How to Test a Potentiometer

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A potentiometer is a type of variable (adjustable) resistor. Potentiometers are widely used to control the output of electrical devices (e.g. volume of a radio or amplifier, speed of a toy or tool, lighting levels, etc.). Its main function is to resist (i.e. reduce) electric current. Turning the potentiometer varies the resistance, which in turn adjusts the volume on the guitar or dims the lights in your house. [1] These devices are usually very affordable. This article explains what you should know about testing one.

Steps

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  1. This is actually the total resistance measured in ohms and it can usually be found written on the bottom or the side. [2]
  2. For example, you can set the ohmmeter to 10000 ohms if the rating of the potentiometer is 1000 ohms. [3]
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  3. Locate the three tabs that should be sticking out of it. [4] Two of those tabs are called “ends” while the third one is called a “wiper”. Most of the time, the two ends are located next to each other, while the wiper is somewhere else.
  4. Put them on the two ends of the potentiometer. What you see on the display should be within only a few ohms of the potentiometer's rated resistance (see Note below). If the reading is way off, then that means that you have put one of the probes of the ohmmeter on the wiper. If you find it difficult to tell which tabs are the ends, and which tab is the wiper, try different combinations with the probes until you get a proper reading. [5]
    Gordon McComb, Electronics Hobbyist

    When testing a potentiometer, take a multimeter and set it to measure resistance at the highest range. Connect the probes to the outer lugs of the pot, then slowly rotate the shaft. The readings should smoothly climb from zero ohms to the full-rated resistance value. If not, the potentiometer could be faulty. Next, put one probe on an outer lug and one on the center wiper terminal. Rotate again - if the resistance doesn't smoothly sweep from zero to the max rating, the wiper may have faulty contact.

  5. Make sure to keep the probes in constant contact with the ends while doing this. The resistance should stay the same or only change very slightly. [6]
    • The actual reading may not be exactly what the potentiometer is rated for. These devices typically have a tolerance of 5-10%. Tolerance may be listed on the device but not always. The reading you get should not be outside of that range (e.g. a 10,000 ohm device rated 5% should read between 9500-10500 ohms).
  6. Now you have to turn the controller slowly all the way to the other end and watch the ohmmeter while doing so. When you reach the end, the resistance should only be a few ohms. At the other end the value should be the maximum resistance of the potentiometer. The resistance should gradually and slowly increase as you turn the controller and there should be no sudden jumps. [7]
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Community Q&A

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  • Question
    Where do I find the wiper on a potentiometer?
    Community Answer
    It's usually in the center terminal. The other method is finding a terminal where the Ohm reading changes between it and the other two terminals, and that one is the wiper. Some pots are tapped at 10, 20, 30, 35 or 50%. These taps will have a reading that stays the same from every other tap except the wiper. You will need to remove the pot from the circuit to be sure.
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      References

      1. ↑ https://www.physics-and-radio-electronics.com/electronic-devices-and-circuits/passive-components/resistors/whatispotentiometer.html
      2. ↑ https://toolsweek.com/how-to-test-potentiometer-with-multimeter/
      3. ↑ https://toolsweek.com/how-to-test-potentiometer-with-multimeter/
      4. ↑ https://toolsweek.com/how-to-test-potentiometer-with-multimeter/
      5. ↑ https://sciencing.com/test-potentiometer-4910467.html
      6. ↑ https://sciencing.com/test-potentiometer-4910467.html
      7. ↑ https://sciencing.com/test-potentiometer-4910467.html

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