Testing a capacitor on a circuit board can be challenging and time consuming, but it’s an important part of maintaining the integrity of the electronics involved. This guide will give you the knowledge to properly test capacitors on circuit boards in order to ensure they are functioning correctly and working as intended. We’ll discuss how to identify capacitors, what tools you need, the test process and other useful tips.
What Is a Capacitor?
It has two conductors called plates separated by an insulator, usually air or a dielectric material such as paper, plastic or ceramic. When a voltage is applied across the capacitors’ plates, electrical charge accumulates on each plate and creates an electric field within the device. This electric field can store energy for a period of time, allowing the capacitor to function as an electrical buffer, or surge protector. [3]
How Does a Capacitor Work?
A capacitor is an electronic device that stores energy in the form of electrical charge. It accomplishes this storage by having two metallic plates separated by a non-conductive material, such as paper or plastic. This separation prevents electrons from flowing between the plates, but allows them to flow around it.
When a DC voltage is applied across the plates of a capacitor, the electrons flow from one plate to the other, creating an electric field. This electrical field stores energy, allowing the capacitor to act as a storage device for voltage and current in a circuit. [3]
Types of Capacitors
Capacitors come in a variety of shapes and sizes, so you must determine what type of capacitor you are testing. The two most common types are electrolytic capacitors and ceramic capacitors. Electrolytic capacitors have an anode and cathode, while ceramic capacitors typically only have two leads that connect to the circuit board. [3]
Tools Required To Test A Capacitor
Testing a capacitor on a circuit board requires the use of specialized tools. The most common tool used is an ohmmeter, which measures resistance or impedance between two points in the electrical circuit. This helps to determine whether there is an issue with the capacitor, such as a short. Other tools that may be needed are a multimeter or voltmeter for measuring voltage and a specialized capacitor tester. [4]
Why do we need to Test a Capacitor?
Testing a capacitor on a circuit board requires the knowledge of basic electricity and how it works. Capacitors are electronic components that store electricity, and they help regulate current flow in a circuit board. It is important to test the capacitors regularly because if they fail or become damaged, other components on the circuit board can be affected. Knowing how to properly test them can help you diagnose and correct problems quickly. [4]
How to Discharge a Capacitor?
Using a Screwdriver
Using a screwdriver to discharge a capacitor is the most common and simplest way of doing so. This method involves using two insulated screwdrivers and touching them together against both ends of the capacitor. When you do this, it will cause an electrical current to flow through the capacitor’s leads and allow any build-up charge to be released safely. However, it is important to note that this method should only be used when the capacitor is not connected to any other components. [1]
Using a Discharge Resistor (Bleeder Resistor)
Another method for discharging a capacitor is to use a discharge resistor, also known as a bleeder resistor. This device works by allowing an electrical current to flow through it until the voltage in the capacitor drops below a certain level. As long as the capacitor is connected to power, this will cause any build-up charge to be safely released from the component. [1]
What is an ESR meter?
It is specifically designed for testing capacitors, and it can be used to detect faulty ones or ones that have aged significantly.
The ESR meter works by sending a current through the capacitor and measuring the voltage drop that occurs. If the voltage drop is higher than expected, it may indicate a faulty capacitor. By measuring the ESR value of a given capacitor, you can get an indication of its overall condition and determine if it needs to be replaced or not. [2]
Testing in-circuit bad capacitors using an ESR meter
An ESR meter is a great tool for testing capacitors while still in-circuit. It requires minimal effort and no disassembly of the circuit board.
To test your capacitor with an ESR meter, first set up your circuit board correctly. Make sure all connections are secure and there are no shorts or breaks in the circuit. Next connect one lead of the ESR meter to the positive end of your capacitor and the other lead to the negative. The ESR meter will then measure the equivalent series resistance (ESR) of your capacitor, which is a good indication of its overall health. [2]
Smart Tweezers
For a quick and precise test of capacitors, we recommend the use of smart tweezers. These handy devices make it easier to measure a capacitor’s capacity without having to open up the circuit board. Smart tweezers allow you to accurately check both ceramic and electrolytic capacitors in just seconds! They also have an LED light that indicates when you’ve completed a successful measurement. [2]
Visually seeing a bad capacitor
Sometimes it’s possible to see a bad capacitor just by looking at the circuit board. Look for bulging, broken solder seals, and signs of corrosion such as white or black spots on the body of the capacitor. If you see any of these signs, then your capacitor has probably failed and needs to be replaced.
Testing a Capacitor With a Multimeter
Testing a capacitor with a multimeter is an easy and effective way to ensure that it’s in good working condition. To do this, you’ll need to identify the capacitor’s connections and make sure your multimeter is set up properly before testing.
Connecting the Multimeter
The first step when testing a capacitor on a circuit board is to identify the capacitor’s connections. Once you know which connection points you need to use, you can set your multimeter accordingly. For most capacitors, you’ll need to connect the negative terminal of your multimeter to ground and the positive terminal to one of the capacitor’s terminals.
Testing With a Multimeter
Once your multimeter is connected to the correct terminals, turn it on and set the meter to “capacitance” or “capacitance measurement”. Then, select the appropriate range for your capacitor’s capacitance rating. When you’re finished with that, you can proceed with testing by pressing the multimeter’s test button and noting its reading. [2]
Measuring Your Capacitor’s Capacitance With a Multimeter
Measuring a capacitor’s capacitance is an important part of testing it on a circuit board. A multimeter is the best tool for this job, and it’s relatively simple to use. Here are the steps you need to follow:
- Make sure your multimeter is switched to “capacitance” mode and set the range setting appropriately.
- Connect the two probes of the multimeter to the capacitor’s terminals. Make sure that you don’t touch any other components on the circuit board, as doing so may cause a short circuit and damage your multimeter or even the circuit itself!
- Read off the capacitance value displayed on the display. This is usually measured in Farads (F).
- Compare the measured value with the nominal value of the capacitor indicated on its label. If there is a significant discrepancy, it may be indicative of a faulty or damaged component and should be replaced as soon as possible. [4]
Measuring Your Capacitor’s Resistance With a Multimeter
One of the simplest ways to test a capacitor on a circuit board is to measure its resistance with a multimeter. To do this, connect one probe of your multimeter to each end of the capacitor, and then switch it to the Ohms option. If you get an accurate reading, then your capacitor is working properly. However, if you don’t get an accurate reading, then your capacitor is either broken or shorted.
If the resistance of your capacitor reads as infinite, then it means that it has been damaged and needs to be replaced. It’s important to note that capacitors are not perfect; over time their performance level can decrease due to aging and heat damage. If you suspect this is the case with your capacitor, then it’s recommended to replace it with a new one.
If the resistance of your capacitor reads as zero, then it may be shorted. This can happen if the capacitor has been exposed to too much heat or voltage and could cause issues in your circuit board. In this case, you should also replace the damaged component with a new one. [4]
Testing a Capacitor by measuring the Time Constant
Measuring the time constant (or RC constant) of a capacitor can help you determine its value and condition. To test a capacitor in this way, you will need an oscilloscope or frequency counter and a function generator. Connect the two leads of the capacitor to the input and output of your signal generator, then connect the oscilloscope or frequency meter to measure the voltage across the capacitor.
Set your function generator to produce a square wave pulse and adjust the amplitude of the signal, as well as its frequency. This will cause current to flow through the capacitor, which is then measured by the oscilloscope or frequency meter. [5]
Test a Capacitor with a simple Voltmeter
Testing a capacitor on a circuit board is easy with the help of a voltmeter. To use this method, you will need to connect the leads of the meter to both ends of the capacitor and measure the voltage across it. If the reading is 0 volts, then your capacitor is functioning correctly. However, if you get any other value than 0 volts, then it’s likely that the capacitor needs to be replaced.
To complete this test, make sure you select the correct range on your voltmeter. If you try to measure a voltage greater than what your meter can handle, then it will not give an accurate result and could also cause damage to your circuit board. [5]
Test a Capacitor using Analog Multimeter (AVO Meter)
Testing a capacitor on a circuit board can be done using an analog multimeter (AVO Meter). This method is quite straightforward and requires minimal technical knowledge.
To begin, you’ll need to set the meter to the “Ohms” setting. Next, make sure that the two terminals of the capacitor are in contact with your leads by pressing the probes firmly against them. The meter should indicate a small but finite resistance value, typically in the range of 0-100 ohms. If the reading is higher than 100 ohms, it may be an indication that the capacitor has failed. [5]
Shorting the Leads of Capacitor (Traditional Method – only for Professionals)
This method will require a professional as it involves shorting the leads of the capacitor. This means that two thin wires must be connected to the leads of each capacitor on the board and then touching each other. An electric current, although faint, will pass through when shorted correctly; meaning the capacitor is working correctly. It’s best to use an ohmmeter to check if the capacitor is working correctly.
The problem with this method is that it has a high risk of damaging both the capacitor and connector. It’s important to be very careful when dealing with capacitors as they can easily get damaged or even explode when mishandled. [5]
FAQ
How do you know if a capacitor is bad on a circuit board?
To test if a capacitor is bad, you can measure its capacitance with a multimeter and compare it to the capacitor’s rated value. You can also visually inspect the capacitor for signs of failure, such as bulging or leaking electroly.
How do you test a capacitor with a multimeter?
To test a capacitor with a multimeter, set the device to measure capacitance. Discharge any stored charge from the capacitor by touching its leads together for several seconds. Now connect the meter’s probes to the capacitor’s terminals and note down the reading displayed on the display. This is known as “capacitance value” in units of farads.
How do you test if a capacitor is bad?
Testing if a capacitor is bad can be done in two ways: visually and with a multimeter. Visually, look for signs of damage such as bulging or leaking electrolyte. With a multimeter, measure the capacitance value of the capacitor and compare it to its rated value. If they don’t match up, the capacitor is likely bad and will need to be replaced.
If you suspect a capacitor may be the cause of an issue on your circuit board, it’s best to replace it with a new one as soon as possible. This will ensure that no further damage is done to other components or the circuit board itself.
What are the 2 typical signs that a capacitor is bad or has failed?
The two typical signs that a capacitor has failed are bulging and leaking electrolyte. In both cases, the capacitor will need to be replaced. Other signs of failure may include discoloration or internal corrosion.
Should a capacitor have continuity?
No, a capacitor should not have continuity. If there is continuity between the leads of a capacitor, it means that the device has failed and should be replaced.
What if a capacitor reads 0 ohms?
If a capacitor reads 0 ohms, it means that the device has failed and should be replaced. This is because capacitors are designed to not have any electrical resistance, so if it reads 0 ohms then something has gone wrong with the component.
How many ohms should a capacitor have?
A capacitor should not have any ohms. This is because capacitors are designed to not have any electrical resistance, so if it reads 0 ohms then something has gone wrong with the component. If a capacitor reads anything other than 0 ohms, it means that the device has failed and should be replaced.
Useful Video: EEVblog 1474 – Can You Measure Capacitors IN Circuit?
Conclusion
Testing a capacitor on a circuit board is easier than it seems. By following the steps outlined in this article, you can accurately test capacitors on a circuit board and find any faulty ones. If any of your tests result in abnormal readings, it’s best to replace the component rather than risk further damage to other components in the system.
To ensure the best results, always check the manufacturer’s specifications for your capacitors and circuit board. Remember that testing capacitors on a circuit board requires special equipment such as a multimeter or an oscilloscope in order to get accurate readings. If you don’t have these tools handy, it’s best to consult with a professional or take your device to an electronics repair shop.
With the right tools and knowledge, you can now easily test capacitors on a circuit board like a pro! So go ahead and get to work troubleshooting any faulty capacitors in your device. Good luck!
References
- https://www.yamanelectronics.com/test-capacitor-without-desoldering/
- https://www.makeuseof.com/how-to-test-a-capacitor/
- https://electrouniversity.com/how-to-test-a-capacitor-with-a-multimeter/
- https://www.electronicshub.org/how-to-test-a-capacitor/
- https://chintglobal.com/blog/capacitors-types-and-how-to-test-capacitor/
