Devices that have a reading measured capacitance of the capacitor produced on a dial meter scale, called faradometers or microfaradometers. The capacitor microfaradometer described below is distinguished by a wide range of measured capacitances, simplicity of circuit and setup.
The operating principle of the microfaradometer is based on measuring the average value of the discharge current of the measured capacitor, which is periodically recharged with a frequency F. In Fig. Figure 1 shows a simplified diagram of the measuring part of the device, powered by a rectangular pulse voltage coming from the pulse generator G. In the presence of voltage
Rice. 1. Simplified diagram of the measuring part of the device
U imp at the output of the generator through diode D1, capacitor C x is quickly charged. The circuit parameters are selected in such a way that the capacitor charging time is significantly less than the pulse duration t and,therefore, the capacitor C x manages to be fully charged to the voltage U imp even before the end of the latter. In the time interval t and between pulses, the capacitor is discharged through the internal resistance of the generator R g and microammeter μA1, measuring the average value of the discharge current. Time constant of the capacitor discharge circuit C x significantly less pause time t p , therefore, the capacitor has time to almost completely discharge during the break between pulses, the frequency of which
Thus, in steady state, the amount of electricity stored by the capacitor C x for one period and given by it during discharge, Q = C x U imp . At pulse repetition rate F, the average value of the current passing through the microammeter during periodic discharges of the capacitor C x, equals:
I and = QF = C x U imp F, whence
From the resulting formula it follows that the measured capacitance of the capacitor WITH x is proportional to the strength of the discharge current and, therefore, at stable values U imp and F the μA1 dial meter can be equipped with a uniform scale, graduated in C x values (practically, the existing linear scale of the microammeter of the magnetoelectric system is used).
In Fig. Figure 2 shows a schematic diagram of a microfaradometer, which allows you to measure capacitances of capacitors from approximately 5 to 100,000 pF on the scales: 0-100; 0-1000; 0-10,000 and 0-100,000 pF. The value of the measured capacitance is read directly from the existing microammeter scale, which allows for quick and fairly accurate measurements. A 7D-0.1 battery or a Krona battery is used as a power source for the microfaradometer. On a scale of 0-100 pF, the current is much less and its strength does not exceed 4 mA. The measurement error is no more than 5-7% of the upper limit of the scale.
Capacitor charge C x carried out by rectangular voltage pulses created by non-symbolic
metric multivibrator mounted on transistors T1, T2 with different conductivity. The multivibrator generates a periodic sequence of rectangular voltage pulses with a high duty cycle. Frequency hopping
Rice. 2. Schematic diagram of a microfaradometer
pulse repetition is carried out by the section B1a switch B1, including one of the capacitors C1- in the positive feedback circuit C4 smooth - variable resistor R3. The same switch makes the transition from one measurement limit to another.
Rectangular voltage pulses generated across a resistor R1, via contacts 1-2 buttons B2 and diode D1 charging one of the model capacitors C5 - C8 or measured capacitor C x (with the button pressed AT 2). In the intervals between pulses, one of the specified capacitors (depending on the measurement limit and the position of the button AT 2) discharged through resistors R1, R5 and microammeter μA1. Diode D1 does not affect the readings of the microammeter, since its reverse resistance is significantly greater than the resistance of the meter circuit(R p + R5). Capacitors C5 - C8 are intended for calibration of the device and must be selectedperhaps more accurately, with no deviation from the nominal value by more than ±2%.
The design uses small-sized resistors BC = 0.125, capacitors KSO, SGM, KBGI. Pere
Rice. 3. Front panel of the device
exchange resistor R3 type SP-1. Switch IN 1 biscuit type with 4 positions and 2 directions. Microammeter - magnetoelectric system at 50 μA.
One of the options for the location of controls on the front panel is shown in Fig. 3. The dimensions of the structure are determined by the dimensions of the microammeter and switch IN 1 and therefore are not given. If necessary, the device can be powered from an alternating current network using a stabilized rectifier, providing an output voltage of 9 V with a load current of at least 10 mA. In this case, it is advisable to place the rectifier in the device body.
The scale of the capacitance meter, as already indicated, is practically linear, so there is no need to apply special marks between zero and the last division on the existing microammeter scale. Scale
microammeter, which has, for example, digitized marks 0, 20, 40... 1000 μA, is correct at any limit for measuring the capacitance of capacitors. Only the division price changes. So on the range 0-100; 0-1000; 0-10,000 and 0-100,000 microammeter readings must be multiplied by 1, respectively; 10; 10 2 and 10 3. If the microammeter scale has only 50 divisions, then the readings of the microammeter, depending on the specified measurement limits, must be multiplied by 2; 2 10; 2 10 2 ; 2 10 3
Setting up a device usually does not cause any difficulties if it is assembled from known good parts and no errors were made during installation. The operation of the multivibrator can be judged on the scale of a microammeter, the readings of which should change when the position of the variable resistor slider changes. R3 at any of the four measurement limits.
Setting the switch B1 to position 1 (scale 0-100 pF), variable resistor R3 is used to deflect the microammeter needle to the full scale. If this cannot be achieved, the resistor motor R3 set to the middle position and select the capacitance value of the capacitor C1. More precisely, the arrow is installed at the end of the scale with a resistor R3 . After this the switch IN 1 transferred to position 2 (scale 0-1000 pF) and without touching the resistor R3 , select the capacitance of the capacitor C2 so that the microammeter needle is near the end of the scale. Similarly, the value of the capacitance of capacitors is specified SZ and C4 in positions 3 and 4 of switch B1 (on scales 0-10,000 and 0-100,000 pF).
This completes the setup of the device. The procedure for measuring the capacitance of capacitors is as follows. By connecting the capacitor C x to sockets Gn1 , turn on the device with switch B3 and switch IN 1 set the desired measurement limit. Then with a resistor R3 set the microammeter needle to the last division of the scale and, pressing the button AT 2 , the measured capacitance is counted on the scale, taking into account the value of its division. If the microammeter needle goes off scale when the button is pressed, the switch IN 1 transfer to a higher measurement limit and repeat the measurements. If the arrow is set at the very beginning
scale, the switch is moved to a lower measurement limit.
In conclusion, we point out that the minimum value of capacitance measured on a scale of 0-100 pF depends on the initial capacitance between the sockets Gn1 , which should be kept to a minimum during installation. Before connecting the capacitor to the device, you should make sure that there is no breakdown in it, since the latter can lead to damage to the microammeter and diode. If the order of the capacitance being measured is unknown, the measurement process should begin with the highest measurement limit (0-100,000 pF).
If you want to increase the measurement accuracy, you can increase the number of limits (scales). To do this you need to use the switch IN 1 with a large number of positions (equal to the number of limits), install new standard capacitors, the capacitances of which must correspond to the upper value of the selected measurement limits, and also select capacitor ratings (instead of C1-C4 ), which determine the repetition rate of the multivibrator voltage pulses.
DIY capacitor capacitance meter— below is a diagram and description of how, without much effort, you can independently make a device for testing the capacitance of capacitors. Such a device can be very useful when purchasing containers on the radio-electronic market. With its help, low-quality or defective electrical charge storage element can be easily identified. The schematic diagram of this ESR, as most electronics engineers usually call it, is not anything complicated and even a novice radio amateur can assemble such a device.
Moreover, the capacitance meter does not require a long time and large financial costs for its assembly; it literally takes two to three hours to manufacture a probe of equivalent series resistance. It is also not necessary to run to a radio store - any radio amateur will probably have unused parts suitable for this design. All you need to replicate this circuit is a multimeter of almost any model, but preferably one that is digital and has a dozen parts. There is no need to make any alterations or upgrades to the digital tester; all that needs to be done with it is to solder the pins of the parts to the required pads on its board.
Schematic diagram of the ESR device:
One of the main components of the device is a transformer, which should have a turns ratio of 11:1. Ferrite ring core M2000NM1-36 K10x6x3, which must first be wrapped with insulating material. Then wind the primary winding on it, arranging the turns according to the principle - turn to turn, while filling the entire circle. The secondary winding must also be made with a uniform distribution around the entire perimeter. The approximate number of turns in the primary winding for the K10x6x3 ring will be 60-90 turns, and the secondary should be eleven times smaller.
You can use almost any silicon diode D1 with a reverse voltage of at least 40v; if you don’t really need super accuracy in measurements, then the KA220 is quite suitable. To more accurately determine the capacitance, you will have to install a diode with a small voltage drop in the direct connection version - Schottky. The protective suppressor diode D2 must be designed for reverse voltage from 28v to 38v. Low-power silicon pnp transistor: for example KT361 or its analogue.
Measure the ESR value in the voltage range of 20v. When connecting the connector of an external meter, the ESR attachment to the multimeter immediately switches to the capacitance testing operating mode. In this case, a reading of about 35v will be visually displayed on the device in the test range of 200v and 1000v (this depends on the use of a suppressor diode). In the case of testing capacitance at 20 volts, the reading will be displayed as “out of measurement limits”. When the connector of the external meter is disconnected, the EPS attachment instantly switches to operating mode as an ordinary multimeter.
The principle of operation of the device is that to start operating the device, you need to plug in the adapter into the network, and the ESR meter turns on; when the ESR is turned off, the multimeter automatically switches to the mode of performing standard functions. To calibrate the device, you need to select a constant resistor so that it matches the scale. For clarity, the picture is below:
When the probes are shorted, 0.00-0.01 will be displayed on the multimeter scale; this reading means the instrument’s error in the measurement range up to 1 ohm.
A huge selection of diagrams, manuals, instructions and other documentation for various types of factory-made measuring equipment: multimeters, oscilloscopes, spectrum analyzers, attenuators, generators, R-L-C, frequency response, nonlinear distortion, resistance meters, frequency meters, calibrators and much other measuring equipment.
During operation, electrochemical processes constantly occur inside oxide capacitors, destroying the junction of the lead with the plates. And because of this, a transition resistance appears, sometimes reaching tens of ohms. Charge and discharge currents cause heating of this place, which further accelerates the destruction process. Another common cause of failure of electrolytic capacitors is “drying out” of the electrolyte. In order to be able to reject such capacitors, we suggest that radio amateurs assemble this simple circuit
Identification and testing of zener diodes turns out to be somewhat more difficult than testing diodes, since this requires a voltage source exceeding the stabilization voltage.
With this homemade attachment, you can simultaneously observe eight low-frequency or pulse processes on the screen of a single-beam oscilloscope. The maximum frequency of input signals should not exceed 1 MHz. The amplitude of the signals should not differ much, at least there should not be more than a 3-5-fold difference.
The device is designed to test almost all domestic digital integrated circuits. They can check microcircuits of the K155, K158, K131, K133, K531, K533, K555, KR1531, KR1533, K176, K511, K561, K1109 and many others series microcircuits
In addition to measuring capacitance, this attachment can be used to measure Ustab for zener diodes and test semiconductor devices, transistors, and diodes. In addition, you can check high-voltage capacitors for leakage currents, which helped me a lot when setting up a power inverter for one medical device
This frequency meter attachment is used to evaluate and measure inductance in the range from 0.2 µH to 4 H. And if you exclude capacitor C1 from the circuit, then when you connect a coil with a capacitor to the input of the console, the output will have a resonant frequency. In addition, due to the low voltage on the circuit, it is possible to evaluate the inductance of the coil directly in the circuit, without dismantling, I think many repairmen will appreciate this opportunity.
There are many different digital thermometer circuits on the Internet, but we chose those that are distinguished by their simplicity, small number of radio elements and reliability, and you shouldn’t be afraid that it is assembled on a microcontroller, because it is very easy to program.
One of the homemade temperature indicator circuits with an LED indicator on the LM35 sensor can be used to visually indicate positive temperature values inside the refrigerator and car engine, as well as water in an aquarium or swimming pool, etc. The indication is made on ten ordinary LEDs connected to a specialized LM3914 microcircuit, which is used to turn on indicators with a linear scale, and all internal resistances of its divider have the same values
If you are faced with the question of how to measure the engine speed of a washing machine. We'll give you a simple answer. Of course, you can assemble a simple strobe, but there is also a more competent idea, for example using a Hall sensor
Two very simple clock circuits on a PIC and AVR microcontroller. The basis of the first circuit is the AVR Attiny2313 microcontroller, and the second is PIC16F628A
So, today I want to look at another project on microcontrollers, but also very useful in the daily work of a radio amateur. This is a digital voltmeter on a microcontroller. Its circuit was borrowed from a radio magazine for 2010 and can easily be converted into an ammeter.
This design describes a simple voltmeter with an indicator on twelve LEDs. This measuring device allows you to display the measured voltage in the range of values from 0 to 12 volts in steps of 1 volt, and the measurement error is very low.
We consider a circuit for measuring the inductance of coils and the capacitance of capacitors, made with only five transistors and, despite its simplicity and accessibility, allows one to determine the capacitance and inductance of the coils with acceptable accuracy over a wide range. There are four sub-ranges for capacitors and as many as five sub-ranges for coils.
I think most people understand that the sound of a system is largely determined by the different signal levels in its individual sections. By monitoring these places, we can evaluate the dynamics of the operation of various functional units of the system: obtain indirect data on the gain, introduced distortions, etc. In addition, the resulting signal simply cannot always be heard, which is why various types of level indicators are used.
In electronic structures and systems there are faults that occur quite rarely and are very difficult to calculate. The proposed homemade measuring device is used to search for possible contact problems, and also makes it possible to check the condition of cables and individual cores in them.
The basis of this circuit is the AVR ATmega32 microcontroller. LCD display with a resolution of 128 x 64 pixels. The circuit of an oscilloscope on a microcontroller is extremely simple. But there is one significant drawback - this is a fairly low frequency of the measured signal, only 5 kHz.
This attachment will make the life of a radio amateur a lot easier if he needs to wind a homemade inductor coil, or to determine unknown coil parameters in any equipment.
We suggest you repeat the electronic part of the scale circuit on a microcontroller with a strain gauge; the firmware and printed circuit board drawing are included in the amateur radio design.
A homemade measurement tester has the following functionality: frequency measurement in the range from 0.1 to 15,000,000 Hz with the ability to change the measurement time and display the frequency and duration on a digital screen. Availability of a generator option with the ability to adjust the frequency over the entire range from 1-100 Hz and display the results on the display. The presence of an oscilloscope option with the ability to visualize the signal shape and measure its amplitude value. Function for measuring capacitance, resistance, and voltage in oscilloscope mode.
A simple method for measuring current in an electrical circuit is to measure the voltage drop across a resistor connected in series with the load. But when current flows through this resistance, unnecessary power is generated in the form of heat, so it must be selected as small as possible, which significantly enhances the useful signal. It should be added that the circuits discussed below make it possible to perfectly measure not only direct, but also pulsed current, although with some distortion, determined by the bandwidth of the amplifying components.
The device is used to measure temperature and relative humidity. The humidity and temperature sensor DHT-11 was taken as the primary converter. A homemade measuring device can be used in warehouses and residential areas to monitor temperature and humidity, provided that high accuracy of measurement results is not required.
Temperature sensors are mainly used to measure temperature. They have different parameters, costs and forms of execution. But they have one big drawback, which limits the practice of their use in some places with a high ambient temperature of the measured object with a temperature above +125 degrees Celsius. In these cases, it is much more profitable to use thermocouples.
The turn-to-turn tester circuit and its operation are quite simple and can be assembled even by novice electronics engineers. Thanks to this device, it is possible to test almost any transformers, generators, chokes and inductors with a nominal value from 200 μH to 2 H. The indicator is able to determine not only the integrity of the winding under test, but also perfectly detects inter-turn short circuits, and in addition, it can check p-n junctions of silicon semiconductor diodes.
To measure an electrical quantity such as resistance, a measuring device called an Ohmmeter is used. Devices that measure only one resistance are used quite rarely in amateur radio practice. The majority of people use standard multimeters in resistance measurement mode. Within the framework of this topic, we will consider a simple Ohmmeter circuit from the Radio magazine and an even simpler one on the Arduino board.
One of the most common reasons for the failure of electronic equipment or the deterioration of its parameters is a change in the properties of electrolytic capacitors. Sometimes, when repairing equipment (especially those manufactured in the former USSR) made using certain types of electrolytic capacitors (for example, K50-...), in order to restore the functionality of the device, they resort to complete or partial replacement of old electrolytic capacitors. All this has to be done due to the fact that the properties of the materials included in the electrolytic (precisely electrolytic, since the composition uses an electrolyte) capacitor change over time under electrical, atmospheric, and thermal influences. And thus the most important characteristics of capacitors, such as capacitance and leakage current, also change (the capacitor “dries out” and its capacity increases, often even by more than 50% of the original, and the leakage current increases, i.e. internal resistance, shunting the capacitor decreases), which naturally leads to a change in characteristics, and in the worst case, to a complete failure of the equipment.
The meter has the following qualitative and quantitative characteristics:
1) capacitance measurement on 8 subranges:
2) assessment of the capacitor leakage current using the LED indicator;
3) the ability to accurately measure when changing the supply voltage and ambient temperature (built-in calibration of the meter);
4) supply voltage 5-15 V;
5) determination of the polarity of electrolytic (polar) capacitors;
6) current consumption in static mode............ no more than 6 mA;
7) capacitance measurement time .................................... no more than 1 s;
8) current consumption during capacitance measurement increases with each subrange,
But................................................. ................................ no more than 150 mA on the last subrange.
The essence of the device is to measure the voltage at the output of the differentiating circuit, Fig. 1.
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Voltage across the resistor: Ur = i*R,
where i is the total current through the circuit, R is the charging resistance;
Because the circuit is differentiating, then its current is: i = C*(dUc/dt),
where C is the charging capacitance of the circuit, but the capacitor will be charged linearly through the current source, i.e. stabilized current: i = С*const,
This means the voltage across the resistance (output for this circuit): Ur = i*R = C*R*const - is directly proportional to the capacitance of the capacitor being charged, which means that by measuring the voltage across the resistor with a voltmeter, we measure on a certain scale the capacitance of the capacitor under study.
The diagram is shown in Fig. 2.
In the initial position, the test capacitor Cx (or calibration C1 with toggle switch SA2 on) is discharged through R1. The measuring capacitor, on which (not on the subject directly) the voltage proportional to the capacitance of the subject Cx is measured, is discharged through the contacts SA1.2. When the SA1 button is pressed, the test subject Cx (C1) is charged through the resistors R2 ... R11 corresponding to the sub-range (switch SA3). In this case, the charging current Cx (C1) passes through the LED VD1, whose brightness allows us to judge the leakage current (resistance shunting the capacitor) at the end of the capacitor charge. Simultaneously with Cx (C1), through a stabilized current source VT1, VT2, R14, R15, the measuring (known to be good and with a low leakage current) capacitor C2 is charged. VD2, VD3 are used to prevent the discharge of the measuring capacitor through the supply voltage source and current stabilizer, respectively. After charging Cx (C1) to a level determined by R12, R13 (in this case to a level of approximately half the voltage of the power source), comparator DA1 turns off the current source, the charge of C2 synchronous with Cx (C1) stops and the voltage from it is proportional to the capacitance of the test Cx (C1) is indicated by microammeter PA1 (two scales with values that are multiples of 3 and 10, although it can be adjusted to any scale) through voltage follower DA2 with high input impedance, which also ensures long-term charge retention on C2.
Settings
When setting, the position of the calibration variable resistor R17 is fixed in some position (for example, in the middle). By connecting reference capacitors with precisely known capacitance values in the appropriate range, resistors R2, R4, R6-R11 calibrate the meter - such a charge current is selected so that the reference capacitance values correspond to certain values on the selected scale.
In my circuit, the exact values of the charging resistances at a supply voltage of 9 V were:
After calibration, one of the reference capacitors becomes calibration capacitor C1. Now, when the supply voltage changes (changes in ambient temperature, for example, when a ready-made, debugged device is heavily cooled in the cold, the capacitance readings turn out to be underestimated by 5 percent) or simply to control the accuracy of measurements, just connect C1 with the SA2 toggle switch and, by pressing SA1, use the calibration resistor R17 to adjusting PA1 to the selected value of capacitance C1.
Design
Before starting to manufacture the device, it is necessary to select a microammeter with a suitable scale(s), dimensions and current of maximum needle deflection, but the current can be any (of the order of tens, hundreds of microamps) due to the ability to configure and calibrate the device. I used an EA0630 microammeter with In = 150 µA, accuracy class 1.5 and two scales 0 ... 10 and 0 ... 30.
The board was designed taking into account the fact that it will be mounted directly on the microammeter using nuts on its terminals, Fig. 3. This solution ensures both mechanical and electrical integrity of the structure. The device is placed in a housing of suitable dimensions, sufficient to accommodate also (except for the microammeter and board):
SA1 - KM2-1 button of two small-sized switches;
- SA2 - small-sized toggle switch MT-1;
- SA3 - small-sized biscuit switch with 12 positions PG2-5-12P1NV;
- R17 - SP3-9a - VD1 - any, I used one of the KIPkh-xx series, red in color;
- 9-volt Corundum battery with dimensions 26.5 x 17.5 x 48.5 mm (excluding the length of the contacts).
SA1, SA2, SA3, R17, VD1 are fixed on the top cover (panel) of the device and are located above the board (the battery is strengthened using a wire frame directly on the board), but are connected to the board with wires, and all other radio elements of the circuit are located on the board (and under microammeter directly too) and are connected by printed wiring. I did not provide a separate power switch (and it would not have fit into the selected case), combining it with the wires for connecting the test capacitor Cx in the SG5 type connector. The “female” XS1 connector has a plastic case for installation on a printed circuit board (it is installed in the corner of the board), and the “male” XP1 is connected through a hole in the end of the device body. When connecting the male connector, its contacts 2-3 turn on the power to the device. It would be a good idea to attach a connector (block) of some design in parallel to the Cx wires to connect individual sealed capacitors.
Working with the device
When working with the device, you need to be careful with the polarity of connecting electrolytic (polar) capacitors. For any connection polarity, the indicator shows the same capacitance value of the capacitor, but if the connection polarity is incorrect, i.e. “+” of the capacitor to the “-” of the device, LED VD1 indicates a large leakage current (after charging the capacitor, the LED continues to light brightly), while with the correct polarity of the connection, the LED flashes and gradually goes out, demonstrating a decrease in the charging current to a very small value, almost completely extinction (should be observed for 5-7 seconds), provided that the capacitor under test has a low leakage current. Non-polar, non-electrolytic capacitors have a very low leakage current, as can be seen from the very fast and complete extinguishing of the LED. But if the leakage current is large (the resistance shunting the capacitor is small), i.e. the capacitor is old and “leaking”, then the glow of the LED is visible already at Rleakage = 100 kOhm, and with lower shunt resistances the LED lights up even brighter.
Thus, it is possible to determine the polarity of electrolytic capacitors by the glow of the LED: when connected, when the leakage current is less (the LED is less bright), the polarity of the capacitor corresponds to the polarity of the device.
Important note!
For greater accuracy of readings, any measurement should be repeated at least 2 times, because for the first time, part of the charge current goes to create the oxide layer of the capacitor, i.e. Capacity readings are slightly underestimated.
RadioHobby 5"2000
| Designation | Type | Denomination | Quantity | Note | Shop | My notepad |
|---|---|---|---|---|---|---|
| DA1, DA2 | Chip | K140UD608 | 2 | K140UD708 or KR544 | To notepad | |
| VT1, VT2 | Bipolar transistor | KT315B | 2 | To notepad | ||
| VD2, VD3 | Diode | KD521A | 2 | KD522 | To notepad | |
| C1 | 2.2 µF | 1 | To notepad | |||
| C2 | Electrolytic capacitor | 22 µF | 1 | To notepad | ||
| R1 | Resistor | 1.3 Ohm | 1 | To notepad | ||
| R2, R4, R6 | Trimmer resistor | 100 kOhm | 3 | To notepad | ||
| R3 | Resistor | 470 kOhm | 1 | To notepad | ||
| R5 | Resistor | 30 kOhm | 1 | To notepad | ||
| R7, R8 | Trimmer resistor | 10 kOhm | 2 | To notepad | ||
| R9 | Trimmer resistor | 2.2 kOhm | 1 | To notepad | ||
| R10, R11 | Trimmer resistor | 470 Ohm | 2 | To notepad | ||
| R12, R13 | Resistor | 1 kOhm | 2 | To notepad | ||
| R14 | Resistor | 13 kOhm | 1 |
DIY ESR meter. There is a wide list of equipment breakdowns, the cause of which is precisely electrolytic. The main factor in the malfunction of electrolytic capacitors is “drying out,” familiar to all radio amateurs, which occurs due to poor sealing of the housing. In this case, its capacitive or, in other words, reactance increases as a result of a decrease in its nominal capacity.
In addition, during operation, electrochemical reactions take place in it, which corrode the connection points between the leads and the plates. The contact deteriorates, eventually forming “contact resistance”, sometimes reaching several tens of ohms. This is exactly the same if a resistor is connected in series to a working capacitor, and moreover, this resistor is placed inside it. This resistance is also called “equivalent series resistance” or ESR.
The existence of series resistance negatively affects the operation of electronic devices by distorting the operation of capacitors in the circuit. Increased ESR (about 3...5 Ohms) has an extremely strong impact on performance, leading to the burning of expensive microcircuits and transistors.
The table below shows the average ESR values (in milliohms) for new capacitors of various capacities depending on the voltage for which they are designed.
It is no secret that reactance decreases with increasing frequency. For example, at a frequency of 100 kHz and a capacitance of 10 μF, the capacitive component will be no more than 0.2 Ohm. When measuring the drop in alternating voltage having a frequency of 100 kHz and higher, we can assume that with an error in the region of 10...20%, the result of the measurement will be the active resistance of the capacitor. Therefore, it is not at all difficult to assemble.
The pulse generator with a frequency of 120 kHz is assembled using logic elements DD1.1 and DD1.2. The generator frequency is determined by the RC circuit on elements R1 and C1.
For coordination, element DD1.3 was introduced. To increase the power of pulses from the generator, elements DD1.4...DD1.6 were introduced into the circuit. Next, the signal passes through the voltage divider across resistors R2 and R3 and goes to the capacitor Cx under study. The alternating voltage measurement unit contains diodes VD1 and VD2 and a multimeter as a voltage meter, for example, M838. The multimeter must be switched to DC voltage measurement mode. The ESR meter is adjusted by changing the R2 value.
The DD1 - K561LN2 microcircuit can be replaced with K1561LN2. Diodes VD1 and VD2 are germanium, it is possible to use D9, GD507, D18.
The radio components of the ESR meter are located on, which you can make yourself. Structurally, the device is made in the same housing with the battery. Probe X1 is made in the form of an awl and attached to the body of the device, probe X2 is a wire no more than 10 cm in length with a needle at the end. Capacitors can be checked directly on the board; there is no need to unsolder them, which makes it much easier to find a faulty capacitor during repairs.
1, 5, 10, 15, 25, 30, 40, 60, 70 and 80 ohms.
It is necessary to connect a 1 Ohm resistor to the probes X1 and X2 and rotate R2 until the multimeter reads 1 mV. Then, instead of 1 Ohm, connect the next resistor (5 Ohms) and, without changing R2, record the multimeter reading. Do the same with the remaining resistances. The result is a table of values from which the reactance can be determined.
