Electronic circuits use capacitors to store voltage. Every electrical and electronic circuit needs a capacitor. Test capacitor with a multimeter while troubleshooting an electronic circuit may involve. There are multiple ways to test an AC capacitor like a digital multimeter, voltage meter, and ohmmeter.
Before testing a capacitor, make sure to disconnect the capacitor from the circuit. And short the terminals of the capacitor using a resistor of at least 1k. Try to avoid contact with the terminals during the process. Otherwise, the charge on the capacitor may cause you an electric shock.
Testing an AC Capacitor with a Multimeter
Testing a capacitor with a multimeter is the easiest and quickest way. The required instrument for the test is a digital multimeter with a capacitance testing feature.
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- Remove the capacitor from the circuit and short the terminal to avoid electric shocks.
- Set the digital multimeter to a capacitance setting.
- Connect the probes of the multimeter to the capacitor terminals.
- For the polarized capacitor, connect the red probe to the positive and black to the negative terminal of the capacitor.
- For nonpolarized, you can connect it in either way.
- Now, look at the digital multimeter’s screen to read the capacitor’s capacitance.
- You can compare the reading with the rating printed on the capacitor. If they are close, the capacitor is good.
- In case of large variation, the capacitor may be considered a bad capacitor.
- A bad capacitor can be replaced with a new similar rating capacitor.
Testing an AC Capacitor with Voltmeter
Testing a capacitor with a voltmeter can give you an idea if the capacitor is good or bad. For this method, you need a voltmeter and a power supply. The voltage of the power supply must be less than that of the capacitor.
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- Disconnect the capacitor from the circuit and discharge.
- Connect the capacitor to the power supply and charge it for at least 4 to 6 seconds.
- Make sure the voltage of the power supply is less than the printed voltage on the capacitor.
- Now disconnect the capacitor from the power supply.
- Do not touch or short the capacitor terminals.
- Connect the capacitor to the voltmeter.
- Read the voltmeter reading if it is close to the power supply voltage or not.
- If it is close to the supply voltage the capacitor is good.
- If the reading is much less the capacitor is bad.
Conclusion
- Always disconnect the capacitor from the circuit to test it.
- A digital multimeter may give you the exact capacitance of the capacitor.
- Testing a capacitor with a voltmeter may tell you if it is a good or bad capacitor.
FAQs
How do you tell if a capacitor is bad with a multimeter?
A shorted capacitor shows zero ohms on a multimeter. Surface mount capacitors are often open, and visible under magnifiers.
When should I replace my AC capacitor?
Consider replacing your AC capacitor every 20 years or earlier if your AC unit is older. For units surpassing 20 years, enlist a professional AC technician for inspection and potential replacement.