The principle of operation of the ESR container measurement devices. ESR meter oxide capacitors. How to check the condenser. Theoretical information about condensers

Meter ESR.

To test the capacitors, I decided to collect the so-called "ESR meter". After all, it does not occur with the testing of diodes and resistors, but it's more difficult with condensers. As you know, ESR is a reduction from the Equivalent Serial Resistance, "means" equivalent sequential resistance ". Explain easier. In a simplified form, the electrolytic capacitor is two aluminum belt pads, separated by a gasket from a porous material impregnated with electrolyte (hence the name electrolytic). The dielectric in such capacitors is a very thin oxide film formed on the surface of the aluminum foil when the voltage is filled with a certain polarity. Wire conclusions are joined to these tape plates. Ribbons are folded into the roll, and all this is placed in a sealed case. Due to the very low thickness of the dielectric and the large area of \u200b\u200bthe plated, the oxide capacitors at small dimensions have a large container.

In the process of operation inside the condenser, electrochemical processes that destroy the location of the conjunction with the plates are processed. The contact is broken, and as a result, the so-called transient resistance reaches the values \u200b\u200bof dozens of dozens and more, which is equivalent to inclusion in series with a condenser of the resistor, which is located in the condenser itself. Charging and discharge currents cause the heating of this "resistor", which further enhances the destructive process. Another reason for the failure of the electrolytic capacitor is "drying" when the electrolyte evaporates due to bad sealing. In this case, the reactive capacitive (xc) resistance of the capacitor increases, since the latter capacity decreases. The presence of consistent resistance negatively affects the operation of the device, disrupting the logic of the condenser's operation in the scheme. (If you enable, for example, in series with a condenser of the rectifier filter, the resistance resistance resistance resistance, at the output of the latter will sharply increase the ripples of the straightened voltage). The increased value of ESR capacitors is particularly strongly affected (and only a pair of OM) at the work of pulsed power supplies.

The principle of operation of this ESR meter is based on measuring the capacitive resistance of the capacitor, i.e., in fact, this is an almeter operating on alternating current.

As known, XC \u003d 1 / 2πFCwhere

XC - capacitive resistance, Ohms;
F - frequency, hertz;
C - Capacity, Farad.

On the DD1 chip, the rectangular pulse generator is assembled (elements D1.1, D1.2), buffer amplifier (elements D1.3, D1.4) and an amplifying cascade on transistors. The generation frequency is determined by the elements C1 and R1 and is equal to 100 kHz. Rectangular pulses through the C2 separator capacitor are fed to the primary winding of the boiling transformer T1. In the secondary winding after the rectifier on the diode, a micro ammeter is included, on the scale of which is counted the ESR value. Capacitor C3 smoothes the ripple of straightened voltage. When power is turned on, the microamer arrow is deflected on the final scale mark (achieved by the selection of the resistor R2). This position corresponds to the value of the "infinity" of the measured ESR. If you connect a good oxide capacitor in parallel winding I transformer T1, then due to the low capacitive resistance the capacitor hoses the winding, and the arrow of the meter approaches zero. With the same in the measured defect, it increases the ESR value. . Part of the AC will flow through the winding, and the arrow will continue to deviate from the "infinity" value. The greater ESR, the larger the current flows through the winding and smaller through the capacitor, and the closer to the position "Infinity" is the arrow.

The transformer is wound on a ferrite ring with an external diameter of 10 ... 15 mm. The primary winding contains 10 turns of the wire PEV-2 with a diameter of 0.5 mm, the secondary - 200 turns of the PEV-2 with a diameter of 0.1 mm. Diode must be Germany, for example D9, D310, D311, GD507. Silicon diodes have a large threshold opening voltage (0.5 ... 0.7 V), which will lead to a strong nonlinearity of the meter scale in the measurement area of \u200b\u200bsmall resistance. The ESR meter is graduated with several resistance resistance resistance resistance. By closed the probes, noted where the zero scale mark will be. Due to the presence of resistance in connecting wires, it may not coincide with the position of the arrow when the power is turned off. Therefore, the wires going to the junctions should be short enough. Next, two parallel connected resistors are connected to 1 Ohm and the position of the arrow corresponding to the measured resistance of 0.5 ohms is noted. Then the resistors are connected to 1, 2, 3, 5 and 10 Ohm and the positions of the arrow are noted when measuring these resistances. This can also be stopped, as the electrolytic capacitors with a capacity of more than 4.7 μF with ESR is greater than 10 ohms, although they can work, but not long :)

When repairing technicians, radio mechanics professionals face various problems - damaged tracks on cards, oxidation, burnt elements that swollen capacitors. These faults are perfectly visible with the primary inspection of equipment and eliminate them with the help of the most basic tools of any engineer is not difficult. But there are cases in which the visual inspection is not enough.

Capacitors are of different capacities, both very large (4000, 10000 μF), and very small (0.33 μF, for example, such parts are actively used when assembling components of various office equipment). And if the upper cover is perfectly noticeably due to their size, then with the second, the identification of their malfunction can deliver a lot of problems.

This will help a simple device for testing capacitors - ESR-meter. Its hands to make it easy, having sufficient knowledge in circuitry. It can be both an independent device and is made in the form of a prefix to a digital multimeter. With it, you can easily establish such malfunctions as a breakdown and drying.

Electrolytic capacitors They have a number of parameters important for their proper operation in the device scheme. It is its container, and the resistance of the dielectric between the leads and the case, and their own inductance, equivalent to the consistent resistance or, on the American manner, Equivalent Series Resistance. ESR is the resistance of the condenser's plates and its legs, which it rolls to the board, conclusions.

There are special formulas for the calculation of this indicator, but in real practice no one uses. It is much easier to assemble the device for its measurement, and the results obtained to check with the ESR table of electrolytic capacitors, in which the indicators are given in millios, depending on the characteristics of parts - tanks and supported voltage.

Capacitors are used practically everywhere. No diagram of a device with at least minimal complexity is not necessary without them.

In personal computers, they are found in power blocks, monitors, near important nodes of motherboards - network and sound microcircuits, in the power supply system of the processor, southern and north bridges, RAM.

In acoustic systems and network equipment (routers, switches, for example), they are found near amplifiers and LAN ports. All of them provide stable food of these elements, and the slightest nutritional problems, as you know, can lead to problems in work - hang, braking, and to a banal failure to work.

The dried and punched capacitors cannot be detected by a simple inspection, so the ESR meter can determine the cause of the fault. For this, the details on which the suspicion fell from the board and are checked by the device. It is not recommended to check them without falling - indicators in this case may be too inaccurate. If the resistance rate is too high, the component must be replaced with an analogue with the lowest ESR.

Basic elements of the device

Based on eSR-meter schemes Lies a chip of a K561LN2 type pulse generator, operating at a frequency up to 120 kHz. For additional convenience, the chip itself can not be directly in a fee, and use a special panel with the necessary number of legs. This will allow you to quickly change the outstanding item and replace it without additional operations with a soldering iron and a solder suction. As an analogue of this generator, you can use similar by the characteristics K1561LN2.

The frequency setting is performed by a chain consisting of a resistor and a condenser. Adjustment and adjustment of the ESR measurement is carried out by a trim resistor.

As a nutrition, either a standard CR2032, outstanding voltage up to 3 volts, or, if it is not enough to work, a 9-volt battery, connected through a special terminal (such can be found in some hours with autonomous power, for example, or in old batteries type crown). The variable voltage meter includes a multimeter that needs to be translated into the appropriate mode, and germanium diodes.

Assembling tester condensers You can produce both on a dumping board in size about 4 per 6 centimeters and on special printed circuit boards. The second option will be a bit more expensive, but its advantage is the presence of the designations of all the desired elements and tracks that connect them.

The printed circuit boards are made of foil textolite and before making the elements of the elements of contacts to them must be selected.

When using bias, placement of elements and their connection is made independently. To create a scheme, the wires of sufficient thickness with fluoroplastic insulation are used to prevent their damage during thermal exposure.

As probes, you can use both purchased and homemade. In the second case, it is necessary to independently take care of the good conductive ability of the material used and the sufficient thickness of the wire going to the multimeter. Use long wires, more than 10 centimeters, is not recommended.

Possible disadvantages and comments on this device:

1. In case of unstable diet of the battery, strong deviations are possible on the accuracy of measurements, do not forget to periodically check the battery multimeter and not allow its discharge more than 1 volt.
2. Even with a fully serviceable battery, the device made in this way does not claim the title of high-precision. It can be used as a certain element performance indicator and determine whether the condenser is suitable for installation or replacement.

The first and second drawbacks have a general solution - it is enough to install a stabilizer that is powered directly from the battery, and two capacitors. This increases the reliability and accuracy of the device, which makes it possible to throw off the situations in which, if the measured element has a resistance too small, the multimeter signalized the short circuit instead of the expected value.

The order of calibration of the device

After installing the device on the board and primary tests, it must be calibrated. To do this, you will need an oscilloscope and a set of adjustment resistors with a par value from 1 to 80 ohms. Calibration Order:

1. We measure the oscilloscope frequency on the senses. It must be within 120-180 kHz. At a lower or higher frequency, it is adjusted by the selection of the resistor from the set.
2. Connect the multimeter to the superstam, select the measurement mode in Millylololt.
3. Resistor in 1 ohms connect to the sup. Using a trimming resistor in the diagram, set the voltage value of 1 million on the multimeter.
4. We connect the following to the nominal resistor, without changing the value, and write a multimeter reading. We repeat with the whole set and make a sign.

After calibration, the instrument can be used. It will help in the detection of faults associated with reactive resistance. They are impossible to diagnose in another way.

Equivalent Series Resistance (equivalent sequential resistance - EPS), as one of the significant parasitic parameters of electrolytic capacitors, in recent years has gained wide popularity among the repairmen of electronic equipment. ESR meters and probes for many masters have become a matter of essentially, along with a tester or multimeter.
An increase in the ESR capacitor into several Ohms, and sometimes for several tenths of Ohm, it may cause an inoperability of the device in which it is established that it is sometimes impossible to identify existing capacity meters that are not capable of considering other condenser parameters.

Typically, repair practice does not require special accuracy in the ESR measurement, therefore, the tangible error of the probes more often does not cause inconvenience in finding faulty elements, and the definition of the condition of the capacitor can be simplified before assessing its quality on the principle - suitable or not suitable for working in a specific device node.
But, it should be noted, for capacitors operating at high pulse currents, for example, in converter filters, sometimes more objective quality assessment is required, and the error in the tenths and even hundredths of the OBO can be essential.

The majority of popular and used ESR appliances and test equipment used in the repair practice are based on the measurement of the impedance of the variable current at a frequency of 40 - 100 kHz. At the frequencies of this order for electrolytic capacitors of large denominations, such devices will show the values \u200b\u200bas close to the value of ESR, which will be the main part of the impedance at these frequencies.
The disadvantage of this method is a significant error in measuring small capacitance ratings (less than 10 UF), when the condenser reactive resistance at this frequency is commensurate and may exceed ESR.
Then the device will show the impedance value, and the actual ESR value can be several times less.

One of the requirements in terms of the practicality of the use of ESR probes is the ability to perform measurements without falling out the capacitor from the board. Consequently, the measurement process should occur at a sufficiently low voltage drop on the tested condenser, excluding unlocking the transitions of semiconductor elements of the circuit.

In most cases, such simple Master's impedance meters are collected independently according to the schemes widely distributed on the Internet, but someone also applies their development, taking into account personal preferences in terms of convenience of use or measurement accuracy.
There are on sale both simple probes with LED or shooter display and meters with a digital scale of varying degrees of complexity.

It is not necessary to stop in detail on the principles and methods of measuring the impedance, such discussions and descriptions there are quite a lot and it is easy to find on the Internet. But some features of individual structures can still deserve attention.

This article proposes to consider one of the methods of measuring ESR and containers, as separate parameters of the condenser.

A fairly accurate and simple method, which is used in many amateur and industrial devices, is implemented in the Micro Member, popular among masters - participants in the repair forums Monitor.Net.ru and Monitor.espec.ws.

If the tested capacitor capacitance C. charge from a dc source I., the voltage on its conclusions will linearly increase from the value U R. according to law:

C du / dt \u003d i \u003d const.

U R. - Drop voltage on the active resistance of the condenser (ESR).

In this case, the capacitor capacity will be determined by the expression:

Calculate U R. It is possible in several ways to calculate ESR in several ways, for example, making the equation direct along two points and find the y coordinate for the zero value of X, or geometrically, based on the ratio of the sides of similar triangles ...

The active resistance of the condenser (ESR) in this case will be:

To implement such a method, there is no need to use ADC, the threshold values \u200b\u200bof the voltage to control the timer are set by comparators, and the mathematical calculations of the container and ESR are produced by a microcontroller with the output of information on the LCD display.

In some similar structures, the ESR measurement is used a simpler, but less accurate way.
Voltage level is measured U R. Through the ADC at the initial moment of time.
Despite the fact that the measuring impulse is quite short (1-2 US), the capacitors of a smaller capacity have time to charge to a larger value than the capacitors of a large capacity, which creates some error in measuring ESR different capacitor ratios.

It should be borne in mind that ESR, measured by direct current, is a relative indicator of the quality of the electrolytic capacitor.
The meaningful component ESR is dielectric losses that significantly change with changing the frequency of AC.

There are more complex and accurate techniques and measurement methods based on the phase shift analysis in the condenser. In this case, ESR will determine the product of the impedance and tangent of the corner of the loss.

Comments and suggestions are accepted and welcome!

Recently, in radio amateur and professional literature, a lot of attention is paid to such devices as electrolytic capacitors. And it is not surprising, because frequencies and power grow "in the eyes", and these capacitors are huge responsibility for the performance of both individual assemblies and schemes in general.

I want to immediately warn that the majority of nodes and circuit solutions have been drawn from the forums and magazines, so I do not declare any authorship for my part, on the contrary, I want to help beginner repairmen to decide in endless schemes and variations of meters and probes. All schemes provided here were not once collected and verified in the work, and the corresponding conclusions are made to work one or another design.

So, the first scheme, which is almost a classic for beginners of ESR Metrolybuts "Manfred" - so it is kindly called forum users, named Her Colder, Manfred Ludens.cl/electron/esr/esr.html

It was repeated hundreds, and maybe thousands of radio amateurs, and remained mostly satisfied with the result. Its main advantage, this is a sequential measurement scheme, due to which, the minimum ESR corresponds to the maximum voltage on the shunt resistor R6, which, in turn, useful affects the operation of the detector diodes.

I myself did not repeat this scheme, but I came to similarly by samples and errors. From the disadvantages, you can note the "walk" of zero from temperature, and the dependence of the scale from the parameters of diodes and the OU. Increased supply voltage required for the device. The sensitivity of the device can be easily increased by reducing the resistors R5 and R6 to 1-2 Ohm and, accordingly, increasing the strengthening of the OU, it may be necessary to replace it with 2 more speeds.

My first EPS probion, working to date today.

The schemes have not been preserved, and it can be said and did not have to say, gathered from all over the world on a thread, the fact that I was satisfied with schemeshotnically, however, such a scheme from Radio magazine was taken as a basis:

The following changes were made:

1. Powered by Mobile Lithium Battery
2. The stabilizer is excluded, since the limits of lithium battery voltages are quite narrow
3. Transformers TV1 TV2 are shunted by resistors 10 and 100 ohms, to reduce emissions when measuring small eucosities
4. The output 561ln2 was buffered 2 complementary transistors.

In general, it turned out such a device:

After assembling and calibrating this device, 5 digital telephones "Meredian" were repaired, which were already 6 years old in the box with the inscription "hopeless". Everyone in the department began to make similar probes :).

For greater universalization, I have added additional functions:

1. Infrared radiation receiver, for visual and hearing inspection of remote controls, (very popular function for telephone repairs)
2. Illumination of the touch of condensers
3. "Vibrik" from the mobile phone helps to localize bad soldering and microphone effect in detail.

Video checks of the console

And recently on the Radiokot.ru forum, Mr. Simurg laid out an article dedicated to a similar instrument. In it, it applied low-voltage nutrition, a bridge measurement scheme, which made it possible to measure capacitors with an ultra-low level ESR level.

His colleague RL55 taking the SIMURG scheme as a basis, utterly simplified the instructor, according to his statements, without worsening the parameters. His scheme looks like this:

The device is lower, I had to collect on an ambulance hand, as they say "by need." He was visiting relatives, so there the TV broke, no one could repaired him. Rather, the repair managed, but not more than a week, all the time the transistor of the line sweep was burned, there was no TV scheme. It was remembered that I saw a simple probication in the forums, I remembered the scheme by heart, the relative was also a little radio advantage, audio amplifiers "Klepal", so all the details were quickly found. A couple of hours of smelling a soldering iron, and this tider was born:

There were 5 minutes and replaced with 4 refrigerated electricity, which were determined by a multimeter as normal, recruited for success of a certain amount of noble drink. A telephone after repair is already working regularly for 4 years.

The device of this type has become like a panacea in difficult moments when not with a normal tester. It is going to quickly, repair is made, and finally be solemnly given the owner for memory, and "in case of what". After such a ceremony, the soul of the paying is usually revealed by twice, and then and three times wider :)

I wanted something synchronous, I began to think over the implementation scheme, and here in the magazine "Radio 1 2011", as an article was published in the marvel in the marvel, it was not necessary to think. I decided to check what kind of beast. Assemmed, it turned out like this:

Special delight did not cause the product, it works almost like all the previous ones, there is, of course, the difference in readings in 1-2 divisions, in certain cases. Maybe his testimony is more reliable, but the probe has a probe, it is almost nothing to be reflected on the quality of defectation. Also provided the LED to watch "where you are?".

In general, it is possible to do for the soul and repair. And for accurate measurements, it is necessary to search the ESR meter scheme is more violent.

Well, on the last on the MONITOR.NET website, the BURATINO member laid out the simplest project, as an ESR probique from a typical cheap digital multimeter. The project so I was intrigued that I decided to try, and that's what I had it from it.

The body has adapted from the marker

What is ESR?

Equivalent sequential resistance (ESR) is an exceptionally important parameter of the electrolytic capacitor, which characterizes its performance, quality and degree of aging. From the point of view of repair of electronic equipment, this parameter is even more important than the container. If, for example, we measured the capacitance of the capacitor with a par value of 1000 microfarad and it turned out to be 650 microfarades, the capacitor can still work in the device for almost no noticeable deterioration (this is certainly highly dependent on the specific scheme), in case its ESR remains in an acceptable framework. . On the other hand, if the capacitor has greatly increased ESR, then in many schemes, especially in pulsed power blocks, such a capacitor can no longer perform its functions even if it has a nominal container. However, in practice it happens not often, since the capacity and ESR - the parameters are interrelated and the capacitor capacitance is very often reduced. Usually an ESR increases as the electrolyte of the capacitor is drying.

It must be said that the permissible ESR is not a permanent parameter, it depends on the tank and the working voltage of the capacitor. Therefore, it is possible to conclude an output about the suitability of the capacitor after measuring its ESR using a special table of the maximum permissible ESR values. You can see it on the photo of the device on its front panel. I printed the table and glued it to the instrument panel:

How to measure ESR?

Equivalent consistent resistance, as well as the usual resistance, is measured in Oma. Unlike an ordinary ohmmeter, the device measuring ESR produces not at a constant current, but on an alternating current of a relatively high frequency, usually in the region of 100 kilohertz. At this frequency, the capacitance of the capacitor practically does not affect the resistance of the condenser, therefore, it is measured precisely the consistent equivalent resistance, and not the capacitor capacity. In fact, this is the main and only difference between the ESR meter from a simple ohmmeter.

In general, the ESR measurement method is shown in the diagram below:

Most meters work precisely on this principle. We have an alternator G, a resistor of the known resistance R and the measured CX capacitor. This resistor together with the measured capacitor form a voltage divider. Then there is a detector that converts alternating voltage into a constant and indication node of this constant voltage recalculated in ohms. It can be an analog or digital indication circuit, the essence does not change.

Device scheme

Described device It is exceptionally convenient because it can check capacitors without falling out of them from the scheme and in most cases it works. An exception can be for example if you want to check the capacitor parallel to which other condensers are included. Such an inclusion sometimes happens in power blocks. In this case, the device will show the smallest ESR (that is, the ESR of the best condenser).

ESR meter diagram (click to enlarge)

The device is assembled based on the microcontroller PIC16F873. The microcontroller measures the straightened voltage, recalculates its value to the resistance in Oma. In addition, the microcontroller generates an alternating voltage of the rectangular form of a frequency of 100 kHz, which is used for measurements.

In order to make it possible to measure ESR capacitors without paying out of them from the circuit, the measuring voltage should be low enough, usually 0.2-0.4 volts, that is, there is less than the opening threshold PN - semiconductor transitions.

The facts are a digital ohmmeter working on alternating voltage of the frequency of 100 kHz and allowing measurement of resistance from 0 to 25.5.

A node for the formation of an exemplary voltage 2.5 V for the controller ADC in the original scheme is assembled on the TL431 chip. At the time when I collected this meter, I did not have such a chip and I replaced it with a stabilion at 3.3 in and a stroke resistor on 10 K. Running room I installed on the leg 5 controller Required 2.5 V.

Source node on TL431

I replaced it like this

Now TL431 is a very common and cheap microcircuit and there is no problems with its acquisition. So if you use my printed circuit board, install TL431. The trimmer does not need to be installed in this case.

The power supply is assembled on a network transformer T1, a diode bridge and voltage stabilizer LM7805 (K142EN5A). In my version of the device, I refused the transformer, leaving, however, the diode bridge on the printed circuit board. I used a small-sized pulse power supply unit (adapter) to 12 volt voltage,

which, due to the presence of a diode bridge, can be connected in any polarity or use an alternating voltage adapter at all (simply transformer).

In principle, you can get rid of the power supply at all if you use a five-volt adapter - charging from the smartphone.

Meander with a frequency of 100kHz is removed from the RC2 legs of the microcontroller and through the R3 resistor is supplied to the current amplifier collected on the transistors VT1, VT2. I used CT3102 and CT3107. A good idea here will use modern transistors BC547 and BC557. The load of the amplifier is the R1 resistor and VD5 diodes, VD7, included in the counter-parallel to limit the amplitude on the measurable condenser. Next, alternating voltage, through the C1 condenser and the measured CX capacitor enters the primary winding of the T2 enhancing transformer. Next, the pulses are removed from the secondary winding and straighten with the VD6 diode, after which the resulting pulsating voltage is smoothed by a C3 capacitor. Next, the formed constant voltage through the R4 stroke resistor enters the input of the analog-digital converter of the microcontroller D3. CONDACTOR C9 eliminates possible high-frequency interference.

Information is displayed on a three-digit seven-segment LCD indicator. Transistors VT3, VT4, VT5 are the switching keys of the LCD indicators (the principle of dynamic indication is used.

Network transformer (if you decide to use it) with a secondary winding by 9-12 volts. A boost transformer T2 is wound on the M2000NM ferrite ring and the size of K10X6x3 (you can use the ring of other sizes that do not differ much differently from the specified. It is not critical). The primary winding is wound with a wire with a diameter of 0.26mm, and consists of 42 turns. The secondary winding contains 700Vettes with a diameter of 0.08mm.

Device setting. We connect the resistor of the known resistance in the range of the measuring instrument in the range of 1 .. 5 Ohm and the trimming resistor we achieve correct readings on the display. After such a setting, my device with connected together shifts showed resistance different from zero, so I still slightly adjusted the position of the resistor's engine so that the display was zero with closed probe.

The printed circuit board of the device was once diluted in the PCAD2006 program, and later I imported the board file to the DipTrace program.