Electronic – the equation for a potentiometer with dual power supply

passive-networkspotentiometerpower electronicsswitch-mode-power-supplyvoltage divider


simulate this circuit – Schematic created using CircuitLab

Suppose we setup a potentiometer with two power supplies +10V and -10V as shown above. A digital voltmeter is setup to measure the voltage.

If the potentiometer is turned all the way up, a digital voltmeter would read +10V, if the potentiometer is setup all the way down, the digital voltmeter would read -10V.

My question is

When writing the equation for calculating the voltage across the voltmeter, how can we include the +10V and as well as -10V in our potential divider equation and calculate the voltage at the voltmeter?

Best Answer

How about, V = 20x-10 where x is the potentiometer wiper position as a fraction from 0 to 1.

Other related points (to consolidate those made in the follow-up comments and answers):

  • General form: \$ V_{out} = x(V^+-V^-)+V^-\$
  • Potentiometers (pots) are generally used in low power applications. Make sure to check your part's specs to ensure it will operate properly in your circuit.
  • Pot wiper terminals are typically designed to carry low current. Again, check the datasheet.
  • In response to your question in the comments section: if you intend to test your device with an ohmmeter, be sure to first disconnect the power source in order to obtain accurate measurements.