Are you finding it difficult to differentiate between a good capacitor and a fault capacitor? Maybe you have been troubleshooting a circuit and don’t know how to test the capacitor component of the circuits. Worry no more and take your time to go through this post as how to test a capacitor using a multimeter is well-discussed here.
With a multimeter, (analog or digital) one can easily test and check if a capacitor is bad or good. Follow this step-by-step tutorial to learn the different ways to test an electronic capacitor.
Note: Checking whether the capacitor is bad or good is different from checking the value of the capacitor. To test the capacitance of a capacitor using a multimeter, the multimeter whether analog or digital should have a capacitance measuring features on it.
Testing a capacitor using a digital multimeter – Resistance mode.
Just like we said before, there are several methods to test a capacitor using a multimeter. So here we will see how we can use a digital multimeter in resistance mode (Ohm method ) to test a capacitor.
To carry out this test follow the step-by-step guide below;
- Discharge the capacitor to be tested. You can do is by connecting a high resistance across the two terminals of the capacitor. Make sure the capacitor is fully discharged.
- Set the digital multimeter to an Ohm range or resistance range, depending on the one the meter is labeled with.
- Connect the multimeter probes to the capacitor terminal Black probe to the negative(-) and the red probe to the positive(+).
- Immediately you connect the meter probes to the terminal of the capacitor. monitor the meter screen to note the readings. The meter will show a reading of numbers for a sec.
- If the meter shows several numbers and displays OL (open line) or Infinity ♾️, it shows that the capacitor is good and OK. But when there is no change on the meter, it signifies that the capacitor is dead.
Testing a Capacitor Using Analog Multimeter – Ohm Mode.
Here we shall look at how the AVO (Ampere, Volt, Ohm meter) meter can be used to check a capacitor using the “Resistance mode or Ohm Mode”. The following procedure explains how we can carry out the task.
- Get the capacitor you wish to test and discharge the stored energy on it.
- Set the AVO meter to a resistance measurement mode. This is done by rotating the meter mob to Ohm mode. Always position the knob to a high resistance when carrying out this test.
- Test the capacitor using the AVO meter by connecting the meter probes to the capacitor terminals. The COM probe to the negative and the Red probe to the positive terminal of the capacitor.
- Take note of the readings, and analyze the result to know the state of the capacitor.
- When the analog meter reads very low resistance, it show that the capacitor is short circuit.
- If the meter doesn’t read at all. i.e. the meter pointer didn’t deflect at all. It means the capacitor is open circuit.
- When the capacitor is good, immediately you connect the testing probe to its terminals, it will show a very low resistance which will increase gradually toward infinite. In this case, the capacitor is good
How to test the capacitance of a Capacitor using a mulitmeter
Another way of testing a capacitor using a multimeter is by using the meters Capacitance Mode. However, not all digital and analog multimeters have this feature.
Before deciding to use this method make sure that your multimeter has the feature to measure the capacitance of a capacitor. For the multimeter to have this feature, it must have a “Farad” mode or capacitance Mode C. Is used in testing tiny capacitors. Follow the procedure below, to measure the capacitance of a capacitor using a multimeter.
- Discharge the capacitance and make sure it has no charge on it.
- Remove the capacitor from the circuit board befor testing.
- Set up your multimeter to capacitance “C mode”. This is done by rotating the meter knob to the capacitance side of the meter. It is labeled on the body of the meter.
- Test using the meter leads. Connect the Red probe to the positive terminal of the capacitor and the black to the negative terminals.
- The reading will immediately show up on the multimeter screen.
- When the displayed reading is close to the actual value of the printed value on the capacitor body, then the capacitor is good.
- The reading of the capacitor capacitance on the multimeter can be less but the tolerance should should not be less or above + or – 10 or + or – 20.
- But when the capacitor doesn’t read at all or reads significantly lower capacitance, then it means that the capacitor is dead and needs to be changed with a new one.
Testing capacitor using a simple voltmeter.
Another way to test a capacitor using a multimeter is the use of volt-meter mode to measure the voltage of the capacitor. The method of testing a capacitor applies to both polar and nonpolar capacitors.
In carrying out this type of test on a capacitor using a multimeter, you first need to check the capacitor voltage. The capacitor voltage is printed on the body of the capacitor. Follow the procedures below to carry out a simple volt meter test on a capacitor.
- Disconnect the capacitor from the circuit board.
- Check the capacitor voltage on the body of the capacitor. It always written at the body of the capacitors.
- Charge up the capacitor using a DC voltage lower than the capacitor voltage. Connect the positive terminal to the positive terminal of the DC source and the negative to the negative terminals to chart the capacitor. For instance, if I want to charge an 18V capacitor, I will use a 12V DC Volt. Do not try charging the capacitor with an exact voltage of the capacitor. This is to avoid busting and damaging the capacitor.
- Set your multimeter to DC voltage mode. This is done bay rotating the meter knob to DC Volt.
- Test the capacitor using the meter probe, red to the positive terminal while back to the negative terminal.
- Immediately the readings will show up on the meters screen. The multimeter will read the capacitor voltage.
- The capacitor starts discharging itself immediately after charging. So test immediately after charging. If the voltage is close to the supplied voltage used to charge the capacitor, then it is good. But when the voltage reads lower voltage far from the voltage used to charge the capacitor, then the capacitor is bad.
Testing the capacitor using a Multimeter in Continuity test mode.
The continuity test mode of a DMM or AVO meter can be used to ascertain if a capacitor is good or bad. And here in this post is how you can carry out this test on a capacitor using a digital or analog multimeter. The step below explains how to carry out the test.
- Remove the capacitor to be test from the circuit board.
- Discharge fully the capacitor by connecting a resistor across the terminals.
- Set the meter to continuity test mode by rotating the meter knob to continuity.
- Touch the two leads of the meter and observe the multimeter. If it makes a beeping sound while the two probes are in contact, then the meter is in continuity mode and ready to test. But when you touch the probes and there is no beeping sound, then check the meter probes’ connections and know if they are properly connected.
- Test the ccapacitor by placing the positive probe to the (+) Anode of the capacitor and the negative probe to the (-) cathode.
- If the multimeter reads continuity, that is beeps sound and suddenly stops and shows OL – open line. Then it shows that the capacitor is ok
- But when you test and it didn’t beep sound or show LED light, then it means the capacitor is open. And not good.
- When you test and the multimeter makes a continuous beeping with the LED ON. It shows that the capacitor is short-circuited and should be replaced with a good one.
Visual and Apparent checking of capacitors
This is always the first step to take when checking the working condition of a capacitor. Most time the damaged capacitors show on their case bodies like bulging or busting.
These are the following signs to visualize if a capacitor is bad.
Bulging of the top vent of the capacitor.
The top vent of the electrolytic capacitor is designed in such a way that when it releases the capacitor pressure during capacitor failure. The top vent which can have the shape of K T or X is made to be weak so that when the capacitor has so much pressure that can bust the capacitor, the top can easily open and vent out the pressure without causing arms to the surrounding equipment.
Each time you find a capacitor and the top vent is swollen up or already bust, it a clear evidence that the capacitor is damaged already. Each time the capacitor is about to fail, it releases a gas pressure which will break the top or cause it to be swollen.
Bulging of the Bottom of the capacitor.
Sometimes, during the capacitor failure, the capacitor top vent might not bulge intended the button of the capacitor will swell up. Pushing out the button rubber packing. When you observe a bulge in the bottom side of the capacitor, it is a sign of a fall capacitor. So replacing it with a good one becomes a good option.
visual checking of SMD and Ceramic Capacitor.
Before now we talked about the visual checking of an electrolyte capacitor. But moving forward a little, let’s also look at the way we can identify failed smd and ceramic capacitors without using testing instruments.
When you inspect a capacitor on the circuit and manage to find any of this following signs, it mean the capacitor is bad.
- cracked/ broken housing casing.
- Hole on the housing casing.
- Broken terminals.
- Burnt and signs of burnt on the casing or around the terminals.
Traditional Method to check if Capacitor is good or bad.
Among all the listed ways to test a capacitor, this particular method is more dangerous and needs more care when testing. And because of that, we recommend it only to the professionals in the electrical field. So if you are still a novice in the field, I recommend every other method but not this particular traditional method.
When carrying out this test, follow the produce below;
- Remove the capacitor from the circuit board. You can do this by soldering out one of the capacitor legs from the board.
- Fully discharge the capacitor using a resistor or other options.
- You can use a lead wire to extend the capacitor terminal for easy testing.
- Charge the capacitor with 12- 24V DC or 120 230V AC. 12V to 24V DC should be used to charge both polar and nonpolar capacitors but a resistor should be connected in series with the positive terminal of the battery to the capacitor. A 1k ohm to 10K ohm, 5-50W resistor should be used to limit execs current when charging.
- Now, charge by connecting the capacitor lead to the provided DC source or AC. Make sure the resistor is put in place. This is done within a short period like 1-4 seconds and removes the capacitor.
- Short the capacitor terminals ( flash from the voltage spike might occur and that is while is ad isable you wore a safety goggle glas)
- So, if it makes strongg spark when short the capacitor terminals then the capacitor is good. But when it makes little or no spark at all, it shows the capacitor is bad.
Note: polar capacitors should not be connected to an AC source as a means of charging it.