Circuit boards are assembled from electronic components, such as transistors, capacitors, integrated circuits (IC). If for any reason a component faulty, it needs to be replaced with a new one to repair the device. The first step in troubleshooting is to determine which component of the system is defective by measuring it with tools or by visual inspection.
For instance, if we discuss capacitors, they are highly sensitive to spikes, and over-voltage can permanently damage the capacitor. How to test capacitors to identify defective or working conditions to repair is the topic of this article. Troubleshooting a capacitor with a multimeter or other tools.
What is a capacitor?
The capacitor is a component that stores energy as an electric charge and is often found in electronic appliances like air conditioning fans and compressors to perform various functions.
Further, these capacitors can be divided into two types: Electrolytics, associated mainly with vacuum and transistor power supplies, and Non-Electrolytics, compatible with direct current regulation.
How to Test a Capacitor with a Multimeter
This tutorial will show you how to test an AC capacitor with a digital multimeter, as well as how to test it without one.
1. Using a Digital Multimeter With Capacitance Setting
Testing capacitors with a digital multimeter that has a capacitance meter feature is one of the easiest and most common ways. In modern digital multimeters you can find a capacitance meter as well as a voltage meter
Similarly, this method works on tiny SMD components as well. Step-by-step instructions on how to test an AC capacitor using your digital multimeter can be found below
- Remove the capacitor from the circuit and make sure that it has been fully discharged before measuring its value.
- Note that the capacitor value on its body is in Farads, as the unit for capacitance is the farad normally expressed in microfarads (F).
- Set your multimeter to “capacitance” mode by turning the knob
- The multimeter probe should be connected to the capacitor terminals. Connect the positive terminal with a red multimeter probe and the negative terminal with a black probe if it is polarity.
- Make a note of the actual reading on a piece of paper after checking the multimeter.
- Compare both readings and if there is a large difference between the printed reading and the measured reading or the measured reading is zero, the capacitor is faulty and needs to be replaced with an OK one.
2. Using a Digital Multimeter Without Capacitance Setting
Several Digital Multimeters do not include a capacitance feature, so the above method is not applicable, but we can still test the capacitor by measuring its resistance. Step by step instructions on testing a capacitor with a multimeter by measuring its resistance
- Remove the capacitor from its circuit and make sure it is fully discharged.
- Set the Multimeter knob to Ohm (unit of Resistance) or the Greek letter omega (*) as shown in Figure 1.
- Connect the multimeter leads to the capacitor terminals again, ensuring that the red one is on the positive terminal and the black one is on the negative terminal.
- The first resistance reading that appears on the display should be noted. Within a few seconds, it sets to display a value of infinity (Open).
- Disconnect the probes and respect them repeatedly. This indicates that the capacitor is in good working order if the results are the same as the first time.
- The capacitor is faulty (dead) if it doesn’t change in any of the repeated tests.
3. Test a Capacitor using Simple Analog Multimeter
By using other parameters, such as current (A), voltage (V), and resistance (O), we can test the capacitor just like we can with digital multimeters. This section explains how you can test the capacitor with a resistance measurement. This is a step-by-step guide on how to test a capacitor with a simple analog multimeter
- Follow the same steps again: remove the capacitor from its circuit and inspect it for full discharge.
- Make sure your multimeter is set to its resistance setting (Ohmmeter *) and select the higher range.
- The red probe should go on the positive terminal, while the black probe should go on the negative terminal.
- The needle pointer on the display of an analog multimeter measures the reading and the position of the needle determines the capacitance result.
- It indicates that the capacitor is functioning properly if the needle initially displays a low value and then moves to the right side and displays a higher value after some time.
- When the needle initially shows the low value and does not move further, it indicates a faulty capacitor.
- It is possible that the needle in the third case shows no resistance value or does not move for any value. This indicates that the capacitor is open and faulty.
3. Testing a Capacitor With a Voltmeter
To check whether a capacitor is defective or not, we will use a simple voltmeter to measure its voltage rating. You can follow these steps to test a capacitor with a voltmeter in the following section: Testing a Capacitor With a Voltmeter
- After a capacitor has been fully discharged, desolder it and remove it from the circuit. For measurement, you can also remove one lag.
- The voltage rating of the capacitor should be written on a piece of paper on the meter and checked outside of the capacitor body. You can find the number after the capital “V” on any part of the body. For example, 16V,50V, or another value.
- The capacitor now needs to be charged with a voltage less than its rating. If the rated voltage of the capacitor is 30 V, charge it with 9 V and charge it with 600 V at least.
- Make sure the positive terminal is connected to the red probe, and the negative terminal to the black probe.
- Connect the red probe to the positive terminal and connect the black probe to the negative terminal of your voltmeter. Now you’re ready to measure the voltage of the charged capacitor.
- A capacitor that measures close to its rated value is a good capacitor. The capacitor is faulty if the voltage gap is higher.
4. Shorting the Capacitor Terminal
This method was more popular in the old days, as it did not require any measuring devices for validation. In this article, we will discuss how to test a capacitor without a multimeter
The method is risky and not recommended by professionals, but if it is required, safety precautions must be taken. Safety gloves must be worn and metal surfaces cannot be touched. Following is a step-by-step guide on how to short the capacitor terminal to test a capacitor. The following steps are involved in testing a capacitor
- Remove the capacitor from the circuit board by de-soldering, and the capacitor must be discharged completely.
- For one to four seconds, connect red to the positive terminal and black to the negative terminal of the power supply.
- As a safety precaution, short the capacitors to a metallic wire or rod.
- A spark’s intensity can be used to determine the charging capacity of a capacitor. The capacitor is in good condition if the spark is strong and long. Otherwise, the capacitor is faulty.
How to test a capacitor with a multimeter in a circuit
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 On the 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 the 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 it from the circuit board. This device can not measure the capacitance but can test the capacitor. You Can Buy online (ESR meter (Amazon Link)
- To test the capacitor first and important step is to discharge the capacitor completely. To discharge you can short the capacitor terminal with the help of metallic items.
- Turn on the ESR meter and contact the red leg with the capacitor positive terminal and black with the 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 datasheet and compare it with the measured value.
2. Smart Tweezers
Smart Tweezers are more handy and Portable to do jobs more fun and comfortable.ESR Meter is not more reliable in dealing with the tiny SMD component.
But the drawback of smart tweezers is 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 the 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 – Wrapping it up
With this information you will be able to answer the question of How to Test a Capacitor with a Multimeter in both conditions: without removing it from the circuit board and with it attached to the circuit board. Also, how to check capacitors without a multimeter.
With the use of digital multimeters and ESR meters, as well as smart tweezers, you can identify faulty capacitors. A multimeter is used to measure the ESR of a capacitor in a circuit, and smart tweezers are used for capacitor inspection.