How to measure voltage across an electrolytic capacitor

Written by j.t. barett
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How to measure voltage across an electrolytic capacitor
You can measure the voltage across an electrolytic capacitor with a multimeter (capacitor image by naolin from

It is a fairly simple task to measure voltage across an electrolytic capacitor with a multimeter. Simply find the capacitor in question in the circuit and note its polarity. Turn the circuit on and touch the multimeter probes to the capacitor's leads, matching their polarity to the capacitor's. Since you will be working on a live circuit, be aware of any high voltages present while it is turned on. If you read a low voltage, the capacitor is probably shorted out and needs replacing.

Skill level:

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Things you need

  • Multimeter
  • Rubber gloves

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  1. 1

    Turn off the power to your circuit. Expose the circuit board by removing any cover or case. Locate the two contact points for the electrolytic capacitor you are interested in. Note the polarity markings -- positive or negative -- on the body of the capacitor or the contacts on the circuit board.

  2. 2

    Turn on the power to your circuit. Turn on your multimeter and set it to read DC volts. If this capacitor is part of a high voltage (over 100 volts) circuit, put on rubber gloves. Touch the red (positive) multimeter probe to the capacitor's positive contact and the black (negative) probe to the negative contact. Read the voltage on the multimeter and note it down. Withdraw the probes from the circuit.

  3. 3

    Turn off the circuit and replace the case or cover.

Tips and warnings

  • If the capacitor is cracked, smoking or leaking, you do not need to measure it. Check other connected components for problems, then replace them and the capacitor.

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