How to Test a Capacitor with a Multimeter or Capacitor Tester

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Capacitors are the devices in appliances, electronics and machinery which store an electrical charge. Capacitors come in two main types — electrolyte capacitors and non-electrolyte.

And just like any other piece of equipment, they wear out with time and may need repair or replacement.

When an electrolyte capacitor fails, it does so either by discharging too much current or not being able to hold any charge; while non-electrolyte capacitors will leak the charge inside them. That is why frequent tests need to be done on them to verify if they are still functioning well.

One of the ways you can realize a capacitor has reached its point of satiety is when gadgets suddenly refuse to function well, even when turned on. When you begin to notice such incidences, it is time to test your capacitor and know whether it can still serve you or it is time to replace it.

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To test a capacitor, you will need a multimeter or capacitor tester, which will tell you instantly if your capacitor is dead or not. You can either use an analog or a digital multimeter to check for capacitance.

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Testing a Capacitor Using an Analog Multimeter

Multimeters are used to check whether a capacitor is dead or functioning. A capacitor might be in a bad condition but will still be functioning. Use the following steps to test your capacitor if you are using analog multimeter:

  • Remove the capacitor from the circuit it is connected to. To use a multimeter, you must disconnect the capacitor from the circuit since it has to be in direct contact with the multimeter to get the correct readings.
  • Calibrate the multimeter by checking the resistance settings to read at zero, or in some instances it may be marked with an omega sign (Ω).
  • Join the multimeter to the capacitor using the appropriate terminals. There are positive and negative terminals on the capacitor while the multimeter has red and black lead ends. The red goes to the positive terminal while the black goes to the negative.
  • Now check the readings on the screen of your multimeter. Analog readers use a needle to show you the results. If the needle moves steadily to a higher value then your capacitor is still functional. If the resistance is low but the needle is not moving then the capacitor is dead and will need instant replacement.

Testing a Capacitor Using Digital Multimeter

If you are using a digital multimeter to test a capacitor, these are the steps to follow.

  • Whether you are using analog or digital multimeter, the initial step is to disconnect the multimeter from the circuit.
  • On your multimeter, there is a button that you have to rotate to set it to a resistance level. The unit for resistance is OHM, and it is always marked on the digital multimeter.
  • Connect the terminals on the capacitor and the multimeter. The red terminal goes into positive and the black, negative terminal.
  • Note down the initial value on your multimeter reading before it captures the reading after connecting the two devices, then also note down the reading that appears after connection and compare.
  • To be sure, disconnect the multimeter from the capacitor and connect again, you should be able to see the same readings. If the results are same then your capacitor is good. But if the value of resistance does not change, then your capacitor is dead and needs replacement.

Quick Tips for Testing Capacitors

When removing your capacitor from the circuit, be careful not to touch the terminals with bare hands because if the capacitor is not dead, chances are it still has charge and that may lead to a shock.

You can remove the charge from the capacitor using a screwdriver with an insulated handle. You should be able to see a spark, if not, it doesn’t mean the capacitor is dead, it may just be without charge therefore, put your multimeter into use to find out if it is dead or not.

When testing the capacitor, it is best to repeat the process in order to verify the results.

If you are considering purchasing a multimeter and are concerned that it’s a one trick pony that can only be used for testing capacitors, not to worry. Yes, if you are someone who does electrical work or appliance repair, this is an essential tool. But multimeters are actually quite versatile and can be used in many ways by anyone.

The first, and perhaps most obvious use for a homeowner for a multimeter is to test your batteries to see how much juice is left. They can also be used to test incandescent light bulbs. Either of these uses can not only save you time, but also help you clear out that junk drawer or closet.

Multimeters are also used to check the current for light switches and electric outlets, but their uses are not limited to the home. You can use them to test your car battery or audio system if either are not working properly. This is just the tip of the iceberg in terms of how you can use a multimeter.

As you can see, a multimeter is a multi functional tool to have around!

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