Variable resistor

Resistance set by the input signal.

  • signal
  • electrical
  • Modelica Standard Library
  • 3 ports
BlockVariable resistorKindvariableResistorLibraryElectrical

Description

A linear resistor whose resistance is set at each instant by an input signal. Use it for loads, sensors, or resistances that change during a run.

Example

Variable parts A resistor, an inductor, and a capacitor whose values follow signals, and a potentiometer.

R = 10 + 5 sin 2πtDC 10 VVariable resistori RGround RL = 2 + sin(πt/2)DC 1 VVariable inductori LGround LC₀ = 1 mF+1 mF at 0.5 sCDC 1 mAVariable capacitorv CGround CWiper positionDC 10 V (pot)PotentiometerWiper voltageGround P
In Gradara, select a Variable resistor block and press F1, then choose Open example. It opens as a new model in My models, ready to run.

Also in this example:DC voltageVoltage sensorCurrent sensorSumConstantStepGroundRampSine waveVariable capacitorVariable inductorPotentiometerDC current

Ports

Inputs 1

  • Rsignal · Ω

    Resistance, in ohms.

Conserving terminals 2

  • +pelectrical

    Positive pin. Current into p is counted as positive.

  • −nelectrical

    Negative pin.

Equations

Modelica
v = p.v − n.v, i = p.i, p.i + n.i = 0
v = R · i

Implementation

Modelica Standard Library 4.1.0Modelica.Electrical.Analog.Basic.VariableResistor
MSL documentation

Assumptions and limitations

  • No temperature dependence.
  • The input is not checked: a negative value gives a negative resistance, which supplies power.

Tips

  • An input of exactly 0 is a short circuit. Keep it above 0 unless the circuit tolerates a short.

See also

Select a block in Gradara and press F1 to open its page offline.