On the seemingly outdated 2051 controller, we have repeatedly thought about assembling a similar meter, but on a more modern controller, in order to provide it with additional capabilities. There was basically only one search criterion - wide measurement ranges. However, all similar schemes found on the Internet even had software range restrictions, and quite significant ones at that. To be fair, it is worth noting that the above-mentioned device on the 2051 had no limitations at all (they were only hardware), and its software even included the ability to measure mega and giga values!
Somehow, while studying the circuits once again, we discovered a very useful device - LCM3, which has decent functionality with a small number of parts. The device can measure inductance, capacitance of non-polar capacitors, capacitance of electrolytic capacitors, ESR, resistance (including ultra-low) within the widest range, and evaluate the quality of electrolytic capacitors. The device operates on the well-known principle of frequency measurement, but is interesting in that the generator is assembled on a comparator built into the PIC16F690 microcontroller. Perhaps the parameters of this comparator are no worse than those of the LM311, because the stated measurement ranges are as follows:
We liked the solutions used in the meter, and we decided not to assemble a new device on an Atmel controller, but to use a PIC. The circuit was partially (and then completely) taken from this Hungarian meter. Then the firmware was decompiled, and a new one was written on its basis, to suit our own needs. However, the proprietary firmware is so good that the device probably has no analogues.
Click to enlarge
LCM3 Meter Features:
Then:
Printed circuit board: lcm3.lay (one of the options from the vrtp forum).
On the supplied printed circuit board, the display contrast of 16*2 is set by a voltage divider across resistors with a resistance of 18k and 1k. If necessary, you need to select the resistance of the latter. FB is a ferrite cylinder; you can replace it with a choke. For greater accuracy, instead of a 180 Ohm resistor, two 360 Ohms are used in parallel. Before installing the calibration button and the measurement mode switch, be sure to check their pinout with a tester: there is often one that does not fit.
The housing for the device, following tradition (one, two), is made of plastic and painted with black metallic paint. Initially, the device was powered from a 5V 500mA mobile phone charger via a mini-USB socket. This is not the best option, since the power was connected to the meter board after the stabilizer, and how stable it is when charging from a phone is unknown. Then the external power supply was replaced with a lithium battery with a charging module and a boost converter, possible interference from which is perfectly removed by a conventional LDO stabilizer present in the circuit.
In conclusion, I would like to add that the author has put maximum capabilities into this meter, making it indispensable for a radio amateur.
The stereo volume, balance and tone control on the TCA5550 has the following parameters: Low nonlinear distortion no more than 0.1% Supply voltage 10-16V (12V nominal) Current consumption 15...30mA Input voltage 0.5V (gain at a supply voltage of 12V unit) Tone adjustment range -14...+14dB Balance adjustment range 3dB Difference between channels 45dB Signal to noise ratio...
The schematic diagram of the transmitter is shown in Fig. 1. The transmitter (27 MHz) produces a power of about 0.5 W. A 1 m long wire is used as an antenna. The transmitter consists of 3 stages - a master oscillator (VT1), a power amplifier (VT2) and a manipulator (VT3). The frequency of the master oscillator is set square. resonator Q1 at a frequency of 27 MHz. The generator is loaded on the circuit...
Amplifier parameters: Total range of reproduced frequencies 12...20000 Hz Maximum output power of mid-high frequency channels (Rn = 2.7 Ohm, Up = 14V) 2*12 W Maximum output power of low-frequency channel (Rn = 4 Ohm, Up = 14 V) 24 W Nominal power of mid-range HF channels at THD 0.2% 2*8W Rated power of the LF channel at THD 0.2% 14W Maximum current consumption 8 A In this circuit, A1 is an HF-MF amplifier, and ...
The VHF receiver operates in the range 64-108 MHz. The receiver circuit is based on 2 microcircuits: K174XA34 and VA5386; in addition, the circuit contains 17 capacitors and only 2 resistors. There is one oscillatory circuit, heterodyne. A1 has a superheterodyne VHF-FM without ULF. The signal from the antenna is supplied through C1 to the input of the IF chip A1 (pin 12). The station is tuned in...
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, a 7D-0.115 battery, 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 positive alternating current feedback between the collector and base circuits of the transistors, due to which the multivibrator self-excites 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 from its load resistor R5 enter the power 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. The appearance and design of the device are shown in Fig. 54. Most of the parts are placed on a mounting plate made of getinax, fixed in the housing on U-shaped brackets 35 mm high. You can install an autonomous battery for the device under the circuit board. 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 of the 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 on the inside of the case.
The design of the terminals for connecting resistors, capacitors and inductors to the device, the parameters of which must 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 the circuit diagram of the 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.
For quite some time now I have been using a homemade capacitance and ESR meter for capacitors, assembled according to a circuit from the author of GO from the ProRadio forum. Along the way, I also use another, no less popular FCL meter from the cqham website.
Today we are reviewing a device that has the above stated accuracy, and also actually combines both of the above devices.
Attention, many photos, little text, may be critical for users with expensive traffic.
It’s probably worth starting with the fact that this device is sold in its entirety, i.e. already assembled. But in this case, the designer was chosen purposefully, since at a minimum it allows you to save a little money, and at maximum, just enjoy the assembly. And probably the second is more important.
In general, I have long wanted to change the previous model of the C-ESR meter. In principle, it works, but after at least one repair it began to behave inappropriately when measuring ESR. And since I work a lot with switching power supplies (although this is also true for conventional ones), this parameter is even more important to me than just capacity.
But in this case, we are not dealing with just a C-ESR meter, but with a device that measures ESR + LCR, and the full list of measured values is even longer, in addition, good accuracy is also claimed.
Inductance 0.01 uH - 2000H (10 uH)
Capacitance 200pF - 200 mF (10pF) Resolution 0.01pF
Resistance 2000mΩ- 20MΩ (150mΩ) Resolution 0.1 mOhm
Accuracy 0.3 – 0.5%
Test signal frequency 100 Hz, 1 kHz, 7.831 kHz
Test voltage 200 mV
Automatic calibration function
Output impedance 40 ohms
The device can measure -
Q - Quality factor
D - Loss factor
Θ - Phase angle
Rp - Equivalent parallel resistance
ESR - Equivalent Series Resistance
Xp - Equivalent parallel capacitance
Xs - Equivalent series capacitance
Cp - Parallel capacitance
Cs - Series capacitance
Lp - Parallel inductance
Ls - Series inductance
In this case, the measurement is carried out using the bridge method using a four-wire connection to the component.
In my opinion, the closest competitor is E7-22, but it has less stated measurement accuracy (0.5-0.8%), a test frequency of only 120 Hz and 1 kHz and a test voltage of 0.5 Volts against 0.3% , 120 Hz - 1 kHz - 7.8 kHz, 0.2 Volta at the monitored.
This device is sold in several configuration options; almost the most complete version is used in the review. Prices from the seller's page.
1. Only the device itself without the housing - $21.43
2. Device + one type of probes - $25.97
3. Device + second type of probes - $26.75
4. Device + two types of probes - $31.29
5. Housing for the device. - $9.70 
Everything was packed in a bunch of small bags. 
Since when delivering through an intermediary the weight of the parcel is usually taken into account, I decided to weigh it additionally, without cables it came out to 333 grams, with cables it was noticeably more, 595 grams.
In general, it is quite possible to buy without cables, especially if you have something to make them yourself from, since the difference in the price of the set alone is about 10 dollars, not counting the weight. 
By the way, I’ll start with cables.
Packed in separate bags, it even just feels like a decent weight. 
The first set is essentially ordinary “crocodiles”, but larger in size and made of plastic. But in reality, not everything is so simple, the jaws are connected to different wires (connectors) to implement the correct four-wire connection.
The cable is moderately flexible, the rigidity is rather added by the fact that there are four cables, and they are shielded. The probes are connected to the device itself using regular BNC connectors; the screen is connected only on the side of the BNC connector.
There are no complaints about the quality, the only thing I didn’t really like was the lack of color markings near the connectors, since the crocodiles themselves have them. As a result, to connect, you have to look at each time which one you connect where. The solution is to make a mark with electrical tape near the connectors. 
But the second set is much more interesting; it allows you to work with small components, since it is a tweezers.
The photo shows that the central cores of the wires are connected not at the ends of the tweezers, but at some distance, i.e. This option is slightly worse than the previous one, but implementing a system like the “crocodiles” is more difficult here. There is no color coding.
For ease of use, the tweezers have a guide that protects the jaws from moving relative to each other. I don’t know how long they will last, but so far it’s quite convenient to use, although there is a note - you need to squeeze closer to the jaws themselves; if you squeeze the tweezers near the middle of the body, the jaws may not come together completely. 
Just a few words about what a four-wire connection or Kelvin connection is. Pictures taken, text mine :)
The principle of measuring resistance is quite simple. We connect the component to a current source and measure the voltage on the component. But since we have wire resistance, we end up with a sum consisting of the real resistance of the component and the resistance of the wire.
If the resistance is large, then usually this does not play a special role, but if we are talking about values of 1-10 ohms or less, then the problem comes out in full force.
To solve this problem, the circuits through which current flows through the component and the circuits directly measuring are separated. 
In real life it looks something like what is shown in the diagram. 
In addition, a similar method is used, for example, in power supplies. For example, a photo from my review of a powerful converter. Here you can also separate the power circuit and the feedback circuit, then the voltage drop on the wires will not affect the voltage across the load.
You've probably also seen something similar in computer power supplies using a 3.3 Volt circuit (orange wires). only there a three-wire circuit is used (the same additional thin wire to the power connector) 
Power supply 12 Volt 1 Ampere, looks good. However, I tried connecting it just to a load, it works fine.
But because of the plug with flat pins it is inconvenient to use, I will replace it with something else, fortunately the voltage is standard.
In reality, the device can be powered by a voltage of 9-15 Volts.
It’s a pity that you can’t choose a configuration without a power supply; I think many radio amateurs will have such a power supply at home. 
The main part of the kit was split into three separate packages. 
One of them has the most common 2004 display (20 characters, 4 lines) with backlight. 
The device board was carefully wrapped in “air” film. 
This is exactly the case when in the photo in the store the board seems smaller than it actually is :)
Actual dimensions 100x138mm. 
The front part of the board is occupied by space for probe connectors. 
The middle part is the measuring unit, switches, operational amplifiers. Apparently this unit was supposed to be shielded, but the shield itself is not included in the kit. 
At the top are the “brains” and nutrition. 
In the first versions of the device, linear power stabilizers were used, in this version they are replaced with pulse ones.
Also visible is the connector for connecting the power supply and the switch.
Replacing stabilizers with pulse ones can significantly help when powered by batteries. For example, the aluminum case comes with a cassette for 3 18650 batteries. 
Everything is controlled by a microcontroller. It is based on the old 8051 core and has an eight-channel 10-bit ADC on board. In the first versions of the device it was in a DIP-40 package, in new versions it was replaced with an SMD version. 
The board also has a connector for connecting to the programmer. 
Several individual photos of installed components. 
The bottom is empty, only the soldering points of the screen and the control points of the outputs of stabilizers and power converters are displayed here. 
Well, the last bag, with radio components that will actually need to be installed on the board. 
This includes the keyboard board, as well as all sorts of resistors, capacitors, connectors, etc.
In general, the design is quite well thought out, small components are already soldered on the board, only larger ones need to be installed and soldered. Those. the element of “assault” is retained, but there is no masochism for beginning radio amateurs in terms of soldering small components, and it’s much more difficult to “mess up”. As a result, you can assemble the device quite quickly and get a positive impression from the process. 
The components are divided into bags, but mostly several denominations in one bag. 
All resistors included in the kit are precision grade. At the initial stage, just in case, I measured their real resistance.
It helps in the assembly that there are few values, but at the same time they can be easily measured even with a cheap tester, since there are no resistors too close to each other in value.
Above is what needs to be soldered; there are essentially only six ratings - 40 Ohm, 1, 2, 10, 16 and 100 kOhm.
At the top are the resistors from the signed package; they are not soldered onto the board, but are used to check and calibrate the device. At first I thought that they needed to be soldered into some critical places, which is why I measured the resistance. But then it turned out that they were “superfluous”, and the number (16 pieces) of installed resistors coincided with the number that were in the first package. 
The kit includes capacitors with ratings of 3.3, 10, 22, 47 nF, 0.1, 0.2 and 0.47 µF.
In the photo below I have labeled the capacitors as they are labeled on the board. 
In addition, connectors, a pair of electrolytic capacitors, a relay and a tweeter are additionally installed. 
While I was waiting for my parcel, I searched the Internet for more information about the device. It turned out that there is not only a diagram, but also different versions of the printed circuit board, firmware, and in general quite a lot of people are working on this model.
The diagram is, of course, quite conventional, but it gives a general understanding. 
But along the way I remembered that about 8-9 years ago, in my city, a person was developing . If you look at the diagram, you can see a lot of similarities, and it was developed before the one being reviewed. 
The seller's comment on the product page really cheered me up, sorry for the Google translation.
In a simple form (well, very exaggerated) it means - I check all the boards, send them in excellent condition, so there is no need to send me your crafts, soldered with a hot nail on the knee with orthophosphorus instead of flux.
Love your board and treat it like your beloved friend :) 
It is worth noting that both the quality of the board and the soldering of components are 5 points. Everything is not only neatly soldered, but also thoroughly washed!
In this case, all installation locations are marked and have both a position designation and an indication of the component rating. Honestly, 5 points. 
Unboxing video and description of the kit.
Let's move on to assembly. In general, when I opened all these packages and laid them out on the table, I really wanted to sit down and solder this structure right away, the only thing that stopped me was that it was decided to make some small instructions for assembly, if suddenly one of the beginners decided to do it.
First of all, we pour resistors onto the table and find those that are most numerous, these are the values of 2 and 10 kOhm. 
We install and solder them first. This will allow you to quickly remove most of the free spaces from the board and make it easier to find the remaining ones later. 
I understand perfectly well that my instructions are completely for beginners, so I’ll hide the rest of the assembly under a spoiler.
Assembly of the device board.
We do the same with the remaining resistors, fortunately there are few of them left. 
The situation is similar with capacitors; first we solder the 10nF capacitors (103), since there are the most of them. 
Then the values are 0.1 and 0.22 uF (104 and 224). 
Well, and a few more capacitors, literally 1-2 of them. 
It is extremely difficult to install relays and connectors incorrectly; the tweeter is marked + both on the board and on the tweeter itself (the long lead is a plus).
A pair of electrolytic capacitors is also unlikely to cause problems, there is one of each value, the minus (short terminal) is indicated in white on the board. 
The BNC connectors were soldered surprisingly well. In general, during the entire assembly I did not use flux; what was in the solder was enough. 
The final touch is installing the racks. Here everyone already does it in their own way.
In general, I don’t quite understand why there are 16 racks in the kit. 8 long ones are needed to install the keyboard board and indicator, let's say 4 short ones on the bottom or top, but why 8? 
In the end, I did it my way, 8 long ones are on top of the board, and 4 short ones are on the bottom. This option makes it more convenient to temporarily use the board without a housing. In this case, the upper indicator posts stand with the screws up, and the short ones are screwed into them. 
A couple of photos of the soldered board for control. 
After assembly, we get a pretty beautiful printed circuit board, the main thing is not to mess anything up in the process :) 
I molded the resistor leads using a small device, but it turned out that the distance between the leads was a little larger than necessary. In the end, I decided to raise the resistors a little above the board, but rather for beauty, at least I like it better. 
After soldering, be sure to wash the board, since there was little flux, I made do with alcohol. 
After assembly, I noticed that the board could be shortened a little from the base 138mm. Approximately up to 123-124mm if you leave the programming connector or up to 114mm if you cut it out too. In this case, the probe connectors are connected with wires into specially designed holes. Perhaps it will be useful when “packing” into a small case. 
There are only buttons on the keyboard board, and they accidentally gave not 8, but 9 buttons. One button stuck to another. 
But they didn’t include one “comb” in the kit; I had to gut the “stash” a little, and at the same time I took out the mating parts.
True, in my case there were only corner connectors, but there were a lot :)
In general, it is useful to have a set of such connectors in your household; they often help out. 
Solder the connectors to the keyboard board and indicator. By the way, the keyboard connection is fully implemented, i.e. Each button has its own processor output, rather than using resistors and an ADC, as is sometimes the case. 
That's all, the kit is completely ready. 
When assembled, the layout resembles a multimeter, with an indicator on top, buttons below, and connectors even below. 
As you can understand from what I wrote above, this is the second version of the device, essentially modified. But I like the case version of the previous version better and I plan to make just such a case version. True, such a case costs about 9-10 dollars, and if you buy it with a keyboard board and front panel, then even more. By the way, I already had a review of such a case, where I assembled an regulated power supply in it. 
My version is designed for installation in an aluminum case. 
And according to the idea it should look like in this photo. But let’s just say that design is more individual; I came across various options on the Internet. 
After assembly, I was left with test resistors, a button and some fasteners. Well, and a power supply with probes, of course. 
Now we move on to a description of the capabilities of the device and the specifics of its operation.
When turned on, there is a welcome message, then the basic operating screen. By the way, everything worked right away, there are no trimming elements in the device at all, assemble it, turn it on, use it.
If your device works after assembly, but does not measure correctly (or does not measure at all), you need to reset the calibration settings to factory settings.
Press and hold the “M” button to get to the menu (it may work on the second press).
Press the "RNG" button to get to the calibration menu.
Press the "C" button five times to reset.
Press the "L" button to save your changes.
Next, return to the menu by holding the "M" button.
Press the "X" button to exit the menu
The device can operate in four main modes:
1. Automatic selection. Here the device itself determines what to measure. The choice is made according to the prevailing value. Those. if the component has a predominant capacitive component, it will switch to the capacitance measurement mode, if inductive, then to the inductance measurement mode. Sometimes it can be wrong, especially if the component has several distinct components, for example some resistors can be defined as inductance.
To help the automation, manual selection was added -
2. Capacitance measurement
3. Inductance
4. Resistance.
The indicator also displays the frequency of the test signal and the measurement limit. The measurement limits are somewhat “non-standard” and number as many as 16 pieces - 1.5, 4.5, 13, 40, 120, 360 Ohms. 1, 3, 9, 10, 30, 90, 100, 300, 900 kOhm and 2.7 MOhm.
By default, the device starts in automatic measurement mode at a frequency of 1 kHz. 
A little about management.
There are eight buttons under the indicator, it is labeled.
M- Menu, from here the necessary calibrations and factory resets are performed.
RNG- Range. In the menu, this button gives access to the calibration submenu.
WITH- Fast automatic calibration.
L- Switching the display mode (first photo). In the menu - memory
X- Switching operating modes of the device. In menu mode - exit.
R- Decrease value in calibration mode (X-increase)
Q- relative measurement mode. Can be used to select two identical components. we connect the sample component, press the button, turn off the sample component and connect the selected ones. The percentage of discrepancy will be displayed on the screen (second photo).
F- Selectable frequency 100 Hz - 1 kHz - 7.8 kHz. 
Device menu view. 
The quick calibration mode by pressing button C has two options:
1. When measuring capacitance and inductance, it is carried out with open probes.
2. When measuring resistance - with closed ones. In both options, the device self-calibrates three times for each frequency.
3, 4. Calibration in resistance mode, you can see the resistance of the probes before and after calibration. 
In the mode of measuring small resistances, calibration is quite important, since the capabilities of the device allow you to even “see” the resistance of the capacitor terminals, not to mention the different wires. 
All sorts of other tests.
Naturally, in this mode it is convenient to measure the resistance of low-resistance resistors, as well as such “non-standard” measurements as the resistance of button contacts, relays or connectors. 
In terms of resistance measurement accuracy, the device can easily compete with my Unit 181. 
When measuring inductance, the device also behaved quite well. The photo shows an inductance of 22 μH and three tests with different frequencies of inductance with a nominal value of 150 μH. 
Now we can move on to the main thing, which is what I mainly need it for, measuring the parameters of capacitors.
At first I just poked different capacitors and saw what it showed, but one (or rather a pair) surprised me.
I measured a pair of identical capacitors that were soldered from old (about 20 years old) Hungarian or Czechoslovak equipment. One showed 488 μF, and the second almost 600. Everything would be fine, but initially these are 470 μF 40 Volt capacitors.
Moreover, they behave differently at a frequency of 7.8 kHz. Or rather, the difference in capacity is not proportional to each other. 
Then I took another capacitor (like Matsushita), bought a long time ago, but still lying in the stash.
The device was able to measure capacitance normally at frequencies of 100 Hz and 1 kHz, but at high frequencies the capacitance was displayed somewhat incorrectly. In general, at a frequency of 7.8 kHz the device sometimes behaves a little strangely, sometimes increasing the capacitance relative to the first two frequencies. Sometimes (when measuring capacitive capacitors) it falls into the ----OL---- mode or shows an excess of more than 20 mF.
By the way, the resolution of the device even allows you to see the difference in the connection location to the output. And using the example of one pin, you can see how the internal resistance changes. What I mean is that people sometimes ask me if it’s possible to connect a capacitor on the wires if it doesn’t fit into place. You can connect, but the performance will decrease slightly. 
As you understand, it’s not interesting to simply measure capacitors, so I asked a friend for his E7-22. Along the way, I noticed that even the control of devices has a lot in common. 
The first step was film capacitors. At the bottom is a precision 1% capacitor with a stated capacitance of 0.39025 µF. 
1, 2. 100uF polymer capacitor
3, 4. But the E7-22 has problems with measuring large capacities. The device under review easily measures a capacitance of 10,000 μF at a frequency of 1 kHz; the E7-22, even at 4700, was already producing an overload. 
1, 2. Capxcon KF series with a capacity of 330 uF.
3, 4. A capacitor from the same company (allegedly), it just lay in a box for several years and became swollen. 
And this is just for the sake of curiosity. A couple of capacitors from my old motherboard that ran 24/7 for about 10 years.
1. 2200uF
2. 1000uF
The capacity of the first capacitor has dropped noticeably, but the internal resistance is fine. More often it happens the other way around: the capacitance remains the same, but the internal resistance increases. 
Video of the work process and tests.
If you have any other test suggestions, then for now I have two devices on hand, I could experiment. It only occurred to me to check the scope of the test signal.
Shown below is the test signal swing relative to ground. The top two are monitored at frequencies of 100 Hz and 7.8. kHz, lower - E7-22 at frequencies 120 Hz and 1 kHz. The difference is about 2.5 times. 
I wrote above that I plan to use a housing where the indicator is located not parallel to the surface, but perpendicular.
But in the process it turned out that although the indicator was used and was relatively good, it was focused specifically on what would be viewed from the front or from the front-bottom. 
At large angles, and even more so when viewed from above or from the side, the image disappears or begins to invert. 
This is actually why I decided to finally try a display made using VATN technology. In general, I wanted OLED, which I already did, but it’s almost impossible to buy 2004, and as it turned out later, VATN is also sold online in very few places.
As a result, I had to go to our offline store and buy there.
There were three models to choose from, with blue, green and white font, I liked the white one better, model - , price about 15-16 dollars, . Manufacturer: WINSTAR.
At first glance, the indicators differ little from each other, at least the size of the board is completely identical - 98x60 mm. 
More details about the indicator and connection nuances
There is a slight difference at the bottom, but seemingly insignificant. 
The new indicator is approximately 0.5mm thinner. 
The general connection principle is almost the same, with the exception of a few nuances, which I will discuss below. 
To begin with, the difference is that VATN displays need a negative voltage to adjust the contrast, so a voltage converter based on the well-known 7660, which I also reviewed, is mounted on the board.
Nearby there is a place for a tuning resistor. The middle pin goes to the contrast adjustment contact, the other two to + 5 and - 5 Volts, respectively. 
At first I wanted to install a trimming resistor, giving full control to the indicator board, but then I decided not to bite out the extra contact of the connector and simply turned on the resistor so that one contact went to the standard contrast adjustment pin (number 3 on the common connector), and the second to the negative 5 output Volt.
I adjusted the image, soldered out the tuning resistor, it turned out that I needed a constant resistor with a resistance of 2.6 kOhm, the closest one at hand was 2.49 kOhm, and I already soldered it “stationary”. 
But that wasn't all.
And now Attention, Pin 15 of the connector for conventional indicators is the positive output of the backlight, here it is the negative voltage output and in no case should you simply change the indicator from one to another, in the end you will simply burn it out.
I did it a little differently, out of 16 contacts I soldered only 14.
Pin 16 is the minus of the backlight, and the plus is connected to the input +5 Volts, so I just threw a jumper between the minus of the backlight and the common wire of the indicator board.
And here attention second time!
Initially, I thought of simply leaving pin 16 in place, since a regular indicator has the backlight minus displayed there, reasoning that it makes no difference where it is connected to the common wire. And it would work normally if not for one BUT.
On the device board, the indicator is powered by + 5 Volts, and the backlight by -5 Volts. Therefore, having connected the new indicator in this way, literally after 10-20 seconds I accidentally noticed that its backlight began to warm up wildly. Having connected with a tester, I found out that not 5, but 10 Volts (+5 and -5) were used for the backlight.
Therefore, with this device it was necessary to connect the minus of the backlight to the common contact of the board. 
Change the indicator and try.
Well, what can I say, this is certainly not an OLED, but it is far from an ordinary LCD.
Of the minuses, it is more oriented towards the fact that they will look at it in any way, but not from below, in this version it will become “blind” from the flash.
At the same time, I measured the current consumption with the old indicator and the new one.
1. old - 48 mA all together or 12 mA only indicator.
2. new - 153 mA or 120 mA indicator only.
Yes, for a battery-powered version, a regular LCD indicator is much more profitable. 
If viewed from above, i.e. As I planned, visibility is good, but inactive pixels begin to appear.
You can easily get rid of the latter, but then, when viewed directly, it shows dimly; I set it to something in between. 
The viewing angles are, of course, head and shoulders above those of a conventional LCD; the image is readable even when looking almost parallel to the screen.
But an interesting effect emerged (last photo). If you smoothly turn the screen away from you, then at some point (at about 30 degrees of rotation) the image fades, tries to invert, and with further rotation it almost sharply becomes normal again. Therefore, the display is perfect for vertical installation, but sometimes it can be annoying when installed horizontally. 
This is the position in which I intended it to be used; I have no complaints here. 
Next, I planned to “settle” it, for which I bought a Z1 case. At first glance everything is neat. 
But the case is very large, actually one and a half times larger than required, but I would like something more compact.
Case dimensions (external) - 188 width, 70 height and 197 depth. This is the last size and I would like to reduce it to 140-150, even if you take it and drink it :(
Does anyone know suitable housings? 
Well, probably the review would be incomplete if I did not show what I used until recently.
The calibration is quite extensive to describe, I'll catch up sometimes.
ForenMenber Blueskull kindly translated chapter 6 from Chinese to English for me.
How useful this is now I'll have to try, but my meter seems to be well calibrated, I'm a little shy.First, I'll look at the included reference resistors. I have a more accurate ohmmeter (DMM PM 2534)
(Under construction!)6. LCR meter calibration
There are 7 calibration menus that need to be calibrated, a total of 10 (15?) parameters, respectively M0 ~ M8 and "M3.", "M5.", "M6.", "M7." And "M8."M0 - zero offset at 100 Hz, LSB unit, default - 20.
M1 - zero offset by 1 kHz, LSB unit, default - 20.
M2 - zero offset at 7.8 kHz, LSB unit, default 14.
M3 - phase compensator for VI converter in the 20 Ohm range, unit 0.001rad, default 0.
M4 is a phase compensator for VI converter in the 1Kohm range, unit 0.001rad, default 0.
M5 - phase compensator for VI converter in the range of 10 kOhm, unit 0.001rad, default 0.
M6 - phase compensator for VI converter in the range of 100 kOhm, unit 0.001rad, default 20.
M7 - second stage phase compensation, unit 0.001rad, default 16.
M8 - first stage PGA phase compensation, unit 0.001rad, default 20."M3." - calibration of the lower arm for the VI converter at 20 Ohms, unit 1%, default - 0.
"M4." - calibration of the lower arm for the VI converter at 1 kOhm, unit 1%, default - 0.
"M5." - calibration of the lower arm for the VI converter at 10 kOhm, unit 1%, default - 0.
"M6." - calibration of the lower arm for the VI converter at 100 kOhm, unit 1%, default - 0.
"M7." - second PGA gain calibration, unit 1%, default 0.
"M8." - first PGA gain calibration, unit 1%, default 0.In the LCD1602 version these parameters are named Z0, Z1, Z2, R1X, R2X, R3X, R4X, G1X, G2X, R1, R2, R3, R4, G1 and G2.
To restore factory settings, press the C key 5 times to restore the default settings, then press the L key to save.
Before calibration, you need to prepare several resistors:
To calibrate the VI converter, 20R, 1k, 10k, and 100k resistors are required.
To calibrate the PGA, 3.3k and 10k resistors are needed (translator's note: you also need 330R and 100R).
At 1KHz and 7.8KHz, connect 20R, 1k, 10k and 100k resistors when calibrating the corresponding ranges, the gain setting of the upper and lower arms should be identical for amplitude and phase calibration. Press M+R key to enter the control menu, if "1, 1" is displayed, then both hands are balanced and the gains are identical. If "0, 1" or "1, 0" is displayed, the signal amplitude is incorrect.
Offset calibration (M0, M1, M2)
Ensuring zero offset is the basis for measuring accuracy and hence it is recommended to take the first step in calibration. Using a given specification, the offset zero points are also identical for individual assemblies, so preset values can be used. If calibration is necessary, do the following (note: the translator added this sentence):
For M0 at 100 Hz:
1, Set f=100Hz, range=100k.
2, Connect 1% 10R resistor as DUT
3, Read R value from menu 1In the 10k (100 kHz) range, measuring a 10R resistor will result in a larger error, and this is normal. If the error is higher than 2%, you need to adjust M0 to bring it to 2%.
M1 and M2 can be calibrated using the same method at different frequencies (1 kHz and 7.8 kHz).
The buzzer will beep whenever a key is pressed, causing the I/O current through the MCU to increase and causing an error. Please read the values after the buzzer has stopped beeping.
Phase compensation for VI and PGA converter (M3~M8)
Set f = 7.8 kHz, range = 1k
1, Connect 20R resistor as DUT, measure Q in 20R range, record Q. Subtract Q from Q0, set M3 to this value (Note: Q0 should be Q reading with open circuit DUT. Multiply this number by 1000).
2, Connect the 1k resistor as DUT, measure Q in the 1k range, record Q. Subtract Q from Q0, set M4 to this value.
3, Connect the 10k resistor as DUT, measure Q in the 10k range, record Q. Subtract Q from Q0, set M5 to this value.
4, Connect the 10k resistor as DUT, measure Q in the 100k range, record Q. Subtract Q from Q0, set M6 to this value.
5, Connect 330R resistor as DUT, measure Q in 1k range, record Q. Subtract Q from Q0, set M7 to this value. This calibrates the PGA gain = 3x.
6, Connect 100R resistor as DUT, measure Q in 1k range, record Q. Subtract Q from Q0, set M8 to this value. This calibrates the PGA gain = 9x.For example, to get M8, measure a 100R resistor, write Q. For example, Q = 0.020, then set M8 = 20.
Note: At 1KHz, 1KHz, when DUT is between 640R~1k, it is (1, 1) (note: WTF? I can't understand what he means), when R=440R~640R, it is in the hysteresis region, When R = 280R ~ 440R, it is (0, 1), when R = 250R ~ 280R, is in the hysteresis region. When R=85R~250R is (0, 2), then R=75R~85R is in hysteresis mode when R<75, это (0, 3).
Amplitude calibration for VI and PGA transducer (point M3 to point M8)
Multiply the error values by 10000.
In the corresponding 1kHz ranges, connect 20R, 1k, 10k and 100k resistors, measure the error, then save the calibration values to point M3 to point M8 respectively.
This process is similar to that described earlier.
That's all for now, I plan to make a short continuation, where I'm going to put it all in the case, and at the same time talk about my impressions after long-term use.
At the moment I have been using the device for several days and I have only good impressions so far.
Among the advantages:
1. Enjoy the assembly process
2. Excellent quality of PCB and soldering.
3. High precision work
4. Availability of a frequency of 7.8 kHz and a larger measurement range at a frequency of 1 kHz than that of the E7-22.
5. Four-wire connection diagram
6. Low consumption.
7. No need for debugging, with basic calibration they declare an accuracy of 0.5%, with manual calibration they write about 0.3%
8. Quite a large community of users, albeit foreign ones.
9. Low price.
Among the shortcomings
1. In some situations, readings at a frequency of 7.8 kHz are not entirely adequate. But here I will try again.
In summary, I can say that the device under review, both functionally and in terms of accuracy, is no worse, and most likely even better, than the more expensive E7-22. But of course there is a difference, E7-22 can be trusted, but the one being reviewed is only for personal use.
I bought it through an intermediary, the cost of the set is about 32 dollars, the cost of delivery depends on the country, the weight of the components is indicated in the review.
As always, I welcome questions, advice, test suggestions and just comments, I hope that the review was useful.
The product was provided for writing a review by the store. The review was published in accordance with clause 18 of the Site Rules.
I'm planning to buy +85 Add to favorites I liked the review +127 +235A huge selection of diagrams, manuals, instructions and other documentation for various types of factory-made measuring equipment: multimeters, oscilloscopes, spectrum analyzers, attenuators, generators, R-L-C, frequency response, nonlinear distortion, resistance meters, frequency meters, calibrators and much other measuring equipment.
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