Potentiometer Calculator

Understanding Potentiometer Calculator

A potentiometer is a three-terminal variable resistor used as an adjustable voltage divider.

How to use this calculator

1. Enter the input voltage, \(V_{in}\).
2. Enter the wiper resistance, \(R_{wiper}\), which is the resistance from one end of the potentiometer to the wiper.
3. Enter the total resistance, \(R_{total}\).
4. Use the calculator to find the output voltage, \(V_{out}\).

The formula explained

The formula \(V_{out} = V_{in} \times \frac{R_{wiper}}{R_{total}}\) computes the fraction of the input voltage that appears at the wiper. If the wiper is halfway along the resistance, the output is about half of the input.

• \(V_{out}\) = the output voltage at the potentiometer wiper
• \(V_{in}\) = the input voltage applied across the full potentiometer
• \(R_{wiper}\) = the resistance from one end of the potentiometer to the wiper
• \(R_{total}\) = the total resistance of the potentiometer

Step by step method

1. Find the fraction of the total resistance represented by the wiper position, \(\frac{R_{wiper}}{R_{total}}\).
2. Multiply that fraction by the input voltage, \(V_{in}\).
3. Check that the result is between \(0\) and \(V_{in}\) for a normal divider connection.

Worked example

Problem. A \(10\,\text{k}\Omega\) potentiometer is connected across a \(12\,\text{V}\) supply. The wiper is at \(2.5\,\text{k}\Omega\) from the lower end. Find the output voltage.

1. Substitute the values into \(V_{out} = V_{in} \times \frac{R_{wiper}}{R_{total}}\), so \(V_{out} = 12 \times \frac{2.5}{10}\).
2. Simplify the fraction, \(\frac{2.5}{10} = 0.25\), then multiply, \(12 \times 0.25 = 3\).
3. So the output voltage is \(3\,\text{V}\).

Tips and common mistakes

• Make sure \(R_{wiper}\) is measured from the same end of the potentiometer used as the reference in the circuit, because swapping the end changes the result.
• This formula gives a simple divider output, so it works best when the load on the output is very small compared with the potentiometer resistance.

Frequently asked questions