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How to Test a Capacitor (in-circuit or after De-solder)- 5 Methods

In the circuit board assembly there are a lot of electronic components like transistors,capacitors, integrated circuit (IC) etc are used.When due to any reason components get defective, they need to be replaced with a new one to repair the device.

During troubleshooting it needs to identify the faulty component by doing measurement with the help of tools or visual verification.

Specifically if we talk about the capacitor because they are highly sensitive to spikes and over voltage can burnout and damage the capacitor permanently.   

In this article we are going to discuss How to test capacitors to identify defective or working conditions to repair. How to test a capacitor with a multimeter or other tools to troubleshoot.

The capacitor is a component that stores energy in the form of Electric Charge and often used in electronics home appliances like air conditioning fan motors and compressors to perform a variety of functions.

The capacitors are further classified in two types, Electrolytic that is mainly used in vacuum and transistor power supplies and another is used to regulate direct current called Non Electrolytic capacitor.

How to Test a Capacitor by Digital & Analog Multimeter


1 Using a Digital Multimeter With Capacitance Setting

This is most common and the easiest way to test capacitors with the help of digital multimeter having capacitance meter feature. Nowadays maximum digital multimeters have the inbuilt capacitance meter. This method is also applicable to tiny SMD components as well. 

How to test a capacitor with a digital multimeter to get answer needs to follow the below steps

  • De-solder the capacitor from the circuit and make sure that capacitor must be fully discharged to get an accurate measured value.
  • Not down the capacitor value on its body that was mentioned in Farads as the unit for capacitance is the farad normally in micro farad ( µF).
  • Turned the knob and Select “Capacitance” settings on your multimeter
  • Connect the multimeter probe to the capacitor terminals. If it is polarity Connect the positive terminal with red and the other with black multimeter probe.
  • Check the multimeter reading on display and note down actual reading  on paper. 
  • Compare the both readings and If there is a huge gap between the printed value and measured value or shows zero value it means the capacitor is faulty and replace it with OK one.

2 Using a Digital Multimeter Without Capacitance Setting

A few Digital Multimeters do not have the capacitance feature so the above method is not applicable but still we can check the capacitor by measuring resistance value.

Below are the Step by step activities how to test a capacitor with multimeter with resistance value

  • De-solder and remove the capacitor from its circuit and ensure that must be fully discharged.
  • Set the Multimeter knob to Ohm ( unit of Resistance) or geek letter omega (Ω) as shown in fig.
  • Connect the multimeter leads to the capacitor terminals and ensure again for red one on positive and black for negative terminal.
  • Check and write down initial resistance reading shown on display. Soon after showing some value for a short time it sets to display an infinity (Open) value.
  • Disconnect the probes and respect it again and again. If shown the same results as the first time it means that the capacitor is OK.
  • And if there is no change in any of the repeated tests it means that the capacitor is faulty (dead).

3 Test a Capacitor using Simple Analog Multimeter

We can check the capacitor just like the digital Multimeters by using other parameters like Current (A), Voltage (V) and Resistance (O) etc. In this section we will test the capacitor with help of resistance measurement.

Below are the Step by step activities how to test a capacitor with using Simple Analog Multimeter

  • Repeat the same Step again -De-solder and remove the capacitor from its circuit and ensure that must be fully discharged.
  • Set your multimeter knob on to its resistance setting ( Ohmmeter Ω) and select for higher range.
  • Put the red probe on the positive terminal and black probe on the negative terminal. 
  • In analog multimeters the needle pointer on display measures the reading and the position of the needle determines the capacitance outcome.
  • If a needle on display initially has a low value and after some times moves to the right side and displays a higher value it means that the capacitor is OK.
  • If the needle initially shows low value and does not move further it indicates that the capacitor is faulty and internally short.
  • In the third scenario the needle does not show any resistance value and does not move right or further for any value it means the capacitor is open and faulty.

4 Testing a Capacitor With a Voltmeter

Here we learn how to test the capacitor by using a simple voltmeter and get voltage rating of a capacitor to check for defective or good identification.

Below are the Step by step activities how to test a capacitor with Testing a Capacitor With a Voltmeter

  • De-solder a capacitor and remove it from the circuit after getting fully discharged. You can also try removing one lag for measurement.
  • Check the capacitor’s voltage rating outside the capacitor body and note down on paper displaying it on the meter. It is a number printed on the body followed by a capital “V,” like 16V,50V or any other value.
  • Now Charge the capacitor with a known voltage source that has less than the rated value. For example if rated capacitor voltage is 30 V Charge it with 9 V and 600 Volt charge it at least with 400 V.
  • Let it charge for a few seconds but ensure that the Red probe connects positive terminal and black for negative terminal. 
  • Now the next step is Set your voltmeter to read DC voltage settings and measure the voltage of the charged capacitor by connecting the red probe to positive and black probe from negative terminal. 
  • If the measured value is close to the rated value it indicates that the capacitor is good. If the voltage gap is higher than the capacitor is faulty.

5 Shorting the Capacitor Terminal 

In the old time this method was more popular because it did not require any measuring device for validation.How to test a capacitor without a multimeter will discuss steps here

This method is risky and not recommended by professionals but if required to conduct needs to take safety precautions. Need to wear safety gloves and do not touch any conductive metal surface.Below are the Step by step activities how to test a capacitor by Shorting the Capacitor Terminal.How to test the capacitor below steps are involved

  • Disconnect the capacitor by de-solder from the circuit board and the capacitor must be discharged completely. 
  • Connect red to positive terminal and black with negative terminal of power supply for 1 to 4 seconds..
  • Now short the capacitors from a metallic wire or rod while taking safety precautions to prevent electric shock.
  • The strength of spark gives the indication of capacitor charging capacity.If spark is strong and long the capacitor is in good condition. If not, the capacitor is faulty.

How to test the capacitor without Desoldering

Now another question is how to test the capacitor without desoldering or without removing the capacitor from the circuit board.

When a capacitor is mounted In circuit board it is not possible to measure the actual rated value through the multimeter or capacitance meter because there are several other components placed in the same circuit board.Due to that capacitor gets equivalent value rather than actual.

Now again the question is again the same: how to test the capacitor without desoldering the component and if yes how it is possible.


Yes it is possible by using an equivalent series resistance (ESR) meter or smart tweezers both work fine but ESR meter more suitable for through hole components and smart tweezers for tiny SMD components. How to test capacitor without Desoldering Below 3 methods are used to identify the faulty capacitor.

1 Test a capacitor with ESR Meter

The ESR meter device used to determine the equivalent series resistance of a capacitor without desoldering or removing from the circuit board.This device can not measure the capacitance but can test the capacitor.You Can Buy online (ESR meter (Amazon Link)
 

Below are the  steps that need to be followed to test capacitor insight into the circuit.

  • To test the capacitor first and important step is discharge the capacitor completely. To discharge you can short the capacitor terminal by help of metallic items.
  • Turn on the ESR meter and contact the red leg with capacitor positive terminal and black with negative terminal.and short its leads till display zero reading.
  • Note the reading of the ESR meter and note it down.
  • Now compare the noted table reading on the body of the ESR meter. If the gap is within range then the capacitor is OK and no need to change. 
  • ESR is not giving any table you can check with a capacitor data sheet and compare with measured value.

2 Smart Tweezers

Smart Tweezers are more handy and Portable to do jobs more fun and comfortably.ESR Meter are not more reliable dealing with the tiny SMD component.

But the drawback of smart tweezers are that they are too costly otherwise they work very smart and effectively.(Smart Tweezer (Amazon link)

3 Visual inspection for Bad Capacitor

Sometimes you can check the capacitor by visual inception rather than using the smart tweezers or ESR meter easily. 
 
A faulty capacitor gets swallowed on top side and gets some damage or burnt remarks on the body.If you find such observations during inspection then replace the suspected capacitor for fresh.

Conclusion

Now you will get the answer of the query for how to test a capacitor in both conditions removing from circuit board or with circuit board.

Faulty capacitors can be identified by digital multimeters, ESR meter and also usage of smart tweezers.how to test a capacitor with a multimeter in a circuit answer is ESR meter and smart tweezers.

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