How to Test a Capacitor with a Multimeter: A Step-by-Step Guide

Testing Capacitors with a Multimeter

To check a capacitor using a multimeter, follow these steps:

  • Set the multimeter to Capacitance (Capacitance) measurement mode.
  • Disconnect the capacitor from any electrical circuits it was connected to.
  • Connect the multimeter probes to the capacitor, ensuring correct polarity.
  • Read the capacitance value displayed on the multimeter screen.
  • Compare the measured value with the value specified on the capacitor’s label or in its technical documentation.

Testing a capacitor using probes
Monitoring the rise in resistance
Observing high resistance

Note that some multimeters may require additional settings or procedures before using them in Capacitance measurement mode. Please consult your multimeter’s user manual.

Can You Test a Capacitor for Continuity?

Yes, you can test a capacitor for continuity. This procedure helps determine whether the capacitor is functioning. It is carried out as follows:

  1. Disconnect the capacitor from all electrical circuits it was connected to.
  2. Connect a speaker to the capacitor, ensuring correct polarity.
  3. Apply alternating voltage to the capacitor and listen for sound from the speaker.
  4. If sound is heard, it indicates that the capacitor is working and can be used further.

Note that testing a capacitor for continuity only provides a rough indication of its condition and should not be considered a substitute for precise measurements with a multimeter.

Continuity test of a capacitor

If the multimeter beeps and shows zero when the probes touch the capacitor, this indicates a short circuit in the capacitor. If the multimeter immediately shows one, it indicates a break in the capacitor. In either case, the capacitor should be discarded as it is non-functional.

How to Check if a Capacitor is Working

There are several methods to test a capacitor’s functionality:

  1. Resistance Measurement Method: You can measure the resistance of a capacitor using a multimeter. If the resistance value is zero, the capacitor is defective.
  2. Continuity Test Method: You can test a capacitor by connecting it to a speaker and applying alternating voltage. If you hear sound from the speaker, the capacitor is functional.
  3. Capacitance Measurement Method: You can measure the capacitance of a capacitor using a multimeter. If the measured capacitance value does not match the specified value, the capacitor is defective.

Capacitor measurement

Incorrect polarity in a capacitor can lead to malfunction, up to explosion.

Imported capacitors have a small cross or other figure indented into their top, where the casing is thinner. This is a safety feature, so if an imported capacitor explodes, only its top will open up. The image shows a bulged capacitor from a computer motherboard, with the rupture along the line.

Safety feature on a capacitor
Bulged capacitor on a motherboard

Testing a Capacitor with a Multimeter

To test a capacitor using a multimeter, follow this rule: the capacitor’s capacitance should not be less than 0.25 microfarads.

Before testing a capacitor with a multimeter, determine its polarity. The polarity of a capacitor can usually be identified by markings on its body. The minus sign is indicated by a tick mark. A black tick mark on a thick gold stripe indicates the negative terminal.

Determining capacitor polarity

Now, set the multimeter to continuity (or resistance) mode and touch the probes to the contacts. Since the multimeter in continuity and resistance mode emits constant voltage, the capacitor will charge, and the resistance reading will rise during charging.

As the charging occurs, the resistance value increases until it becomes very high. Let’s see what this should look like.

Analog multimeters are convenient for testing capacitors as it’s easier to track the needle movement than flickering numbers on a digital multimeter.

Testing non-polarized capacitors is simpler. Set the multimeter dial to megaohms and press the probes to the capacitor’s terminals. If the resistance value does not reach 2 megaohms, the capacitor is considered faulty.

Video: Testing a Capacitor with a Tester

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