Advanced XJW01 LCR Meter DIY Kit

I've been using a homemade capacitance and ESR meter for quite a while, built from a circuit by GO, a member of the ProRadio forum. I also use another, equally popular meter, the FCL from the cqham website.
Today's review is of a device with higher claimed accuracy that effectively combines both of the meters mentioned above.
Warning: lots of photos, little text. This may be an issue for users on expensive data plans.


I should probably start by mentioning that this device is also sold fully assembled. In this case, though, I deliberately chose the kit: at the very least, it saves a little money, and at best, you simply get the pleasure of putting it together. The latter is probably more important.
I've wanted to replace my previous C-ESR meter for a long time. It basically works, but after at least one repair, it started behaving erratically when measuring ESR. Since I work with switching power supplies a lot (though this matters for conventional ones too), this parameter is even more important to me than capacitance alone.
But this isn't just a C-ESR meter: it measures ESR + LCR, and the full list of measured parameters is even longer. It also claims pretty good accuracy.

Inductance 0.01 uH - 2000H (10 uH)
Capacitance 200pF - 200 mF (10pF) Resolution: 0.01pF
Resistance 2000mΩ- 20MΩ (1.5 Ω) Resolution: 0.1 mΩ
Accuracy 0.3 – 0.5 %
Test signal frequency 100 Hz, 1 kHz, 7.831 kHz
Test voltage 200 mV
Calibration function automatic
Output resistance 40 Ω

The meter can measure -
Q - Quality factor
D - Dissipation 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

Measurements are made using a bridge method with a four-wire connection to the component.

In my opinion, its closest competitor is the E7-22, but its claimed measurement accuracy is lower (0.5-0.8%), it only has test frequencies of 120 Hz and 1 kHz, and its test voltage is 0.5 V, compared with 0.3%, 120 Hz - 1 kHz - 7.8 kHz, and 0.2 V for the device under review.

This device is sold in several configurations; for this review, I used almost the most complete one. Prices are from the seller's page.
1. Meter only, without enclosure - $21.43
2. Meter + one type of test leads - $25.97
3. Meter + the other type of test leads - $26.75
4. Meter + both types of test leads - $31.29
5. Enclosure for the meter. - $9.70


Everything was packed in a pile of small bags.


Since shipping through a forwarding service usually depends on the parcel's weight, I decided to weigh everything too. Without the cables, it came to 333 grams; with them, quite a bit more: 595 grams.
You can certainly buy it without the cables, especially if you have the parts to make your own. The difference in the kit price alone is about $10, not counting the weight.



I'll start with the cables, by the way.
They're packed in separate bags, and even just by feel, they're quite heavy.


The first set is essentially a pair of ordinary alligator clips, only larger and housed in plastic. But there's more to it than that: the jaws connect to separate wires (connectors) to provide a proper four-wire connection.
The cable is reasonably flexible; most of the stiffness comes from having four shielded wires. The probes connect to the meter using standard BNC connectors, with the shield connected only at the BNC end.

No complaints about the quality. The only thing I didn't like was the lack of color coding by the connectors, since the alligator clips themselves are color-coded. So you have to check which connector goes where every time. The solution: mark them with electrical tape near the connectors.


The second set is much more interesting: it's a tweezer probe for working with small components.
As you can see in the photo, the center conductors are joined some distance from the tweezer tips, rather than right at the ends. So this design is slightly worse than the previous one, but it's also harder to implement the same arrangement as in the alligator clips. There's no color coding.
For easier handling, the tweezers have a guide that keeps the jaws from shifting relative to each other. I don't know how long they'll last, but they're quite convenient to use so far. One thing to note: you need to squeeze them close to the jaws themselves. If you squeeze the tweezers around the middle of the body, the jaws may not close all the way.


A couple of words about what a four-wire connection, or Kelvin connection, actually is. The illustrations are from here, the text is mine :)

When measuring resistance in the usual way (and, by the way, not just resistance), something parasitic like the test leads can have a significant effect. I think many people know that few multimeters show 0 when the probes are shorted and the meter is set to its lowest range. The display usually shows some value around 0.05–0.5 Ω, which is the parasitic resistance.
Sometimes you can compensate for it by enabling the relative measurement function (Rel), but this isn't always convenient, and it certainly isn't always accurate.


The principle behind resistance measurement is quite simple. Connect the component to a current source and measure the voltage across it. But since the wires have resistance, the result will be the sum of the component's actual resistance and the resistance of the wires.
This usually doesn't matter much when measuring high resistance, but when we're talking about values of 1–10 Ω or less, the problem becomes very apparent.
To solve this problem, the current path through the component is separated from the measurement circuit.


In practice, it looks roughly like this, as shown in the diagram.


This method is also used, for example, in power supplies. Here's a photo from my review of a high-power converter. The power circuit and feedback circuit can be separated here too, so the voltage drop in the wires won't affect the voltage at the load.
You've probably also seen something similar in computer power supplies on the 3.3 V rail (orange wires). Only there, a three-wire arrangement is used (that extra thin wire going to the power connector).


A 12 V, 1 A power supply that looks pretty good. I also tried connecting it directly to a load, and it works fine.
But the flat-pin plug makes it inconvenient to use, so I'll replace it with something else. Fortunately, the voltage is standard.
The device can actually run on 9–15 V.
It's a shame you can't choose a package without the power supply. I think many radio hobbyists will have one at home.


The main part of the kit was split into three separate packages.


One of them contained a standard 2004 display (20 characters, 4 lines) with a backlight.


The device's circuit board was carefully wrapped in bubble wrap.


This is one of those cases where the board looks smaller in the store photo than it really is :)
Its actual dimensions are 100 × 138 mm.




The front section of the board is taken up by the connectors for the test probes.


The middle section contains the measurement circuitry, switches, and op-amps. It looks like this section was meant to be shielded, but no shield is included.


The top section contains the “brains” and the power supply.


The first versions of the device used linear voltage regulators; in this version, they've been replaced with switching regulators.
You can also see the power supply connector and the switch.
Replacing the regulators with switching ones can make a noticeable difference when powering the device from batteries. For example, the aluminum case kit includes a holder for three 18650 batteries.


Everything is controlled by a 12C5A60S2 microcontroller. It's based on the rather old 8051 core and has an onboard 8-channel, 10-bit ADC. In the first versions of the device, it used a DIP-40 package; in newer versions, this has been replaced with an SMD part.


There is also a connector on the board for connecting a programmer.


A few close-up photos of the installed components.


The underside is empty; it only has the screen solder pads and test points for the outputs of the voltage regulators and power converters.


And finally, the last bag contains the radio components that still need to be installed on the board.


This includes the keypad board, along with various resistors, capacitors, connectors, and so on.
The design is quite well thought out: the small components are already soldered to the board, so you only need to install and solder the larger ones. In other words, you still get to do some hands-on assembly, but beginners don't have to endure the masochism of soldering tiny components, and it's much harder to mess things up. The result is that you can assemble the device fairly quickly and enjoy the process.


The components are sorted into bags, though most bags contain several different values.


All the resistors included in the kit are precision parts. As a precaution, I measured their actual resistance before getting started.
Assembly is easier because there aren't many different values, and they're easy to measure even with a cheap tester, since none of the resistor values are too close to one another.
The ones at the top are the resistors to solder; there are only six values: 40 Ω, 1, 2, 10, 16, and 100 kΩ.

The resistors at the top are from a labeled bag. They aren't soldered onto the board; they're used to test and calibrate the device. At first I thought they had to be soldered into some critical spots, which is why I measured their resistance. But it turned out they were extras, and the number of resistors to install (16) matches the number in the first bag.


The kit includes capacitors rated at 3.3, 10, 22, and 47 nF, and 0.1, 0.2, and 0.47 µF.
In the photo below, I've labeled the capacitors to match the markings on the board.


A few more parts need to be installed: connectors, a couple of electrolytic capacitors, a relay, and a buzzer.


While waiting for my package, I looked online for more information about the device. It turned out there was not only a schematic, but also different versions of the PCB and firmware, and quite a few people working with this model.
The schematic is, of course, fairly simplified, but it gives you a good general idea.


That also reminded me that about 8–9 years ago, someone in my own city was developing a similar device. Looking at the schematic, you can see a lot of similarities—and it was developed before the one I'm reviewing here.


The seller's comment on the product page really made my day. Sorry about the Google translation.
Put simply (and very loosely), it means: I inspect all the boards and ship them in excellent condition, so don't send me your homemade contraptions, soldered with a hot nail on your kitchen table and phosphoric acid instead of flux.
Love your board and treat it like your favorite girlfriend :)


It's worth noting that both the PCB quality and the component soldering are top-notch. Everything is not only soldered neatly, but has also been thoroughly cleaned!
All the component locations are marked, with both reference designators and component values. Honestly, top marks.


Unboxing video and kit overview.


Let's move on to assembly. When I opened all these bags and laid everything out on the table, I honestly wanted to sit down and solder the whole thing right away. The only thing that stopped me was the decision to put together a short assembly guide in case a beginner wanted to build one.
First, pour the resistors out onto the table and find the ones there are the most of: the 2 kΩ and 10 kΩ values.


Install and solder those first. This will quickly fill most of the empty spaces on the board and make it easier to find the remaining ones later.


I realize this guide is very much for beginners, so I’ll hide the rest of the assembly under a spoiler.


After assembly, we get a rather nice-looking circuit board—as long as we don't mix anything up along the way :)


I shaped the resistor leads with a small jig, but it turned out the lead spacing was a little wider than needed. In the end, I decided to raise the resistors slightly above the board, mostly for looks—I just like it better that way.


After soldering, be sure to clean the board. There wasn't much flux, so alcohol was enough.


After assembling it, I noticed that the board could be shortened a little from its original 138 mm. It can be reduced to about 123–124 mm if you keep the programming connector, or to 114 mm if you cut that out too. In that case, the probe connectors are wired to the holes provided for them. This may come in handy when fitting it into a small enclosure.


The keypad board has only the buttons on it. By mistake, they sent 9 buttons instead of 8—one button had been stuck to another.


On the other hand, they left out one pin header, so I had to rummage around in my stash. I also dug out the matching connectors while I was at it.
In my case, though, I only had right-angle connectors—but plenty of them :)
It's generally useful to keep a set of these connectors around; they come in handy quite often.


Solder the connectors to the keypad board and the display. By the way, the keypad is fully implemented: each button has its own processor pin, rather than using resistors and an ADC, as is sometimes done.


And that's it—the whole kit is ready.


Once assembled, the layout is reminiscent of a multimeter: the display at the top, buttons below it, and connectors below those.


As you can tell from what I wrote above, this is the second, improved version of the instrument. But I like the enclosure from the previous version better, and that's the one I plan to make. The trouble is, that enclosure costs around $9–10, and even more if you buy it with the keypad board and front panel. By the way, I've already reviewed this type of enclosure, when I built an adjustable power supply in one.


My version is designed to be installed in an aluminum enclosure.


And the idea is for it to look like the one in this photo. But design is a matter of personal taste, and I've seen various versions online.


After assembly, I had some test resistors, a button, and a few fasteners left over. And, of course, the power supply and probes.



Now let's move on to the instrument's features and how it works.
When you turn it on, a welcome message appears, followed by the main screen. Everything worked right away, by the way. The instrument has no trimmers at all: assemble it, turn it on, and use it.


The instrument has four main operating modes:
1. Automatic selection. The instrument determines what to measure. It chooses based on the dominant component. That is, if a component is predominantly capacitive, it switches to capacitance measurement; if it's predominantly inductive, it switches to inductance measurement. It can sometimes get it wrong, especially when a component has several pronounced characteristics. For example, some resistors may be identified as inductors.
To complement the automatic mode, manual selection is also available:
2. Capacitance measurement
3. Inductance measurement
4. Resistance measurement.

The display also shows the test signal frequency and measurement range. The ranges are somewhat “unusual,” with no fewer than 16 of them: 1.5, 4.5, 13, 40, 120, 360 Ω; 1, 3, 9, 10, 30, 90, 100, 300, 900 kΩ; and 2.7 MΩ.

By default, the instrument starts in automatic measurement mode at 1 kHz.


A little about the controls.
There are eight labeled buttons below the display.
M - Menu. This is where you perform the necessary calibrations and reset the settings to factory defaults.
RNG - Range. In the menu, this button opens the calibration submenu.
C - Quick automatic calibration.
L - Switches the display mode (first photo). In the menu, it accesses memory.
X - Switches the instrument's operating mode. In the menu, it exits.
R - Decreases the value in calibration mode (X increases it).
Q - Relative measurement mode. Can be used to match two identical components. Connect the reference component, press the button, disconnect the reference, then connect the components you want to match. The screen will show the percentage difference (second photo).
F - Select frequency: 100 Hz - 1 kHz - 7.8 kHz.


The instrument's menu.


Quick calibration by pressing the C button has two options:
1. For capacitance and inductance measurements, the probes are left open.
2. For resistance measurements, the probes are shorted. In both cases, the instrument self-calibrates three times at each frequency.
3, 4. Calibration in resistance mode, showing the probe resistance before and after calibration.


Calibration is quite important when measuring low resistances, since the instrument is sensitive enough to even "see" the resistance of a capacitor's leads, not to mention different wires.



Naturally, this mode is useful for measuring low-value resistors, as well as for "non-standard" measurements such as the contact resistance of buttons, relays, or connectors.


In terms of resistance measurement accuracy, the instrument can easily hold its own against my Unit 181.


The instrument also performed quite well when measuring inductance. The photo shows a 22 µH inductor and three tests of a nominal 150 µH inductor at different frequencies.


Now we can get to the main point—what I mainly need it for: measuring capacitor parameters.

At first, I just tried different capacitors and checked the readings, but one (or rather, a pair) surprised me.
I measured a pair of identical capacitors removed from some old (about 20 years old) Hungarian or Czechoslovak equipment. One measured 488 µF, while the other was almost 600 µF. Nothing unusual there, except that they were originally 470 µF, 40 V capacitors.
What's more, they behave differently at 7.8 kHz. More precisely, the difference in capacitance isn't proportional between them.


Then I took another capacitor (I think it was Matsushita), bought a long time ago but still sitting in my parts stash.
The instrument measured its capacitance correctly at 100 Hz and 1 kHz, but gave a somewhat inaccurate reading at the higher frequency. In general, the instrument sometimes behaves a little strangely at 7.8 kHz, occasionally showing a higher capacitance than at the first two frequencies. Sometimes, when measuring high-capacitance capacitors, it switches to ----OL---- mode or shows an overrange reading above 20 mF.

By the way, the instrument's resolution is good enough to show how the connection point on a lead affects the reading. Even on a single lead, you can see the internal resistance change. The reason I mention this is that people sometimes ask whether a capacitor can be connected using wires if it won't fit in place. You can connect it that way, but its characteristics will be slightly worse.


As you can imagine, just measuring capacitors isn't very interesting, so I borrowed a friend's E7-22. I also noticed that the controls on the two instruments have a lot in common.


First up were film capacitors. At the bottom is a precision 1% capacitor with a stated capacitance of 0.39025 µF.


1, 2. 100 µF polymer capacitor
3, 4. The E7-22 has trouble measuring large capacitances. The instrument under review measures 10000 µF without any problems at 1 kHz, while my E7-22 already showed an overload at 4700 µF.


1, 2. 330 µF CapXon KF series capacitor.
3, 4. A capacitor from the same brand (supposedly), which had simply been sitting in a drawer for several years and has bulged.


This one is just for curiosity's sake. A pair of capacitors from my old motherboard, which ran 24/7 for about 10 years.
1. 2200 µF
2. 1000 µF

The capacitance of the first capacitor has dropped noticeably, but its internal resistance is still fine. More often, it's the other way around: capacitance stays the same while internal resistance increases.


Video of the operation and tests.


If you have any other test suggestions, I have both instruments on hand for now, so I could try them out. The only thing I could think of was checking the test signal's amplitude.
Below is the test signal amplitude relative to ground. The top two traces are from the instrument under review at 100 Hz and 7.8 kHz; the bottom two are from the E7-22 at 120 Hz and 1 kHz. The difference is about 2.5 times.


Above, I mentioned that I planned to use a case where the display would be positioned perpendicular to the surface rather than parallel to it.
But during testing, it turned out that although the display is reasonably good, it is designed to be viewed from the front or from slightly below.


At steep angles, especially when viewed from above or from the side, the image disappears or starts to invert.


That’s why I finally decided to try a display made using VATN technology. I actually wanted an OLED, like the one I used in this review, but a 2004 is almost impossible to buy, and as it turned out, VATN displays are also hard to find online.
In the end, I had to go to a local brick-and-mortar store and buy one there.
There were three models to choose from, with blue, green, and white text. I liked the white one best. The model is WH2004A-SLL-CTV, priced at around $15–16, link. Made by WINSTAR.

At first glance, the displays don’t look very different. At least, the board dimensions are exactly the same: 98 × 60 mm.


There’s a small difference on the underside, but it doesn’t seem significant.


The new display is about 0.5 mm thinner.


The overall connection method is almost the same, apart from a few details I’ll cover below.


First, VATN displays need a negative voltage to adjust the contrast, so the board has a voltage converter based on the well-known 7660, which I’ve also reviewed.
There’s a spot for a trimmer nearby. The center pin goes to the contrast adjustment contact, and the other two go to +5 V and -5 V, respectively.


At first, I wanted to install the trimmer and leave the adjustment entirely to the display board, but then I decided not to remove an extra connector pin. Instead, I simply wired the resistor so that one lead went to the standard contrast adjustment pin (pin 3 on the main connector) and the other to the -5 V output.
I adjusted the image, desoldered the trimmer, and found that I needed a fixed 2.6 kΩ resistor. The closest one I had on hand was 2.49 kΩ, so I soldered that in as a permanent solution.


But that wasn’t all.
Now, pay attention: pin 15 on the connector of a standard display is the positive backlight pin. Here, it’s the negative voltage output, so under no circumstances should you simply swap one display for the other—you’ll just burn it out.

I did things a little differently: I soldered only 14 of the 16 pins.
Pin 16 is the backlight negative, while the positive is connected to the +5 V input, so I simply added a jumper between the backlight negative and the display board’s ground.

And here’s the second warning!
At first, I thought I’d just leave pin 16 in place, since on a standard display it’s connected to the backlight negative. I figured it wouldn’t matter where it was connected to ground. And it would have worked fine, if not for one catch.
The instrument’s display board is powered from +5 V, while the backlight is powered from -5 V. So after connecting the new display this way, I happened to notice just 10–20 seconds later that its backlight was getting extremely hot. I checked it with a multimeter and found that the backlight was getting 10 V, not 5 V (+5 V and -5 V).
So with this instrument, I had to connect the backlight negative to the board’s ground.


Let’s swap the display and give it a try.
Well, it’s not OLED, of course, but it’s a long way from an ordinary LCD, too.
One downside is that it’s designed to be viewed from pretty much any angle except from below. From below, it “blinds” you with a flash.

While I was at it, I measured the current draw with the old and new displays.
1. Old: 48 mA total, or 12 mA for the display alone.
2. New: 153 mA total, or 120 mA for the display alone.

So yes, for a battery-powered device, a standard LCD is much more efficient.


Viewed from above, as I’d planned, it’s easy to read, but inactive pixels start to show up.
It’s easy to get rid of them, but then the display looks dim when viewed straight on, so I settled on a compromise.


The viewing angles are obviously much better than those of a standard LCD; the image is readable even when viewed almost parallel to the screen.
But an interesting effect showed up (in the last photo). If you slowly tilt the screen away from you, at some point (at around 30 degrees) the image fades and starts to invert, then with a little more tilt it almost suddenly looks normal again. So the display is great for vertical installation, but can sometimes be annoying in horizontal orientation.


This is how I intend to use it, and I have no complaints about it in this position.


Next, I planned to give it a permanent home, so I bought a Z1 case. At first glance, it looks neat.


But the case is very large—about one and a half times bigger than necessary—and I was hoping for something more compact.
The case's external dimensions are 188 wide, 70 high, and 197 deep. It's that last dimension I'd like to reduce to 140–150. I could always get out the saw :(
Does anyone know of any suitable cases?



And I guess the review wouldn't be complete without showing what I used until recently.
In the middle is an FCL meter from the cqham website, and on the right is a C-ESR meter by Go from the Pro-radio forum.




There is also a discussion about this instrument, but there's much more information on foreign websites. One Pro-radio user even put together a collection of all the information, firmware, boards, drawings, and so on that he could find. Many thanks to him!

For example, one radio amateur abroad posted a calibration procedure for the instrument.
You won't make sense of it without a few drinks.


That's all for now. I plan to do a short follow-up where I'll finally put all this in a case and share my impressions after using it for a while.

I've been using the instrument for a few days now, and so far my impressions are all positive.
Pros:
1. The satisfaction of building it
2. Excellent PCB and soldering quality.
3. High measurement accuracy
4. It has a 7.8 kHz frequency and a wider measurement range at 1 kHz than the E7-22.
5. Four-wire connection
6. Low power consumption.
7. No need for debugging; the manufacturer claims 0.5% accuracy with basic calibration and 0.3% with manual calibration.
8. A fairly large user community, although mostly overseas.
9. Low price.

Cons:
1. In some situations, the readings at 7.8 kHz aren't quite right. I'll keep testing this.

Overall, I can say that the instrument reviewed here is no worse in functionality or accuracy than the more expensive E7-22, and is probably even better. Of course, there is a difference: the E7-22 can be calibrated and certified, while this instrument is for personal use only.


As usual, I'm looking forward to your questions, advice, test suggestions, and comments. I hope you found the review useful.