How to identify a faulty capacitor. How to test a capacitor with a multimeter: simple methods

When assembling any modern electrical equipment today, special current storage devices are used - capacitors. Being a small device and experiencing a constant current load, capacitors quickly become unusable. Because of this, electrical equipment begins to work incorrectly. Therefore, the repair of any electrical device begins with the diagnosis of current storage devices. Read the article on how to check the performance of capacitors.

What is a capacitor used for and how does it work?

A capacitor is a two-pole device that can accumulate electrical charges and transfer them to other participants in the electrical circuit. The simplest capacitor has two metal electrodes separated by a dielectric. When a capacitor is connected to a power source, electrons are charged by positive and negative particles. At the same time, you can charge a discharged drive from a regular outlet.

Thus, until completely discharged, the capacitor turns into an independent power source.

The speed at which a drive discharges is affected by its capacity. Thus, a non-polar capacitor has a capacity of only a few microfarads and discharges quite quickly, while a polar storage device is able to hold a charge longer due to its capacitance in the range from 100 to 100,000 microfarads.

What is an electrolytic capacitor used for?

Capacitors can be used:

For compensation of reactive energy in industry;
Electric motor connections for 220-380 V;
As a power source for low-power electrical devices;
As a battery that allows you to diagnose electrical equipment (for example, optocoupler, electric convector, electric motor);
As a filter to suppress high-frequency and low-frequency interference, AC surges.

In addition, with the help of capacitors you can ring circuits and check electrical appliances. True, such a power source will be less efficient than rechargeable batteries, because its ability to store energy is lower than that of batteries due to leakage (self-discharge) of currents after disconnecting the drive from the charger.

Visually check the capacitor for functionality

Today, capacitors are used in most household appliances (washing machine, microwave oven, etc.). For example, for audio equipment (subwoofer), TNS 2th type capacitors are most often used, for computers (in the motherboard device) - SMD capacitors. For electromagnetic relays of DC motors and electromagnetic valves, ULN2003A type boards with electrolytic capacitors are used. When repairing such electrical equipment, there is often a need to check the functionality of capacitors.

You can determine whether the equipment malfunction concerns the capacitor by the appearance of the drive.

So, a punctured drive will have a swollen head, splits and cracks, and a dried one will have smudges left by liquid electrolytes. Traces of combustion will indicate that the capacitor has burned out. In the worst case, the drive will be torn. Then, equipment malfunction may be associated not only with the capacitor, but also with the elements surrounding it. After all, a ruptured or burnt capacitor could damage them too. How to understand that the drive is not working if its integrity is not compromised? To do this, you will have to measure the electrical capacitance of the element. This can be done using several devices.

Choosing a device for testing capacitors

Testing of capacitors is usually carried out with a multimeter (both modern and Soviet “tseshka”). This device is suitable for testing not only drives, but also voltage stabilizers. At the same time, it should be taken into account that some stabilizers (such as, for example, cw7805) have three terminals. Therefore, to check them you need to know the designation of the terminals. Using a multimeter, you can also check the operation of a transistor (for example, such as GB10Nb37LZ, which is often used in automotive technology), and diagnose ignition elements (for example, check the distributor contacts).

In addition to a multimeter, you can use the following to test the capacitor:

LC meter is a special device for testing the inductance and capacitance of capacitors;
A probe or tester with which you can measure the voltage of the drive and check it for a short circuit;
An ohmmeter with which you can find current leakage;
A tester of oxide capacitors, which will make it possible to select a used capacitor for the microcircuit.

In order to check a car capacitor, you can use a regular portable light bulb. To do this, you need to connect a light bulb to the contacts of the capacitor. If the light comes on, the capacitor has failed. When checking the voltage regulator Y112A1, the light on will indicate its serviceability. The regulator should be connected via a power supply and a jumper.

The capacitor itself can be used to shoot through the kinescope to restore its functionality.

In this case, the capacitor must have a capacity of 100-200 microfarads. This procedure will allow you to use the TV for some time.

Instructions: how to test a capacitor for functionality with a multimeter

In order to ring a high-voltage capacitor after desoldering it from the circuit using a multimeter, you must first discharge the terminals of the capacitor. This can be done using a screwdriver with an insulated handle or a powerful light bulb.

Then follows:

Place the meter for continuity or resistance measurement.
Touch the probes of the multimeter to the contacts of the capacitor, observing the polarity. You can distinguish plus from minus on an electrolytic capacitor by knowing the designations of the contacts. So, a short leg will indicate a plus, a long leg will mean a minus. On imported capacitors, the identification is even simpler - there are symbolic marks.
If the indicators on the display of the measuring device increase, then the device is functioning. In this case, the nominal value stated on the drive label must match the measurements. A lower value will indicate a drive failure.

In this way, you can check any starting working condenser (such as, for example, on a fan). The most common drives of this type are labeled cbb61 (svv61) and cbb60 (svv60).

The continuity test, in this case, must be carried out with a tester with an operating voltage not exceeding the storage voltage.

In order to test a bipolar capacitor, the measurement limit on the multimeter must be set to megaOhms. At the same time, it is not necessary to observe polarity. A bipolar capacitor, like ceramic, paper and film (mkp), can be connected in any direction. After this, you should measure the voltage. If the reading on the display is less than 2 megaohms, the drive is faulty and must be replaced. When choosing a new capacitor, you should not take the word for its labeling: Chinese drives (for example, cy400) have an overestimated voltage.

How to test a capacitor with a multimeter without desoldering

To measure the capacity of drives with a digital multimeter, you must first remove them from the circuit. This is due to the fact that when several capacitors are connected in parallel, their capacitances add up. When connected in series, the reciprocals are added. Therefore, the multimeter will always give a higher value - the total capacitance of all connected capacitors.

Thus, checking the serviceability of the drives with a multimeter without removing them from the circuit will only be possible through a breakdown.

You can measure the storage capacity on the board without desoldering using an oscilloscope with a signal generator connected. The connection diagram, in this case, should be a simple differentiating chain in which the generator will be connected in series with a resistor. In this case, the resistor must have a resistance equal to the output resistance of the generator. To check, a homemade device must be connected to the contacts of the capacitor through a tee with a load of 75 ohms, and the probes must be shorted.

The storage capacity is determined by the appearance of the signal:

If a signal appears on the oscilloscope screen in the form of sharp peaks located at the same distance, then the drive has lost capacity;
If the peaks have a smooth descending amplitude, then the storage capacity is 1 µF;
If the signal looks like rectangles, then the storage capacity is 100 microfarads.

Measurements must be carried out after calibrating the device: after a rectangular signal appears on the screen. When checking capacitors, do not forget about additional diagnostic tools. For example, the FurMark program and similar software will allow you to accurately diagnose a video card on a computer. You can restore your phone after incorrect firmware using a test point, through the GND and KCOLO contacts.

Procedure: how to check a capacitor with a voltmeter

A voltmeter will help you find out whether a capacitor, which is designed for a voltage of 1000 volts or more, is working correctly. In order to measure the storage capacity, you can use an ammeter and a voltmeter or two voltmeters. The device connection diagram will be the same. Measurements will need to be carried out using AC bridges.

In order to calculate the storage capacity you will need:

When measuring with a voltmeter and ammeter, the product of the measured current and ten to the sixth power is divided by the product of the voltage on the capacitor and the angular frequency of the network;
When measuring with two voltmeters, ten to the sixth power is divided by the product of the angular frequency of the network, the internal resistance of the voltmeter and the reactive power factor.

In this case, when measuring with a pair consisting of a voltmeter and an ammeter, the alternating voltage should change according to a sinusoidal law.

How to test a capacitor with a multimeter (video)

Checking capacitors for capacity, breakdown and leakage is an important component of the repair and design of electrical equipment. The performance of most modern electrical appliances and automotive equipment depends on the serviceability of capacitors. Use the above recommendations and instructions and check drives on any equipment yourself!

In this material we will talk about how to check a capacitor with a multimeter, if you do not have a device that checks the capacitance of capacitors - with an LC meter.

There are two types of capacitors: polar (electrolytic capacitors), and non-polar, which include all the rest. Polar type capacitors got their name due to the fact that they are soldered to radio equipment in a strict order: the positive contact of the capacitor to the positive contact of the circuit.

If the polarity of such a capacitor is violated, it may fail, even explode.

Imported capacitors are located on their upper part with a small cross or other figure, which is pressed into the case. In these places the body is thinner.

This is done to ensure safety. For this reason, if an imported capacitor explodes, its upper part will simply open. In the image you can see a swollen capacitor from the computer motherboard. The breakthrough was made exactly along the line.

Checking the capacitor with a multimeter

To check a capacitor using a multimeter, you need to adhere to one rule - the capacitance of the capacitor should not be less than 0.25 μFarad.

Before you test a capacitor with a multimeter, you should determine its polarity. To determine the polarity of the capacitor, just look carefully at its body; there should be markings on it. A minus sign is indicated using a tick. A black tick drawn over a bold gold stripe and a negative pin indicator.

Now, you should take a multimeter and set the toggle switch to dial mode (or resistance) and use the probes to touch the contacts. Since the multimeter produces a constant voltage in the continuity and resistance measurement mode, the capacitor will charge and as it charges, the capacitor's resistance will increase.

While charging is being done, the resistance value increases until it becomes too high. Let's see what it should look like.

Here only the contacts are touched using probes.

We continue to hold and watch the resistance grow

until it gets very big

It is convenient to test capacitors with an analog multimeter, since it is easy to track the rotation of the arrow, rather than the non-blinking numbers in a digital multimeter.

If, when the probes touch the capacitor, the multimeter beeps and shows zero, then this indicates a short circuit in the capacitor. If the multimeter immediately shows one, then there is a break in the capacitor. In any of the situations described, you should throw away the capacitor, since it is not working.

Testing non-polar capacitors is easier. We set the multimeter toggle switch to megaOhms and press the probes to the capacitor terminals. If the resistance value does not reach 2 MegaOhms, then the capacitor can be considered faulty.

Checking the capacitor with a tester video

Well, that's all, now you know how to test a capacitor with a multimeter. If you need to test a capacitor with a capacity of less than 0.25 μFarad, you will have to use a special device.

A capacitor helps store electrical charge. And if it is faulty, this property is lost.

They are classified into:

electrolytic, the connection of which to the circuit must be strictly defined;
non-polar, connected in any order.

To check the functionality of the capacitor, you should use a simple multimeter. This equipment helps in finding faults in the electrical circuit (voltage measurement, its “ringing”), and in analyzing the performance of individual electrical components.

Since a capacitor is an integral part of any electrical circuit and its non-working state is often the result of its expiration date, then a multimeter will come to the rescue, which will detect distortions in the signal of the electrical circuit.

Checking the serviceability of the electrolytic capacitor

The inspection begins with a visual inspection of the part. An explosion is a natural phenomenon with increased pressure inside the electrolyte housing if they are damaged. Even with a small explosive power, the harm will be to splash their contents around.

To prevent this, a cross-shaped notch is made at the top of the capacitors, which helps relieve pressure inside the housing. Swelling and rupture of the case already indicates a malfunction of the device.

In other cases, you will need to check the functionality of the capacitor with a multimeter, which will measure the battery resistance.

To do this, connect the device to the terminals of the capacitor, observing polarity.

Initially the resistance will be close to 0 due to the sparseness of the device. But when charging the capacitor from a battery, you can observe an increase in the resistance value. When charging is complete, the multimeter will display an infinitely large resistance.

Before checking the capacitor, it will need to be discharged, which can be done by shorting the terminals together. The limit value of the measurement is the maximum possible. The positive output of the part is connected to its red counterpart on the device. Connect the negative black output to another output.

When measuring resistance, monitor the constantly increasing readings of the multimeter. There should be no reductions. Contacts between outputs must be reliable.

The process must not be interrupted. It is prohibited to touch them due to the resistance of the human body, which will interfere with charging and determining the performance of the part.

Test results: The readings are 0 and there is no or only slight increase.
This means that there is a short circuit between the plates. And if the capacitor is connected to the working circuit, a short circuit will occur. A noticeable increase in instrument readings, but without them reaching infinity.

This means that there is a leakage current, with a significant decrease in the capacity of the product. The result is ineffective operation of the element without fully fulfilling its functional purpose. The signal will be distorted.

The multimeter voltage is up to 1.5 V, and in working circuits with a capacitor it is much higher. Therefore, if there is a leak in the device and its installation at operating voltage, its complete breakdown is possible.

Checking the serviceability of non-polar capacitors. The polarity of the connection is not important. A smaller capacity will not allow you to notice changes on the device. When the capacity indicators determined by a digital device are greater than its nominal value, the element is considered faulty. The multimeter readings are correct if there is an obvious short between the plates.
Testing a part with a voltage of 400 V or more is possible when charging it from the network at a point protected from a short circuit of the circuit breaker.

A resistor must also be connected in series with the capacitor, whose resistance is at least 100 ohms, to limit the initial current surge. At the moment after charging and after a while, the voltage is measured at the terminals of the part. At the same time, long-term charge retention is important. Afterwards, you will need to discharge the element using the resistor through which it was charged.

How to test a capacitor without desoldering it

Unfortunately, when heated with a soldering device during soldering, restoration of the properties of the capacitor part is a rare phenomenon.

And, unfortunately, there is no universal method for checking its serviceability without unsoldering this element from the circuit. Other elements surrounding it will bypass it with their resistance.
That's why: After soldering in the tested capacitor element, it is possible to turn on the equipment that has undergone repair in order to observe changes in its operation.
When improving or restoring the performance of this equipment, the tested part is replaced with a new one; To reduce the time for testing, only 1 of the terminals is desoldered
, which is not always possible for most electrolytic-type parts due to the design of their housing;

When connecting the element being tested in series with another

it is possible to determine its serviceability directly on the board by desoldering it;

In a complex circuit with many capacitors, the fault of the capacitor parts is determined by measuring the voltages across them. They have connection probes, a liquid crystal display and a range switch.

To check a capacitor element, first recognize its capacitance by the markings on its body, select the required measurement limit and connect it to the measuring device. There are models that measure capacitance without soldering elements from the circuit.

Given the existing scatter of parameters, the measured value of the part must be within the regulated tolerance. Otherwise the capacitor element is faulty.

You can purchase multimeters with this function built-in. There are models with standard probes for connecting the elements being tested and sockets on their body. However, the limits of these models are limited.

In case of failures in the circuit, the release date of the capacitor element is checked. Over a 5-year service life, this part may dry out by 55–75%. Therefore, it is better to immediately replace a part that is too old, because even the working element will introduce some distortions.
For maximum accuracy of measurement results before the verification process A new battery must be installed in the equipment.
Before checking, it is recommended to unsolder the capacitor completely or only 1 leg from the circuit. If the element is large and has wire connections, then 1 of them is disconnected. Otherwise the result will be distorted.
Touching the capacitor terminals with your hands when checking it is strictly prohibited. This is explained by the fact that the human body has a resistance of 4 ohms, which can distort the verification result.
For modern multimeters, the maximum measurement limit will be a capacitance of up to 200 μF. Elements with a capacity of up to 0.25 µF are tested for short circuits. If you exceed the permissible measurement values, the multimeter is in danger of breaking, even despite the fuse installed inside it.
When working with high-voltage circuits, do not forget about safety precautions. Any such repair must begin after the equipment being repaired has been turned off and the electrical component has been discharged by the discharge circuit.
To test a high-capacity part, a more extreme method may be appropriate. After the element is fully charged, its terminals are short-circuited to a metal object. This item must first be coated with an insulator, and it makes sense to work with rubber gloves. The appearance of a spark and at the same time a characteristic sound will be the result of the discharge process.

What to do before checking:

From the very beginning, the testing element must be unsoldered from the board, if it is located there.
After that, the capacitor is discharged - you need to short-circuit its output contacts with a conductive material (a simple metal tweezers will do) or connect a 5-10 kOhm resistance to its terminals for a smooth discharge if it has a large capacity (high voltage).
This is not recommended touch the output contacts of the element with your hands for personal safety. All this is done to ensure that the measuring device itself does not fail, because there may be a fairly high voltage on the plates of the part being measured.

Check procedure

contacts touching with probes

A multimeter can identify causes of malfunction such as breakdown, which entails the destruction of the dielectric separating the plates, and the current flows directly, while the capacitor itself, in fact, becomes a simple conductor. Or it does this partially, losing its capacity, becoming an additional active resistance in the electrical circuit.

The capacitor itself, due to its operating principle, passes only alternating current, but constant in no case, therefore its resistance, measured between the terminals, is quite large and is limited by a very small leakage current through the dielectric separating its working plates, which accumulate charge.

In non-polar capacitors, the role of dielectric of which is played by mica, ceramics, paper, glass, air, the leakage current is infinitely small, and the resistance is very large and when measured between the terminals with a digital multimeter, the device will show infinity in the form of 1 on the digital display. Therefore, in the event of a breakdown, its resistance, measured at the terminals, is quite small - up to several tens of ohms.

You can test a non-polar capacitor for breakdown in the following way:

Digital multimeter switch to resistance measurement mode, setting it to the highest possible limit.
After, connect the measuring probes of the device to the exposed terminals of the element under test.
If he is a worker, then on the display of the multimeter there will only be an infinity sign - 1. This is an indicator that the internal resistance (leakage resistance) is above 2 MΩ. Therefore, there is no breakdown and, perhaps, the element being tested is working. Otherwise, the breakdown is obvious. As a result, it is required to replace it with a similar one or with a larger capacity, with a rated voltage not lower than the original.
When checking Do not touch the bare leads of the capacitor or the measuring probes of the device with your hands, because the resistance of your body will be measured, not the element being measured. It will be much smaller, therefore the result will be erroneous.

Polar electrolytic capacitors have some features when measuring their internal resistance:

It is usually at least 100 kOhm. If manufactured well, their leakage resistance can be at least 1 mOhm. As mentioned above, the element being measured must be completely discharged before testing. How this is done is described above.
When measuring resistance The measurement limit on the multimeter is set to more than 100 kOhm. After, observing the polarity of connecting the probes, we take measurements. Due to its relatively large capacity, during testing the capacitor will be charged within a short amount of time. The charging process will proceed with a simultaneous increase in resistance, displayed on the display of the device, after which the measured value will stop growing and will have a fixed and final value.
If the indicator is not more than 100 kOhm, then most likely this is an indicator that the capacitor is working.

When checking with a dial multimeter, everything is done in a similar way:

The capacitor is being prepared(fixed and discharged).
Exhibited measured parameter (resistance is not less than the maximum limit).
A measurement is made in some cases, observing polarity.
The result is recorded and compared with operating values.

The peculiarity of measuring resistance using this method is that when it is charged, the parameter itself also grows proportionally and, accordingly, the pointer device indicating the resistance value itself moves from the zero mark to the final fixed one.

It was possible to visually estimate the capacity of the element being measured by the time the needle moved. Thus, the longer the arrow took to reach the final value, the greater the capacitance of the capacitor and vice versa.

The value of the internal resistance of a capacitor is not the main indicator of its performance, so only the capacitance measured with a multimeter can serve as a serious argument.

Capacity test

A change in the capacitance of capacitors is easy to detect when measuring it with a multimeter that has this measurement mode.

The measurement occurs as follows:

Test leads are connected to the connectors for measuring capacitance (symbol Cx) observing their (probes) polarity. It is mandatory to completely discharge the capacitor before measuring this parameter.
Then, the working surfaces of the probes are connected to the terminals of the element being measured, also observing polarity in the case of taking readings from the polar type of the element being measured.
When the multimeter shows equal to 0 or significantly different in value from those indicated on the capacitor, the latter is considered not working and requires replacement.

Possible causes of failure

Failure to comply with basic operating parameters, such as:

Rated voltage. When the rated voltage increases, a breakdown occurs due to the electrical characteristics of the dielectric that insulates the capacitor plates.
Design capacity. A discrepancy between the capacity (lower than the calculated one) entails an overestimation of the rated voltage on the element in question, therefore, when replacing it, if there is no analogue, an element with a larger capacity is installed.
Polarity in some cases. Polarity is a mandatory parameter for electrolytic and tantalum capacitors due to the design features.

The operating temperature directly depends on compliance with the above parameters. An exception is aging that occurs in the electrolytic type and the location of the element on the printed circuit board, as a result of which its operating temperature may be higher than the critical temperature due to the placement of other units of the electrical circuit that have a higher temperature regime.

This is the reason for the failure of an oxide semiconductor element, since it itself is an explosive: it contains tantalum, which is flammable, and the oxidizing agent is manganese dioxide.

Each component- it's a powder and it's all mixed together. Isn't it an explosive mixture? That is why an increase in temperature due to breakdown or non-compliance with polarity can lead to an explosion that can destroy not only neighboring elements, but also the entire board.

Purpose of the capacitor

By definition, a capacitor is an element of an electrical circuit that has the ability to accumulate and release an electrical charge at the right time. It is similar to a miniature battery with the difference that its charging when connected directly to a DC circuit and complete discharge when closing the output contacts occurs almost instantly.

It consists of 2 parallel plates located at a very short distance from each other and insulated with a dielectric.

The essence of the work is that when a capacitor is connected to a direct current source, when a positive polarity (“+”) is connected to one plate and the opposite negative polarity (“-“) to the other, charge will accumulate to a certain limit.

All this happens because unlike charges attract, and the plates themselves are insulated from each other by a dielectric and are located at a very short distance. It is this attraction that allows the capacitor to accumulate charge.

There are several types of them:

Constant capacity.
Polar capacitor with strictly assigned polarity to the outputs.
Trimmers(variable capacity).

Here are some of its main parameters:

Capacity, measured in Farads.
Rated voltage.
Operating frequency.
Polarity(optional parameter - depends on the type).

These indicators are mainly influenced by:

Plate area.
Their distance between themselves (the smaller the distance, the larger the capacity).
Dielectric resistance(as it increases, the parameter under consideration also increases).

Capacitors are widely used in:

Radioelectronics(various frequency filters, oscillatory LC circuits, obtaining current with different characteristics).
Electrical engineering(for operation of electric motors).
Some specimens with a very large capacity are needed as an auxiliary device for starting internal combustion engines (starting a diesel locomotive engine in railway transport).

What is a multimeter?

This is a compact device that allows you to measure the basic parameters of both an electrical circuit and its individual elements for testing and troubleshooting.

There are 2 types:

Analog

Consists of the following elements:

Switch magnetoelectric indicator.
Additional resistors to take voltage readings,
Shunts for measuring current.

Digital

A more complex and accurate device (the most common are multimeters with an accuracy of 1%), consisting of a set of chips and a digital indicator, which is usually liquid crystal.

Some of the characteristics measured by a multimeter:

Voltage(AC and DC).
Current strength(variable and constant).
Resistance(with a sound signal if it is less than 50 ohms).
Capacity.
Examination semiconductors for integrity and polarity.
Temperature.

Capacitors are widely used in electrical engineering as elements that smooth out alternating current ripples, frequency filters, or energy storage devices. In addition, these radio components can be used as galvanic isolation. There are many manufacturing technologies, the principle is common: between the two plates, in addition to the dielectric, a special chemical substance is placed that determines the characteristics. For DC electrical installations, electrolytes are used. This is an inexpensive technology, but has a serious drawback: the liquid can boil from overload or high temperature, and then the capacitor literally explodes. Fortunately, such an “extreme” rarely happens: in most cases, the case simply collapses, loses its seal, and the electrolyte leaks onto the circuit board.

Therefore, in critical components, capacitors made using a different technology are used. Instead of a liquid electrolyte, a conductive organic polymer is used. It has a virtually solid consistency, so it does not pose a danger under extreme loads (including temperature). Such capacitors are called solid-state (due to the absence of liquid fractions). The characteristics of these elements are not inferior to traditional “electrolytes”, but the cost of the parts is significantly higher. There is another drawback to the solid-state design - voltage limitations. The upper voltage limit is no more than 35 Volts. Considering the scope of application (computers, household appliances, cars), this is not a big problem.

Due to the high cost, DIYers try to avoid buying expensive parts by using used components for replacement. In any case, in order not to spend extra money, you need to know how to test a solid-state capacitor.

How does a polymer capacitor work?

To test any device, it is advisable to understand the mechanism of its operation. Since the topic of our material is solid-state capacitors (analogs of electrolytic ones), it means we will talk about radioelements for direct current, that is, polar ones. Everyone remembers this illustration from school:

Two metal plates with a dielectric between them (even air will do for the laboratory). If a potential is applied to the contacts, opposite charges accumulate between the plates, and an electric field arises in the space between them. In the absence of an electrical circuit, this field can persist for quite a long time (modern elements provide charge leakage tending to zero). It is this property that underlies the use of capacitors.

The element has certain basic characteristics:

The operating voltage is determined by the value at which dielectric breakdown does not occur. Capacitors look completely different from what we are used to seeing on a laboratory table in physics class. The parts are very compact, therefore the distance between the plates is minimal. Hence the limitation on the maximum voltage.
The capacitance of the capacitor is its main parameter. It determines how much electrical energy a part can accumulate and hold within itself. The value directly depends on the area of the plates.

Secondary characteristics:

Leak parameters. They can be determined by the current loss of accumulated charge or dielectric resistance. Ideal performance is only possible in a vacuum, but such capacitors are not produced for domestic use.
Temperature coefficient: determined by the delta change in capacitance as a function of temperature.
Accuracy - indicated as a percentage. Shows the spread of capacity parameters from the reference (marking) value.

Important: despite the large number of parameters, only two of them are subject to measurement (checking): capacitance and dielectric resistance.

Design of electrolytic and solid capacitors

Radio components of this class are used in electronic devices with high size requirements. Therefore, the issue of compromise between the area of the plates (capacity depends on this) and the dimensions of the case is a headache for developers. The problem can be solved technologically simply:

A so-called sandwich is made, consisting of two very thin plates, between which a layer of electrolyte-impregnated paper (in electrolytic models) or a conductive polymer (solid-state capacitors) is laid. Typically tantalum or aluminum foil is used. The natural oxide layer of one of the plates is used as a dielectric. It has low conductivity, which determines the leakage current of the capacitance.

Such a design can occupy a fairly large (by the standards of radio components) capacity. Therefore, it is rolled into a tight roll, where thin electric paper acts as a separator between the layers (see illustration). It is not involved in the operation circuit of the capacitor.

The outer shell is made of aluminum, and information about the characteristics is applied to it.

Benefits of Solid Capacitors

Compared to an electrolytic design, the equivalent series resistance is significantly reduced. Thanks to this, the part practically does not heat up at high frequencies.
A significant amount of ripple current makes operation more stable, especially in power supply circuits.
Solid-state capacitors are practically independent of temperature. In addition to physical protection from the case swelling, this property allows you to maintain parameters when heated.
Lifespan. If we take the operating temperature of 85 °C as the standard, the service life (without loss of characteristics) is 6 times longer than that of electrolytes. Typically these parts work without problems for at least 5 years.

Self-diagnosis of the capacitor

Since we're talking about DC parts, it doesn't matter whether the technology is electrolytic or polymer. Testing polar capacitors is performed in the same way.

First of all, an external inspection is performed. Electrolytes should not have any signs of swelling, especially at the end where there is a notch in the form of a cross. When examining solid-state packages, you can see thermal damage with a violation of the geometry.

Of course, you need to check the fastening of the legs. The compact design means that all components are small in size. The legs can simply come off during the assembly stage.

If the external examination does not produce results, we carry out testing using a multimeter

In any case, to perform this work it is necessary to desolder the part from the board. This must be done carefully so as not to pull the contact legs out of the housing.

If your device has a specialized connector for testing, diagnostics are performed in accordance with the instructions for the multimeter. The full range of testing (if such an algorithm is available) must be carried out. You need to connect correctly, observing polarity. The marking must be present on the body of the part. With such a check, you will not only check the serviceability, but also see the capacity value.

Checking the interplate closure

Even such a reliable capacitor as a solid-state one can have banal physical damage. For example, a short circuit between plates or to the body. In the first case, the resistance will not increase indefinitely, although at first it will gradually increase. In the event of a breakdown on the body, the resistance between one of the legs and the outer shell will be critically small.

In both cases, such capacitors should be classified as defective and cannot be restored.

Checking true capacitance values

We have already looked at how to check parts using a specialized multimeter. However, to check a solid-state (electrolytic) capacitor, it is not enough to simply record the fact that it is working. Especially if the radio element is suspect, or you want to use a used part. It is necessary to use a device with a sufficient capacitance measuring range.

Testing is carried out in several stages:

We connect the capacitor several times to the terminals of the device, then discharge it by shorting it, and check again;
We heat the radio component using a hot air gun to a temperature of 60–85°C, and check the capacitance value: the spread of parameters should not exceed the permissible error (indicated on the case).

Important: Be sure to observe polarity when taking measurements. This is necessary not only to obtain the true value. If the supply voltage of the device is at least 9 volts (such multimeters are common), the capacitor may fail due to polarity reversal.

Practical application on a car

Not all home craftsmen will test the element base of computer motherboards. But the skills of how to check a distributor capacitor will be useful to any car enthusiast. Let's study the technique using the example of a classic VAZ.

Bottom line

In order to test solid-state or electrolytic capacitors, it is not necessary to have the education of a radio engineer. Following our advice, you can accurately determine the serviceability of radio components and save money on the purchase of new elements. Considering the high cost of just such capacitors, the reduction in repair costs will be noticeable.