Potentiometer Output
Vout = Vin × Rpos / Rtotal
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Formula
Description
A potentiometer is a three-terminal resistor with an adjustable wiper that creates a variable voltage divider. As the wiper moves from one end to the other, the output voltage varies from 0 V to Vin. The ratio Rpos/Rtotal represents the fractional wiper position (0 to 1). Linear taper pots have uniform resistance per unit travel, while logarithmic (audio) taper pots concentrate most resistance change in the upper half of travel, matching human hearing perception. Digital potentiometers (digipots) use resistor ladders with FET switches.
Variables
- Vout — Output voltage at the wiper (V)
- Vin — Voltage across the full potentiometer (V)
- Rpos — Resistance from ground to wiper (Ω)
- Rtotal — Total end-to-end resistance (Ω)
Practical Notes
This assumes no load on the wiper. Any load resistance in parallel with the lower section will reduce Vout and introduce nonlinearity. For accurate voltage setting, use a buffer amplifier (voltage follower) on the wiper output. Common total resistances: 1 kΩ, 5 kΩ, 10 kΩ, 50 kΩ, 100 kΩ.
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