The ESR (Equivalent Series Resistance) of Capacitors

For many electronics enthusiasts, the world of capacitors is a fascinating one. These small components are fundamental in a wide variety of applications, from power supplies to audio circuits. However, there is one critical property that often goes unnoticed but has a substantial impact on their performance: ESR (Equivalent Series Resistance). In this article, we will explore the ESR of capacitors, from its definition to its measurement and its impact on electronic circuits.

Understanding the ESR (Equivalent Series Resistance) of Capacitors

A "perfect" capacitor or "ideal"It should be a pure capacity, without any added resistance, but in practice, all capacitors have an internal resistance. It is as if there were a resistor in series with the capacitance.

In essence, we could say that, just as a resistor has a resistance to direct current that we can measure with a multimeter on the ohm scale, a capacitor has a resistance to alternating current, only in this case we cannot measure it with a normal multimeter on the ohm scale.

ESR (Equivalent Series Resistance) and DC resistance are two concepts related to the opposition to the flow of electric current, but differ in several important aspects:

1. Type of Current:

• ESR: Refers to the equivalent series resistance that a capacitor presents to alternating current (AC). ESR is relevant in circuits that operate with high frequency signals, such as switched circuits.
• Direct Current Resistance: This type of resistance is applied to components in direct current (DC) circuits, such as resistors in a simple circuit. The DC resistance is constant and does not vary with signal frequency.

Frequency of Operation:

• ESR: ESR manifests itself mostly in high-frequency circuits, where the alternating current changes direction rapidly. ESR can affect the efficiency and stability of these circuits.
• Direct Current Resistance: DC resistance is constant and applies to DC circuits, where the polarity of the current does not change.

3. Related Components:

• ESR: ESR is mainly related to capacitors and refers to the internal resistance of an actual capacitor. It is an intrinsic property of capacitors that affects their performance in high frequency applications.
• Direct Current Resistance: It applies to a wide variety of components, such as resistors, wires, and other electrical devices, and is an inherent property of these components.

4. Measurement:

• ESR: ESR is usually measured with specialised instruments, such as ESR meters or capacimeters.
• Direct Current Resistance: DC resistance is measured with an ohmmeter or multimeter in DC circuits.

In summary, ESR and DC resistance are concepts related to the opposition to the flow of electric current, but they apply to different types of current and components. ESR is critical in high-frequency circuits, while DC resistance is a fundamental property in DC circuits. Both concepts are essential to understanding and designing effective electronic circuits.

Definition of ESR

The ESR, or Equivalent Series Resistanceis an electrical property that refers to the electrical resistance found in series with a capacitor in a circuit. Essentially, it represents the internal resistance of an actual capacitor, which is an inherent characteristic of all capacitors, even those considered to be of high quality.

For anyone to understand: if I were to tell a friend, who has no idea about electronics, at a bar counter what ESR is, I would say something like "It represents the losses of a capacitor and increases over time, like grey hair".

Why You Should Know It

Having a thorough knowledge of capacitor ESR is not easy (nor is it necessary to be a competent hobbyist), but it is important to understand why you need to be aware of it and how to measure it and identify if it is causing you problems.

Impact of ESR on Switched Mode Power Supplies

Increased ESR of electrolytic capacitors is the most frequent cause of failure in switching power supplies.

Understanding why switching power supplies can experience problems when the ESR of capacitors is high is essential for electronics hobbyists.

Here are some key reasons:

1. Energy Loss: The ESR dissipates energy in the form of heat due to the resistance in series with the capacitor. In switching power supplies, where efficiency is crucial, any power loss is undesirable. A high ESR can result in higher heat dissipation, which reduces the overall efficiency of the power supply.
2. Output Voltage Stability: Switch-mode power supplies generate an accurate output voltage. However, ESR can cause fluctuations in the output voltage, which can have a negative impact on connected electronic devices. Lack of output voltage stability can damage sensitive components and cause devices to malfunction.
3. Response to Transitorios: Switching power supplies often must respond quickly to changes in load or input voltage. ESR can limit the ability of capacitors to filter out transients and noise, which can lead to inadequate power supply response to sudden changes in load.
4. Lifetime of the Power Supply: An excessively high ESR can cause an increase in the temperature of the internal components of the power supply. This temperature rise can shorten the life of the power supply and increase the risk of premature failure.

The "direct effects" that I have just mentioned can cause other "indirect effects", which are very common and can become "the visible problem": It is normal for switch-mode power supplies to include some kind of monitoring and protection system that causes, for example, an instability in the output voltage to activate this system and the power supply to stop working "for protection".

In other words, the "visible problemIf there is no output voltage from a power supply, it may be that it has no output voltage, but it may be due to the "power supply", but it may also be due to the "power supply".real problem"The controller integrated detects that the high ESR of a capacitor is causing the voltage to be unstable and the controller integrated detects this and cuts the output as protection.

To avoid ESR problems in switching power supplies, it is essential to select and use high quality capacitors with a low ESR. High quality tantalum capacitors and aluminium electrolytic capacitors are often a suitable choice for power supply applications.

Why does ESR increase over time?

The Equivalent Series Resistance of a capacitor can increase over time due to various factors and conditions.
This is one of the main causes of failures in switch-mode power supplies.

Here are some common reasons:

1. Electrode or electrolyte ageing: In electrolytic capacitors, electrode or electrolyte ageing is a major cause of ESR increase over time. The internal components of an electrolytic capacitor can degrade over time due to factors such as temperature, operating voltage and electrical stress. This can lead to a decrease in conductivity and therefore an increase in ESR.
2. Electrode wear: In electrolytic capacitors, the electrodes are in contact with the electrolyte. Over time, due to corrosion or degradation processes, the electrodes may deteriorate, which increases the ESR. This is especially true in applications where the capacitors are subjected to adverse conditions, such as high temperatures.
3. High Temperatures: High temperatures accelerate the ageing of electronic components, including capacitors. When a capacitor operates at temperatures above the recommended specifications, its ESR tends to increase more rapidly over time.
4. Overvoltage and Overcurrent: Exposure to overvoltages and overcurrents, which sometimes occur in electrical circuits, can damage capacitors and increase their ESR. This is especially true in applications where capacitors are subjected to extreme conditions.
5. Vibrations and Mechanical Stress: In environments where capacitors are subjected to vibration or mechanical stress, physical stress can damage the internal structure of the capacitors, which in turn can increase the ESR over time.
6. Contamination or Humidity: The presence of moisture or contaminants inside the capacitor can cause changes in its electrical properties, including an increase in ESR. Moisture can adversely affect the performance of capacitors.
7. Cyclical Warming: On/off cycling of electronic equipment, such as switching power supplies, can cause temperature changes that contribute to the ageing of components, including capacitors, which can increase ESR over time.

Measuring ESR

Tools for measuring ESR

Measuring ESR is easy if you have the right instrument, but not so easy if all you have is a multimeter (even if it is a good one) as it is not a commonly measured parameter.

The good news is that, more often than not, it is not necessary to measure ESR accurately. Note that when repairing switching power supplies, an electrolytic capacitor that is causing them to malfunction will have an ESR value several times higher than desired. We may, for example, find a capacitor of 470µF and 10V (it should be over 0.42Ω ESR, as we will see later) and measuring 5Ω (this is an increase of more than 10 times).

There are several ways to do this, some better than others, and here are the main ones.

Measurement with a dedicated ESR meter

This is the proper way to measure the ESR of capacitors.

There are many ESR meters on the market, commercial or in kits, or we can build our own.

There is a huge range of prices, qualities, functionalities... it can be difficult to decide which one to buy, and this is not intended to be a guide to buying ESR meters.

I'll just tell you which one I have, and give you a brief summary of its characteristics.

ESR meter measurement with a MESR-100

MESR-100 ESR Meter

My ESR meter is a "MESR-100 ESR Meter".. A mid-range meter and currently costing about 50-60€ on AliExpress.

There are better (and more expensive) meters but this is a meter that has been on the market for years and, especially for its price, has a good reputation.

You can find by clicking on here is the AliExpress page where I bought the MESR-100. It took me 5 days to get it home and it was the best price I found by far (42,73€, including shipping, with the discounts I was able to apply).

Specifications:
Range accuracy (after zero, update time (manual mode)
Tested with 1.10, 100R auto mode takes 0 to 2S, longer
Resistance) depends on the capacitance value.
0.000 to 1.000R 1% + 2 Digits ~ 0.0-
1.000 to 10.00R 1% + 1 digit ~ 0, 0, 2, 2,
10.00 to 100.0R 2% + 1 digit ~ 0, 0, 2, 2, 0, 2, 2, 2, 2, 1 digit
Accuracy: Up to 1% (details in the table above)
Wide measuring range: >1uF
High resolution: 4 digits, or 0.001Ohm @ 1 Ω range
Measuring voltage: <~ 40mV RMS (TEST VOLTAGE)
External power supply: 5V micro USB
Operating current: 0.02A
Battery: 2 x 1.5 V AA batteries (not included)
Battery life: >80 hours
Item size: approx. 14,5*8*3cm/5,7*3,1*1.2in
Item weight: approximately 139.6g/4.9oz
Package size: approximately 17*9*5cm/6,7*3,5*2.0in
Package weight: approximately 218g/7.7oz

The advantages of a specific ESR meter (this one in particular) could be said to be the following:

• It is a specialised instrument that measures ESR in a "proper" way and provides a reliable and accurate measurement over a wide range of different capacitors.
• Allows ESR measurement "in circuit".. It is not necessary to desolder the capacitor from the board in order to measure it.
• By applying less than 40mV RMS to the circuit to make the measurement, it does not activate other semiconductors that may be connected, falsifying the measurement.

Measurement with component meter "Transistortester" or TC-1

This device is simply amazing. I couldn't live without it (well, yes, but my life would be a bit harder). It is a device a must-have for the electronics enthusiast.

A great thing about this meter is that it doesn't just do the measurement we tell it to do, it automatically identifies the component we connect to it, and CHARACTERISE IT (i.e. give us together and at the same time all parameters that define a component and differentiate it from another of the same type).

Measuring ESR with the TC-1 meter is child's play. This is all there is to it:

1. Condenser ConnectionTo measure the ESR of a capacitor, you must first connect the capacitor to the TC-1 meter. Make sure that the capacitor is downloaded before taking the measurement.
2. Click on the analysis buttonThe TC-1 component meter will generate a test signal of a specified frequency, usually in the kilohertz range. The frequency is important to obtain an accurate ESR measurement, as the series resistance of the capacitor can vary with frequency.
3. Impedance MeasurementThe meter will send a test signal through the capacitor and measure the resulting impedance. Impedance is a measure of the opposition to current flow in a component and is made up of two main components: the resistance (ESR) and the capacitive reactance. The meter isolates the series resistance (ESR) of the capacitor in the measurement.
4. Viewing ResultsESR measurement results will be shown on the TC-1 meter display. Typically, the ESR value will be displayed in ohms.

The good thing about buying a meter like this is that, apart from its low priceThe ESR of the capacitors is not only useful for measuring the ESR of the capacitors, but will be much more useful with its additional functionalities.

My LCR-TC1 meter

This is my meter. I bought it in 2019 and it is still working great. At the moment it costs less than 14€ on AliExpress and, in Spain, it is delivered in 5 days.

Some versions are very nice, with nice menus and colours, but they leave a lot to be desired. Apparently the main problem with these versions is that they have been ported to a different microprocessor.in any case"I recommend you buy the LCR-TC1, which is a model that has been around for many years and works very well. I recommend that you buy the LCR-TC1, which is a model that has been around for many years and works very well.

You have an article where you can see the LCR-TC1 in more detail here:

ESR measurement with a multimeter

Normal multimeters do not measure the ESR of capacitors (at least I don't know of any that do, although I'm not saying that there aren't exceptions).

If all you have is a multimeter, I'm sorry, but you won't be able to measure it.

However, two possibilities remain:

• If, in addition to the multimeter, you have a function generator, you can approximate the ESR.
• Using an oscillator circuit (which you can easily build yourself) of known frequency and wave amplitude.
• Using an Arduino (or other controller, such as an ESP8266, ESP32, STM32, PIC or similar)

ESR measurement with a multimeter and a function generator

Measuring the ESR (Equivalent Series Resistance) of a capacitor with a multimeter and a function generator can be a slightly more complex process than with specialised measuring instruments, but it is still feasible. Here is an overview of how to carry out this process:

Tools and materials needed:

1. Multimeter: A digital multimeter that is capable of measuring resistance and alternating current (AC) is essential. Make sure it is in good condition and correctly calibrated.
2. Function Generator: A function generator is required to apply a test signal to the capacitor. Make sure that the function generator is configured correctly.
3. Capacitor to be measured: The capacitor for which you wish to measure the ESR.

Steps to measure ESR with a multimeter and a function generator:

1. Configure the function generator:
   • Set the function generator to generate a square wave signal at a specific frequency. The frequency depends on your needs, but a frequency of 100 kHz is commonly used. This frequency is suitable for measuring the ESR of electronics capacitors.
2. Circuit connection:
   • Connect the positive terminal of the function generator to the positive terminal of the capacitor.
   • Connect the negative terminal of the function generator to the negative terminal of the capacitor.
   • Make sure that the polarity of the capacitor is respected.
3. Peak current measurement:
   • Sets the multimeter to the alternating current (AC) measurement function.
   • Connect the multimeter in series with one of the capacitor terminals to measure the peak current. This is done to calculate the ESR.
4. Peak voltage measurement:
   • Set the multimeter to the voltage measurement function (AC or AC) and connect it in parallel with the capacitor to measure the peak voltage across the capacitor.
5. ESR calculation:
   • Use Ohm's law (V = I * R) to calculate the ESR of the capacitor. Where:
     • V is the peak voltage across the capacitor (measured in step 4).
     • I is the peak current (measured in step 3).
     • R is the ESR you are calculating.
6. Repetitions and averages:
   • Take several measurements to obtain an accurate average ESR, as measurements may vary slightly.

It is important to note that this method of measuring ESR is an approximation and may not be as accurate as using a dedicated ESR meter. Multimeters are not specifically designed to measure ESR, so results may be subject to errors due to the influence of other circuit components.

An important detail is that the multimeter must be able to accurately measure the AC voltage of the frequency we are using. Many cheap multimeters are designed to measure AC current only at 50 or 60hz and are not capable of measuring at relatively high frequencies.

To give an example, my Uni-T UT71C handheld multimeter, which is of average quality, is capable of measuring alternating current (AC) voltage in a frequency range from 10 Hz to 100 kHz.

Note that measurement accuracy may vary depending on frequency and other factors, so it is always advisable to consult the multimeter manual or the manufacturer's specifications for detailed information on its ability to measure in different frequency ranges.

ESR measurement with a multimeter and an oscillator

If you do not have a function generator, you can perform the measurement with the help of an oscillator.

It is not necessary for the oscillator to have high stability and accuracy.

An oscillator is easy to assemble, cheap and fast. There are many types: with one transistor, with two, with an integrated circuit like the NE555, an OpAmp, with an L-C network... see which one suits you best and you will probably have the components at hand and you can build it in a while (even recovered from any device that is no longer useful).

On the internet you will find thousands of projects and tutorials for oscillator construction. Building an oscillator is an affordable project, so I encourage you to build your own!

Once you have the oscillator, the mechanics are exactly the same as with the function generator in the previous point.

Remember that, for most uses, you don't need to measure ESR accurately. Any oscillator that "more or less fits" will do.

ESR measurement with a multimeter and an Arduino (ESP8266, ESP32, etc.)

An Arduino, ESP8266, ESP32, etc. can be converted into a simple and accurate 100 kHz oscillator.

The code can be as simple as this:

#include 
//UNO only

void setup()
{
pinMode(9,OUTPUT);
pinMode(10,OUTPUT);

Timer1.initialize(10); // Frequency, 10us = 100khz
Timer1.pwm(9,512); // 50% DC on pin 9

//Timer1.pwm(10,255); // 25% DC on pin 10
}

void loop()
{
}

Once we have the Arduino working as an oscillator, we can follow exactly the procedure described above.

If we want to improve the meter, we can get a lot more out of our Arduino to measure ESR.

With very few additional components, we can use an Arduino Analog-to-Digital converter to measure the voltage drop and directly display the ESR, even by connecting a display.

There are many Arduino ESR meter projects on the internet, from basic to complete. If you're up for building one, I recommend you do a Google search and find the one you want to build or look for inspiration to design your own.

ESR Measurement with an Oscilloscope

If you have an oscilloscope at your disposal, you will find out how to use it to measure the ESR of a capacitor. With detailed instructions and a comparison of advantages and disadvantages compared to other methods.

This section is in preparation, as I want to accompany it with a video detailing the whole process.

In-circuit" measurement

Sometimes, when we are diagnosing a switching power supply, we have to measure many capacitors and this can be a bit tedious, because of the time-consuming process of desoldering, measuring and soldering them back together again.

The good news is that it is possible to measure the ESR of capacitors "in circuit", without disconnecting them from the board.

However, it is important to understand what we are doing and its implications, to avoid writing off bad capacitors or replacing good capacitors.

The important thing to understand is that, connected to the capacitor we are measuring, there are other components connected, which can affect the measurement.

For example, if the capacitor we are measuring has another capacitor in parallel with low ESR (or another component with low resistance), the result will be influenced by this other component in parallel and the apparent ESR will be very low and we could take it for good.

Some of these implications of measuring the ESR of in-circuit electrolytic capacitors include:

• Possibility to measure without disconnecting the capacitor: An advantage of measuring ESR in-circuit is that it is not necessary to desolder the capacitor from the circuit, which saves time and avoids damaging the component or the circuit. However, this is only possible if the circuit is switched off and discharged, and if there are no other components interfering with the measurement, such as low-value resistors in parallel to the capacitor.
• Need for a specific ESR meterESR in-circuit measurement requires a specialised instrument that applies a high-frequency (usually about 100 kHz), low-voltage alternating signal, so as not to activate the semiconductors connected to the capacitor (often around 100mV).
• Need to be very observant about what is being really we are measuringMeasurement of the ESR in circuit means that we will have to be very aware of how the whole capacitor environment affects the measurement in order to interpret it correctly.

Other uses of the ESR meter

If you have an ESR meter, it is good to know that it can do more than just measure the ESR of capacitors, and can sometimes be useful.

An ESR meter, after all, measures the resistance of a capacitor, and does so at AC current (usually at 100 kHz). The result is usually (especially for large, high-voltage capacitors) a very low resistance, in the order of milli-ohms.

ESR meter as milliohmmeter

What happens if we measure a resistance with an ESR meter?

Well, we can measure it very well and very accurately, as long as it is a low value. So, if we have a good ESR meter, we will also have a hidden milli-ohm meter, possibly with good accuracy.

Measuring the internal resistance of batteries with an ESR meter

I know that some people use the ESR meter to measure the internal resistance of the batteries but I have never done it before and I have no idea how to do it.

I think this is a good topic to investigate. If you have already done so, leave your experience in the comments.

Typical ESR of Different Capacitors

Typical ESR values

Here is a table showing typical ESR values for electrolytic capacitors of different capacitances and sizes.

This table is for guidance only and refers to good quality capacitors. It is normal that the cheap Chinese capacitors that we often buy on AliExpress, eBay or similar sites, have much higher values.

Personally, and as a general rule and for repairs of medium quality, cheap things, if the capacitor I am going to use has a maximum ESR of twice what it says in the table, I'll take it for granted.

The quality of the capacitors in a switched-mode power supply largely determines the quality of the power supply itself. If you want to improve a power supply with mediocre capacitors, by replacing its capacitors with high quality capacitors, you will have improved it significantly.

When repairing switch-mode power supplies, you must also be careful in selecting the capacitors you will use, and strike the right balance between price and availability and the result of the repair.

Good quality capacitors are not cheap, nor are they so easy to buy on AliExpress at a good price, so it is not so easy for the hobbyist to have a lot of capacitors in stock, of different capacitances and voltages, ready for when you need them.

Beware of shorted capacitors

Although not very common, it is important to always keep in mind that a capacitor can be short-circuited.

The problem is that when the capacitor is shorted its ESR will be almost 0Ω, and a basic ESR meter will tell us that the capacitor is perfect.

For this reason, we should not only measure the ESR in order to judge a capacitor as good, but we should also measure its capacitance and continuity with a multimeter.

Some ESR meters do this check automatically and tell us if the capacitor we are measuring is shorted.

ESR and impedance are not the same thing.

Impedance and ESR are two different concepts in electrical circuit theory and are good to know, although for practical purposes, when we are repairing switch-mode power supplies, we can ignore them most of the time.

Impedance is a measure of a circuit's opposition to a current when a voltage is applied. Impedance extends the concept of resistance to alternating current (AC) circuits, and has both magnitude and phase, unlike resistance, which has only magnitude.

In other words, impedance is a measure of how difficult it is for a circuit to allow alternating current to flow. Impedance is measured in ohms (Ω) and is made up of two components: resistance and reactance.

Resistance is the component of impedance that opposes the flow of direct current (DC) and is measured in ohms. Reactance, on the other hand, is the component that opposes the flow of alternating current (AC) and is also measured in ohms. Reactance can be either inductive or capacitive, depending on the type of component that is present in the circuit.

The main difference between impedance and ESR is that impedance is a measure of the total opposition of a circuit to an alternating current, whereas ESR refers only to the resistance of a capacitor to an alternating current. Furthermore, while impedance is composed of both resistance and reactance, ESR only refers to the resistance of the capacitor.

At 100 Khz the impedance is practically zero in large capacitors, say more than 10 uF.

Where to buy low ESR capacitors and which brands?

When repairing switching power supplies, it is very important to pay attention to which electrolytic capacitors we use as substitutes.

For a long time there was a consensus that only low ESR capacitors of Japanese origin were reliable. It seems that in recent times it has been admitted that some Chinese brands are also reliable. can be acceptable.

It should be noted that, according to most experts, the majority of Japanese capacitors that can be bought on sites such as AliExpress, eBay, etc. are counterfeits.

Some brands that say they are acceptable are:

• If you want something cheaper, but of decent quality, buy Samxon, Samwha, SAMYOUNG, Lelon, Yageo, Jamicon (acquired by Yageo), Elite, L-tec, Hitano.
• Rubycon, Panasonic, Nippon/United Chemi-con, Nichicon, Elna are the best, but they are also very expensive.

Most unbranded low ESR capacitors from AliExpress are too bad to take a chance with other than for experimentation.

Don't just look at the brand, there are many different series that differ greatly in lifetime and acceptable stress.

A good place to buy capacitors in Europe, knowing that they are original and of good quality, is TME.EU. They ship from Poland and have reasonable prices and shipping costs.

A more exhaustive list that I found on the internet, and with which I largely agree, is as follows:

First-tier low ESR capacitors (Japan)

• Nichicon
• United Chemi-Con (Nippon Chemi-Con)
• Rubycon (beware, there is Rulycon which is almost the same, but much worse (last grade)).
• Sanyo/Sancon
• Panasonic (most of the time there is an M logo on the condenser)
• Hitachi
• FPCAP (functional polymer capacitor)
• ELNA
• Marcon (if you see them, they are at least 25 years old, there are four numbers written on them, for example: 9110, that means the capacitor was manufactured in the 10th week of 1991. Some other capacitors also have this information)

Low ESR top-tier capacitors (US and Europe)

• Cornell Dubilier (USA)
• Illinois Capacitor (now owned by Cornell Dubilier)
• Kemet Corporation (USA) (you probably won't find Kemet or Vishay capacitors in consumer equipment because most are for automotive, telecommunications and industrial use, but the ceramic and tantalum capacitors are very good).
• Vishay (US) (same as Kemet. ROE is also a Vishay capacitor)
• EPCOS (now TDK, Germany)
• Würth Elektronik (Germany)

Low ESR second level capacitors:

• Teapo
• Taicon (belongs to Nichicon)
• SamXon (worse than other second-tier capacitors)
• Toshin Kogyo
• Elite
• Daewoo (sometimes only the logo is shown, and it looks a bit like the Huawei logo).

Low ESR third level capacitors (the first six capacitors are better than the others):

• Jamicon
• CapXon
• Su'scon
• OST
• Partsnic
• Lelon
• Aircon
• Canicon
• Chhsi
• Choyo
• CTC
• DST
• Fuh Yin
• Fuhjyyu
• Gloria
• G-Luxon
• GL
• Gsc
• Hec
• Hermei
• I.Q.
• Jackcon
• JDEC
• Jee
• Jpcon
• Jun Fu
• Licon
• Nkcon
• Nrsy
• Pce-tur
• Raycon
• Rubysun
• Rulycon
• Skywell
• Stone
• Supacon
• Tayeh
• Tocon
• Wendell
• Yec

Do you want to know more about ESR?

This article is not intended to be academic, just something to give the hobbyist a general idea to start considering the ESR.

The main purpose of the article is to make the ESR understandable for a hobbyist, especially on a practical level, away from the technicalities that most websites use when talking about SRE.

On the other hand, SRE is a very broad topic and one could write not one article but several books, a whole encyclopaedia, and still not deal with it in all its depth.

In the following blog article you have a practical application of ESR measurement, and a failure caused by high ESR:

I hope you found this article enjoyable and interesting. Check back from time to time as I will be adding to it.