By Isaiah David | Updated Mar 24, 2022
A potentiometer is a versatile, low‑cost variable resistor that controls the flow of electric current in devices ranging from dimmer switches to electric guitars. Ensuring it functions correctly is essential for reliable performance.
Locate the total resistance value printed on the body of the potentiometer. This figure, expressed in ohms, is the maximum resistance the device can present.
Adjust the multimeter (or ohmmeter) to a range that exceeds the potentiometer’s rating. For example, a 1,000 Ω potentiometer should be tested on a 10,000 Ω setting to avoid overloading the meter.
Three contacts protrude from the potentiometer: two are the fixed “end” terminals, and the third is the movable “wiper.” The ends are typically adjacent, while the wiper sits on a separate slot.
Place the meter probes on the two end terminals. The reading should approximate the rated resistance within a few ohms. If the value deviates, reposition the probes until the correct pair is identified.
With the probes on the end terminals, rotate the potentiometer shaft from one extreme to the other. The resistance should remain essentially constant or change only marginally, confirming the ends are stable.
Disconnect one probe from an end terminal and attach it to the wiper. Turn the shaft slowly while watching the meter display. At one extreme, the resistance should be near zero; at the opposite extreme, it should reach the maximum rating. The transition should be smooth, without abrupt jumps, indicating proper linearity.
If any of the measured values differ from the expected range, replace the potentiometer to avoid performance issues.
