Digital ESR and capacitance meter on the controller. Electrical diagrams for free. Diagram of a simple capacitor capacitance meter Do-it-yourself capacitance meter from a computer

Thank you very much for the work done. Another conclusion based on what I read: The 1 mA head turned out to be stupid for such a detector. after all, it is the connection in series with the resistor head that stretches the scale. Since great accuracy is not needed, you can try a head from a tape recorder. (one problem is that it gets quite electrified, I barely touched it with the sleeve of my sweater and the needle itself jumps half the scale) and the total deflection current is about 240 µA (the exact name is M68501)
In general, to reject a capacitor, isn’t the ohm scale up to 10-12 enough?

Multimeter attachment - meterESR

An ideal capacitor, operating on alternating current, should have only reactive (capacitive) resistance. The active component should be close to zero. In reality, a good oxide (electrolytic) capacitor should have an active resistance (ESR) of no more than 0.5-5 Ohms (depending on the capacitance and rated voltage). In practice, in equipment that has been in use for several years, you can find a seemingly serviceable capacitor with a capacity of 10 μF with an ESR of up to 100 ohms or more. Such a capacitor, despite the presence of a capacitance, is unusable and is most likely the cause of a malfunction or poor-quality operation of the device in which it operates.

Figure 1 shows a circuit diagram of a multimeter attachment for measuring the ESR of oxide capacitors. To measure the active component of the capacitor resistance, it is necessary to select a measurement mode in which the reactive component will be very small. As is known, the reactance of capacitance decreases with increasing frequency. For example, at a frequency of 100 kHz with a capacitance of 10 μF, the reactive component will be less than 0.2 ohms. That is, by measuring the resistance of an oxide capacitor with a capacity of more than 10 μF by the drop across it of an alternating voltage with a frequency of 100 kHz or more, we can say that. with a given error of 10-20%, the measurement result can be taken practically only as the value of active resistance.
And so, the circuit shown in Figure 1 is a pulse generator with a frequency of 120 kHz, made on logical inverters of the D1 chip, a voltage divider consisting of resistances R2, R3 and the tested capacitor CX, and an alternating voltage meter on CX, consisting of a detector VD1 -VD2 and a multimeter turned on to measure small DC voltages.
The frequency is set by the R1-C1 circuit. Element D1.3 is a matching element, and elements D1.4-D1.6 are used as an output stage.

By adjusting resistance R2, the device is adjusted. Since the popular M838 multimeter does not have a mode for measuring small alternating voltages (namely, the author’s attachment works with this device), the probe circuit has a detector using germanium diodes VD1-VD2. The multimeter measures the DC voltage at C4.
The power source is Krona. This is the same battery as the one that powers the multimeter, but the attachment must be powered from a separate battery.
The installation of the set-top box parts is carried out on a printed circuit board, the wiring and location of the parts of which are shown in Figure 2.
Structurally, the console is made in the same housing with the power source. To connect to the multimeter, the multimeter's own probes are used. The body is a regular soap dish.
Short probes are made from points X1 and X2. One of them is rigid, in the form of an awl, and the second is flexible, no more than 10 cm long, windowed with the same pointed probe. These probes can be connected to capacitors, both unmounted and located on the board (no need to solder them), which greatly simplifies the search for a defective capacitor during repairs. It is advisable to select “crocodile clips” for these probes for the convenience of checking unmounted (or dismantled) capacitors.

The K561LN2 microcircuit can be replaced with a similar K1561LN2, EKR561LN2, and with changes in the board - K564LN2, CD4049.
D9B diodes - any harmanium diodes, for example, any D9, D18, GD507. You can try using silicon ones.
Switch S1 is a microtoggle switch presumably made in China. It has flat terminals for printed circuit mounting.
Setting up the console. After checking the installation and functionality, connect the multimeter. It is advisable to check the frequency on X1-X2 with a frequency meter or oscilloscope. If it lies within the range of 120-180 kHz, it’s normal. If not, select resistance R1.
Prepare a set of fixed resistors with resistances of 1 ohm, 5 ohm, 10 ohm, 15 ohm, 25 ohm, 30 ohm, 40 ohm, 60 ohm, 70 ohm and 80 ohm (or so). Prepare a sheet of paper. Connect a 1 Ohm resistor instead of the capacitor under test. Turn slider R2 so that the multimeter shows a voltage of 1 mV. Write down “1 Ohm = 1mV” on paper. Next, connect other resistors, and, without changing the position of R2, make similar entries (for example, “60Ohm = 17mV”).
You will get a table decoding the multimeter readings. This table must be carefully drawn up (by hand or on a computer) and pasted onto the body of the set-top box so that the table is convenient to use. If the table is made of paper, place adhesive tape on its surface to protect the paper from abrasion.
Now, when testing capacitors, you read the multimeter reading in millivolts, then use the table to roughly determine the ESR of the capacitor and decide on its suitability.
I would like to note that this attachment can also be adapted to measure the capacitance of oxide capacitors. To do this, you need to significantly reduce the frequency of the multivibrator by connecting a capacitor with a capacity of 0.01 μF in parallel with C1. For convenience, you can make a “C / ESR” switch. You will also need to make another table with the values of the capacities.
It is advisable to use a shielded cable to connect to the multimeter to eliminate the influence of interference on the multimeter readings.

The device on whose board you are looking for a faulty capacitor must be turned off at least half an hour before starting the search (so that the capacitors in its circuit are discharged).
The attachment can be used not only with a multimeter, but also with any device capable of measuring millivolts of direct or alternating voltage. If your device is capable of measuring low alternating voltage (an AC millivoltmeter or an expensive multimeter), you can not make a detector using diodes VD1 and VD2, but measure the alternating voltage directly on the capacitor under test. Naturally, the plate must be made for a specific device with which you plan to work in the future. And if you use a device with a dial indicator, you can add an additional scale to its scale to measure ESR.

Radioconstructor, 2009, No. 01 pp. 11-12 Stepanov V.

Literature:
1 S Rychikhin. Oxide capacitor probe Radio, No. 10, 2008, pp. 14-15.

For more than a year I have been using the device according to the scheme of D. Telesh from the magazine "Scheme Engineering" No. 8, 2007, pp. 44-45.

On the M-830V millivoltmeter in the range of 200 mV, the readings, without an installed capacitor, are 165...175 mV.
Supply voltage 3 V (2 AA batteries worked for more than a year), measurement frequency from 50 to 100 kHz (set to 80 kHz by selecting capacitor C1). In practice, I measured capacitances from 0.5 to 10,000 μF and ESR from 0.2 to 30 (when calibrated, the device readings in mV correspond to resistors of the same value in Ohms). Used to repair switching power supplies for PCs and BREA.

An almost ready-made circuit for checking EPS, if assembled on CMOS, it will work from 3 volts... .

ESR meter

That is, a device for measuring ESR - equivalent series resistance.

As it turned out, the performance of (electrolytic - in particular) capacitors, especially those that operate in power pulse devices, is largely influenced by the internal equivalent series resistance to alternating current. Different capacitor manufacturers have different approaches to the frequency values at which the ESR value should be determined, but this frequency should not be lower than 30 kHz.

The ESR value is to some extent related to the main parameter of the capacitor - capacitance, but it has been proven that the capacitor can be faulty due to a large intrinsic ESR value, even with the declared capacitance.

outside view

The KR1211EU1 microcircuit was used as a generator (frequency at nominal values on the circuit is about 70 kHz), bass reflex transformers from AT/ATX power supplies can be used - the same parameters (transformation ratios in particular) from almost all manufacturers. Attention!!! Transformer T1 uses only half of the winding.

The device head has a sensitivity of 300 μA, but other heads can be used. It is preferable to use more sensitive heads.

The scale of this device is stretched by a third when measuring up to 1 ohm. A tenth of an ohm is easily distinguishable from 0.5 ohm. The scale fits 22 ohms.

The stretch and range can be varied by adding turns to the measuring winding (with probes) and/or to windings III of a particular transformer.

http://www. matei. ro/emil/links2.php

http://www. . au/cms/gallery/article. html? slideshow=0&a=103805&i=2

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When a working capacitor is connected, the LED should go out completely, since short-circuited turns completely disrupt generation. If the capacitors are faulty, the LED continues to light or goes out slightly, depending on the ESR value.

The simplicity of this probe allows it to be assembled in a body from a regular felt-tip pen; the main place in it is given to the battery, the power button and the LED protruding above the body. The miniature size of the probe allows you to place one of the probes in the same place, and make the second one with the shortest possible wire, which will reduce the influence of the probe inductance on the readings. In addition, you will not need to turn your head to visually control the indicator and install probes, which is often inconvenient during operation.

Construction and details.
The transformer coils are wound on one ring, preferably of the smallest size; its magnetic permeability is not very important; generator coils have a number of turns of 30 vit. each, indicator - 6 vit. and measuring 4 vit. or 3 vit. (selected during setup), the thickness of all wires is 0.2-0.3 mm. The measuring winding should be wound with a wire of at least 1.0 mm. (A mounting wire is quite suitable - as long as the winding fits on the ring.) R1 regulates the frequency and current consumption within small limits. Resistor R2 limits the short circuit current created by the capacitor being tested; for reasons of protection from a charged capacitor that discharges through it and the winding, it should be 2 watts. By varying its resistance, you can easily distinguish the resistance from 0.5 Ohms and higher by the glow of the LED. Any low-power transistor will do. Power is supplied from one 1.5 volt battery. During testing of the device, it was even possible to power it from two probes of a pointer ohmmeter connected to units of Ohm.

Parts ratings:
Rom
R2* - 1om
C1- 1 µF
S2- 390pF

Setup.
Doesn't present any difficulties. A correctly assembled generator starts working immediately at a frequency of 50-60 kHz; if the LED does not light up, you need to change the switching polarity. Then, by connecting a 0.5-0.3 Ohm resistor to the measuring winding instead of a capacitor, a barely noticeable glow is achieved by selecting turns and resistor R2, but usually their number ranges from 3 to 4. At the end of everything, they check on a known good and a faulty capacitor. With a little skill, the ESR of a capacitor up to 0.3-0.2 Ohm is easily recognized, which is quite enough to find a faulty capacitor, from a capacitance of 0.47 to 1000 μF. Instead of one LED, you can put two and connect a 2-3 volt zener diode into the circuit of one of them, but you will need to increase the winding, and the design of the device will become more complicated. You can make two probes at once coming out of the housing, but you should provide a distance between them so that it is convenient to measure capacitors of different sizes. (for example - for SMD capacitors you can use the idea of Barbos's uv - and design the probe in the form of tweezers)

Another use of this device: it is convenient for them to check control buttons in audio and video equipment, since over time, some buttons give false commands due to increased internal resistance. The same applies to checking printed conductors for breaks or checking the contact resistance of contacts.
I hope the probe will take its rightful place in the ranks of the “bug builder’s” assistant devices.

Impressions from using this sampler:
- I forgot what a faulty capacitor is;
- 2/3 of the old capacitors had to be thrown away.
Well, the best part is that I don’t go to the store or market without a sample.
Capacitor sellers are very unhappy.

Capacitance and inductance meter

E. Terentyev
Radio, 4, 1995

http://www. *****/shem/schematics. html? di=54655

The proposed dial meter allows you to determine the parameters of most inductors and capacitors encountered in the practice of a radio amateur. In addition to measuring the parameters of elements, the device can be used as a generator of fixed frequencies with decade division, as well as a generator of marks for radio engineering measuring instruments.

The proposed capacitance and inductance meter differs from a similar one ("Radio", 1982, 3, p. 47) in its simplicity and low manufacturing complexity. The measurement range is divided ten-day into six subranges with capacitance limits of 100 pF - 10 μF for capacitors and inductance 10 μH - 1 H for inductors. The minimum values of the measured capacitance, inductance and the accuracy of measuring parameters at the limit of 100 pF and 10 μH are determined by the structural capacitance of the terminals or sockets for connecting the terminals of the elements. In the remaining subranges, the measurement error is mainly determined by the accuracy class of the pointer measuring head. The current consumed by the device does not exceed 25 mA.

The operating principle of the device is based on measuring the average value of the discharge current of the capacitor capacitance and the self-induction emf of the inductance. The meter, the circuit diagram of which is shown in Fig. 1, consists of a master oscillator based on elements DD1.5, DD1.6 with quartz frequency stabilization, a line of frequency dividers on microcircuits DD2 - DD6 and buffer inverters DD1.1 - DD1.4. Resistor R4 limits the output current of the inverters. A circuit of elements VD7, VD8, R6, C4 is used when measuring capacitance, and a circuit VD6, R5, R6, C4 is used when measuring inductance. Diode VD9 protects microammeter PA1 from overload. The capacitance of capacitor C4 is chosen to be relatively large in order to reduce needle jitter at the maximum measurement limit, where the clock frequency is minimal - 10 Hz.

The device uses a measuring head with a total deviation current of 100 μA. If you use a more sensitive one - 50 μA, then in this case you can reduce the measurement limit by 2 times. The seven-segment LED indicator ALS339A is used as an indicator of the measured parameter; it can be replaced with the ALS314A indicator. Instead of a quartz resonator at a frequency of 1 MHz, you can turn on a mica or ceramic capacitor with a capacity of 24 pF, however, the measurement error will increase by 3-4%.

It is possible to replace diode D20 with diodes D18 or GD507, zener diode KS156A with zener diodes KS147A, KS168A. Silicon diodes VD1-VD4, VD9 can be any with a maximum current of at least 50 mA, and transistor VT1 can be any of the types KT315, KT815. Capacitor SZ - ceramic K10-17a or KM-5. All element values and quartz frequencies may differ by 20%.

The setup of the device begins in the capacitance measurement mode. Switch switch SB1 to the top position according to the diagram and set range switch SA1 to the position corresponding to the measurement limit of 1000 pF. By connecting a model capacitor with a capacity of 1000 pF to terminals XS1, XS2, the slider of the trimming resistor R6 is brought to a position at which the needle of the microammeter PA1 is set to the final scale division. Then switch SB1 is switched to the inductance measurement mode and, by connecting a 100 μH inductor to the terminals, in the same position of switch SA1, a similar calibration is performed with trimming resistor R5. Naturally, the accuracy of instrument calibration is determined by the accuracy of the reference elements used.

When measuring the parameters of elements with the device, it is advisable to start with a larger measurement limit to avoid the arrow of the device head suddenly going off scale. To provide power to the meter, you can use a direct voltage of 10...15 V or an alternating voltage from a suitable winding of the power transformer of another device with a load current of at least 40...50 mA. The power of a separate transformer must be at least 1 W.

If the device is powered by a battery of batteries or galvanic cells with a voltage of 9 V, it can be simplified and increased efficiency by eliminating the diodes of the supply voltage rectifier, the HG1 indicator and the SB1 switch, by placing three terminals (sockets) on the front panel of the device from points 1, 2, 3, indicated on the schematic diagram. When measuring capacitance, the capacitor is connected to terminals 1 and 2; when measuring inductance, the coil is connected to terminals 1 and 3.

Editor's note. The accuracy of an LC meter with a dial indicator to a certain extent depends on the section of the scale, so the introduction of a switchable frequency divider into the circuit by 2, 4 or a similar change in the frequency of the master oscillator (for the version without a quartz resonator) makes it possible to reduce the requirements for the dimensions and accuracy class of the indicating device.

LC meter attachment for digital voltmeter

http:///izmer/izmer4.php

A digital measuring device is now not uncommon in a radio amateur's laboratory. However, it is not often possible to measure the parameters of capacitors and inductors, even if it is a multimeter. The simple set-top box described here is intended for use in conjunction with multimeters or digital voltmeters (for example, M-830V, M-832 and the like) that do not have a mode for measuring the parameters of reactive elements.

To measure capacitance and inductance using a simple attachment, the principle described in detail in the article by A. Stepanov “Simple LC meter” in Radio No. 3, 1982 was used. The proposed meter is somewhat simplified (instead of a generator with a quartz resonator and a ten-day frequency divider, multivibrator with a switchable generation frequency), but it allows you to measure capacitance within 2 pF...1 μF and inductance 2 μH... 1 H with sufficient accuracy for practice. In addition, it produces square wave voltage with fixed frequencies of 1 MHz, 100 kHz, 10 kHz, 1 kHz, 100 Hz and adjustable amplitude from 0 to 5 V, which expands the application range of the device.

The master oscillator of the meter (Fig. 1) is made on the elements of the DD1 microcircuit (CMOS), the frequency at its output is changed using switch SA1 within the range of 1 MHz - 100 Hz, connecting capacitors C1-C5. From the generator, the signal is sent to an electronic switch assembled on transistor VT1. Switch SA2 selects the measurement mode “L” or “C”. In the switch position shown in the diagram, the attachment measures inductance. The inductor being measured is connected to sockets X4, X5, the capacitor to X3, X4, and the voltmeter to sockets X6, X7.

During operation, the voltmeter is set to DC voltage measurement mode with an upper limit of 1 - 2V. It should be noted that at the output of the set-top box, the voltage varies within 0... 1 V. At sockets X1, X2 in capacitance measurement mode (switch SA2 is in position “C”) there is an adjustable rectangular voltage. Its amplitude can be smoothly changed using variable resistor R4.

The set-top box is powered by battery GB1 with a voltage of 9 V ("Corundum" or similar) through a stabilizer on transistor VT2 and zener diode VD3.

The K561LA7 microcircuit can be replaced with K561LE5 or K561LA9 (excluding DD1.4), transistors VT1 and VT2 with any low-power silicon of the appropriate structure, zener diode VD3 can be replaced with KS156A, KS168A. Diodes VD1, VD2 - any point germanium, for example, D2, D9, D18. It is advisable to use miniature switches.

The device body is homemade or ready-made in suitable sizes. Installation of parts (Fig. 2) in the housing - hinged on switches, resistor R4 and sockets. A variant of the appearance is shown in the figure. XZ-X5 connectors are homemade, made of sheet brass or copper with a thickness of 0.1...0.2 mm, their design is clear from Fig. 3. To connect a capacitor or coil, it is necessary to insert the leads of the part all the way into the wedge-shaped gap of the plates; This ensures fast and reliable fixation of the leads.

The device is adjusted using a frequency meter and an oscilloscope. Switch SA1 is moved to the top position according to the diagram and by selecting capacitor C1 and resistor R1, a frequency of 1 MHz is achieved at the generator output. Then the switch is sequentially moved to subsequent positions and by selecting capacitors C2 - C5 the generation frequencies are set to 100 kHz, 10 kHz, 1 kHz and 100 Hz. Next, the oscilloscope is connected to the collector of transistor VT1, switch SA2 is in the capacitance measurement position. By selecting resistor R3, a vibration shape close to a meander is achieved in all ranges. Then switch SA1 is again set to the top position according to the diagram, a digital or analog voltmeter is connected to sockets X6, X7, and a standard capacitor with a capacity of 100 pf is connected to sockets X3, X4. By adjusting resistor R7, the voltmeter readings of 1 V are achieved. Then switch SA2 is switched to the inductance measurement mode and a model coil with an inductance of 100 μH is connected to sockets X4, X5, and the voltmeter readings are set with resistor R6, also equal to 1 V.

This completes the setup of the device. On other ranges, the accuracy of the readings depends only on the accuracy of the selection of capacitors C2 - C5. From the editor. It is better to start setting up the generator with a frequency of 100 Hz, which is set by selecting resistor R1; capacitor C5 is not selected. It should be remembered that capacitors SZ - C5 must be paper or, better, metafilm (K71, K73, K77, K78). If the possibilities for selecting capacitors are limited, you can use section SA1.2 to switch resistors R1 and select them, and the number of capacitors should be reduced to two (C1, SZ). The resistor resistance values in this case will be: case 4.7: 47; 470 k0m.

(Radio 12-98

List of sources on the topic of EPS capacitors in the magazine "Radio"

Khafizov R. Oxide capacitor probe. - Radio, 2003, No. 10, pp. 21-22. Stepanov V. EPS and not only... - Radio, 2005, No. 8, pp. 39,42. Vasiliev V. Device for testing oxide capacitors. - Radio, 2005, No. 10, pp. 24-25. Nechaev I. Estimation of the equivalent series resistance of a capacitor. - Radio, 2005, No. 12, pp. 25-26. Shchus A. ESR meter for oxide capacitors. – Radio, 2006, No. 10, p. 30-31. Kurakin Yu. EPS indicator of oxide capacitors. - Radio, 2008, No. 7, pp. 26-27. Platoshin I. ESR meter for oxide capacitors. - Radio, 2008, No. 8, p. 18-19. Rychikhin S. Oxide capacitor probe. - Radio, 2008, No. 10, pp. 14-15. Tabaksman V., Felyugin V. ESR meters for oxide capacitors. - Radio, 2009, No. 8, pp. 49-52.

Capacitor capacitance meter

V. Vasiliev, Naberezhnye Chelny

This device is built on the basis of a device previously described in our magazine. Unlike most such devices, it is interesting in that checking the serviceability and capacity of capacitors is possible without removing them from the board. The proposed meter is very convenient to use and has sufficient accuracy.

Anyone who repairs household or industrial radio equipment knows that it is convenient to check the serviceability of capacitors without dismantling them. However, many capacitor capacitance meters do not provide this capability. True, one similar design was described in. It has a small measurement range and a non-linear countdown scale, which reduces accuracy. When designing a new meter, the problem of creating a device with a wide range, linear scale and direct reading was solved, so that it could be used as a laboratory one. In addition, the device must be diagnostic, i.e., capable of testing capacitors shunted by p-n junctions of semiconductor devices and resistor resistances.

The principle of operation of the device is as follows. A triangular voltage is applied to the input of the differentiator, in which the capacitor being tested is used as a differentiator. In this case, its output produces a square wave with an amplitude proportional to the capacitance of this capacitor. Next, the detector selects the amplitude value of the meander and outputs a constant voltage to the measuring head.

The amplitude of the measuring voltage on the probes of the device is approximately 50 mV, which is not enough to open p-n junctions of semiconductor devices, so they do not have their shunting effect.

The device has two switches. Limit switch "Scale" with five positions: 10 µF, 1 µF, 0.1 µF, 0.01 µF, 1000 pF. The "Multiplier" switch (X1000, X100, X10, X1) changes the measurement frequency. Thus, the device has eight capacitance measurement subranges from 10,000 μF to 1000 pF, which is practically sufficient in most cases.

The triangular oscillation generator is assembled on op-amp chips DA1.1, DA1.2, DA1.4 (Fig. 1). One of them, DA1.1, operates in comparator mode and generates a rectangular signal, which is fed to the input of the integrator DA1.2. The integrator converts rectangular oscillations into triangular ones. The generator frequency is determined by elements R4, C1-C4. In the feedback circuit of the generator there is an inverter based on op-amp DA1.4, which provides self-oscillating mode. Switch SA1 can be used to set one of the measurement frequencies (multiplier): 1 Hz (X1000), 10 Hz (x100), 100 Hz (x10), 1 kHz (x1).

Rice. 1

Op-amp DA2.1 is a voltage follower, at its output is a triangular signal with an amplitude of about 50 mV, which is used to create a measuring current through the capacitor Cx being tested.

Since the capacitance of the capacitor is measured in the board, there may be residual voltage on it, therefore, to prevent damage to the meter, two back-to-back bridge diodes VD1 are connected parallel to its probes.

Op-amp DA2.2 works as a differentiator and acts as a current-voltage converter. Its output voltage: Uout=(R12...R16) Iin=(R12...R16)Cх dU/dt. For example, when measuring a capacitance of 100 μF at a frequency of 100 Hz, it turns out: Iin = Cx dU/dt = 100 100 mV/5 ms = 2 mA, Uout = R16 Iin = 1 kOhm mA = 2 V.

Elements R11, C5-C9 are necessary for stable operation of the differentiator. Capacitors eliminate oscillatory processes at the meander fronts, which make it impossible to accurately measure its amplitude. As a result, the output of DA2.2 produces a meander with smooth edges and an amplitude proportional to the measured capacitance. Resistor R11 also limits the input current when the probes are shorted or when the capacitor is broken. For the input circuit of the meter the following inequality must be satisfied: (3...5)СхR11<1/(2f).

If this inequality is not satisfied, then in half the period the current Iin does not reach the steady-state value, and the meander does not reach the corresponding amplitude, and an error in the measurement occurs. For example, in the meter described in, when measuring a capacitance of 1000 μF at a frequency of 1 Hz, the time constant is determined as Cx R25 = 1000 μF 910 Ohm = 0.91 s. Half of the oscillation period T/2 is only 0.5 s, so on this scale the measurements will be noticeably nonlinear.

The synchronous detector consists of a switch on a field-effect transistor VT1, a key control unit on an op-amp DA1.3 and a storage capacitor C10. Op-amp DA1.2 outputs a control signal to switch VT1 during the positive half-wave of the meander, when its amplitude is set. Capacitor C10 stores the constant voltage generated by the detector.

From capacitor C10, the voltage, which carries information about the value of capacitance Cx, is supplied through repeater DA2.3 to microammeter RA1. Capacitors C11, C12 are smoothing. The voltage is removed from the variable calibration resistor R22 to a digital voltmeter with a measurement limit of 2 V.

The power supply (Fig. 2) produces bipolar voltages ±9 V. The reference voltages are formed by thermally stable zener diodes VD5, VD6. Resistors R25, R26 set the required output voltage. Structurally, the power source is combined with the measuring part of the device on a common circuit board.

Rice. 2

The device uses variable resistors of the SPZ-22 type (R21, R22, R25, R26). Fixed resistors R12-R16 - type C2-36 or C2-14 with a permissible deviation of ±1%. Resistance R16 is obtained by connecting several selected resistors in series. The resistances of resistors R12-R16 can be used in other types, but they must be selected using a digital ohmmeter (multimeter). The remaining fixed resistors are any with a dissipation power of 0.125 W. Capacitor C10 - K53-1 A, capacitors C11-C16 - K50-16. Capacitors C1, C2 - K73-17 or other metal film, SZ, C4 - KM-5, KM-6 or other ceramic with TKE no worse than M750, they must also be selected with an error of no more than 1%. The remaining capacitors are any.

Switches SA1, SA2 - P2G-3 5P2N. In the design, it is permissible to use the KP303 transistor (VT1) with the letter indices A, B, V, Zh, I. Transistors VT2, VT3 voltage stabilizers can be replaced by other low-power silicon transistors of the corresponding structure. Instead of the K1401UD4 op-amp, you can use the K1401UD2A, but then at the “1000 pF” limit, an error may occur due to the bias of the differentiator input created by the input current DA2.2 on R16.

Power transformer T1 has an overall power of 1 W. It is permissible to use a transformer with two 12 V secondary windings, but then two rectifier bridges are required.

To configure and debug the device, you will need an oscilloscope. It is a good idea to have a frequency meter to check the frequencies of the triangle oscillator. Model capacitors will also be needed.

The device begins to be configured by setting the voltages +9 V and -9 V using resistors R25, R26. After this, the operation of the triangular oscillation generator is checked (oscillograms 1, 2, 3, 4 in Fig. 3). If you have a frequency meter, measure the frequency of the generator at different positions of switch SA1. It is acceptable if the frequencies differ from the values 1 Hz, 10 Hz, 100 Hz, 1 kHz, but among themselves they must differ exactly 10 times, since the correctness of the instrument readings on different scales depends on this. If the generator frequencies are not a multiple of ten, then the required accuracy (with an error of 1%) is achieved by selecting capacitors connected in parallel with capacitors C1-C4. If the capacitances of capacitors C1-C4 are selected with the required accuracy, you can do without measuring frequencies.

DIY capacitor capacitance meter

Let me show you how simple it is will do b capacitor ESR meter, which is assembled in just a couple of hours literally “On my knees”. I warn you right away that I am not the author of this idea; this scheme has already been repeated a hundred times by different people. There are only ten parts in the circuit, and any digital multimeter, you don’t need to do anything with it, we just solder to the points and that’s it.

Scheme devices eps meter:

About Meter Parts:

Transformer with a turns ratio of 11\1. The primary winding needs to be wound turn to turn on the M2000 K10x6x3 ring, along the entire circumference of the ring (insulated), it is advisable to distribute the secondary evenly, with a slight interference.

Diode D1 can be anything, with a frequency of more than 100 KHz and a voltage of more than 40V, but Schottky is better.

Diode D2 is a 26V-36V suppressor. Transistor - type KT3107, KT361 and similar.

ESR measurements are carried out at a measuring limit of 20V. When the connector of the remote measuring “head” is connected, the device “automatically” switches to the ESR measurement mode, this is evidenced by the reading of approximately 36V of the device at the limit of 200V and 1000V (depending on the suppressor used), and at the limit of 20V - the reading “exceeding the measurement limit”.

When the connector of the remote measuring “head” is disconnected, the device automatically switches to the normal multimeter mode.

Total: turn on the adapter - the meter automatically turns on, turn it off - the standard multimeter. Now calibration, nothing fancy, just a regular resistor (not a wire resistor) we adjust the scale. This is roughly what it looked like:

If you short-circuit the probes, on the indicator 0.00-0.01, here is one hundredth and there is an error in the measurement interval up to 1 Ohm, I compared the ESR values of the capacitors with the factory meter.

This circuit, despite its apparent complexity, is quite simple to repeat, since it is assembled on digital microcircuits and, in the absence of errors in installation and the use of known-good parts, practically does not require adjustment. However, the capabilities of the device are quite large:

measurement range – 0.01 – 10000 µF;
4 subranges – 10, 100, 1000, 10,000 µF;
sub-range selection – automatic;
result indication – digital, 4 digits with floating decimal point;
measurement error – least significant unit;

Let's look at the device diagram:

click to enlarge

On the DD1 chip, or more precisely on two of its elements, a quartz oscillator is assembled, the operation of which requires no explanation. Next, the clock frequency is sent to a divider assembled on DD2 – DD4 microcircuits. Signals from it with frequencies of 1,000, 100, 10 and 1 kHz are supplied to the DD6.1 multiplexer, which is used as an automatic subband selection unit.

The main measurement unit is a single-vibrator assembled on elements DD5.3, DD5.4, the pulse duration of which directly depends on the capacitor connected to it. The principle of measuring capacitance is to count the number of pulses during the operation of a monovibrator. A unit is assembled on elements DD5.1, DD5.2 that prevents bouncing of the contacts of the “Start measurement” button. Well, the last part of the circuit is a four-digit line of binary-decimal counters DD9 - DD12 with output to four seven-segment indicators.

Let's consider the algorithm of the meter's operation. When you press the SB1 button, the DD8 binary counter is reset and switches the range node (DD6.1 multiplexer) to the lowest measurement range - 0.010 - 10.00 µF. In this case, pulses with a frequency of 1 MHz are received at one of the inputs of the electronic key DD1.3. The second input of the same switch receives an enabling signal from the one-shot device, the duration of which is directly proportional to the capacitance of the capacitor being measured.

Thus, pulses with a frequency of 1 MHz begin to arrive at the counting decade DD9...DD12. If a decade overflow occurs, the carry signal from DD12 increases the readings of the counter DD8 by one and allows zero to be written to the trigger DD7 at input D. This zero turns on the driver DD5.1, DD5.2 and it, in turn, resets the counting decade and sets DD7 again to “1” and restarts the monostable. The process is repeated, but the counting decade now receives a frequency of 100 kHz through the switch (the second range is turned on).

If before the completion of the pulse from the one-shot device the counting decade overflows again, then the range changes again. If the one-shot switches off earlier, the counting stops and the indicator can read the value of the capacitance connected for measurement. The final touch is the decimal point control unit, which indicates the current measurement subrange. Its functions are performed by the second part of the DD6 multiplexer, which illuminates the desired point depending on the included subband.

IV6 vacuum luminescent indicators are used as indicators in the circuit, so the power supply of the meter must produce two voltages: 1 V for filament and +12 V for anode power supply of lamps and microcircuits. If the indicators are replaced with LCDs, then you can get by with one +9V source, but the use of LED matrices is impossible due to the low load capacity of the DD9...DD12 microcircuits.

It is better to use a multi-turn resistor as a calibration resistor R8, since the measurement error of the device will depend on the accuracy of the calibration. The remaining resistors can be MLT-0.125. Regarding microcircuits, you can use any of the K1561, K564, K561, K176 series in the device, but you should keep in mind that the 176 series is very reluctant to work with a quartz resonator (DD1).

Setting up the device is quite simple, but it should be done with special care.

Temporarily disconnect the SB1 button from DD8 (pin 13).
Apply rectangular pulses with a frequency of approximately 50-100 Hz to the connection point between R3 and R2 (any simple generator on a logic chip will do).
In place of the capacitor being measured, connect a standard one, the capacitance of which is known and lies in the range of 0.5 - 4 µF (for example, K71-5V 1 µF ± 1%). If possible, it is better to measure the capacitance using a measuring bridge, but you can also rely on the capacitance indicated on the case. Here you need to keep in mind that how accurately you calibrate the device, so it will measure you in the future.
Using trimming resistor R8, set the indicator readings as accurately as possible in accordance with the capacitance of the reference capacitor. After calibration, it is better to seal the trimming resistor with a drop of varnish or paint.

Based on materials from “Radio Amateur” No. 5, 2001.

Homemade measuring instruments

V. VASILIEV, Naberezhnye Chelny
Radio, 1998, No. 4

Anyone who repairs household or industrial radio equipment knows that serviceability of capacitors comfortable check without dismantling them. However, many capacitor capacitance meters do not provide this capability. True, one similar design was described in. It has a small measurement range and a non-linear countdown scale, which reduces accuracy. When designing a new meter, the problem of creating a device with a wide range, linear scale and direct reading was solved, so that it could be used as a laboratory one. In addition, the device must be diagnostic, i.e., capable of testing capacitors shunted by p-n junctions of semiconductor devices and resistor resistances.

Device diagram

The principle of operation of the device is as follows. A triangular voltage is applied to the input of the differentiator, in which the capacitor being tested is used as a differentiating one. In this case, its output produces a square wave with an amplitude proportional to the capacitance of this capacitor. Next, the detector selects the amplitude value of the meander and outputs a constant voltage to the measuring head.

The device has two switches. Limit switch "Scale" with five positions: 10 µF, 1 µF, 0.1 µF, 0.01 µF, 1000 pF. The "Multiplier" switch (X1000, x10O, x10, X1) changes the measurement frequency. Thus, the device has eight capacitance measurement subranges from 10,000 μF to 1000 pF, which is practically sufficient in most cases.

The triangular oscillation generator is assembled on op-amp chips DA1.1, DA1.2, DA1.4 (Fig. 1). One of them, DA1.1, operates in comparator mode and generates a rectangular signal, which is fed to the input of the integrator DA1.2. The integrator converts rectangular oscillations into triangular ones. The generator frequency is determined by elements R4, C1 - C4. In the feedback circuit of the generator there is an inverter based on op-amp DA1.4, which provides self-oscillating mode. Switch SA1 can be used to set one of the measurement frequencies (multiplier): 1 Hz (X1000), 10Hz (x10O), 10 Hz (x10), 1 kHz (X1).

Op-amp DA2.1 is a voltage follower, at its output is a triangular signal with an amplitude of about 50 mV, which is used to create a measuring current through the capacitor Cx being tested.

Op-amp DA2.2 works as a differentiator and acts as a current-voltage converter. Its output voltage:

Uout=(Rl2...R16)·IBX=(Rl2...Rl6)Cx-dU/dt.

For example, when measuring a capacitance of 100 μF at a frequency of 100 Hz, it turns out: Iin=Cx dU/dt=100-100MB/5MC = 2MA, Uout= R16 lBX= 1 kOhm mA= 2 V.

Elements R11, C5 - C9 are necessary for stable operation of the differentiator. Capacitors eliminate oscillatory processes at the meander fronts, which make it impossible to accurately measure its amplitude. As a result, the output of DA2.2 produces a meander with smooth edges and an amplitude proportional to the measured capacitance. Resistor R11 also limits the input current when the probes are shorted or when the capacitor is broken. For the input circuit of the meter the following inequality must be satisfied:

(3...5)CxR1<1/(2f).

If this inequality is not satisfied, then in half the period the current IBX does not reach the steady-state value, and the meander does not reach the corresponding amplitude, and an error in the measurement occurs. For example, in the meter described in, when measuring a 1000 µF capacitance at a frequency of 1 Hz, the time constant is determined as

Cx R25 = 1000 uF - 910 Ohm = 0.91 s.

Half of the oscillation period T/2 is only 0.5 s, so on this scale the measurements will be noticeably nonlinear.

The device uses variable resistors of the SPZ-22 type (R21, R22, R25, R26). Fixed resistors R12 - R16 - type C2-36 or C2-14 with a permissible deviation of ±1%. Resistance R16 is obtained by connecting several selected resistors in series. The resistances of resistors R12 - R16 can be used in other types, but they must be selected using a digital ohmmeter (multimeter). The remaining fixed resistors are any with a dissipation power of 0.125 W. Capacitor C10 - K53-1A, capacitors C11 - C16 - K50-16. Capacitors C1, C2 - K73-17 or other metal film, SZ, C4 - KM-5, KM-6 or other ceramic with TKE no worse than M750, they must also be selected with an error of no more than 1%. The remaining capacitors are any.

Switches SA1, SA2 - P2G-3 5P2N. In the design, it is permissible to use a CVD transistor (VT1) with the letter indices A, B, C, G, I. Transistors VT2, VT3 voltage stabilizers can be replaced by other low-power silicon transistors of the corresponding structure. Instead of the K1401UD4 op-amp, you can use the K1401UD2A, but then at the “1000 pF” limit, an error may occur due to the bias of the differentiator input created by the input current DA2.2 on R16.

Power transformer T1 has an overall power of 1 W. It is permissible to use a transformer with two 12 V secondary windings, but then two rectifier bridges are required.

The device begins to be configured by setting the voltages +9 V and -9 V using resistors R25, R26. After this, the operation of the triangular oscillation generator is checked (oscillograms 1, 2, 3, 4 in Fig. 3). If you have a frequency meter, measure the frequency of the generator at different positions of switch SA1. It is acceptable if the frequencies differ from the values 1 Hz, 10 Hz, 100 Hz, 1 kHz, but among themselves they must differ exactly 10 times, since the correctness of the instrument readings on different scales depends on this. If the generator frequencies are not a multiple of ten, then the required accuracy (with an error of 1%) is achieved by selecting capacitors connected in parallel with capacitors C1 - C4. If the capacitances of capacitors C1 - C4 are selected with the required accuracy, you can do without measuring frequencies.

Next, check the operation of op-amp DA1.3 (oscillograms 5, 6). After this, set the measurement limit to “10 µF”, the multiplier to the “x1” position and connect a standard capacitor with a capacity of 10 µF. The output of the differentiator should be rectangular, but with prolonged, smoothed fronts, oscillations with an amplitude of about 2 V (oscillogram 7). Resistor R21 sets the instrument readings - the needle deflects to full scale. A digital voltmeter (at a limit of 2 V) is connected to sockets XS3, XS4 and resistor R22 is used to set the reading to 1000 mV. If capacitors C1 - C4 and resistors R12 - R16 are precisely selected, then the instrument readings will be multiples on other scales, which can be checked using standard capacitors.

Measuring the capacitance of a capacitor soldered into a board with other elements is usually quite accurate within the range of 0.1 - 10,000 uF, except when the capacitor is shunted by a low-resistance resistive circuit. Since its equivalent resistance depends on the frequency Xc = 1/ωС, to reduce the shunting effect of other elements of the device it is necessary to increase the measurement frequency with a decrease in the capacitance of the measured capacitors. If, when measuring capacitors with a capacity of 10,000 μF, 1000 μF, 100 μF, 10 μF, frequencies of 1 Hz, 10 Hz, 100 Hz, 1 kHz are used, respectively, then the shunting effect of the resistors will affect the reading of the device with a parallel connected resistor with a resistance of 300 Ohms (an error of about 4%) or less. When measuring capacitors with a capacity of 0.1 and 1 μF at a frequency of 1 kHz, an error of 4% will be due to the influence of a parallel-connected resistor with a resistance of 30 and 3 kOhm, respectively.

At the limits of 0.01 μF and 1000 pF, it is advisable to check the capacitors with the shunt circuits turned off, since the measuring current is small (2 μA, 200 nA). It is worth recalling, however, that the reliability of small capacitors is noticeably higher due to their design and higher permissible voltage.

Sometimes, for example, when measuring some capacitors with an oxide dielectric (K50-6, etc.) with a capacity from 1 µF to 10 µF at a frequency of 1 kHz, an error appears, apparently associated with the capacitor’s own inductance and losses in its dielectric ; The instrument readings are lower. Therefore, it may be advisable to carry out measurements at a lower frequency (for example, in our case at a frequency of 100 Hz), although in this case the shunting properties of parallel resistors will be reflected already at a higher resistance.

LITERATURE
1. Kuchin S. Device for measuring capacitance. - Radio. 1993, ╧ 6, pp. 21 - 23.
2. Bolgov A. Tester of oxide capacitors. - Radio, 1989, ╧ 6, p. 44.

In this article we will give the most complete instructions that will allow you to make a capacitor capacitance meter with your own hands, without the help of qualified craftsmen.

Unfortunately, equipment often fails. There is most often one reason - the appearance of an electrolytic capacitor. All radio amateurs are familiar with the so-called “drying out”, which occurs due to a violation of the tightness of the device housing. Reactance increases due to a decrease in rated capacitance.

Further, during operation, electrochemical reactions begin to occur, they destroy the terminal joints. As a result, the contacts are broken, forming a contact resistance that sometimes amounts to tens of Ohms. The same thing will happen when a resistor is connected to the working capacitor. The presence of this same series resistance will negatively affect the operation of the electronic device; the entire operation of the capacitors in the circuit will be distorted.

Due to the strong influence of resistance in the range of three to five ohms, switching power supplies become unusable, because expensive transistors and microcircuits in them burn out. If the parts were checked during assembly of the device, and no errors were made during installation, then there will be no problems with its setup.

By the way, we suggest you look for a new soldering iron on Aliexpress - LINK(excellent reviews). Or look for some soldering equipment in the VseInstrumenty.ru store - link to the section with soldering irons .

Scheme, principle of operation, device

This circuit is used using an operational amplifier. The device that we are going to make with our own hands will allow us to measure the capacitance of capacitors in the range from a couple of picofarads to one microfarad.

Let's understand the given diagram:

Subbands. The unit has 6 “subranges”, their high limits are 10, 100; 1000 pF, as well as 0.01, 0.1 and 1 µF. The capacitance is measured using the measuring grid of the microammeter.
Purpose. The basis of the device's operation is the measurement of alternating current; it passes through the capacitor, which needs to be examined.
The DA 1 amplifier contains a pulse generator. The oscillations of their repetition are subject to the capacitance C 1-C 6 of the capacitors, as well as the position of the toggle switch of the “tuning” resistor R 5. The frequency will be variable from 100 Hz to 200 kHz. We determine for the trimming resistor R 1 a commensurate model of oscillations at the output of the generator.
The diodes indicated in the diagram, such as D 3 and D 6, resistors (adjusted) R 7-R 11, microammeter RA 1, make up the alternating current meter itself. Inside the microammeter, the resistance must be no more than 3 kOhm, so that the measurement error does not exceed ten percent on a range of up to 10 pF.
Trimmer resistors R 7 - R 11 are connected to other subranges in parallel with P A 1. The desired measuring subrange is adjusted using the toggle switch S A 1. One category of contacts switches capacitors (frequency setting) C 1 and C 6 in the generator, the second switches resistors in the indicator.
In order for the device to receive energy, it needs a 2-polar stabilized source (voltage from 8 to 15 V). The values of the frequency-setting capacitor may vary by 20%, but they themselves must have high temporal and temperature stability.

Of course, for an ordinary person who does not understand physics, this may all seem complicated, but you must understand that in order to make a capacitor capacitance meter with your own hands, you need to have certain knowledge and skills. Next, let's talk about how to set up the device.

Setting up the measuring device

To make the correct adjustment, follow the instructions:

First, symmetry of oscillations is achieved using resistor R 1. The “slider” of resistor R 5 is in the middle.
The next step is to connect the 10 pf reference capacitor to the terminals marked cx. Using resistor R 5, move the microammeter needle to the corresponding scale of the capacitance of the reference capacitor.
Next, the oscillation shape at the output of the generator is checked. Calibration is carried out on all subranges; resistors R 7 and R 11 are used here.

The mechanism of the device may be different. Size parameters depend on the type of microammeter. There are no special features when working with the device.

Creating different meter models

AVR series model

You can make such a meter based on a variable transistor. Here are the instructions:

We select a contactor;
We measure the output voltage;
negative resistance in the capacitance meter is no more than 45 ohms;
If the conductivity is 40 microns, then the overload will be 4 Amperes;
To improve measurement accuracy, you need to use comparators;
There is also an opinion that it is better to use only open filters, since they are not afraid of impulse noise in case of heavy load;
It is also recommended to use pole stabilizers, but only grid comparators are not suitable for modifying the device;

Before turning on the capacitance meter, you need to measure the resistance, which should be approximately 40 ohms for well-made devices. But the indicator may differ, depending on the frequency of modification.

The module based on PIC16F628A can be of an adjustable type;

It is better not to install high conductivity filters;

Before we start soldering, we need to check the output voltage;

If the resistance is too high, then change the transistor;

We use comparators to overcome impulse noise;

Additionally we use conductor stabilizers;

The display can be text, which is the easiest and most convenient. They need to be installed through channel ports;

Next, using the tester, we set up the modification;

If the capacitance values of the capacitors are too high, then we change transistors with low conductivity.

You can learn more about how to make a capacitor capacitance meter with your own hands from the video below.