I will continue the description of the LIMP program from the company’s package Arta Software. With its help, you can determine the values of resistances, inductances, and capacitances. All you need is a computer, free program and hardware consisting of one resistor and several cords.
Of course, this meter cannot replace specialized instruments either in terms of convenience or measurement accuracy, but buying an expensive device for the sake of several measurements is not always advisable. The proposed tool is purely amateur radio - measurements are slow and require some brain and hand work, but it’s free and you can do it yourself.
Hardware
From the parts you need 2 3.5 mm connectors for sound card with shielded wires, a resistor of approximately 100 Ohms, a switch with one group of contacts (or an analogous button) of any kind, two alligator clips or clamps.
I was interested in digging around myself. ARTA writes that for accuracy it is desirable that Z be less than 100 ohms, much less than the input impedance of the sound card (supposedly it is about 20 kOhms). I think that a very low Z when measuring very large capacitances also worsens the accuracy, but in practice it is of little interest - a capacitance of 20,000 µF or 22,000 µF, it is more important to know that this capacitance is there, has not dried out, and if there is a need to select identical capacitances, then absolute value not that important either. I remind you once again - look at the result when the phase for capacitors is about -90, and for inductances +90. By the way, for capacitors with poor thermal dependence, you can see how Z changes due to the heat of the fingers.
You can check ancient containers from stocks (ESR is not visible, which is a pity), the drop in capacity due to drying out or breakage is immediately visible.
There are no words, special devices are 1000 times better, but they cost money and take up space.
Resistance measurements
At first I even wanted to omit this point - everyone has cheap digital Chinese testers, but after thinking about it, I found cases when this method may be useful.This is a measurement of low resistances - up to 0.1 Ohm inclusive. First you need to calibrate the device and short-circuit its probes. With a long cord I got 0.24 ohms. We will subtract this value from all measurements of low-resistance resistors. I have a handful of S5-16MV-5 resistors at 3.9 Ohms with an accuracy of 1%.
All resistors tested gave this result. 4.14 – 0.24 = 3.9
To check, a handful of other low-resistance resistors were measured, without any comments. The lowest resistance was 0.51 Ohm + - 5%. Measured value 0.5 ohm. Unfortunately, I could not find 0.1 Ohm in my supplies, but I am sure that there would be no problems with them either, you only need clamps with good contacts.
In addition to measuring the resistance of low-impedance resistors, their inductance is of interest, especially for speaker filters. They are wire, wound in a coil. How significant is their inductance? I checked mainly low-resistance (up to 20 Ohms) resistors (high-resistance ones are not installed in acoustics and amplifiers) of types S5-16MV, S5-37V, S5-47V, PEVR-25, S5-35V. Their inductance was in the range of 2...6 microHenry. When measuring resistors of hundreds of ohms, their inductance was an order of magnitude higher.
Inductance measurements
Let's move on to inductances. I don’t have precise inductances at the moment, so I just checked the qualitative, but not the quantitative, performance of the method.
These are measurements of the DM-0.1 inductor at 30 μH, it turned out plausible.
Here is the choke from the switching power supply. It also seems true. I can't vouch for the accuracy - there is room for research here.
Capacitance measurements
The most interesting part is that there is something unclear, but the results are very interesting. Measuring range from 0.1 µF to 100,000 µF. Accuracy - several percent. More or less tolerable results are obtained from 0.01 µF, but measurements at low frequencies with a long cord with a large capacitance are impractical. I proceeded from the fact that capacitances of the order of fractions of a few microfarads for filters of acoustic systems and tone controls, and ULF coupling capacitors are of interest. There was hope to see ESR (it didn’t come true). Since I did not find precision containers at my place, I had to use the statistical method and common sense. At first I made and wanted to present a large table, but then the obvious truth came to me, for you only the results.
This is a 0.15 MKP X2 capacitor. At what frequency should I measure? Arta's coverage of this is vague. They say that it is necessary to measure at an impedance of less than 100 Ohms (one cell on the graph on the left is 800 Ohms) ...
At 200 Hz it turns out 0.18 µF, at 20 kHz - 0.1 µF. From the basics of electrical engineering it is known that the current in a capacitance leads the voltage (-90 degrees), in inductance - vice versa (+90 degrees), so we are guided by the gray curve and the phase shift number on the right. It is better if the shift is close to 90 degrees. Unfortunately, due to the limited frequency range, this does not always work out; in addition, often around 20 kHz the phase shift decreases, let’s not go into this area!
Here's an example. This is a 2.2 uF 15 V non-polar oxide capacitor. There is a strong suspicion of its poor quality and unsuitability for audiophiles. Non-electrolytic capacitors at higher voltages have a different phase diagram. Here the most reliable results are in the region of 0.5...1 kHz.
Capacitor 1 µF K10-47V for 50 V TKE N30. Reliable and stable results in the frequency range 1...20 kHz with a phase shift of 85...90 degrees.
Curiosity drew me to see: what would happen if we measured oxide (electrolytic) capacitors? It turned out that it is possible to measure! The result is absolutely independent of the connection polarity; I even measured 4 banks of 10,000 uF connected in parallel and got a reliable result. I can judge the reliability because I have previously measured dozens of capacitors from 1 to 15,000 µF.
The result was 44 milliFarads. Pay attention to the phase characteristic in the region of several kHz; it takes on the character of inductance. Is this an imperfection of the instrument or is it really true that at such frequencies the capacitance of the plates works worse, and the inductance of the winding roll speaks louder and louder? Parallel connection the small film capacity did not affect the graph.
Due to the fact that loading graphics into the post is limited, I give a minimum of examples, so I’ll just repeat that you need to measure at the most “correct” phase (when you go through 0, you will get “inductance” from the capacitance and vice versa).
Sometimes it happens. This is one of the old soldered oxide containers. Clearly it belongs in a landfill. Can you imagine what such a container will do to the sound?!
You can fall into such a trap.
We tried to make it so
So that you enjoy
How to assemble and configure this device,
So does its operation.
Oleg, Pavel
1. Specifications
|
Measured parameter |
Test signal frequency |
||
|
100Hz |
1kHz |
10kHz |
|
| R |
0.01 Ohm – 100 MOhm |
0.01 Ohm – 100 MOhm |
0.01 Ohm – 10 MOhm |
| C |
1pF – 22000uF |
0.1pF – 2200uF |
0.01pF – 220uF |
| L |
0.01 µH – 20 kH |
0.1 µH – 2 kH |
0.01 µH – 200H |
Operating modes:
- test signal frequency 100Hz, 1kHz, 10kHz;
- test signal amplitude 0.3V;
- series/parallel (s/p) equivalent circuit;
- automatic/manual selection of measurement range;
- reading hold mode;
- compensation of short-circuit and short-circuit parameters;
- display of measurement results in the form:
R+LC
R+X
Q + LC (quality factor)
D + LC (tg loss angle)
- supplying a DC bias voltage to the element under test 0-30V (from the internal source);
- Offset voltage measurement (0.4V-44V);
- innings direct current offsets to the element under test (from an external source):
- debug mode.
Maximum measuring time for:
- 100Hz – 1.6s;
- 1kHz, 10kHz – 0.64s.
2. Operating principle
The operation of the device is based on the method of voltmeter and ammeter, i.e. the voltage drop across the element under test and the current through it are measured, and Zx is calculated as Zx=U/I. Of course, the values of current and voltage must be obtained in complex form. To measure the real (Re) and imaginary (Im) components of voltage and current, a synchronous detector (SD) is used, the operation of which is in turn synchronized with the test signal. By applying a meander to the control of the LED keys with a shift of 0º or 90º relative to the test signal, we obtain the required Re and Im parts of the voltage and current. Thus, for one Zx measurement, four measurements must be made, two for current and two for voltage. The double integration ADC converts the signal from the LED into digital form. The choice of this type of ADC is due to its low sensitivity to noise, and the fact that the ADC integrator plays the role of an additional signal filter after the SD. The test signal is obtained from the meander after LPF1 (low-pass filter on switched capacitors) and LPF2 (regular double RC filter), which removes the remaining frequency F*100.
The device for measuring current uses an active (op-amp) current-voltage converter. Guided by the “little-normal-many” principle, the MK controls the selection of R range and K amplifier according to the table below, achieving maximum ADC readings:
| Range | R range | Ku for current |
KU for voltage |
| 100 Ohm | 1 | 100 | |
| 1 | 100 Ohm | 1 | 10 |
| 2 | 100 Ohm | 1 | 1 |
| 3 | 1 to | 1 | 1 |
| 4 | 10k | 1 | 1 |
| 5 | 100k | 1 | 1 |
| 6 | 100k | 10 | 1 |
| 7 | 100k | 100 | 1 |
3. Scheme
The diagram is divided into three parts:
- analog part;
- digital part;
- power unit.
| [Scheme and drawings of boards] | 187 kB | |
| [Payments from Igor] | 2372 kB | |
| [Scheme] | 172 kB | |
| 41 kB | ||
| 50 kB | ||
| 50 kB | ||
| 69 kB | ||
| 69 kB |
Nothing is born out of nowhere, so in our case. Some components and ideas were “borrowed” from industrial device circuits available in free access– LCR-4080 (E7-22), RLC-9000, RLC-817, E7-20.
The device works as follows.
The PIC16F876A microcontroller (MC) generates a SinClk (RC2, pin 13) square wave with a frequency of 10 kHz, 100 kHz or 1 MHz. The signal is supplied to the input of a divider made on microcircuits DD12 and DD13. At pin 10 of DD12 we get the frequency SinClk/25, which in turn is further divided by 4. At the outputs of the shift register, signals are obtained that are shifted relative to each other by 90º, necessary for the operation of the LED. The 0_Clk signal is supplied to the DA6 chip, which is an 8th order elliptic filter. This filter selects the first harmonic. The filter cutoff frequency is determined by the frequency of the signal supplied to the digital input (pin 1 of DA6). The resulting sinusoidal signal (first harmonic) is additionally filtered by a double RC circuit R39, C27, R31, C20. On the lower ranges of 1 kHz and 100 Hz, additionally C28, C21 and C26, C25 are connected, respectively. After the output buffer on DA3, a sinusoidal signal through limiting resistors R16, R5 and coupling capacitor C5 is supplied to Zx. The amplitude of the test signal at idle is approximately 0.3V.
The voltage drop across Zx (voltage channel) is removed through capacitors C6 and C7 and fed to the input of the instrumental op-amp (IOU), made on DA4.2, DA4.3 and DA4.4. The gain of this IOU is determined by the ratio R28/R22=R27/R23=10k/2k=5. Through an analog switch DA7.3, the signal is fed to an amplifier with variable Ku. The required gain (1, 10 or 100) is set by control signals Mul10 and Mul100. Then the signal is sent to the DA9 LED. A square wave with the frequency of the test signal with a shift of 0º and 90º is supplied to control the LED keys. Thus, the real and imaginary components of the signal are separated. The signal after the LED switches is integrated by chains R41-C30 and R42-C31 and fed to the differential input of the ADC.
The current through Zx is converted to voltage on DA1 with a set of 4 resistors (100, 1k, 10k and 100k) in the feedback switched by DA2. The differential conversion signal is removed through C18 and C17 and fed to the input of the IOU made on DA5. From its output the signal goes to the analog switch DA7.3.
The reference voltage of 0.5V ADC is obtained using the parametric stabilizer R59–LM385-1.2V and the subsequent divider R56, R55. The ADC clock signal AdcClk (frequency 250 kHz for measurements at 1 kHz and 10 kHz, frequency 100 kHz for 100 Hz) is generated by the USART module in synchronous mode from the RC5 output. At the same time, it is supplied to the RC0 pin, which is set by the program as the TMR1 input in counter mode. The digital conversion code of the ADC is equal to the number of AdcClk pulses minus 10001 during the time the ADC Busy signal is at “1”. This feature is used to input the results of ADC conversion into the MC. The Busy signal is applied to pin RC1, which is configured as an input to the Compare and Capture Module (CPP). With its help, the value of TMR1 is remembered at the positive edge of the Busy signal, and then at the negative edge. Subtracting these two values, we obtain the desired result of the ADC.
4.Details
We tried to select parts based on the criteria of their availability, maximum simplicity and repeatability of the design. In our opinion, the only microcircuit that is in short supply is the MAX293. But its use has made it possible to significantly simplify the node that generates the reference sinusoidal signal (compared to a similar node, say, in the RLC4080). We also tried to reduce the variety of types of microcircuits used, resistor and capacitor values.
Requirements for details.
Separating capacitors C6, C7, C17, C18, C29, C36, C34, C35, C30, C31 must be film type MKP10, MKP2, K73-9, K73-17 or the like, the first four for a voltage of at least 250V, for C29, C36, C34, C35, C30, C31 63V is enough.
The most critical element in terms of its parameters is the integrating capacitor C33. It must have low dielectric absorption rates. Based on the description on the ICL7135, it is necessary to use a capacitor with either a polypropylene or Teflon dielectric. The widely used K73-17 as an integrating capacitor gives an error of 8-10 ADC units in the middle of the scale, which is completely unacceptable. The necessary polypropylene dielectric capacitors were found in old monitors. If you choose a monitor for disassembly, take one with a thick video cable, there are good flexible insulated shielded wires that will be used to make probes for the device.
Transistors VT1-VT5 can be replaced with almost any other NPN in the same package. Sound emitter SP - electrodynamic, from the old one motherboard. If its resistance is 50-60 Ohms, then additional R65 can be set to 0. Parts that are recommended to be selected in pairs:
R41=R42, C30=C31 – for SD;
R28=R27, R22=R23 – for voltage IOU;
R36=R37, R32=R33 – for current IOU.
R6, R7, R8, R9 – the thermal and long-term stability of the device readings depends on the stability of these resistors;
C20, C21, C25, C26, C27, C28 - especially pay attention to capacitors rated 0.1 µF;
R48, R49, R57, R58 – depends on their ratio amplification kit scaling amplifier. LCD standard 2x16 characters, made on HD44780 or a controller compatible with it. It should be noted that there are indicators with different pinouts of pins 1 and 2 - ground and power. Incorrect switching on will lead to failure of the LCD! Check the documentation for your display carefully and visually the board itself!
5. Design
The device is assembled on three boards:
a. Main board of analog and digital parts;
b. Display board;
c. Power unit.
The main board is double-sided. The upper side is solid and serves as a common ground. Through vias (marked as through in RLC2.lay) the ground from the top layer is connected to the bottom. On the holes for the output parts on the top side (ground), you need to chamfer with a 2.5mm drill. First we solder (or rivet with copper wire and solder) the ground jumpers, then the output jumpers. Next we solder SMD components: resistors, capacitors, diodes, transistors. Behind it are the output parts: pads, capacitors, connectors.
The display board is also double-sided. The top layer of earth plays the role of a screen from the LCD. Via holes also serve to connect the upper and lower layers of the earth.
It is advisable to connect the LCD board to the main board with a shielded cable. It is made of 4 wires, on top of which a regular braid and an insulating tube are placed. The braid is grounded only from the side of the main board. The cable is passed through a ferrite ring from some computer equipment. That. Interference from LCD operation is reduced to a minimum.
The power supply board is one-sided. There are two options for wiring parts different sizes. On
The boards do not have capacitors installed at the input (220V) of the transformer and parallel to the bridge diodes; it is better to complete the wiring and install it if necessary. A special feature of the board is the method of distributing the ground “to one point”. If you redeploy for some reason, save this configuration. It is important to choose a transformer with low losses (low current). Before choosing or manufacturing a transformer, we recommend that you read the article
V.T. Polyakov “Reducing the stray field of a transformer”, published in Railway Radio, No. 7 for 1983. Practice has shown that Chinese consumer goods do not work normally without rewinding. Most likely, you will have to wind the transformer yourself based on the formula “Revolutions/volts = 55-60/S”. This is not a typo specifically 55-60/S, in this case the losses and interference from the transformer will be less. It is advisable to choose a transformer design in which the network and secondary
the windings are located in separate sections. This will reduce the capacitance between the windings.
5.1 Housing
One body was made of 1mm thick steel, the other of plastic. If made fromplastic, the main unit board must be shielded. Approximate housing drawings are given infiles “Box1.pdf” and “Box2 .pdf”.
| [Scheme and drawings of boards] | 187 kB | |
| [Payments from Igor] | 2372 kB | |
| [Scheme] | 172 kB | |
| [Firmware and sources version 1.0] | 41 kB | |
| [Firmware and sources version 1.1] | 50 kB | |
| [Firmware and sources version 1.1a] | 50 kB | |
| [Firmware and sources version 1.2] | 69 kB | |
| [Firmware and sources version 1.3] | 69 kB |
LCD buttons are “extended” with a thick wire (6mm2). Insert the wire into the caps and fillepoxy. We fix the caps on buttons with regular cambrics or heat shrinksuitable diameter.
Housing assembly:
5.2 Clamps and adapters
Kelvin clamp
To make the clips you will need 4 regular alligator clips (do not choose the mostsmall, take a slightly larger size), the halves on which the cord is attached are used.We measure the length and width of the tooth area to obtain the dimensions of the insulating scarf. Approximatelyit turns out 12x4mm (hereinafter the dimensions are given for guidance only). The scarf shouldprotrude about 0.8mm in width on both sides and about 2mm in length. ExemplaryThe size of the scarf turned out to be 5.5x15mm. It is necessary to use double-sided fiberglass with a thickness0.9-1.1mm. It is not worth installing a thicker one, because... you will have to cut down more of the “crocodiles” sponges and
the strength of the structure will decrease. First you need to cut a strip of textolite 70-long80mm and 5.5mm wide. It needs to be cleaned and tinned on both sides. Then this stripcut into 4 pieces. It’s a good idea to clamp all the pieces together in a vice and adjust them to size. Furtherwe take petals from a telephone relay (or another type, just the thickness should be ~0.15-0.2mm,width ~3.5mm and length 22mm). We make the front profile of the petals (for clamping the SMD part).It is better to make the rear (triangular) profile after soldering the plate to the scarf.We process it with sandpaper and tin the bottom and side surfaces petals.
Then we place the prepared petals on scarves and secure them with crocodiles.First we solder one end surface, turn the crocodiles and solder the secondside. Then you can cut off the back of the petals at an angle.
We disassemble the crocodiles using pliers - carefully squeeze the edges in a circleriveted pin. Remove the spring and assemble two new crocodiles from longhalves, temporarily putting the pin back in place. Now you need to file off the teeth of both partsfuture clamp so that two handkerchiefs with petals soldered on them fit exactly intothe space between the jaws and fit tightly against one another.
We prepare a shielded cord 0.75-1m long. As already mentioned, you canuse thick cable from old VGA CRT monitors, inside there are three shieldedcord, 3mm diameter. We free the central core from the braiding ~20mm. We shorten the screenup to 10mm. We tin the braid by 5mm, the central core by 2mm and solder it onto the petal withbottom side. We clean the front edge of the crocodiles with sandpaper and service it.At the same time, we clean the inner surface of the crocodile (where you need to solder the cord screen) andwe serve. Having prepared this both halves of the “Calvin crocodile”, we assemble it. This is wrongsimply, to make it easier, you can pre-compress the spring with a vice and wrap it with a pair0.5 turns of copper wire, which should be removed after assembly. Be careful and work insafety glasses, the spring is a treacherous thing! When the halves are in place, insert the pin.We adjust the scarves so that they stand in the middle of the crocodiles and protrude ~2mm forward. Solder
both halves of the crocodile to the top surface of the handkerchief. We press the cord and rivet it
pin.
"Kelvin's Crocodile":
And fully assembled:
Tweezers for SMD
The tweezers are made of double-sided foil fiberglass 1.5mm. Layout of the drawingis in RLC2.lay. The second side is a solid screen. Drill two vias with a drill0.5-0.8mm. Insert into holes copper wire the same diameter, cut it on both sidesat a height of 0.5-0.8mm from the surface of the board, rivet and solder. For tweezersThey used the same relay blades as in the Kelvin crocodile. We assemble the tweezers by insertingbetween the halves there is a plastic (PVC) gasket 6mm thick. After checkingWe ennoble it with heat shrinkage.
Scarves before assembly:
Assembled tweezers:
Adapter for lead parts:
To make the adapter, we used a connector from which we sawed off a piece (~16mm)6 pairs of pins. The scarf (“Adapter” from RLC2.lay) is made of double-sided fiberglass1.5mm thick. We insert a 0.7-0.8mm wire into the via holes and rivet them from bothsides The screen is made of tinned sheet metal with a thickness of 0.15-0.2mm. An old one was used for the body.RS232 computer connector.
Materials Assembled
6. Button functions
Before describing the process of setting up the device, we will tell you about the purpose of the buttons. Every buttonThe device has several functions depending on the operating mode and pressing time.There are long and short presses. Short is when the button press time is less than1 sec., accompanied by a single sound signal. If the button is pressed and held for more than1 sec. – this state is processed by the program as a “long press” and is accompanied bywith a second beep. Long presses are designed to switch modes operation of the device.
Measurement mode – the main mode of operation of the device, turns on automatically after power supply.
S1 – changes the frequency of the test signal (100Hz, 1kHz, 10kHz) in a circle
S2 – series (s) / parallel (p) equivalent circuit
S3 – LC/X results display mode (second line of display)
S4 – R/Q/D display (first line)
S5 – measurement range Auto – appears on the display next to the range numbersymbol “A”, after pressing the ranges are moved in a circle from the current one to 7,then 0..7. Reverse autoranging - long pressing S5
S6 – Hold readings (Hold), the symbol “H” is displayed on the screen
Debugging mode (Service mode), activated by long pressing S6
S1 – changes the frequency of the test signal signal (100Hz, 1kHz, 10kHz) in a circle
S2 – switches R range resistor in the I/U converter (100; 1k; 10k; 100k)
S3 – switches the gain set (1x1; 10x1; 1x10 1x100)
S4 – measurement of real (Re), imaginary (Im), both voltage components at once (RI) or current
S5 – current or voltage measurement mode
S6 – long press – exit debugging mode
XX/SC calibration mode, activated by long pressing S1
S1 – switches calibration type (Open-Short-Open, etc.)
S2 – starts calibration of the selected type (Open or Short).
Short press of any other button – exit to the main mode without calibration.
Changing correction factors is activated by long pressing S3. Numbercoefficient corresponds to the range number, i.e., for example, zero set usedto adjust the readings at the zero range. Kit No. 8 corrects the readingsoffset voltage voltmeter.
S1 - digit to the left
S2 - down (decrease digit value)
S3 - up (increasing digit value)
S4 - digit to the right
S5 - next coefficient
S6 - exit coefficient editing mode
- “Long” button presses
S1 – turns on the calibration mode
S2 – not used
(i.e. potentially non-working), or the installation itself was done carelessly, with errors. This leadsusually to additional damage and increased startup and setup timedevices. Therefore, we recommend running RLC separately in blocks. And if possible,Before installing it on the board, check ALL the parts you can check. This will save you frommisunderstandings such as reading inscriptions on inverted SMD resistors, installing driedelectrolytes for nutrition, etc.
First we check the transformer and make sure that the voltage on the secondary windings is ~8-9B. Drive it at idle, check the heating (hardware of transformers from Chinese power suppliesIn an hour it warms up to 60-70 degrees). Connect the transformer and check the power supplyseparately from the rest of the circuit, the output should be ±5V and +29.5-30.5V.We check the LCD board on the short circuit. We only connect power to the display board. On firstBlack rectangles should appear in the line. This indicates that it is normalThe internal initialization of the LCD has passed and the voltage regulating contrast.
You can program the MK with almost any programmer that supportsPIC16F876A. The MK can be programmed both separately - in the programmer, and on the board viaISCP connector. In this case, jumper Jmp1 must be open.We connect power to the main board without any microcircuits installed.We check the presence of voltages +5V and -5V at the corresponding MS terminals. We are convincedthat there is no voltage at the inputs of the op-amp, where the protective diodes are installed. Checking the “support” of the ADC -+0.5V.
We install the MK, connect the display board and turn on the power -> the display shouldThe greeting “RLC meter v1.0” will appear. Until the ADC is installed, the device will not displayother information, and will not respond to button presses. This indicates that it is correctstitched MK. We check the presence of a 250 kHz meander “AdcClk” and a 100 kHz meander “SinClk” (insine mode=1kHz).We install the MS one by one (remembering to turn off the power during installation!) andcheck according to the table: 3
| Range | R |
| 0 | 1 ohm |
| 1 | 10 ohm |
| 2 | 200 Ohm |
| 3 | 2k |
| 4 | 20k |
| 5 | 200k |
| 6 | 2M |
| 7 | 10M |
And in conclusion, we present the results of measurements of a 0.2 pF capacitor and a 1 μH inductor at
frequency 10 kHz, readings are stable:The device allows measure resistance from 1 Ohm to 10 MOhm, capacity from 100 pF to 1000 µF, inductance from 10 mG to 1000 G in seven ranges selected by switch SA1 in accordance with the table shown on the front panel.
The operating principle of a simple RCL meter, proposed by Alexander Mankovsky, is based on the balance of an AC bridge. Balance the bridge with variable resistor R11, focusing on the minimum readings of microammeter P2 or an external AC voltmeter connected to terminals P1. The measured resistor, capacitor or inductor is connected to terminals X1, X2, having previously set switch SA3 to position R, C or L. Wire resistor PPB-ZA is used as R11.
Its scale is calibrated (see sketch of the front panel of the device in Fig. 2) as follows. SA3 is moved to position “R”, SA1 - “3”, and standard resistors with a resistance of 100, 200, 300, ... 1000 Ohms are alternately connected to terminals X1, X2 and the corresponding mark is placed at each bridge balance. The capacitance of capacitor C1 is selected according to the balance of the bridge (minimum deviation of the arrow P2), setting SA3 to position “C”, SA1 to “5”, R11 to mark “1”, and connecting a standard capacitor with a capacity of 0.01 μF to terminals X1, X2 . Network transformer T1 must have a secondary winding of 18 V at a current of up to 1 A.
The device allows you to measure resistance from 1 Ohm to 10 MOhm, capacitance from 100 pF to 1000 μF, inductance from 10 mH to 1000 H in seven ranges selected by switch SA1 in accordance with the table shown on the front panel Fig. 2
Radio amateur No. 9/2010, p. 18, 19.
A huge selection of diagrams, manuals, instructions and other documentation on different kinds factory-made measuring equipment: multimeters, oscilloscopes, spectrum analyzers, attenuators, generators, R-L-C meters, frequency response, nonlinear distortion, resistance, 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. One more common cause The failure of electrolytic capacitors is due to the “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, according to 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 check semiconductor devices, transistors, 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 engine speed from 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 scheme AVR microcontroller Attiny2313, and the second 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 wide range determine with acceptable accuracy the capacitance and inductance of the coils. 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 - it is enough low frequency the measured signal is 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, firmware and drawing printed circuit board included with amateur radio development.
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 electrical circuit is a method of measuring the voltage drop across a resistor connected in series with a 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 high temperature environment 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 capable of determining not only the integrity of the winding under test, but also perfectly detects interturn short circuits, and in addition it can be used to check p-n junctions in 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 simple diagram An ohmmeter from Radio magazine and an even simpler one on the Arduino board.
This measuring laboratory device, with sufficient accuracy for amateur radio practice, allows you to measure: the resistance of resistors - from 10 Ohms to 10 MOhms, the capacitance of capacitors - from 10 pF to 10 μF, the inductance of coils and chokes - from 10 .. 20 μH to 8 ... 10 mH. The measurement method is pavement. Indication of balancing of the measuring bridge is audible using headphones. The accuracy of measurements largely depends on the careful selection of reference parts and the calibration of the scale.
The schematic diagram of the device is shown in Fig. 53. The meter consists of a simple rheochord measuring bridge, a generator of electrical oscillations of audio frequency and a current amplifier. The device is powered by a constant ♦voltage of 9 V, taken from the unregulated output of the laboratory power supply. The device can also be powered from an autonomous source, for example a Krona battery, battery 7D-0.115 or two 3336J1 batteries connected in series. The device remains operational when the supply voltage is reduced to 3...4.5 V, however, the signal volume in phones, especially when measuring small capacitances, drops noticeably in this case.
The generator that powers the measuring bridge is a symmetrical multivibrator with transistors VT1 and VT2. Capacitors C1 and C2 create a positive voltage between the collector and base circuits of the transistors -feedback by alternating current, due to which the multivibrator is self-excited and generates electrical oscillations close in shape to rectangular. The resistors and capacitors of the multivibrator are selected in such a way that it generates oscillations with a frequency of about 1000 Hz. A voltage of this frequency is reproduced by phones (or a dynamic head) approximately like the sound “si” of the second octave.
Rice. 53. Schematic diagram of the RCL meter
The electrical oscillations of the multivibrator are amplified by an amplifier on transistor VT3 and with its load resistor R5 enters the power supply diagonal of the measuring bridge. Variable resistor R5 performs the functions of a slide chord. The comparison arm is formed by standard resistors R6-R8, capacitors SZ-C5 and inductors L1 and L2, alternately switched across the bridge by switch SA1. The measured resistor R x or inductor L x is connected to terminals ХТ1, ХТ2, and the capacitor C x is connected to terminals ХТ2, ХТЗ. Headphones BF1 are included in the measuring diagonal of the bridge through sockets XS1 and XS2. For any type of measurement, the bridge is balanced with an R5 flux rod, achieving complete loss or the lowest volume of sound in the phones. Resistance R XJ capacitance C x or inductance L x is measured on the rheochord scale in relative units.
The multipliers near the type and measurement limits switch SA1 show how many ohms, microhenry. or lycofarad, the reading on the scale must be multiplied to determine the measured resistance of a resistor, capacitance of a capacitor, or inductance of a coil. So, for example, if, when balancing the bridge, the reading read from the slider scale is 0.5, and switch SA1 is in the “XY 4 pF” position, then the capacitance of the measured capacitor C x is equal to 5000 pF (0.005 μF).
Resistor R6 limits the collector τόκ of transistor VT3, which increases when measuring inductance, and thereby prevents possible thermal breakdown of the transistor.
Construction and details. Appearance and the design of the device are shown in Fig. 54. Most of parts are placed on a mounting plate made of getinax, fixed in the housing on U-shaped brackets 35 mm high. The battery can be installed under the circuit board autonomous power supply device. Switch SA1, power switch Q1 and a block with sockets XS1, XS2 for connecting headphones are mounted directly on the front wall of the case.
The marking of the holes in the front wall of the case is shown in Fig. 55. A rectangular hole measuring 30X15 mm in the lower part of the wall is intended for the XT1-KhTZ clamps protruding forward. The same hole on the right side of the wall is the “window” of the scale, the round hole under it is intended for the roller variable resistor R5. A hole with a diameter of 12.5 mm is intended for a power switch, the functions of which are performed by the TV2-1 toggle switch, a hole with a diameter of 10.5 mm is for a roller switch SA1 with 11 positions (only eight are used) and one direction. Five holes with a diameter of 3.2 mm with a countersink are used for screws securing the socket block, a shelf with clamps XT1-KhTZ and a bracket for resistor R5, four holes with a diameter of 2.2 mm (also with a countersink) are for rivets securing the corners to which the cover is screwed.
Inscriptions explaining the purpose of the control knobs, clamps and sockets are made on thick paper, which is then covered with a plate of transparent organic glass 2 mm thick. To secure this pad to the body, the nuts of the power switch Q1, switch SA1 and
Rice. 54. Appearance and design of the RCL meter
three M2X4 screws screwed into the threaded holes in the cover plate with inside housings.
The design of the terminals for connecting resistors, capacitors and inductors to the device, the parameters of which need to be measured, is shown in Fig. 56. Each clamp consists of parts 2 and 3, fixed to the getinach board 1 with rivets 4. The connecting wires are soldered to the mounting tabs 5. The clamp parts are made of solid brass or bronze with a thickness of 0.4... 0.5 mm. When working with the device, press on the upper part of part 2 until the hole in it aligns with the holes in the lower part of the same part and part 3 and insert the lead of the part being measured into them. Necessary
Rice. 55. Marking the front wall of the case
Rice. 56. Design of a block with clamps for connecting the terminals of radio components:
1-board; 2, 3 - spring contacts; 4 - rivets; 5 - mounting tab; 6 - - corner
Rice. 57. Scale mechanism design:
It is advisable to check the lei using a factory-made measuring device.
Model coil L1, the inductance of which should be equal to 100 μH, contains 96 turns of PEV-1 0.2 wire, wound turn to turn on a cylindrical frame with an outer diameter of 17.5 mm, or 80 turns of the same wire wound on a frame with a diameter of 20 mm . As a frame, you can use cardboard cartridge cases for 20- or 12-gauge hunting rifles. The coil frame is mounted on a circle cut from getinax and glued to the circuit board with BF-2 glue.
The inductance of the reference coil L2 is ten times greater (1 mH). It contains 210 turns of PEV-1 0.12 wire, wound on a standardized three-section polystyrene frame, and placed in a carbonyl armored magnetic core SB-12a. Its inductance is adjusted with a trimmer included in the magnetic circuit kit. The latter is glued to the circuit board with BF-2 glue.
It is advisable to adjust the inductance of both coils before installing them in the meter. This is best done using a factory-made device. It should be noted that if the first coil is made exactly according to the description, it will have an inductance close to the required one, and using it in the assembled meter it will be possible to adjust the inductance of the second coil.
Setting up the device, calibrating the scale. If the meter uses pre-tested and selected transistors, resistors and capacitors, the multivibrator and amplifier should work normally without any adjustments. It is easy to verify this by connecting the terminals XT1 and XT2 or XT2 and XTZ with a wire jumper. A sound should appear in the phones, the volume of which changes when the slider slider is moved from one extreme position to another. If there is no sound, it means that there was an error in installing the multivibrator or the power source was connected incorrectly.
The desired pitch (tone) of sound in telephones can be selected by changing the capacitance of the capacitor C1 or C2. As their capacity decreases, the pitch of the sound increases, and as their capacity increases, it decreases.
Rice. 59. RCL meter scale
Since the instrument scale is common for all types and limits of measurements, it can be calibrated at one of the limits using a resistance magazine. Let us assume that the instrument scale is calibrated on a sub-range corresponding to the standard resistor R8 (10 kOhm). In this case, switch SA1 is set to the “ХУ 4 Ohm” position, and a resistor with a resistance of 10 kOhm is connected to the terminals ХТ1 and ХТ2. After this, the bridge is balanced, ensuring that the sound in the phones disappears, and on the rheochord scale opposite the arrow, an initial mark is made with a mark of 1. It will correspond to a resistance of 10 4 Ohms, i.e. 10 kOhms. Next, resistors with a resistance of 9, 8, 7 kOhm, etc. are alternately connected to the device and marks are made on the scale corresponding to fractions of a unit. In the future, mark 0.9 on the rheochord scale when measuring resistance in this subrange will correspond to a resistance of 9 kOhm (0.9-10 4 Ohm = 9000 Ohm = 9 kOhm), mark 0.8 - to a resistance of 8 kOhm (0.8 10 4 0m = 8000 Ohm = 8 kOhm), etc. Next, resistors with a resistance of 15, 20, 25 kOhm, etc. are connected to the device and the corresponding marks are made on the slider scale (1.5; 2; 2.5, etc.) d). The result is a scale, a sample of which is shown in Fig. 59.
You can also calibrate the scale using a set of resistors with a permissible deviation from the nominal values of no more than ±5%. By connecting resistors in parallel or in series, you can obtain almost any values of “standard” resistors.
A scale calibrated in this way is suitable for other types and limits of measurements only if the corresponding standard resistors, capacitors and inductors have the parameters indicated on schematic diagram device.
When using the device, you must remember that when measuring the capacitance of oxide capacitors (the output of their positive plate is connected to the HTZ terminal), the balance of the bridge is not felt as clearly as when measuring resistance, therefore the measurement accuracy in this case is less. This phenomenon is explained by current leakage characteristic of oxide capacitors.
