actually have an exponential taper. That is, the resistance gradient between the moving contact and the left port increases as the resistance increases. The Potentiometer block implements exactly this behaviour. |
For linear and logarithmic potentiometers, the resistance between the position of the movable contact and the R port is equal:
where
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- is the resistance between the moving contact and the port R.
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- is the total resistance between ports L and R.
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- resistance between the movable contact and the L port.
Ports
Input
x - moving contact position control
scalar
Port of the input signal controlling the position of the movable contact.
Non-directional
L - left contact
electricity
Electrical port associated with the left contact of the potentiometer.
R is the right contact
electricity
Electrical port associated with the right contact of the potentiometer.
Dependencies
To use this port, set the Number of visible ports to Three: left, right, and wiper.
W is a movable contact
electricity
Electrical port linked by the moving contact of the potentiometer.
Parameters
Number of visible ports - port display option
Three: left, right, and wiper (by default) | `Two: left and wiper `
Selects the option to switch on the right potentiometer port, R.
Total resistance - total resistance
`1000.0 ohms (by default).
To use this parameter, set the Number of visible ports to Three: left, right, and wiper.
Residual resistance - Residual resistance
1.0 ohms (by default) | `positive scalar'.
Resistance measured between the mobile contact and the nearest port (L or R) when the mobile contact is close to that port. This parameter can be used to indicate the inability of the movable contact to reach the end of the track due to a mechanical stop. This value must be greater than or equal to zero. A typical value is 5000 times the total resistance.
Dependencies
To use this parameter, set the Number of visible ports to `Three: left, right, and wiper'.
CControl input for wiper at L port - value of the input signal to move the movable contact to L port
0.0 (By default).
Input signal value at x port corresponding to the movable contact close to L port.
Dependencies
To use this parameter, set the Number of visible ports to `Three: left, right, and wiper'.
Control input for wiper at R port - value of the input signal to move the movable contact to R port
`1.0 (By default).
Input signal value at x port corresponding to a movable contact close to R port.
Dependencies
To use this parameter, set the Number of visible ports to `Three: left, right, and wiper'.
Minimum resistance - minimum resistance
`1.0 ohms (by default).
The minimum allowable resistance measured between the movable contact and the left port L when the movable contact is at the left port. The value of this parameter must be greater than 0 and less than the value of Maximum resistance.
Dependencies
To use this parameter, set the Number of visible ports to `Two: left and wiper'.
Maximum resistance - maximum resistance
`999.0 ohms (by default).
The maximum allowable resistance measured between the movable contact and the left port L when the movable contact is at the left port. The value of this parameter must be greater than 0 and greater than the value of Minimum resistance.
Dependencies
To use this parameter, set the Number of visible ports to `Two: left and wiper'.
Control input for wiper at minimum resistance - value of the input signal to move the movable contact to the position with minimum resistance
0.0 (By default)
Input signal value at port x corresponding to the movable contact located at port L.
Dependencies
To use this parameter, set the Number of visible ports to Two: left and wiper.
Control input for wiper at maximum resistance - value of the input signal to move the movable contact to the position with maximum resistance
1.0 (By default)
The value of the input signal at port x corresponding to the movable contact located at the furthest position from port L. The value by default is 0.
Dependencies
To use this parameter, set the Number of visible ports to `Two: left and wiper'.
Taper - type of resistance scale
Linear (by default) | Logarithmic.
Resistance scale of the potentiometer.
The parameters Linear and Logarithmic do not model the same scale. A block with linear parameterization cannot be used to model a logarithmic potentiometer because the logarithmic scale is non-linear.
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For the Linear parameter, the relationship between the value of the input signal and the resistance between the L and W ports is:
For the Logarithmic parameter, the relationship between the value of the input signal and the resistance between the L and W ports is:
Resistance when centreed - resistance at the centre
`200.0 ohms (by default).
If you set Resistance gradient to Higher at L, this parameter represents the resistance between port L and port W when the movable contact is centred. Otherwise, if the Resistance gradient parameter is set to Higher at R, then this parameter represents the resistance between ports R and W when the movable contact is centred. Since the resistance scale is exponential, the value of Resistance when centred must be less than half the value of Total resistance.
Dependencies
To use this parameter, set Taper to `Logarithmic'.
Resistance gradient - type of resistance gradient
Higher at R (by default) | Higher at L.
Defines on which side the potentiometer resistance changes more sharply depending on the input signal (gradient value) - on the left or on the right.
Dependencies
To use this parameter, set the Taper parameter to Logarithmic.