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How To Test A Capacitor?Eight Ways To Test Capacitors

How To Test A Capacitor?Eight Ways To Test Capacitors

November 07 , 2023 0

In most electrical and electronic troubleshooting and repair work, there is a common capacitor problem, if you want to know how to test and check the capacitor? Are capacitors good or bad? Short circuit or open circuit? Here, you can check that the capacitor is in good condition with analog (AVO, amperage, voltage, ohm) and digital multimeters, or you can replace it with a brand new capacitor.Here are eight ways to check and test capacitors for good, defective, open, dead, or short circuits

I.Test The Capacitor-Resistance Mode Using A Digital Multimeter

To be in resistance "." Or test capacitance in Ohm mode by DMM (digital multimeter), follow the steps below
1. Ensure that the capacitor is fully discharged.
2.Set the meter in the ohm range (set to at least 1000 ohms = 1kQ)

3.Connect the multimeter probe to the capacitor terminal (negative to negative and positive to positive).
4 The digital multimeter displays the value.
5 will then immediately return to OL (open line) or infinity "oo"
Conclusion:
If every attempt at Step 2 shows the same result as shown in steps 4 and 5, this means that the capacitor is good, if not, then the capacitor is bad.

II.Use An Analog Multimeter To Check The Capacitor-Ohm Mode

To check your capacitance with an AVO (ampere-volt-ohmmeter) in resistance "Ω" or ohm mode, follow these steps.
1, ensure that the suspicious capacitor has been fully discharged.
2. Get an AVO meter.
3. Rotate the knob on the analog meter to select the resistance "OHM" mode (always select the higher ohm range).
4. Connect the multimeter wire to the capacitor terminal. (COM is connected to the -Ve terminal and is connected to the +Ve terminal).
5. Note the readings and compare them with the following results.

Conclusion:
Short-circuit capacitors: Short-circuit capacitors will show very low resistance.
Open capacitors: Open capacitors do not show any movement (deflection) on the ohmmeter scale.
Good capacitance: will initially show low resistance, and then gradually increase to infinity. This means the capacitor is in good condition.

III.Use A Multimeter To Check Capacitance In Capacitor Mode

Note: Capacitors can only be tested in capacitor mode if the analog or digital multimeter has a Farad with capacitor "C" function. The capacitor mode function of the multimeter can also be used to test tiny capacitors. To do this, turn the knob of the multimeter to capacitor mode and follow the basic instructions below.

1. Ensure that the capacitor is fully discharged.
2. Remove the capacitor from the circuit board.
3. Now select Capacitor "C" on the multimeter.
4. Now connect the capacitor terminal to the multimeter lead. (Red to positive and black to negative).
5, if the reading is close to the actual value of the capacitor (that is, the printed value on the capacitor container box).
6. Then the capacitor is in good condition. (Note that the reading may be less than the actual value of the capacitor (the capacitor's rating is ±10 or ±20 depending on the difference).

Conclusion:
If you read a significantly lower capacitance value or none at all, it indicates that the capacitor is exhausted and you should replace it with a new one to ensure proper operation.

IV.Test Capacitance With A Simple Voltmeter

This method is applied to polar and non-polar capacitors, and the nominal voltage value of the capacitor must be known. The voltage level is printed on the nameplate of the electrolytic capacitor. Although specific codes are printed on the ceramic and SMD capacitors, you can also proceed as follows.
In addition, you can perform this test using the DC voltage "V" or voltage mode in a digital or analog multimeter. 1, make sure that the single lead of the capacitor is disconnected from the circuit (don't worry about the positive (long) or negative (short)) (if necessary, you can also completely disconnect the connection) 2, check the capacitor voltage rating printed on it (as shown in the example below, the voltage = 16V) 3, now charge this capacitor for a few seconds to the rated voltage. (Not an exact value but less than that, using a 9V battery to charge a 16V capacitor. If the battery voltage value is greater than the nominal voltage of the capacitor, it will damage or explode the capacitor. Make sure to connect the positive (red) wire of the voltage source to the positive (long) wire of the capacitor and the negative to the negative. 4, set the value of the voltmeter to DC voltage, and connect the capacitor to the voltmeter by connecting the positive wire of the battery to the positive wire of the capacitor and the negative electrode to the negative electrode. You can use a digital or analog multimeter while choosing a DC voltage range for the same purpose.

Conclusion:

Pay attention to the initial voltage reading in the voltmeter. If it is close to the supply voltage provided to the capacitor, the capacitor is in good condition. If it shows much less reading, then the capacitor is dead. Note that the voltmeter will display the reading for a very short period of time because the capacitor will release the voltage it has stored in the voltmeter.

V.The Capacitance Is Tested By Measuring The Value OF The Time Constant

If the capacitance value of the capacitor is known in microfarads (symbol µF) printed on it, that is, the capacitor does not fuse and burn at all, we can find the value of the capacitor by measuring the time constant (TC or τ = Tau). In short, when a capacitor is charged through a resistance with a known value, the time it takes to charge the capacitor to about 63.2% of the applied voltage is called the capacitance time constant (τ = Tau is also called the RC time constant) and can be calculated by: τ = R x CR = known resistance in ohms C = Capacitance τ = Tau (time constant)

For example, if the supply voltage is 9V, 63.2% of the supply voltage is around 5.7V. We will use the stopwatch to charge the capacitor until the value reaches 5.7V, stop the watch and note the time reading in seconds. Now find the value of the capacitor by measuring the time constant (note: the oscilloscope can measure better with the exact value) 1 Make sure to disconnect the capacitor from the circuit board and discharge it. 2, the known resistance value (such as 5-10kΩ resistance) and the capacitor in series. 3, apply a known power supply voltage value. (e.g. 12V or 9V) to a capacitor in series with a 10kΩ resistor. 4. Now, measure the time it takes the capacitor to charge to approximately 63.2% of the applied voltage. For example, if the supply voltage is 9V, 63.2% of it is about 5.7V. 5, according to the value of the given resistance and the time measured by the stopwatch, calculate the capacitance value through the time constant formula, that is, τ = Tau (time constant) 6, now compare the calculated value of the capacitance with the electrical value printed on it.

Conclusion:

If the measured value is the same or nearly equal to the printed value, the capacitor is in good condition. If you find a significant difference between the two values, you need to replace the capacitor because it is not working properly.

VI.Test Capacitors Through Continuity Test Mode

In DMM and AVO meters, whether the capacitor is good, open or short, the on-off test mode can also be used. You can follow these simple instructions.
1. Disconnect the power supply and remove the capacitor from the circuit board.
2. Use a resistor to discharge the capacitor completely.
3. Turn the knob and set the multimeter to continuity test mode.
4. Connect the positive (RED) probe of the multimeter to the anode (+), and the common (black) probe to the cathode (-) terminal of the capacitor.
5, if the multimeter shows signs of normal turn-on (beep or LED light) and suddenly stops and shows OL (open circuit). This means that the capacitor is in good condition.

Conclusion:

If the multimeter does not display a turn-on sign with a beep or LED, the capacitor is open. If the multimeter LED lights up and emits a continuous drip sound, it indicates that the capacitor is short circuited and a new capacitor should be replaced.

VII.Capacitance Is Tested By Visual And Apparent Inspection

Observe the obvious signs of the capacitor, and the failure of the capacitor can be clearly seen without a multimeter. If you find the following 2 situations, the capacitor has failed and damaged:

The Top Vent OF The Capacitor Is Bulging

The top vent of a K, T, or X type electrolytic capacitor is a weak spot where pressure is released when the capacitor fails to avoid serious damage to the surrounding and any other components connected near it.

If the top of the capacitor is found to bulge, it is an electrolytic discharge (black, white, orange, depending on the electrolytic material), that is, the capacitor releases gas pressure and destroys the top vent of the capacitor when it fails.

Among the capacitors shown in the figure above, the capacitor on the left appears obvious bulge, in which case the capacitor may have been damaged, and the appearance on the far right has no obvious problem.

Capacitor Drum Bottom Lifting Housing

If the gas pressure created during a failure does not break the top vent of the capacitor, it will push through the bottom and push the rubber, causing the bottom to bulge and lift the housing.

As shown in the figure above, the three capacitors on the left have obvious bumps, while the one on the far right has no problems from the appearance

Test SMD And Ceramic Capacitors

If the following signs are found on ceramic or miniature SMD capacitors, they are faulty and need to be replaced with the correct capacitor.

The shell is damaged or cracked.
The shell is damaged or has any signs of burning, a hole in the shell.
Terminal failure

VIII.Traditional Methods OF Testing And Checking Capacitors

Note: Not recommended for everyone, only for professionals, because it is more dangerous.

Safety precautions and warnings must be followed before applying this method. This method is suitable for emergency situations where there is no other option to check the quality of the capacitor. If you are unsure, it is still recommended to use 1-7 methods to troubleshoot the capacitor.

If you want to check capacitors (e.g., fan capacitors, indoor air cooler capacitors, or miniature capacitors in circuit boards/PCBS, etc.), test capacitors by Method 8. For proper safety, 12 to 24V DC power supplies are used in the case of polar and non-polar capacitors with 1kΩ~10kΩ and 5~50W resistors. The resistor should be connected in series to the positive terminals of the battery and capacitor. In this way, it will reduce the excessive current when the capacitor is charged. In the absence of DC power (such as batteries), you can use 120-230V AC, but you must connect a series of resistors (such as 1kΩ to 10kΩ, 5 to 50Watts) to the connecting capacitor and 230V AC power. In this way, it will reduce the charging and discharging current. Here is a step-by-step tutorial for checking capacitance with this method.
1. Disconnect the suspicious capacitor from the power supply, or ensure that at least one lead of the capacitor is disconnected from the PCB board.
2. Ensure that the capacitor is fully discharged.
3. Connect the two separate leads to the capacitor terminal. (optional)
4. Now securely connect these wires to a 24VDC or 230V AC power supply for a very short period of time (about 1-4 seconds) [or for a short period of time when the voltage rises to 63.2% of the supply voltage].
5. Remove the safety wire from the 24VDC/230V AC power supply.
6. Now short connect the capacitor terminal (please be careful and make sure to wear safety goggles

Conclusion:
If it produces a strong spark, then the capacitor is good. If it produces a weak spark or no spark at all, then it is a defective capacitor.