Tonghui TH2821A LCR Meter

I bought something like this. There are variations.

Ebay

$40.00 with shipping.

High Precision L/C Inductance Capacitance Digital Meter

Specification:

Measurement accuracy: 1% Capacitance Measuring range: 0.01pF~10uF Minimum resolution: 0.01pF Inductance Measuring Range: 0.001uH ~ 100mH Large Inductance Measuring Range: 0.001mH ~ 100H Minimum resolution: 0.001uH Test Frequency: about 500Hz LCD effective display digits: 4 Display Method: 1602 LCD Power Supply: Mini USB interface, 5V interface Size: 81 x 47 x 30 mm ( L*W*H )

I power it up using my scope USB port.

Most of my apps don't require accuracy. For say around 50nH then I set up a generator and a scope.

Cheap! Cheap! Cheap!

The resistance measurements are now OK once the internal battery is charged. This issue is mentioned in the manual. The unit comes with the battery discharged, so you just have to wait until it is charged before starting to play with it.

It gives 4 digits of resolution on a 30k resistor. This is adequate for most ordinary needs.

Altogether, I'm very pleased. It has already identified a bad electrolytic in a circuit where there are several that could be causing the problem. The rest are fine.

Mike

The TH2821A appears to be discontinued, but there may still be some stock left on eBay.

The replacement is the TH2822C, which goes up to 100KHz and offers averaging, 40,000 counts, 16 hours operation on internal battery, TH2822C has optional rechargeable batteries, Standard Mini-USB interface, etc.

Here's the feature list:

• Basic measurement accuracy: 0.25% * Gorgeous dual-color cast shell * Maximum test signal frequency: 100kHz (TH2822C) * 40,000 counts for primary parameter, D/Q resolution 0.0001 * Typical ultra-low consumption : 25mA * Battery capacity: TH2822/TH2822A continuously used for 16 hours * TH2822C rechargeable batteries are optional * Innovatively compatible terminal configuration : 5-terminal test slot and 3-terminal banana jack * Intelligent Auto LCR function * Measurement speed up to 4 meas/sec * fast automatic range switch design * Constant output impedance: 100 Ohm * Percentage display and 4-tolerance comparator: 1%, 5%, 10%, 20% (20% not available for TH2822) * Automatic OPEN/SHORT correction detection * Data Hold, Max/Min/ Average recording * Utility function configuration and current setup recovery after power-off * Standard Mini-USB interface, SCPI compatible * Firmware update through Mini-USB interface * Free FastAccess communication software on our website

The web page is

The TH2822C are vailable on eBay for around $474.70

It looks like the TH2821A is a pretty good deal for the price, if you can still get one:)

Thanks,

Mike

You talked me into it, Mike. The specs look super to me and I've been needing something like it.

Do you get probes with it so you can test components on a populated board?

Thanks for the find.

John S

Which one are you getting - TH2821A or TH2822C?

The SMD probe I mentioned earlier is for the TH2821A. It is available on eBay:

LCR METER-SMD/CLIP, TWEEZERS, TH26029 FOR TONGHUI, Price: US $36.00 Item : 350502463639

It won't work on the TH2822, but they should have something that does work.

For populated boards, of course you have to watch for other components in parallel. But the measuring voltage seems to be too low to turn on silicon junctions, so it should work OK in most situations.

I was afraid of accidentally testing a charged electrolytic, which is how I destroyed my last capacitance meter. So I tried adding a fast silicon diode in parallel with a large electrolytic.

As far as I can tell, it has little or no effect on the reading. But it makes the instrument go nuts when there is no electrolytic capacitor to measure. I will make a little test fixture that adds two fast 3A diodes back-to-back in parallel with the test probes to try to avoid making the same mistake in the future.

I find sometimes the reading on the TH2821A fluctuates a bit. You have to find the correct test frequency for the component you are trying to measure.

I would really like the ability to average the readings, which is provided in the TH2822C. But the price is way more than I am willing to pay.

Once it gets to that level, I seriously start thinking of making my own unit. With the components available to us these days, it should be possible to beat the performance of almost anything on the market.

For example, there are two vector network analyzers available on the web that you can build yourself. Both are in the Yahoo forums, and they seem to be very good instruments. But already there is a much better version of the DDS than the one they are using. That should improve the performance substantially.

There is also a spectrum analyzer you can build yourself. But I happen to have a 8566 so that is not too interesting at the moment.

The only problem is if the 8566 dies and needs some unobtanium part.

That already happened to a HP 8505 network analyzer that I bought new, and was discontinued the week after I paid cash for it. It ran for a number of years, then it died. It would have cost too much to get it repaired, so I just put it in a dumpster and promised myself I would never buy another expensive instrument. Either get it on eBay for pennies, or build it myself.

Ultimately I would rather have my own stuff. It will take much less room on the bench, have usb interface for control, and be much easier to repair or upgrade as time goes on.

Regards,

Mike

About four years ago I purchased a similar unit, the MCP BR2822 LCR

I also bought a $50 LCR that I use for everyday purposes:

I'm waiting for delivery on:

I'm considering the following unit:

Paul

That looks identical to the TH2821A!

Yes, I have a bunch of dmms. Some measure capacitance, but none measure ESR. You need that to weed out the bad electrolytics in eBay boat anchors.

For the function generator, I've pretty much decided to go ahead and make my own using a DDS. You can get microhertz resolution, 0 to 250MHz sine waves, and USB interface. I think you can get frequency sweep and other functions, and add your own limiter for square waves. Put two in the same box for intermodulation testing and mixer development. Add external filters for high purity sine waves for harmonic distortion. Run it off a GPS-stabilized reference for the ultimate in frequency stability.

The main thing is you can't predict what you may want to do, so having the flexibiity to modify your own generator is much better than getting a commercial unit that may not have the fundamental accuracy and stability you need. You might be reluctant to modify a commercial unit, or maybe you don't even get the schematics. But if it's your own, that is no problem.

Thanks,

Mike

TH2821A

Thanks. I'll look into it.

John S

BTW, these are also available for those large, TH electrolytics already on the board:

Item 320702317637

Cheers, John S

Good News - those came with the TH2821A.

I have been trying to figure out how they make them into Kelvin contacts. The contact pads are two sided pcb. I think they may use one side for the exciting signal and the other side for the sense. It appears they do the same with the clips, since there are separate leads going to each side.

I put a thin dab of vaseline on the contacts. That provides a bit of lubrication to minimize wear. It also removes the surface oxides and grime and allows a true metal-to-metal contact. This reduces the contact resistance by a factor of ten and stabilizes it. Old radio engineer's trick from the 1930's

Thanks,

Mike

There are numerous eBay vendors that still offer the TH2821A. The prices vary quite a bit, but it looks like dealexcel-com has the best offer at the moment. They want US $185.65, but the shipping is now free. That's where I got my unit, but the shipping was extra.

If you are interested in getting one, I'd go with them. They already know about the problem with the 220VAC adapter not working in the US, and they shipped a replacement that goes from 100VAC to 220VAC so it should work anywhere.

They send the Kelvin clips with the unit, so you don't have to buy them separately. They also handle the smd probe, so you can combine the entire order in one package.

Thanks,

Mike

You can build a go/no go ESR "meter" that'll find the bad 'lytics for next to nothing. Worth doing, unless you (psychologically) _must_ have a "real" esr meter.

Ed

Sorry, John. I completely missed your question for some reason. Just to confirm, the TH26027 Kelvin test cable probe comes with the TH2821A. It is listed as an accessory on page 4 of the Operator's Manual:

"

and also listed in the datasheet:

"

I checked the continuity from the two-sided contact pad to the test clip. The connections are all individual and separate from each other, so it is a true Kelvin connection all the way to the component.

Pretty good for a $185US instrument!

Just make sure you get the Universal 100-220VAC adapter.

Thanks,

Mike

Well, I already bought another set. But, that's okay.

Maybe I'll send him an email to remind him.

Thanks for the clue.

John S

You talked me into it. I can think of several projects where this would come in handy. You can never tell when these things will disappear, so I got a set also.

Thanks for the pointer!

Mike

I suspect Mike and John are bots.

I will now test.

Hey Mike! You pathetic blob of useless DNA that didn't get aborted fast enough with a Black and Decker router. You're a parasitic garbage making mindless consumer robot that will die unhappy in your own filth. You're a fat ugly unwanted unsuccessful unloved uninteresting cockless guy who lives in a basement with his psychotic crack addicted mother.

I had a tiny amount of respect for you until you pulled this crap out of your ass.

I do wonder which was more offensive. Being accused of being a bot or my test insults.

I hope you die wondering. Soon.