How to check the capacitor with a multimeter for operability without soldering on the board step by step instructions

ПWhen developing new circuits or repairing electronics, it may be necessary to check the capacitor for performance.

There are many options for this, but the simplest requires a multimeter and a few minutes of free time.

Below we will consider what capacities are and analyze the principles of their operation, let’s talk about the main breakdowns, deciphering the designations on the case and the features of checking the capacitor, including on the board without soldering.

Using the given step-by-step instructions will allow you to do the work yourself and with the help of improvised tools.

The principle of operation of the capacitor

The operation of the capacitor is based on the ability of the device to accumulate charge and then transfer it to power other electrical devices.

Structurally, the part consists of two metal electrodes with a thin dielectric located between them.

The latter is able to accumulate a “plus” and “minus” charge and hold it for a long time.

In this case, the capacitance of the device depends on the distance between the plates, their area and dielectric constant.

Types by method of application

Capacitors are used in 99,9% of modern electronic devices. The latter are divided into general household use and special.

It is the special capacitors according to the functional application that are divided into:

1. Launchers. They provide a reliable start of powerful electric motors and their further uninterrupted operation. Pumps, compressors, machine tools and other powerful consumers of electricity cannot do without starting capacitors.
2. High voltage. As a rule, these are vacuum oil, ceramic and film capacitors used in devices whose power source is high-voltage networks from 380V and above. For this reason, access to them is limited and they are checked and maintained by specialists with the appropriate clearance.
3. Dosimetric. As a rule, fluoroplastics have high insulation resistance and low self-discharge. Used in devices with small current loads.
4. Pulse. Provide large voltage surges. They are used in circuits for testing various electrical devices: electric motors, generators, power supplies, medical equipment, fuses and even pulsed lasers.
5. Interference suppression. The name itself speaks for itself. They have low inductance and provide a reduction in the overall electromagnetic background. For example, in cars, they provide a stable engine start by leveling a short-term impulse in the on-board network, accumulating an extra charge of energy and smoothing the voltage. As a rule, they are connected to the circuit in parallel with the ignition coil.

Types

Among a large number of capacitors, two types of devices are distinguished by polarity, in which air, glass or paper is used as a dielectric. Let’s consider each of the options in more detail.

Polar

This category includes all devices of the electrolytic type with an electrolyte in liquid or solid form. The capacitance of the capacitor can be in the range of 0,1-100000 uF.

When connecting them, it is important to strictly observe the polarity – solder the “minus” and “plus” clearly on their terminals.

In the event of an error, the element will be inoperable, and there is a possibility of an explosion.

Only paper impregnated in electrolyte can act as a dielectric.

non-polar

This group includes capacitors, where ceramics, mica, paper, air or glass act as a dielectric.

They have a small capacitance ranging from 1 to 220 microfarads. Hidden in a cylindrical housing and have an output for connecting to the circuit. They are in demand in AC circuits.

Such devices have a lower leakage current due to the greater dielectric resistance.

Each of the above types of capacitors has its own verification features.

The main malfunctions of capacitors

There are several faults that are characteristic of capacitors:

1. The leakage is above the norm. Occurs due to a change in the resistance of the dielectric material. With such a breakdown, the capacity decreases, and the device is not able to store a charge for a long time.
2. Break. The essence of the damage is the electrical rupture of the conductors, which no longer have an electrical connection. The cause may be an impact, strong shaking or vibration. It is impossible to exclude the marriage of a capacitor or a violation of the rules for its use.
3. Breakdown. Occurs when the operating voltage exceeds the permissible norm. With such a breakdown, further use of the capacitance is impossible due to the appearance of a short circuit in the circuit.

Other faults can be included in the list – reduced capacitance, high equivalent series resistance, etc.

At the highest risk are aluminum electrolytic capacitors, which are often installed as a filter for ripple voltages in various rectifier applications.

The main reasons for failure

Increased operating voltage of devices, for example, as a result of a malfunctioning power supply, is the most common cause of capacitor failure.

For example, a power surge leads to a sharp heating of the part and, as a result, this leads to its swelling.

A change in the properties of the dielectric as a result of its cracking, leakage, drying, leads to a change in the readings of the capacitance of the capacitor, and this is already a sign of a breakdown of the part, which can only be detected by using a multimeter or other measuring instruments.

Deciphering the designations on capacitors

Before taking a capacitor for testing, it is important to be able to navigate the inscriptions on it.

As a rule, manufacturers prescribe capacitance and rated voltage for operation on capacitors. If the part is too small, the parameters according to the EIA standard are indicated on it.

When applied to the surface, only numbers and letters, the first shows the capacity, and the second – the type of construction.

The presence of three digits allows you to find out the capacity from the first two, and the multiplier for zero from the last.

Additionally, the following parameters can be specified:

• polarity;
• year of issue;
• capacity deviation from the nominal parameter;
• capacitance factor;
• operating frequency, etc.

There are a few other things to keep in mind when designating:

1. The presence of a letter between and after the numbers may indicate the presence of a comma. For example, 3n3 – 3300 pF, 33n – 33 nF, 330n – 0,33 uF.
2. Color marking allows you to find out the capacity (the first two strips), the permissible deviation from the nominal value (3rd strip) and the voltage (4th strip).
3. When designating foreign devices, the IEC standard can be used, according to which a marking of 3 numbers is applied to the device. The first two allow you to find out the capacitance of the capacitor, and the third – the number of zeros.
4. SMD capacitors are small in size, so they are labeled using letters (capacity in pF) and numbers (multiplier to the tenth power). The presence of two letters in front allows you to find out the manufacturer and operating voltage.

Safety measures during verification

The main safety condition when testing capacitors is the need for a complete discharge. This rule is especially important when testing parts with large capacitance and high operating voltage.

If you ignore this step, you yourself can get under residual voltage or damage the measuring device (read how to do this in the next section).

This situation is a common occurrence when checking a capacitor in a switching power supply.

In the process of performing work, adhere to the following rules:

1. Do not touch the capacitor/resistor terminal with your hands.
2. Hold your screwdriver, platypus, or pliers by the well-insulated handles.
3. Take care of your eyes, because when the charge is removed, a strong spark may appear. It is recommended to protect the entire face.

Preparing for verification

Capacitors are an invariable element of every circuit, and their damage is most often associated with the end of the resource.

Some devices simply “dry out”, which reduces their capacity. This affects the shape of the signal, the operation of the circuit and other parameters.

In order to identify the problem at an early stage, an element check is carried out.

How to discharge a capacitor before testing

The discharge is made as follows:

1. For capacitors up to 100 microfarads – by closing the contacts at the output with a screwdriver, platypus or other tool.
2. With a larger capacitance (from 100 uF) or more, as well as at a voltage above 63 V, you need to use a resistance of 5 to 20 kOhm with a power of 1 to 2 W. To discharge, it is enough to connect the leads from the resistor to the output of the capacitance for a few seconds.

Selection of a multimeter to test a capacitor

An important step before conducting an inspection is the preparation of the necessary tool.

The best solution is to use a special device for measuring capacitance, namely an LC meter or an inductance meter.

An easier option is to buy a universal measuring device.

On the market you can find a large selection of pointer and electronic multimeters.

The former are considered more understandable in the interpretation of values, and the latter are accurate and convenient to use.

When choosing, you need to look at the presence of several capacitance measurement limits. Most often, the device allows measurements at the level of 20 and 200 nF, 2, 20 and 200 microfarads.

The upper limit is small, given the presence of capacitors of 10 uF and higher.

After choosing a multimeter, you need to prepare it:

1. Move the toggle switch to the measurement position or “signal”.
2. When using a pointer device, check that the pointer is at the 0 mark. To adjust, use the special knob in the center at the bottom of the device.

Step-by-step instructions for checking a capacitor with a multimeter

The most common problem associated with a capacitor is breakdown, which results in a decrease in resistance in the dielectric.

A malfunction can be determined by visual inspection for the fact of swelling, darkening or black spots, as well as a deeper check using the device.

The study of the capacitor for the fact of serviceability is possible after soldering or directly on the board. Below are the different options for doing this work.

Visual inspection

In many situations, a single glance is enough to determine if a part is faulty. In this case, you can speed up the test and avoid using a multimeter.

The capacitor must be changed in the following cases:

• swelling;
• leaking fluid from the inside;
• dents or mechanical damage;
• chips or cracks (typical for ceramic products).

If any of the above damage is found, the part must not be used and must be replaced.

Polar Capacitor Multimeter Check

Capacitors with a capacity of more than 0,25 uF are subject to verification.

The resistance of such capacitances is small, so it is important to be careful when choosing a range.

In many multimeters, the limit range is 100 kOhm, and for more powerful ones, it can reach 1 mOhm.

The algorithm of actions is as follows:

1. Remove the remaining charge by unplugging. How to do it right is discussed above.
2. Set a suitable measurement limit and connect the device to the capacitor, taking into account the “plus” and “minus” (Do not touch the probes with your hands).
3. Look at the parameter indicated on the screen. It should be more than 100 kOhm.

Note that the entire measurement period, the resistance parameter will change upwards. This feature will be visible on the screen.

This is due to the fact that the capacitor is charged by the multimeter, and eventually reaches the “1” mark.

If the number “1” appears immediately, then this will indicate an open circuit in the internal circuit.

If the readings do not change, and the device begins to make a sound, then a short circuit has occurred.

Checking a non-polar capacitor with a multimeter

Even less time is needed to control a non-polar capacitor.

Take the following steps:

1. Remove the remaining charge with an improvised tool, such as a screwdriver.
2. Set the multimeter to the measurement limit in megaohms.
3. Touch the probes to the capacitance terminals.
4. If there is less than 2 MΩ resistance, the capacitor can be discarded.

A feature of non-polar devices is that they do not require polarity. For comparison, you can take two devices so that one is guaranteed to be intact.

If you need to check a part with a capacitance of up to 0,5 microfarads, it will not work with a measuring device. In this case, the multimeter will show a short circuit.

To test a non-polar capacitor with a voltage of more than 400 V, work is done after charging from a source that is protected from short circuits.

A resistor is connected in series with the capacitor, which is designed for a resistance of more than 100 ohms. The use of such an element makes it possible to reduce the primary inrush current.

There is also a spark test method. In this case, the device must be charged to a working value, and then short-circuited with a screwdriver (the handle of the tool must be insulated).

By the intensity of the spark, you can approximately find out about the strength of the discharge (for capacitors with small capacitance, see safety precautions).

Immediately after charging, you can change the voltage. The capacitor is healthy if it retains a charge for a long time.

Discharging the device occurs gradually through the resistor. Due to the strong spark, it will not work to discharge it, for example, with a screwdriver.

Using analog meters

To test a capacitor, it is not necessary to have a new and modern multimeter. You can use the usual Ts4313 if it is left over from the times of the USSR or the YX-1000A.

The measurement method is the same, but the checks themselves are more visually evident.

Here you need to look not at the numbers, but at the movement of the arrow of the device.

To check, do the following:

1. Click on the RX button.
2. Insert the probes into the special sockets.
3. Take a capacitor and discharge it.
4. Touch the probes to the capacitor.
5. If the part is in good condition, the arrow will deviate, and then smoothly return to its original position. The speed of movement depends on the capacitance of the tested capacitor.

If during the test the arrow does not deviate or freezes in a specific position, this indicates a malfunction of the part.

Checking the capacitor for serviceability by taking the necessary readings

In the event of a capacitor failure, you need to know how to check the part for an open, determine the exact capacitance, make sure there is no short circuit, measure the voltage, or perform other work.

Below are step by step instructions for each step.

We measure the capacitance

If there are no difficulties with controlling the resistance, when measuring the capacitance parameter, many beginners run into a “wall”.

To make sure that the part is working, it is necessary to compare the data provided by the manufacturer with the actual situation.

Checking with a multimeter in the standard way using probes will not give a result; for this, the device has special connectors -CX +.

It is provided not in all devices, but, for example, in the Mastech MY-64 model it is.

The plus and minus signs indicate the polarity of the connection.

For example, let’s measure the capacitance of a part with the designation 104K. This means that the capacitance of the capacitor is 104 pF.

Take the following steps:

1. Set the toggle switch to the desired position –CX+.
2. Take the capacitor and insert its legs into this connector. The installation side does not matter, because the capacitor is non-polar.
3. Make sure that the value obtained corresponds to the declared characteristics.

When measuring the capacitance of an electrolytic capacitor at 3,3 uF, you need to set the switch to 200 uF.

In the next step, insert the part into the -CX + connector of the device, taking into account the “plus” and “minus”.

For polarity data, look at the part where the black bar with “zero” indicates “minus”. After measurements, compare the declared and received parameters.

If the measured capacitance differs from the nominal value or is equal to zero, this indicates a malfunction of the capacitor and the need to replace it.

Open circuit test

The malfunction itself occurs when one or two plates are disconnected. In fact, the part turns into an ordinary conductor.

The cause of the malfunction may be an increase in the rated voltage, which is important for electrolytic and noise-suppressing capacitors.

Externally, it will not be possible to determine the defect, so a multimeter is used for work.

Do the following:

1. Discharge the capacitor directly (with a small capacity) or with an additional 5-10 kΩ resistor). Keep safety in mind when doing work.
2. Set your multimeter to resistance mode.
3. Measure this parameter on the outputs.
4. Analyze the received data.

If the value is zero, this indicates a break. In this case, the capacitor will not be charged.

Short circuit test

There are three ways to test a capacitor for a short circuit.

Method number 1 – using a multimeter:

1. Turn on the device in the resistance / continuity measurement mode.
2. Touch the probes to the taps of the capacitor.
3. Look at the instrument readings.

If the part is working, the device shows infinity, or this happens after a certain period of time.

The appearance of a squeak indicates low resistance and a short circuit in the part.

Keep the following points in mind when checking:

• for a polar capacitor, be sure to stick to the polarity;
• in non-polar capacitors, you can connect to any terminal.

Alternatively, you can use a pointer device, which makes it easier to observe the increase in resistance and see the charging process.

Method number 2 – check in the absence of a multimeter:

1. Connect the LED / Bulb to the battery through the capacitance.
2. Pay attention to the light bulb, which, if the part is working, should not glow.
3. In the case of a constant glow of the light bulb, we can talk about a breakdown of the capacitor.

If during the test the resistance is constantly growing, and the light starts to check and goes out, this indicates the presence of some kind of capacitance. In this case, it makes no sense to do a break test.

Method number 3 – for non-polar, for example, starting capacitors of pumps, washing machines or other equipment.

The algorithm is as follows:

1. Connect a 25-40W incandescent light bulb to the capacitor.
2. See if it glows or not.

If the light is off, then the device is working properly.

Measuring voltage

To check the capacitor with a multimeter, you can measure the voltage and compare the obtained data with the factory parameter.

The algorithm of actions is as follows:

1. Find a power source with a voltage that is less than that of the part under test.
2. Connect the leads to the legs, taking into account the “plus” and “minus”.
3. Wait a while.

Sometimes, after a certain period of time, the part is still working, and its parameters may change. In this case, you need to look and record information.

Next, do the following:

1. Set the multimeter to voltage measurement mode.
2. Check the parameter of interest.
3. If a value equal to the rated voltage appears on the screen, the capacitor can be used further. Otherwise, it is better to change the part.

Measuring the increase in leakage currents

In the event of a failure of the dielectric installed between the plates, leakage currents may occur.

In normal mode, they are small, but if they grow, the capacitor can no longer hold a charge.

To check, a conventional multimeter is enough:

1. Charge the capacitor from the power supply.
2. Make several voltage measurements at the terminals at fixed intervals.

A rapid drop in voltage indicates high leakage currents. To avoid measurement errors, use a multimeter with an input resistance of 10 MΩ or more.

Equivalent resistance measurement (ESR)

There are situations when, at the first inspection, the capacitor looks working, but in practice it turns out to be faulty.

In such circumstances, there are two ways: to immediately make a replacement part or use an RLC meter for a more accurate check.

The latter allows you to measure the series equivalent resistance parameter. 

An increase in this indicator leads to heating of the part, and this distorts its parameters and reduces the resource.

The convenience of an RLC meter is the ability to select the frequency to be tested. An example is the MASTECH 13-2039 model.

Such measurements are important when monitoring high-frequency capacitors installed in switching power supplies and when checking Low ESR-type parts.

The analysis of the ESR value is carried out by comparison with the parameter of a similar part or using a special table by Bob Parker.

Checking the capacitor without desoldering from the board

One of the most convenient ways to test a capacitor is to do the job without desoldering the board.

The algorithm of actions is as follows:

1. Examine the condition of the details on the diagram. Signs of a malfunction include discoloration, swelling, splits, and other symptoms. During operation, signs of temperature effects may appear on the surface of the capacitor (darkening of the board, conductive tracks, etc.).
2. Check the quality of the contact by gently shaking it with your finger.
3. Measure the voltage at test points along the discharge circuit.
4. Make sure the capacitor is working.

If visual problems or voltage deviations are detected, connect a knowingly whole part in parallel with the faulty element.

After such an experiment, it is possible to draw a conclusion about serviceability.

The downside is that this method is suitable for circuits with low voltage.

The second way to check is to remove the voltage and measure the resistance directly on the circuit.

The disadvantage is that it is not necessary to count on high accuracy with such a check.

Take the following steps:

1. Set the toggle switch on the multimeter to the resistance measurement position.
2. Insert the probes into the special sockets and touch the leads.
3. See how the resistance indicator increases due to the charge from the device. If so, then the item is correct.

The third method is to check the capacitor with an RLC meter. Connect its probe wires to the outputs of the part and look at the screen.

Please note that with a parallel connection, the parameters of the tanks are added up, and with a serial connection, a special formula is applied (we will discuss this issue below).

How to measure the capacitance of two capacitors connected in series

There is a situation when a multimeter with the capacitance measurement option does not allow you to check the capacitor due to the lack of the required limit.

In most devices, the maximum threshold is 20 or 200 microfarads. But what if you need to measure a capacitance of 1400 uF or more.

Here you can use the following formula: 1/C = 1/C1+1/C2.

Its meaning is that the total capacitance for two capacitors connected in series will be less than the capacitance of the smallest of them.

In other words, when checking two parts with a capacitance of one of them 30 microfarads, the total capacitance will be less than 20 microfarads.

If you have a device with a measurement limitation of 20 uF, you need to connect an unknown capacitor in series with a part with a capacity of up to 20 uF.

All that remains is to measure the total capacitance of the two capacitors and calculate the parameters for the unknown value.

What to do in case of breakdown

Breakdown is one of the most common capacitor failures.

The reason is the insulation of the dielectric, which is characterized by high resistance. This feature eliminates the flow of current between the conductors.

If the capacitor is good, it may leak a little current through the insulation.

In the event of a breakdown, the resistance drops sharply, and the part turns into a simple conductor, and this leads to a short circuit in the circuit.

The cause of damage can be a power surge, and you can recognize the problem by swelling, darkening, or the appearance of black spots. The only solution in this case is replacement.

How to test a capacitor with the ESR-METR

In simple terms, the ESR-METR is a device designed to test capacitors based on a microprocessor (for example, ATmega328). It has a display and contacts for connecting wires.

The device is sold without a case and is powered by a Krona battery.

The downside of the device is that it allows you to measure ESR only for removed capacitors. When measuring on the board, the device shows an incorrect indicator.

To test a capacitor with this device, follow these steps:

1. Calibrate the instrument. To do this, close the contacts on the 1st and 4th columns, and then press the button for automatic calibration. If successful, a corresponding inscription should appear on the screen.
2. Discharge the capacitor.
3. Connect the device to the sockets of interest and perform the measurement.

Each capacitor has a small amount of resistance, resulting in a small loss of 0,5%. If the check showed an overestimated figure, this indicates the drying of the part.

Possible verification difficulties

The main difficulty in measuring the parameters of a capacitor is the need to solder it out of the circuit. If the part is on the board, there are additional verification difficulties and the risk of distorting the readings.

To avoid errors, you can use a special tester with a lower voltage at the terminals. It allows you to take measurements directly on the board and follow the instructions discussed above.

The presence of a small voltage on the terminals minimizes the likelihood of damage to other parts.

For example, you can bring the model of the Digital Multimeter STAYER 45320-T.

Applying Formulas

If there is no device at hand without sockets for measuring a capacitor, you can recall a school physics course and use a number of formulas.

But this is for those who want to completely immerse themselves in the topic and in practice this method is rarely used.

Note that when the part under consideration is charged from a constant voltage source through the resistance, the potential difference on the device will approach the source voltage and will finally be equalized.

Т=RC

To save time, you can do it easier. For example, during the 3 * RC time during charging, the potential difference on the part reaches the level of 95% with respect to the RC circuit.

Therefore, the time parameter is easy to calculate from the current and voltage parameters.

In other words, if you know the number of Volts in the supply unit and the resistance parameter, you can calculate the time constant, and then the capacitance.

Let’s say there is an electrolytic capacitor as a device under test.

To check its capacity, just look at the inscription. For example, it indicates a voltage of 50 volts and a capacitance of 6800 microfarads.

If the part has not been used for a long time, the parameter may not correspond to reality.

To get accurate information, you need to check the capacity.

The algorithm of actions is as follows:

1. Take a multimeter and a 10 ohm resistor. Measure the resistance of the latter, for example, the device gave the figure 000 ohms.
2. Connect the power supply, and transfer the device to voltage measurement.
3. Connect the multimeter to the PSU using the leads.
4. Set the voltage to 12 V on the PSU and note that this figure is displayed on the device screen.
5. Try adjusting the voltage, and if that doesn’t work, write down the results.
6. Build an RC circuit using a resistor and a capacitor.
7. Short the capacitor and apply power to the circuit.
8. Connect a multimeter and check again the voltage that goes to the circuit. Fix this setting.
9. Calculate 95% of the calculated number. So, if the measurement showed 12 V, the result will be 11,4 V. In other words, during the 3RC time, the capacitor receives a potential difference of 11,4 V. The final formula in this case looks like this – 3 * T u3d XNUMX * RC.
10. Determine the time for which you cut the part, start the stopwatch and wait for the voltage to reach 11,4 V. The resulting parameter will be the time that will be used in the calculations.
11. Divide the time parameter (sec) by the resistance of the resistor and by three. It turns out 210 s, which are again divided by three and 9800. It turns out 0,00714 or 7140 microfarads. The permitted deviation cannot be more than 20%. Considering that 6800 is indicated on the part, and the calculation showed 7140 microfarads, the parameter can be considered normal.

The situation is more complicated when it is necessary to calculate the capacitance of a ceramic capacitor.

To do this, use a network transformer.

The algorithm is as follows:

1. Connect the RC circuit to the “secondary” of the transformer.
2. Connect the transformer itself to the circuit.
3. Using the instrument, measure the voltage across the resistor and capacitor.
4. Calculate the current that goes through the resistor, and then divide the voltage by the resistance. The result is Xc (capacitance). The formula itself has the following form – Xc=1/2*π*f*С. If there is a current frequency, there are no problems with measuring the capacitance itself: C u1d 2/XNUMX * π * f * Xc.

For those who found the method with formulas very complicated, just forget about it. But some may find it useful.

Capacitor Test Recommendations

Many do not know that capacitors have a peculiarity – after soldering, due to exposure to high temperatures, they are rarely restored.

On the other hand, a contradiction arises, in order to check the part, it must be unsoldered, since being in the circuit on the board, the capacitor will be shorted out by other elements, and the readings themselves will be erroneous.

Therefore, after soldering already checked and serviceable, at first glance, parts, the device (motherboard, electric motor, radio receiver) must be immediately turned on and checked for their operation.

If everything is fine, then the old capacitor is changed to a new one, this will ensure stable operation of the device in the future.

To avoid misunderstandings, consider the following points:

1. When identifying problems in the operation of the circuit, look at the date of manufacture of the capacitor. On average, the latter dries out by 65 percent after five years of work. Such an element, even if it is still working, is better to unsolder and check, and change if necessary.
2. To speed up the test, it is not necessary to solder both contacts – just one is enough. But there is a nuance. For most electrolytic cells, this method is not suitable due to the design of the housing.
3. When testing a complex circuit with many parts to be tested, damage is best determined by voltage testing. If this indicator deviates from the requirements or there are suspicions of serviceability, you need to solder and check the part.
4. In new versions of multimeters, the maximum measurement parameter is 200 microfarads. If you test a larger capacity, the device may break down despite the protection.
5. Most newer devices have SMD electrocapacitors that are too small and hard to desolder. In such details, it is better to limit ourselves to soldering only one output, lift it up and isolate it from the rest of the circuit, and then solder the second output.

Based on the material studied, we can conclude that the capacitor can be checked for performance on the board, but it is better to do this after soldering.

For measurements, it is worth using an ordinary multimeter, an RLC device and classic calculation formulas from a physics course (in rare cases).

Remember that even a slight deviation from the norm may indicate a deterioration in the parameters of the part, which may affect the operation of the entire device, for example, an electric motor or a computer motherboard.