Tonghui TH2821A LCR Meter

Tue Nov 01, 2011 3:58 am   

Here's something that may interest some folks here. I just got my new
Tonghui TH2821A LCR Meter, and I'm starting to become quite impressed.

After some screwups due to a discharged internal battery and not reading
the instructions, it is starting to give some really impressive results.

5 digits resolution on 1000uf caps, 4 digits on iron-core inductor,
miscellaneous resolution on 30k resistors (I haven't figured out how to
measure resistance yet, but it should be very easy:)

Here's the eBay info:

LCR RCL LC Meter TH2821A inductance Capacitance 10kHz

Price : US $164.93
Shipping : $25.00
Item : 320492041898

It can measure 6 basic parameters: inductance L, capacitance C,
resistance R, impedance Z, dissipation factor D and quality factor
Q.

It has measurement accuracy of 0.3% and 4-bin sorting.

Applied complete 5-terminal measurement configuration solves problem
of measurement for equivalent series resistance and capacitor with
small dissipation that other portable LCR meters can't solve. It can
replace general low-frequency LCR meter.

Only portable LCR meter at home
Large LCD display
Measurement frequency up to 10kHz
Basic accuracy: 0.3% with resolution of 0.01%
5-side measurement technology to provide accurate measurement of ESR
and loss
Sweep Clear Function
battery and external power supply power supply
fourth gear sorting

Measurement Signal

Signal Frequency : 100Hz 120Hz 1KHz,10KHz
OutPut Impedance : Dependent on range
Test level : 0.3Vrms

Measurement display range

R : 0.0001Ohm ~ 99.999Ohm
C : 0.01pF ~ 9999uF
L : 0.01uH ~ 9999H
D,Q : 0.0001 ~ 9.9999
?% : -999.99% ~ 999.99%

Comparator

Comparator : 4bins: NG, P1, P2, P3 with beeper alarm

You can also get smd tongs:

LCR METER-SMD/CLIP,TWEEZERS,TH26029 FOR TONGHUI,
US $36.00

Item : 350502463639

The manual is dated November 2005, 1st Edition Rev 1.0.0

"http://www.pinsonne-elektronik.de/media/daten/TH2821A%20Operation%
20Manual.pdf"

Specifications

"http://www.ekt2.com/_files/40%20TONGHUI%20TH2821.pdf"

Datasheet

"http://www.aet.com.pl/Portals/0/katalogi_pdf/maszyny_zalewy_impregnaty/m
ostki_rlc/th2821.pdf"

You can also get the TH2821B, which goes to 1KHz

Item: 350501591362

Price: US $136.00

The only problem so far is they shipped a 220VAC adapter, which does not
work on 120VAC. After some discussions, they shipped a universal 100-
240VAC adapter which should work anywhere. If you want one, be sure and
tell them to ship the universal 100-240VAC adapter. But they are very
nice to deal with and you should have no problems.

For the performance and price, I don't think you can beat this anywhere.
I especially like being able to measure ESR of large electrolytics, since
I have a lot of eBay boat anchors that need some care.

So far the performance is excellent. I'll post if I come across any
surprises.

Regards,

Mike

Tue Nov 01, 2011 5:10 am   

I bought something like this. There are variations.

Ebay
220766760779

$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!

Tue Nov 01, 2011 9:17 pm   

Mike <spam_at_me.not> wrote:


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

Wed Nov 02, 2011 4:06 am   

Mike <spam_at_me.not> wrote:

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

http://www.tonghui.com.cn/en/goods/index/250.html

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

Wed Nov 02, 2011 11:58 pm   

On 11/1/2011 10:06 PM, Mike wrote:

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

Thu Nov 03, 2011 4:21 am   

John S <sophi.2_at_invalid.org> wrote:


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

Thu Nov 03, 2011 7:14 am   

About four years ago I purchased a similar unit, the MCP BR2822 LCR
http://www.mcpsh.com/BR2821%20BR2822.html
I paid $250 for it and except for some problems with the battery, it seemed
OK. But I have not used it much. I think I got it from these guys:
http://www.multimeterwarehouse.com/BR2822.htm,
who now want $349 for it. Amazon has it for $300.
http://www.amazon.com/MCP-BR2822-Professional-10KHz-Digital/product-reviews/B000TYUZM0

I also bought a $50 LCR that I use for everyday purposes:
http://www.amazon.com/Sinometer-MS8222H-Digital-Multimeter-Meter/dp/B000MFIDC0.
It's OK, but sometimes I have to fiddle with the switch and/or the leads to
get continuity.

I'm waiting for delivery on:
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=190450842291&ssPageName=ADME:L:OU:US:1123
and
http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=190452347958&ssPageName=ADME:L:OU:US:1123

I'm considering the following unit:
http://www.ebay.com/itm/320780815383?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
or maybe this:
http://www.ebay.com/itm/330633195250?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Paul

Thu Nov 03, 2011 8:19 am   

"P E Schoen" <paul_at_pstech-inc.com> wrote:


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

Thu Nov 03, 2011 3:52 pm   

On 11/2/2011 10:21 PM, Mike wrote:

TH2821A


Thanks. I'll look into it.

John S

Thu Nov 03, 2011 5:36 pm   

On 11/2/2011 10:21 PM, Mike wrote:

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

Item 320702317637

Cheers,
John S

Thu Nov 03, 2011 6:32 pm   

John S <sophi.2_at_invalid.org> wrote:


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

Thu Nov 03, 2011 6:46 pm   

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

Thu Nov 03, 2011 6:59 pm   

Mike wrote:

<snip>


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

Thu Nov 03, 2011 9:20 pm   

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:

"http://www.aidetek.com/New_products_info/Datasheet/tonghui/2821A.pdf"

and also listed in the datasheet:

"http://www.aidetek.com/New_products_info/Datasheet/tonghui/2821data%
20sheet.pdf"

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

Thu Nov 03, 2011 9:32 pm   

On 11/3/2011 3:20 PM, Mike wrote:


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