Measuring small capacitance with KS34465A & TH2830 - Page 1
Forum section: electronics / testgear

author: mawyatt
author_rank: Super Contributor
timestamp: September 05, 2021, 05:17:25 pm
content: When still employed a few years back we had all the proper instruments for measuring components and such, so getting timely decent measurement results wasn't difficult since someone else did the measurementsNow retired and having to do everything myself, but still "working" on a project, I need to make these measurements.This ongoing project requires some components that are tightly matched and with tight ratios. Getting accurate matched components before COVID was difficult, now next to impossible without very deep pockets, so the decision was made to select matched components from a large batch of lesser accurate components, which provided the perfect "excuse" to sacrifice some project funds for a proper LRC meterAfter considerable research we selected the Tonghui TH2830 LRC meter, TH26011CS Kelvin leads & TH26009B precision tweezers which has all the features for accurately measuring & binning components, but still working the learning curve on this new instrument. Out of curiosity we decided to check the capacitance measurement capability of the KS34465A & SDM3065X using some leaded film type capacitors covering the range of 1nF to 1uF, the DMMs compared well to the LRC meter. As expected electrolytic, and higher capacitance ceramic capacitors (X5R and X7R types) didn't agree well due to the different measurement techniques (for another discussion).Then we turned to the lower value capacitors with the COG dielectrics which are SMD and require tweezers. We didn't have any proper tweezers for the KS and SDM DMMs except for the cheap two lead tweezers shown here.https://www.aliexpress.com/item/1005002619578037.html?spm=a2g0s.9042311.0.0.523e4c4dUHGAQcThese tweezers don't shield the leads to the probe tips like the 4 wire TH26009B and thus subject to external influences and have almost 50pF distributed capacitance, so how is one supposed to get decent measurements at lower capacitancesTurns out the KS34465A has a few "features" that can help, first is the handy "null" feature to null out resistance in the test leads, this also works on capacitance!! Second is the MX+B "scaling" function to add extra resolution, also works on capacitance!!We were able to get reasonable readings in the 10s of pF utilizing these cheap tweezers employing the features above and some careful technique. If the tweezers are gripped like you intend to use them and the tips carefully positioned opened about the same opening as the intended SMD chip, then the null invoked, the residual probe (and hand) capacitance can be effectively removed from the measurement.This technique can work in a pinch when you don't have a proper LRC meter & fixture handy, but need to get a reasonable estimate of a small value chip capacitor, or match chips caps.We've ordered another set of cheap tweezers, that may prove a little better. These have BNC type connectors which will need to be replaced with banana connectors for the DMM use.https://www.aliexpress.com/item/1005001722184966.html?spm=a2g0s.9042311.0.0.10554c4dVoFphYAnyway, hope this helps when in a measurement pinch.Best,

author: nctnico
author_rank: Super Contributor
timestamp: September 05, 2021, 06:23:10 pm
content: If you need to do a lot of measurements on SMD components then do yourself a favour and get a proper SMD test fixture for the LCR meter. These aren't insanely expensive (the one from GW Instek with part number LCR-09 is around US $200) and save a lot of hassle.

author: mawyatt
author_rank: Super Contributor
timestamp: September 05, 2021, 06:56:21 pm
content: Agree a proper SMD fixture is in order after we get more familiar with this instrument.Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 14, 2021, 09:59:51 am
content: Tonghui TH2830 should be able to tell capacity ? AND series resistance at the SAME time ?and in inductor mode ?L and R at the same time ?

author: 2N3055
author_rank: Super Contributor
timestamp: October 14, 2021, 11:41:21 am
content: Quote from: oz2cpu on October 14, 2021, 09:59:51 amYes it can and much more... it is very capable instrument.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 14, 2021, 12:17:31 pm
content: thanks, i go look on some more detailed measurement demo videosif anyone know some , please add links.anyone tried to place it on top of siglent equipment ?looks like same size ? will they fit nice and stable on top of each other ?

author: mawyatt
author_rank: Super Contributor
timestamp: October 14, 2021, 05:12:03 pm
content: The TH2830 can measure R, L and C in both parallel and series equivalents with D and Q. Also can measure Z, Y, R+-jX and G+-jB.Did some comparison R measurements with the KS34465A and very good agreement. Comes with full calibration sheet showing calibration results.Supplied with a very nice Kelvin TH26011CS probes and TH26048A Test Fixture for leaded components. Also consider getting the TH26009B Kelvin Tweezers, these are really quite good for measuring SMD devices.CAUTION!!!!!Do not purchase from any AliExpress site, none are authorized resellers of any Tonghui Products. OEM Tonghui will not honor the factory warranty if you purchase from an unauthorized site.We purchased from BEICH Official Store on AliExpress and an issue with a 100 ohm range came up (likely a firmware issue, since it's revision 1.0). We contacted the OEM only to find out about the unauthorized AliExpress seller BEICH, and that the seller must provide any warranty support.So now we are stuck waiting to see if Tonghui will provide some help, maybe with a firmware update. Tonghui understands our situation and may decide to help out, so purchase from only authorized sources.We did open up the case to take a look and see if anything was loose. The internal construction is superb, and they are using a nifty toroidal power transformer for the mains power...first class indeed!!Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 14, 2021, 06:03:48 pm
content: thanks as always premium feedback from you :-)please tell me : what authorized dealer you recommend I goto ?here is Europe there is a problem with VAT and shipment cost, so I prefer a contry in the EU if possible.and please try to put it on top of your siglent equipment ? signal generators, multimeters, loads, power supply or similar with rubber edges.and the other way too, fit ? stable ? or looks really bad ?can I take off the handles ? so more rows can be placed closer ?I am a little bit crasy when it come to my lab design,and posibilities to place equipment where it makes most sense in easy access

author: 2N3055
author_rank: Super Contributor
timestamp: October 14, 2021, 06:27:08 pm
content: Quote from: oz2cpu on October 14, 2021, 06:03:48 pmBatterfly from Italy sells them.https://www.batterfly.com/shop/en/testandmeasurement/test-componeti/tonghui-th2830-lcr-meter

author: mawyatt
author_rank: Super Contributor
timestamp: October 14, 2021, 06:30:31 pm
content: I'll send a PM to Tonghui contact, if I get OK from them.2N3055 beat me to itHere's how the TH2830 sits on a HP34401A. The handles seem to just pop out.Best,

author: nctnico
author_rank: Super Contributor
timestamp: October 14, 2021, 06:55:56 pm
content: Quote from: 2N3055 on October 14, 2021, 06:27:08 pmThat is a good suggestion there. I have been eyeballing the Tonghui meters as well for a long time but never found a good source for them until now

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 14, 2021, 09:21:20 pm
content: does not count mike with agilent equipment :-)--See the attached test fixtures, what would you get ?both ?I kind of miss an SMD version ?? does it exist ?as far as i understand, there is nothing inside the test fixture ?only a mecanical stable solition, each side of the spring loaded contacts, connect to the centre, of each of the 4 bncright ?just like the kelvin test leads.

author: 2N3055
author_rank: Super Contributor
timestamp: October 14, 2021, 10:26:57 pm
content: Quote from: oz2cpu on October 14, 2021, 09:21:20 pmI think this one from GW-Instek would fit...https://www.batterfly.com/shop/en/gwinstek-lcr-15

author: TimFox
author_rank: Super Contributor
timestamp: October 14, 2021, 10:40:24 pm
content: I used this fixture with impedance analyzers that used a 50-ohm reflection bridge (as shown in the photograph):https://www.coilcraft.com/en-us/other/smd-a/Both the Coilcraft and the GW-Instek unit show the mechanical requirements to connect to a SMT part, but the GW-Instek is appropriate to 4-wire Kelvin connections.The SMD-B fixture is designed for 4-wire BNC connections.https://www.coilcraft.com/getmedia/33893caa-0cca-48fe-b203-410cc6f83c41/smd-b.pdf(Their website is a bit hard to navigate for these fixtures.)

author: nctnico
author_rank: Super Contributor
timestamp: October 14, 2021, 11:24:39 pm
content: Quote from: 2N3055 on October 14, 2021, 10:26:57 pmI have this one and it is very nice to use for (small) SMT parts. It is being sold at many stores under various brands. The one I have is branded RS-Pro (bought from RS because I needed it quickly).Kelvin clips are almost mandatory to have. The slotted adapter seems not very useful to me; connecting the Kelvin leads is easier.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 15, 2021, 09:55:54 am
content: >I think this one from GW-Instek would fit...>https://www.batterfly.com/shop/en/gwinstek-lcr-15nctnico ?so this means it is CONFIRMED to fit ?the 4 bnc mounts distance and all, is an approved industry standard ?or just pure luck if fit or not ?

author: mawyatt
author_rank: Super Contributor
timestamp: October 15, 2021, 08:05:20 pm
content: Update, Tonghui provided a updated firmware and now the issue with the 100 ohms is correctedSo the OEM Tonghui stepped up and helped us out, so hat's off to themRegarding SMD Kelvin measurements, haven't found anything as good as the TH26009B tweezers. These have a guard shield up to the probe tips, and this allows very good low capacitance measurements by proper calibration of the shorted tweezer and open tweezer with the supplied special cal fixture. You really have to try these out to see how smooth and easy they operate!!The unit comes with the Kelvin Clips TH26011CS and the TH26048A Test Fixture for leaded components, also a calibration short is provided for the TH26048A. We found this TH26048A Test Fixture quite useful when testing leaded components for sorting, much quicker than using the Kelvin Clips.The advantage of the fixtures with the fixed BNC connections is repeatability, and I prefer them over the individual BNC cables. They are just mechanical interfaces for the interconnects, cable interface and instrument BNC interface, but well built and sturdy fixtures.Now that our new DMM6500 just arrived, we have some precision comparisons to make between the TH2830, KS34465A and new DMM6500. Also have a few different types of Kelvin Clips & Tweezers to compare when time permits.Anyway, this Tonghui TH2830 seem like a very good value and accurate LCR Meter. If anyone decides to give one a try, please remove the cover, there's no warranty seal to beakand take a look at the unique mains toroid transformerBest,

author: nctnico
author_rank: Super Contributor
timestamp: October 15, 2021, 08:57:40 pm
content: Quote from: oz2cpu on October 15, 2021, 09:55:54 amI used it on a GW Instek LCR meter but I do believe the distance between the BNC connectors of LCR meters is an (unofficial?) industry standard.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 15, 2021, 09:04:54 pm
content: thanks a lot mike, i am SO close to push the purchase button,but cant find any video material showing real usage,any takers ?I like to see a few caps with value and ESR displayed at the same time,how to change test frequency, for the ESR to make sense on small versus large value.and the same performed on a few inductors,please also try to add a series or parallel resistor,and see if it pick the right results,I assume it is able to measure both series, and parallel resistance on caps ?one will be very low, and the other will be very high of course

author: mawyatt
author_rank: Super Contributor
timestamp: October 16, 2021, 02:19:07 am
content: No video but a very quick set of measurements, used different Kelvin clips for each Meter.Some Vishay ResistorsTH2830 DMM6500 (rec'd new 10/14/21) KS34465A120.029 119.993 119.9933.00235K 3.00299K 3.00298K13.0061K 13.0072K 13.0073K75.0473K 75.0514K 75.0523K2.00229 2.0024 2.0003 (not Vishay)0.12056 0.12056 0.1197 (not Vishay)Film Caps ESR @ 1KHz1.00876uF (0.0179) 1.0087uF 1.0089uF0.47122uF (1.346) 0.4791uF 0.4792uF102.287nF 102.65nF 102.66nF2.25264nF 2.282nF 2.257nFElectrolytic HF Low ESR type {Single C measured at 1,10K, LR measured at 100K since past SRF)423.195uF (0.06748) @ 1K OverRange (DMM650) 425.38uF626.246uF (0.06225) @10K152.046nH (0.07656) @100K (measure cap with L & R series mode)C with ESR and ESL, so resonate frequency of C ~20KHz agrees with LCR meter. Interesting that we could get an equivalent RLC series large electrolytic cap model with just two measurements, series C & R and series L & R. The ESL and series resonate frequency seem reasonable since the cap long leads were probed at the ends.C model:C ESR ESL*-----] (-----^^^^----~~~~~----*Series Resonate Frequency ~ {1/((LC)^1/2)}/(2*Pi)Inductor ESR226.175uH (0.27928) @ 1K225.473uH (0.37788) @ 10K220.041uH (4.36245) @ 100KL with ESRAnyway, hope this helps with some very quick, crude measurements with the TH2830.Best,BTW the case & rubberized moldings on this TH2830 are also superb, equal or actually better IMO than any of the Siglent, HP, Agilent, Keysight and Keithley gear we have. This device just looks like it belongs in a high end lab.

author: mawyatt
author_rank: Super Contributor
timestamp: October 16, 2021, 05:58:20 pm
content: Here's a cheap SMD device including video, that might fit the Tonghui, don't have any idea if it will work, nor how good.https://www.aliexpress.com/item/1005002561014252.html?spm=a2g0o.detail.1000014.7.7fdd4e8eKzjN7D&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.33416.213724.0&scm_id=1007.33416.213724.0&scm-url=1007.33416.213724.0&pvid=8fbaed83-db51-4b3f-8479-fac00af499cb&_t=gps-id:pcDetailBottomMoreOtherSeller,scm-url:1007.33416.213724.0,pvid:8fbaed83-db51-4b3f-8479-fac00af499cb,tpp_buckets:668%232846%238113%231998&&pdp_ext_f=%7B%22sceneId%22:%2223416%22,%22sku_id%22:%2212000021152791964%22%7DHere's the OEM SMD fixture TH26008A.https://www.tonghui.com.cn/en/product_144.htmlBest,

author: Kean
author_rank: Unknown
timestamp: October 17, 2021, 11:43:02 am
content: I have a TH26008A which I use on my CKT5000 LCR Meter. No problems with compatibility.Let me know if you want any measurements (physical or electrical).

author: mawyatt
author_rank: Super Contributor
timestamp: October 17, 2021, 12:34:26 pm
content: Quote from: Kean on October 17, 2021, 11:43:02 amHow does this work for measuring small value capacitors (1~10pF) and inductors (10~100nH, including ferrite bead types)? With small physical size 0603 and 0805 types, do you get good repeatability?Thanks for the help.Best,

author: Kean
author_rank: Unknown
timestamp: October 18, 2021, 07:07:41 am
content: Quote from: mawyatt on October 17, 2021, 12:34:26 pmThe CKT5000 gives pF and uH measurements with 5 decimal places. I performed open and short calibrations on the TH26008A SMD fixture after a 1 hour warmup, then grabbed a few parts: 1pF (C0603C109C5GACTM), 6pF (generic), 39nH (L0603C39NJRMST), and 100nH (L0603CR10JRMST). All 0603 size.With the capacitors I could get stable and repeatable measurements in pF to 3 decimal places (+/-1 LSB) - so 1.003-1.004PF and 5.876-5.877pF (measured at 1kHz). I ran several measurements and sweeps from 1kHz to 1MHz and the values ranged from 0.996-1.006pF and 5.865-5.877pF. I also ran a sweep up to 5MHz, and I could see the capacitance drop off above 1MHz. The SMD fixture is supposedly rated to 120MHz....With the chip inductors, readings were a bit unstable at low frequencies but quite stable and repeatable at 100kHz and above. At 1MHz I measured 0.045uH 327mohm and 0.121uH 514mohm.I did some quick comparison measurements with my Tonghui TH2822C and tweezers, and readings were consistently higher and not as repeatable. Typical readings were: 1.034pF, 5.954pF, 0.053uH, 0.131uH.I swapped parts in an out of the SMD fixture several times, switching measurement modes and frequency. When using the fixture and returning to original settings the readings were often spot on, or over the course of a couple of hours still within 0.010pF of the original measurements.Smaller than 0603 parts is possible with the fixture (I've done 0402), but it becomes very fiddly. I actually lost the 1pF cap near the end of these tests, but that was while using the TH2822C tweezers.I didn't originally bother trying the tweezers that came with the CKT5000 because I knew it would probably lead to parts flying...but I just ran a quick measurement of the 6pF cap at 100kHz with the tweezers and reading was 5.56-5.60pF. So definitely less stable and presumably less accurate. I did re-do the open/short cal after changing to the tweezers. The CKT supplied tweezers are nicely built, and feel quite solid compared to the ones that came with the TH2822C.Hope this helps. This is way overkill for most of the stuff I do.ETA: I forgot to mention, after cal the fixture read 20mohm when shorted.Edit 2: Oops, I've got a TH2822C not a TH2822A

author: Kean
author_rank: Unknown
timestamp: October 18, 2021, 10:21:10 am
content: Attached is photos showing the workings and guts of the TH26008A SMD test fixture. It uses PTFE parts for the holder and probe isolation.You can see each pair of red wires go into some sliding PTFE cylinders, and they then connect into the gold plated probes.I'm not sure I want to open it up any more, but I am quite curious how the wires are terminated.I've had some problems with getting good connection on older parts that are probably a bit oxidised, but otherwise I've found it works really well.

author: mawyatt
author_rank: Super Contributor
timestamp: October 18, 2021, 01:12:03 pm
content: Thanks KeanThe measurements & fixture look really good. The Tonghui tweezers we have are the TH26009B and claim good to 15MHz, they work well and produce repeatable results, but not like the TH26008A fixture you have. Those results are excellent!!Didn't know about the CKT5000 or CKT in general. How do you like the instrument and how is the build quality/design?Thanks again for the measurements and images.Best,

author: Kean
author_rank: Unknown
timestamp: October 18, 2021, 02:57:33 pm
content: I believe CKT may be related to, or copied from Tonghui. There are a lot of similarities. Just look at the attached screen shot and compare to yours. It is so similar with pretty much the exact same text, menu options, etc - just rearranged and more spread out for the larger screen. In fact that screen shot doesn't show the lighter blue band behind the readings but there is one just like on the Tonghui screen.Regarding CKT, I hadn't heard of them before buying this unit a couple of years back. I was buying some Tonhgui gear (a TH3321 AC Power Meter and a TH6412 PSU) from an AliExpress seller I often deal with, and was thinking of also buying either the TH2830 like you have, a TH2827C, or the Applent AT3818 . The bundle was starting to get too expensive with shipping, so the seller then suggested the CKT1000 LCR Meter as a cheaper option. I looked at them and found out they could supply a CKT5000 with good specs for my needs and cheaper than a TH2827C.The CKT LCR came with fixtures just like the Tonghui ones including the tweezers (an extra $100) which look just like the TH28009B ones in your photo from the first post. I had to buy the Tonghui SMT fixture though ($150) as there wasn't a CKT equivalent available. The CKT5000 is bigger and boxier that then Tonghui units (bigger even than some PCs), but that doesn't bother me. It has a nice big screen, and wasn't too difficult to operate without reading the manual. The manual isn't too bad, it is in readable English and gives some useful detail, but it is not as good as Tonghui manuals.Now, would I buy CKT gear again... probably not if I could afford a Tonghui, Keysight, or Keithley alternative. Maybe if I'm on a budget and willing to live with some rough edges. It seems to work fine, saved me money, and I've not had any specific issues with it. I just feel less trusting of it than any of my other gear, but that could probably be fixed by doing a detailed side-by-side comparison with another brand. It certainly seems better than my handheld LCR meters.The companies themselves are apparently just a few blocks (1.1km) apart in Xinbei District, Changzhou. Not uncommon, and it means they probably shared some staff. Tonghui have been around longer though. CKT seem to do more in the temperature measuring/calibration market.TH = Changzhou Tonghui Electronic Co.,LtdCKT = Changzhou Chuangkai Electronic Co. LtdOh, and CKT website lists a bunch of Tonghui and Applent/Anbai products including the TH2830 and AT3818. So that is very confusing...www.cz-ckt.com/pd.jsp?id=239www.cz-ckt.com/pd.jsp?id=273If you have a contact at Tonghui you've been dealing with then maybe you could ask about CKT? Side note: I have some Applent AT8612 DC Loads which I'm quite happy with. Applent (aka Anbai for Chinese market) are yet another lesser known test equipment manufacturer. Their temperature data loggers seem pretty good, and they seem to have gone to some effort to design their own trade dress and UI although commonalities are still seen like e.g. brackets around titles like "<SETUP>".

author: Kean
author_rank: Unknown
timestamp: October 18, 2021, 03:01:04 pm
content: Quote from: mawyatt on October 18, 2021, 01:12:03 pmAnd you just reminded me that I bought the CKT5000 over two years ago and still haven't looked inside. That is a task for another time...

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 22, 2021, 09:57:16 pm
content: wow fixture TH26008A looks nicethanks a lot for the detailed pictures.but how can it be 216 euro + 25% tax = 270 eurothat is a bit intense ?they could be nice to make a bundte prise, if purchased together with the instrument

author: mawyatt
author_rank: Super Contributor
timestamp: October 22, 2021, 10:08:36 pm
content: There's a similar device, but not sure how good this "copy" is. For ~$70, maybe worth a try???https://www.aliexpress.com/item/1005002561014252.html?spm=a2g0o.cart.0.0.40203c000eoQtn&mp=1Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 22, 2021, 11:14:12 pm
content: wow mike, it looks identical to me :-)from same factory ?

author: Kean
author_rank: Unknown
timestamp: October 22, 2021, 11:51:46 pm
content: There wouldn't be a lot of demand for these to cover the original design costs, but the design work has been paid for so not surprising there are cheaper copies.The plastic parts look like they might not be PTFE. Apart from labour costs there is a good chance they've reduced parts costs.

author: mawyatt
author_rank: Super Contributor
timestamp: October 23, 2021, 12:58:55 am
content: These are not the same as the Tonghui OEM version. If you carefully examine the images from AliExpress you can see the differences. Also the center piece is a yellowish and thicker plastic than the OEM, and as Kean indicates likely not Teflon. Suspect the BNCs are not the quality ones I would expect from Tonghui, and the OEM is rated to 120MHz, but there's no mention for the frequency range for the copy.Does this mean the copy isn't any good?? Don't know, but might be perfectly fine for use with the TH2830 which only goes to 100KHz, but doubt it's made as well as what I've seen from Tonghui which is first class.Best,

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 23, 2021, 09:09:35 am
content: Five or six years ago I bought a fixture on eBay for my LCR meter:It's made by Meiruike Electronics:http://www.szmeiruike.com/en/product.asp?page=4&lv1=578&=You can see this fixture (they spell it "fixtue") in that image. Note the model number: RK26001.Compare to this fixture:https://www.tonghui.com.cn/en/product_131.htmlwith model number TH26001A year or so later I bought an SMD fixture also made by Meiruike:The model number is: RK26008. It's not silk-screened on the metal but it's a stick on label. It must be an early unit.Compare to this fixture:https://www.tonghui.com.cn/en/product_143.htmlwith model number TH26008.Here's a picture of the insides of my RK26008:It looks to me like Tonghui may re-badging fixtures made by Meiruike.The TH26008/RK26008 is not usable at 120 MHz with the kind of wiring they used to connect to the gold plated contact pins. I found a more detailed list of specs that said the maximum usable frequency is 200 kHz; I can believe that.There are a large number of SMD fixtures for sale here:https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1312&_nkw=smd+test+fixture&_sacat=181939A close examination of the construction details persuades me that they are all the same as the Meiruike/Tonghui unit.On my unit the plastic wedge that holds the DUT doesn't appear to be PTFE; I think it's Delrin which would be more abrasion resistant.

author: mawyatt
author_rank: Super Contributor
timestamp: October 23, 2021, 01:33:58 pm
content: Quote from: The Electrician on October 23, 2021, 09:09:35 amThis doesn't appear to be exactly like the OEM TH26008 images Kean posted. Note the two center BNC connectors don't have the outside shell and plastic "arms", also note that the OEM using some insulation over the red wires to BNC contacts and the end brackets are not the same (OEM uses swedged threaded inserts).What type LCR meter are you using, and how is the repeatability with this fixture?Agree 120MHz seems like a stretch as claimed by the OEM version, maybe the fixture calibration removes the fixture effects sufficient to allow operation at 120MHz?Anyway, thanks for the information and images.Best,

author: rf-messkopf
author_rank: Regular Contributor
timestamp: October 23, 2021, 05:30:52 pm
content: Quote from: mawyatt on October 22, 2021, 10:08:36 pmInteresting. Rohde & Schwarz sells similar looking test fixtures for use with the Hameg/R&S HM8118 LCR bridge. I opened mine up and it looks exactly identical on the inside. I wonder what the OEM is, maybe Tonghui. Of course a name brand manufacturer will rip you off when it comes to accessories, R&S charge almost 500 Euros for one when ordered separately:https://www.distrelec.de/en/smd-component-test-fixture-hm8118-series-lcr-bridge-rohde-schwarz-hz188/p/11085068.I tried an 1.2 pF 0805 capacitor at various frequencies between 100 Hz and 200 kHz, and the test fixture gives me nice and stable capacitance readings across that frequency range. The LCR bridge was set to 1 V measuring voltage, open and short compensation (at each frequency) was used, and it was set to guard drive mode (BNC outer conductors are driven with a copy of the test signal). However, the dissipation factor reading (parallel mode) is garbage for such a small capacity.

author: TimFox
author_rank: Super Contributor
timestamp: October 23, 2021, 05:38:17 pm
content: The 1.2 pF is obviously C0G/NP0 with a very highQ, so the loss at 1 kHz is not measurable (as you said), compared to the low susceptance. At higher frequencies, where the parallel susceptance of the capacitor is higher, it might be measurable.As a general rule-of-thumb, I have found thatQ> 1000 (orD< 0.001) requires very careful measurement on reasonable equipment.

author: mawyatt
author_rank: Super Contributor
timestamp: October 23, 2021, 05:51:01 pm
content: Quote from: rf-messkopf on October 23, 2021, 05:30:52 pmThis does look like the Tonghui except for the middle 2 BNCs without the shell. Would not be surprised if this is an OEM Tonghui rebranded as R&S, the construction details look the same. Also showing excellent repeatability as did Kean's measurements.Edit: Just noticed that the measurements were at different frequencies, did you evaluate the repeatability by making the same measurement on the same DUT at different times?Thanks for the response and images.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: October 23, 2021, 05:56:05 pm
content: Quote from: rf-messkopf on October 23, 2021, 05:30:52 pmHow was the implemented WRT the guard drive? It seems the BNC outer areas are all tied together and common with the fixture case?Best,

author: rf-messkopf
author_rank: Regular Contributor
timestamp: October 23, 2021, 06:26:01 pm
content: Quote from: mawyatt on October 23, 2021, 05:56:05 pmYou are right, with this fixture, guard drive is ineffective because the outer connectors are shorted together. I wasn't thinking. But it works with Kelvin clamps.

author: rf-messkopf
author_rank: Regular Contributor
timestamp: October 23, 2021, 06:31:20 pm
content: Quote from: mawyatt on October 23, 2021, 05:51:01 pmYou mean by re-inserting the same DUT into the fixture? Give me a minute, I will try that.Edit: Here you go, all measured at 1 kHz, the same C0G cap as above was re-inserted into the fixture ten times, then one measurement (with trigger set to man) was taken:1.3251 pF1.3261 pF1.3258 pF1.3268 pF1.3266 pF1.3277 pF1.3269 pF1.3258 pF1.3265 pF1.3267 pF

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 23, 2021, 06:40:40 pm
content: Quote from: mawyatt on October 23, 2021, 01:33:58 pmI think these are the sort of minor manufacturing changes one might expect after 6 years. Tonghui offers 3 versions of this fixture:https://www.tonghui.com.cn/en/index.php?module=Product&action=ListView&search=th26008Note that two of them have the middle two arms and one doesn't. This insulation over the red wires is different in my earlier unit but it is there. Only one of the end brackets is swaged in Kean's picture (the one on the right; why only one?); the other uses machine screws and nuts. Etc.These differences are trivial and I am persuaded by all the similarities that Meiruike is making at least two of Tonghui's fixtures.Quote from: mawyatt on October 23, 2021, 01:33:58 pmMy favorite meter is the Hioki IM3570:https://hiokiusa.com/product/impedance-analyzer-im3570/It is a high performing instrument, both an LCR meter and impedance analyzer. It can show 7 digit measurements which are far beyond the accuracy spec (.08%), but all those extra digits can be used to match components beyond the accuracy spec.Fixture calibration can't fix those relatively long and arbitrarily oriented red wires for 120 MHz operation. For high frequency measurement of SMD devices one needs something like this:https://hiokiusa.com/?s=IM9201Using the Meiruike fixture (not the SMD fixture), I can get 4 digit repeatability with a 390 pF NPO, but with a 5 pF NPO I can only get 2 stable digits since this is at the limits of the instruments capability. Those two stable digits are, however, repeatable.Edit: The foregoing measurements were made at 1 kHz. At 100 kHz, I get 3 stable digits for the 5 pF, and at 1 MHz I get 4 stable digits. At 1 kHz the measurements of Rs, D, and Q consist of bouncing digits--they are at the noise floor of the instrument.I, (like you, I think) am retired, and some of my instruments and components are in storage and not readily accessible. I found a kit of leaded disc ceramics which is where the 4 pF and 390 pF came from. In a few days I can access a bunch of SMD ceramics.

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 23, 2021, 07:02:19 pm
content: Quote from: rf-messkopf on October 23, 2021, 06:31:20 pmIf you insert the capacitor into the fixture and watch the measurement, are the last two digits bouncing around? Does the instrument have an averaging mode? A measurement of a 1 pF capacitor at 1 kHz is near the limit of what a modern instrument can do.You'll notice in the image of my Hioki's measurement of a 5 pF capacitor that just to the right of the measured quantities, there are two values labeled Vac and Iac. These are the actual voltage applied to the DUT and the current through the DUT. The value of Iac shown there (with 1 volt applied) is 31.85 nA (for a 1 pF capacitor this current would be about 7 nA). That current must measured to calculate the capacitance. As one can imagine, that small current is nearly buried in the front end noise of the instrument, and it's the difficulty of measuring it that leads to bouncing digits in the display. Those bouncing digits are just a measurement of the instrument front end noise.

author: mawyatt
author_rank: Super Contributor
timestamp: October 23, 2021, 07:27:25 pm
content: Those Hioki instruments are some of the best available I believe, nice!!Don't know if the Meiruike is the OEM for Tonghui, or a clone of such, and agree it could be an early version and that's why the slight differences.If the internal fixture wires don't move around and you can get a good fixture cal and null, you might be able to do some useful comparisons/relative measurement at higher frequencies, but not anywhere near 120MHz I suspect.Yes, I'm retired but also consulting and formed a company earlier this year Wyatt Labs LLC to support such.Best,

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 23, 2021, 07:28:25 pm
content: As I said earlier my stock of SMD parts are in storage, but the two caps I mentioned came from a kit of the sort vendors give when you are still working as an EE.I measured every one of the caps in the upper left hand compartment thinking that I may have put some smaller caps in there, and sure enough I found a 1 pF (leaded of course) cap. Here's what it looks like in the Meiruike fixture:Here's what the Hioki says about it:The leading digit "1" really doesn't count as a significant digit (numerical analysis course taught me that), and the last 3 digits are bouncing around, so I'm getting 2 significant digits. Notice what the measured current in the cap is--7 nA!!All, that's all, of the digits in the measured Rs, D, and Q are pure noise, bouncing around like crazy.If I pull the cap out of the fixture about 5 mm, the value increases to 1.03 pF.But consider the noise problem with a measurement at 1 kHz. You can't measure to better than 2 digits, so you can't expect better repeatability than that.If I turn on averaging, and average 100 readings, I can get another stable digit.Edit: Or, of course, make the measurement at 10 kHz or 100 kHz.

author: nctnico
author_rank: Super Contributor
timestamp: October 23, 2021, 07:36:14 pm
content: Interesting that it is branded 'Rek'. Recently I bought a few small switching PSUs with the same 'Rek' logo. Pictures here:https://www.eevblog.com/forum/testgear/rek-kps6003-and-gophert-nps-1602-60v-3a-psu-hack-review/msg3336994/Hmm, reading my own thread back I noticed I posted a link to Rek / Meiruike:https://en.chinarek.com/index.html

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 23, 2021, 07:44:01 pm
content: Quote from: mawyatt on October 23, 2021, 07:27:25 pmDid you look at all those fixtures at:https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1312&_nkw=smd+test+fixture&_sacat=181939Look at the pictures--they are all essentially identical to the Meiruike/Tonghui fixture, and for a little over $100!! I think they are all posted by the same guy (or a few guys) with access to an Asian source.

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 23, 2021, 07:48:31 pm
content: Quote from: nctnico on October 23, 2021, 07:36:14 pmI have persuaded myself that Rek/Meiruike is making those fixtures.The spacing of the BNC connectors seems to fit almost every bench LCR meter out there. It even fit the (very expensive) Agilent 4294 analyzer we had in the lab. And for frequencies up to, say, 200 kHz they work fine.

author: gamalot
author_rank: Super Contributor
timestamp: October 23, 2021, 07:54:10 pm
content: It seems that my NF fixture has an unreasonable design. You can even see that the Kelvin 4 wires have been merged into two wires inside the box.

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 23, 2021, 08:04:14 pm
content: I wonder if the reason the sellers of clones of these fixtures claim 120 MHz performance is because they know that Keysight sells a lot of impedance measuring instruments like this:https://www.keysight.com/us/en/product/E4990A/impedance-analyzer-20-hz-10-20-30-50-120-mhz.htmland claiming 120 MHz performance seems like the thing to do!!

author: rf-messkopf
author_rank: Regular Contributor
timestamp: October 23, 2021, 08:15:58 pm
content: Quote from: The Electrician on October 23, 2021, 07:02:19 pmThe fourth digit is definitely bouncing, the third digit varies around 5 to 7, so I'd say I get two and a half significant decimals out of this measurement.The instrument was set to slow mode (1.5 readings per second). I guess the ADC will run faster, and it will do some averaging in that mode. But you can also set the meter up to do a user selectable number of averages.The resolution of the Iac display of the HM8118 is limited to 1 nA, but I guess it will use more digits internally. As you can see from the picture posted above, the DUT voltage and current at 1 kHz are displayed as 1.105 V and 9 nA with the 1.2 pF cap.

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 23, 2021, 09:36:31 pm
content: Quote from: rf-messkopf on October 23, 2021, 08:15:58 pmHow many good digits are you getting at higher frequencies?

author: rf-messkopf
author_rank: Regular Contributor
timestamp: October 23, 2021, 10:08:13 pm
content: Quote from: The Electrician on October 23, 2021, 09:36:31 pmJust tried it at 100 kHz. I had switched off the meter in the meantime and it has only been warming up for 10 minutes or so. A couple of minutes after inserting the cap all four decimals are stable, with the last digit fluctuating by +/- 1 or 2. When I breathe on the test fixture the capacity jumps up by more than 0.04 pF and then slowly drifts down again. This measurement needs a controlled environment.DUT voltage and current are 167.7 mV and 139 nA.

author: mawyatt
author_rank: Super Contributor
timestamp: October 23, 2021, 11:10:48 pm
content: Quote from: The Electrician on October 23, 2021, 08:04:14 pmTonghui is claiming 120MHz!!http://www.tonghui.com.cn/en/product_144.htmlBest,

author: Kean
author_rank: Unknown
timestamp: October 24, 2021, 09:05:21 am
content: Great to see internal photos of a few other variants to see howmuchlittle they differ. It is weird that Tonghui sell 3 different models, but there are slight mechanical differences that are possibly needed in certain use cases.Quote from: The Electrician on October 23, 2021, 06:40:40 pmIt is interesting to note that the same mix of swaged and normal nuts exist on the R&S/Hameg one posted by rf-messkopf. I was thinking it must be something to do with assembly process if they have both styles of brackets at hand. And yes, it is because the newer (A/B) versions use welded studs on that side, so nuts are necessary.Quote from: mawyatt on October 23, 2021, 11:10:48 pmIt could be interesting to hook it up to a VNA and how it performs at higher frequencies. I'll never actually use it above 5MHz so I don't think I'll bother.

author: rf-messkopf
author_rank: Regular Contributor
timestamp: October 24, 2021, 07:18:26 pm
content: Quote from: mawyatt on October 23, 2021, 11:10:48 pmI tried that real quick with a VNA, just for the fun of it.There are various options to hook up the test fixture to a VNA: grounding one end of the fixture and connecting the other end to the center conductor of a port (one-port shunt), or in series between two ports, or in a shunt configuration between two ports.I opted for the one-port shunt configuration since it is the easiest to set up and it is best for impedances around 50 Ohms. So the right connector of the fixture was connected to a BNC short, and left one to the VNA port. Then full one-port OSM calibration was done in the fixture. As a match standard I used a 47 Ohms 0805 resistor. I did not go to the effort to tell the analyzer to correct for the discrepancy between 47 Ohms and 50 Ohms (open, short and match were assumed all assumed to be ideal), so that displayed values will be off by a few percent (impedances will read about about 6 percent low).I tested the same 1.2 pF 0805 C0G cap as yesterday (capacitor-1p2.png). I got reasonable results although the whole matter is a bit touchy. You can see that the S_22 magnitude is above 0 dB at some frequencies. This is clearly a repeatability issue of the setup (slightly more losses when the cal standards were connected than during the measurement). On the other hand, we are at 0.005 dB/div here. I get a capacitance reading of about 1.2 pF up to 120 MHz. The LCR bridge measured about 1.3pF, but keep in mind that there is a systematic error involved (a quick calculation shows that this is roughly the expected discrepancy).Next I tried a 1 nF 0805 X7R cap (capacitor-1n.png). This is less touchy than the 1.2 pF one, but again, the capacitance is reading systematically too low.Finally I connected a TDK MPZ2012S102AT000 ferrite bead, intended for supply voltage filtering, in a 0805 package and with 1 kOhms impedance at 100 MHz (ferrite-bead.png). The impedance is just as expected, and it is nice and lossy.As a sanity check I re-connected the 47 Ohms resistor used for calibration (load.png).Depending on the DUT impedance a different connection of the test fixture might be better, and one could improve on calibration. But I would say they are not lying about the 120 MHz frequency range of that fixture when used and calibrated properly.Edit:I repeated the calibration several times when I took these measurements. As you can see, the cal it a bit off in the measurement of the 1 nF cap since S_22 is almost at +0.2 dB at some frequencies. You really have to be careful about the calibration.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: October 25, 2021, 05:31:43 pm
content: about cheap kelvin leads from ebay:https://youtu.be/Ffd583jwjpMlook what I got today :-)the total cost was about 11$so as always, you get what you pay for, the kelvin clips works fine, nice and sharp and stable.

author: mawyatt
author_rank: Super Contributor
timestamp: October 25, 2021, 06:02:55 pm
content: Quote from: oz2cpu on October 25, 2021, 05:31:43 pmI have these, or something similar. They work OK and give good readings on DMMs compared to the OEM Tonghui ones (TH26011CS) that come with the LCR Meter. The OEMs ones use a type Kelvin clip I haven't been able to find, they are really quite nice. Also built some Kelvin probes with the smaller clips you find on eBay, they also work OK and give good results with DMMs..Even the cheap SMD Kelvin tweezers work OK, but the OEM Tonghui TH26009B are much easier to use and get a stable, accurate, repeatable reading.Measuring small capacitance is difficult with usual Kelvin probes, the tweezers are better since the connection terminals and cabling are somewhat fixed, of course the best is the special SMD fixtures where everything is fixed except the moveable plunger.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: October 29, 2021, 01:30:05 am
content: Just received the SMA fixture from eBay.https://www.ebay.com/itm/174970844194Ordered on 25th and received 28th!!!This fixtures wasn't packed well and not anywhere near as well made as the Tonghui Fixtures, so doubt this is from the supplier for Tonghui if there is one. The lid doesn't fit properly and the inside is ground down so it will fit, the interior wiring is OK except they didn't heat the heat shrink tubing!! The lever arm was very loose and wobbly, so much for QCAnyway, after some minor fixing work the fixture was mounted, it does fit the TH2830 nicely. Did a fixture calibration of Open and Short and checked some SMD components in 0603, 0805, and 1206 sizes. Have some 0.1% low TC SMD resistors which we measured, and a few SMD NPO/COG capacitors. Removed the fixture and reinstalled it then did another Open/Short cal and got good agreement with the previous measurements. Results were good and showed good repeatability, the fixture seems stable enough for our intended use.Anyway, I'll do more tests and compare to DMM later, but for now this seems like a good addition to the TH2830, and certainly easier than using the Kelvin Tweezers. It's about $110, so ~$100 less than the OEM Tonghui.Best,

author: The Electrician
author_rank: Frequent Contributor
timestamp: October 29, 2021, 04:32:16 am
content: A few days ago I checked the link I posted earlier:https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1312&_nkw=smd+test+fixture&_sacat=181939There were 37 posts with that fixture for sale. Interestingly, every one (I checked them all) said that the item location was in Chino, California. I suspect they are all the same person with an Asian supplier, perhaps a knockoff supplier. I ordered one yesterday, and it's supposed to be next Tuesday. I'll compare it to the one I bought from Meiruike.

author: mawyatt
author_rank: Super Contributor
timestamp: October 29, 2021, 01:12:03 pm
content: That's the link I used to find the fixtures, yes there were a bunch of similar sites. Must say that the measurement repeatability has been good after a proper calibration. To get a really good "Open" calibration you need to space the plunger exactly the same space between ends as length of the SMD you are measuring for small capacitance values, for larger capacitance values this spacing isn't as critical. Obviously this is correcting for the fringe end capacitance from the plunger, and thus the distance between ends is important.Just did another quick check after a 30 minute warm up and then calibration, good agreement in measurements from last night. So this fixture is a keeperBest

author: rf-messkopf
author_rank: Regular Contributor
timestamp: October 29, 2021, 02:06:43 pm
content: Quote from: mawyatt on October 29, 2021, 01:30:05 amThe Tonghui fixture which stood as a model for that one actually seems to be a knock-off of a HP 16034E test fixture:https://microprecision.com/de/calibration/keysight-16034e-test-fixture/.Keysight still sells them, for 1592 Euros plus tax:https://www.datatec.de/keysight-16034e-zubehoer-lcr-meter.They claim a useful frequency range up to 40 MHz.

author: mawyatt
author_rank: Super Contributor
timestamp: October 30, 2021, 05:10:36 pm
content: Quote from: rf-messkopf on October 29, 2021, 02:06:43 pmCertainly looks similar. Maybe Tonghui copied this from HP/AG/KS or maybe they are an OEM supplier?Anyway, happy with the cheap eBay copy version, it's performance is OK so far. No serious complaints except the poor QC and poor lid fitting, also the shipment wasn't packed well.Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: November 06, 2021, 03:32:44 pm
content: batteryfly got 10% off this novemberjust worth mention, the rebate code is easy to find on their webpagejust orderen my unit :-) and the smd fixture

author: jonpaul
author_rank: Super Contributor
timestamp: November 06, 2021, 07:13:07 pm
content: Bonjour just seeing this long thread now.The OP should kindly inform us his goal, and specs he seeks eg 0.3 +/- 0.01 pF or 1000 pf +/- 1 pF etc.It seems the OP is confusing the accuracy and resolution of the various meters.We have a lot of experience in this problem, as the transformer P-S capacitance is critical in some applications.The setting of test freq and stability of the lead/test fixture cfg is critical at small CValues we spec are 0.3 pF, 3 pF and 10 pF.We have used:TEK 130 LC meter (1960s, valves/tubes, analog, very wide lead comp range)HP 4232A RLC meter (analog, down to 1 pF FS)HP 4275A LCR bridge (select F to 10 MHz)HP 4195A 500 MHz network/spectrum analyzer. (100 kHz-500 MHz)The latter has an Impedance adapter test set and many SMD and thru hole adapters. All use APC-5 connectorsSorry but we have never used Chinese equipment and canot recommend "SMD tweezers" for these small C.Just the ramblings of an old retired EEBon Chance,Jon

author: mawyatt
author_rank: Super Contributor
timestamp: November 06, 2021, 09:01:21 pm
content: Quote from: jonpaul on November 06, 2021, 07:13:07 pmBeing the OP if you bothered to read the original post you would find that the goal was to help bin components and ratios of components, and we understand accuracy and resolution quite well thank you, do youWe got caught up with the component worldwide shortage and had to redesign multiple times to accommodate available components on a major ongoing project (this is not a hobby project or a refurb effort, but a very complex advanced effort leading towards a full custom chip development), and thus had to resort to "matching" componentsQuoteAgree fixtures are critical for stable and repeatable small C measurements as mentioned in the various posts above.QuoteThe use of the "tweezers" and "Chinese" equipment was also stated clearly in the original posts. As stated "out of curiosity" which in this context means "give it a try with what you have available" was to see how well the Keysight 34465A and newly acquired DMM6500 agreed with the TH2830 on capacitance measurements since these instruments used entirely different measurement techniques, which is the "curiosity" aspect of the statement.Do agree that measuring small capacitances with the 2 wire tweezers is difficult at best and better left to those that know what they are doing. However the 4 wire tweezers from Tonghui work quite well indeed and have the forearms shielded up to the tips so hand capacitance is minimized. They are supplied with a calibration fixture which allows a proper short and open for a given SMD device size, easily achieving below 100ff repeatability, but not as good as the proper solid SMD fixture as mentioned above.So I would not discount all "Chinese" equipment and all SMD "tweezers" unless you have actually taken the time to study and had some "hands on" before forming an opinion, some are quite good indeed, challenging the "A" tiersBTW was retired, now consultingBest,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 12, 2021, 03:50:57 pm
content: a lot of people recommend batterfly as the place to go, for the TH2830I did place my other, 6th nov, and they took the money right away 6th nov,but then, all i hear is item is not stocked, and no confirmed delivery time..and that only came when i asked for it,so i am getting a bit nervous, it is quite a lot of money,where i come from it is not normal or legal to take the money, before pack and shipment.do I need : patience and just be happy ?or do I need to take actions with my bank ?

author: 2N3055
author_rank: Super Contributor
timestamp: December 12, 2021, 07:25:27 pm
content: Quote from: oz2cpu on December 12, 2021, 03:50:57 pmI never had problems with them. I'm not glad to hear that. Thank you for sharing. I would contact them and ask them for refund if they cannot at least confirm deliver date. Maybe that will wake them up. I don't mind long delivery if that was agreed from the start. This, I would not be happy...

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 12, 2021, 07:30:20 pm
content: i allready asked them...I dont mind waiting, sometimes stuff just have long delivery times.but it is not cool to pull the money from the customer from day 1that is what makes me a bit.. you know..UPDATE : it is here.. i am happy againjust learned about the avarage feature, very usefull to use the last 1-2 digits, now they got stable

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 25, 2021, 07:37:36 pm
content: now i play with my TH2830i realize its DC ohm range is just amazing specially when combined with avarage.And then looking into a few experiments just to get familiar with its features,NOW the funny thing : DCR is NOT performed at DC !! nope, it is pulsedso you get different results when you measure resistance on very inductive things

author: Kleinstein
author_rank: Super Contributor
timestamp: December 25, 2021, 10:16:44 pm
content: Some other meters also measure resistance with a pulsed (more like 50% on/off), when in offset compensated mode. This is kind of the only way to suppress thermal EMF at the DUT.Resistance with highly inductive parts can be tricky - in this case one should turn of auto-scale and offset compensation. It can still fail in rare cases.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: December 25, 2021, 10:45:10 pm
content: i tried all possible settings, in DCR it just will not measure DC,I understand the smart move by using pulsed, forward and reverse, and perform delta,but the timing is just done critical, this means some resistors, wirewound, will read quite a lot off,while others measure spot on.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: January 05, 2022, 05:55:49 pm
content: i am so sad, my brand new Tonghui TH2830 LRC meter is not workinghttps://youtu.be/dMFn2-613Q4please tell me how to reset this ?

author: Kleinstein
author_rank: Super Contributor
timestamp: January 05, 2022, 07:21:28 pm
content: This could be soemthing like a totally off calibration factor. There is a thrird compensation point for "load" - this could be a kind of scale factor calibration, that may be accidentially used.It would definitely be a good idea to have a look at the manual, if this may need to done with a suitable test unit.Normally there should be some warning when changing to calibration factor, with possibly a calibrated setting and a user defined setting, but this should ideally clearly show on the screen.A point one could check would be to have a look at the test waveform. So have somerhing like the 1 K resistor and than use a scope to see if the voltage at one side of the resistor makes sense, especiall if the waveform is a reasonable qualtity sine and not distorted.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: January 05, 2022, 07:59:04 pm
content: manual do not explain what "load" isand the load feature is off, this means as far as i guess, it dont compensate for anything like that

author: The Electrician
author_rank: Frequent Contributor
timestamp: January 05, 2022, 08:00:49 pm
content: Quote from: oz2cpu on January 05, 2022, 05:55:49 pmDo the measurement at 100Hz, 1kHz and 10 kHz as well as the 100 kHz you show. Also show the phase angle at those frequencies..

author: mawyatt
author_rank: Super Contributor
timestamp: January 05, 2022, 08:01:55 pm
content: Quote from: oz2cpu on January 05, 2022, 05:55:49 pmWe just ran a couple resistors, 1K and 10K to check out the TH2830, results were as expected on DCR, R+jX and Rs_Q and Rp_Q modes.You may recall we had an issue with a scale on the TH2830 not reading correctly and reported to Tonghui, which they informed us that they had no authorized resellers on AliExpress where we purchased the TH2830. We contacted the reseller and they made contact with Tonghui and we were allowed to receive an updated firmware which corrected the problem. Recall we had a issue with the 1K range and got correct readings using DCR but not the other modes, worked OK below the 1K and above the 1K range, but not at 1K. You could try different ranges to see if this is a similar effect as we had.Since you purchased from an authorized reseller have them contact Tonghui for the updated firmware. Hopefully this may correct your issue.Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: January 05, 2022, 08:04:59 pm
content: thanks a lot mike, i allready wrote to them both :-)resistors seems to to work in DCR mode, all caps and inductors, dont work

author: mawyatt
author_rank: Super Contributor
timestamp: January 05, 2022, 08:31:21 pm
content: Try other manual ranges, go to setup and select ranges other than "Auto". I just did a quick test and got inaccurate readings on 3K & 10K ranges with 1K resistor, however got accurate readings with 1K, 300, 100, 30 ranges but not 10 ohm range, so it seems the instrument likes actual values below the next range up but not so far as the 10 ohm range for a 1K resistor!!BTW, if you turn on the Vm and Im measurement values you can see the applied voltage and measured current.Edit: Also found it strange that the detailed extensive supplied calibration sheet included measurements in the 1K range that showed it correctly preformed??Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 07, 2022, 07:54:52 pm
content: anyone still monitoring this thread ??is there a better TH2830 support ? tech ? mods thread ?my question TH2830how to use the bias feature ?nothing happens, no matter what i push,i like to test some cheramic caps with different DC added, any ideas how ?

author: mawyatt
author_rank: Super Contributor
timestamp: February 07, 2022, 08:26:35 pm
content: On our TH2830 the DC Bias feature is not enabled.Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 07, 2022, 08:28:59 pm
content: darn it.. mine must be like that too,so how to fix this ?or a workarround ?

author: 2N3055
author_rank: Super Contributor
timestamp: February 07, 2022, 09:53:32 pm
content: Quote from: oz2cpu on February 07, 2022, 07:54:52 pmI believe TH2832 is the one that supports DC bias..

author: jonpaul
author_rank: Super Contributor
timestamp: February 08, 2022, 09:36:59 am
content: Bonjour nether the Keysight DVM nor a Chinese meter are optimized for very low C 1..10pf.In decades of developing very low capacité transformers, we used the various HP bridges and LCR meters before settling on1/ HP vintage LCR and impedancehttps://www.hpmemoryproject.org/collection/lcr.htm#mark1HP 4332A analog mettre has a 0..3 pF lower scale2/ 1960 Tektronix LC meters 130 valves, analog, very high range of residual capacitéhttps://w140.com/tekwiki/wiki/1303/ HP 4195A with impedance test fixtures and SMD adaptersCapable of 100 kHz..500 MHzWe made our own test adapters, a stable mechanical system and guard are much more important than 4 lead Kelvin for such work.Bon courageJon

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 08, 2022, 11:34:47 am
content: thanks 3055 the manual see page 17, attached..this means no bias on my model TH2830, darn it

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 08, 2022, 11:44:52 am
content: the BIAS test workaround , see attached picture.only concern : lets imagine it is 100V caps,and i like to test all the way to max voltage,then one cap get leaky, now broken instrument ?!?!?i like to have the resistors as high as possible, i tested with 10k to gnd, and it did not affect my capacity range muchthe caps i need to test are 10uF

author: Kleinstein
author_rank: Super Contributor
timestamp: February 08, 2022, 12:58:13 pm
content: A test with 100 V and 10 µF is definitely nothing for an delicate instrument. That would more lime something for a separate, more specific test-setup with lower sensitivity and more protection.It depends on how good the instruments are protected. The problem is that protection can interfere with sensitivity with small capacitors.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 08, 2022, 01:05:35 pm
content: good point, maybe i should perform the DC test, using one of my old handheld LCR meters, I cry much less if this blows up

author: gamalot
author_rank: Super Contributor
timestamp: February 08, 2022, 01:19:52 pm
content: Quote from: oz2cpu on February 08, 2022, 11:44:52 amhttps://www.keysight.com/au/en/assets/9018-01469/user-manuals/9018-01469.pdf

author: mawyatt
author_rank: Super Contributor
timestamp: February 08, 2022, 02:10:23 pm
content: I would not consider subjecting the TH2830 to any external applied voltage without a proper fixture that is verified to be instrument safe, but that's just my personal viewpoint considering this particular instrument. If you study the link provided by gamalot, this shows the extent HP goes to to protect the HP instruments.Think a reasonable less risky approach would be to get a cheap LCR meter like being reviewed by Martin52 and make a special fixture similar to the one HP uses for evaluation of capacitance vs DC bias behavior.If/when we decide to do some tests like these, getting a cheap "expendable" LCR meter and adding a special DC bias fixture will be the approach. Since the measurement under consideration is C vs DC bias, the measured values are relative to no DC bias, and these values can be "inferred" to the more accurate no bias measurement from the TH2830. So plot the C vs DC value then shift the zero bias voltage reading to the value acquired from the better instrument, this should yield a reasonable result that can be believed.Anyway, YMMY.Best,

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 08, 2022, 05:33:02 pm
content: Quote from: oz2cpu on January 05, 2022, 05:55:49 pmDid you ever determine why you were getting this odd result?

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 08, 2022, 05:43:37 pm
content: >Did you ever determine why you were getting this odd result?not really, I think it is possible to either create bad settings, or wrong combinations,a factory reset did recover all to perfect working conditions,i tried to play with all possible combinations, i am not able to recreate the issue.

author: mawyatt
author_rank: Super Contributor
timestamp: February 08, 2022, 05:50:55 pm
content: Here's the link I was referring too above regarding the cheap LCR meter. Maybe Martin72 can look into the possibility of external DC bias on this LCR meter?https://www.eevblog.com/forum/testgear/east-tester-et4410-desktop-lcr-meter/msg3989009/#msg3989009Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 08, 2022, 06:01:23 pm
content: did the test, using old crappy lrc meter :-)two 10uF caps in series,

author: mawyatt
author_rank: Super Contributor
timestamp: February 08, 2022, 06:08:21 pm
content: Quote from: oz2cpu on February 08, 2022, 06:01:23 pmIf one of these two caps was very large, then the measurement should converge to the other smaller DUT actual cap value. For polarized (Electrolytics & Tantalum) caps this large cap could be a quality low leakage low ESR cap placing in the proper polarity direction for the applied DC bias.Edit: Also reminds me of the use of polarized capacitors where the AC voltage under test is allowed to become significantly negative WRT the DUT polarity. Think of a common low voltage aluminum electrolytic, where tantalums are known to be less sensitive under modest reverse bias. Long ago many used special tantalums that allowed reverse voltage under normal operation, we did so ~50 years ago in a very low noise & frequency amplifier. These were wet-slug types tantalums and specially selected and specified from a select vendor at the time, we did numerous tests and verification on these caps before factoring into the design.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: February 08, 2022, 06:17:49 pm
content: This shows the importance of understanding how capacitors behave, especially ones that employ high dielectric constant ceramic materials like XR7 and such! Your data shows a decrease in effective capacitance value of 5X over the 90V DC bias span! Also this points to the well known behavior amongst older "seasoned" folks, if you need a minimum value capacitance under DC bias, then either use a much greater capacitance value, or much higher breakdown voltage, or a much less voltage dependent dielectric like COG or NPO ceramic, or all of the above, or a film type dielectric!!Edit: One of the interesting stories behind these capacitors dates back into the 70s, we had put in quite an effort to understand the capacitor materials and capacitors themselves and had the resources on-site to do so. This was to support the requirements for nuclear survivability in which one common requirement was to survive the EMP, the Radiation impulse and long term effects. Some required work-through, others required surviving allowing a equipment "reset" . We had developed considerable knowledge into electrolytic, tantalum, film and ceramic materials/capacitors which was held as proprietary, and knew the amount of energy required from different capacitors types and materials that would destroy a chip under radiation impulse which causes all the PN junctions to become highly conductive.One program called XM21 (Remote Sensing Chemical Agent Detector) required surviving a point-blank Nuclear Detonation!! This was a battlefield instrument purposed to protect solders by early warning of a chemical attack utilizing a remote very controversial (another story, I'll discuss if folks want) technique. We unsuccessfully argued that nuclear battlefield survivability made no sense, as anyone still around surely wouldn't be concerned about a chemical attacks after a nuclear attack!! So we had to design for survivability and the simultaneous EMP and Radiation pulse from a point blank detonation!! This imposed a limit on the decoupling capacitance and type we could use, and required that all the supply inputs and outputs were swiftly crow-bared not to mention all the other things required to pass, which we did but this drove the instrument cost up by ~4X!!Best,

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 12, 2022, 01:16:22 am
content: I scored an HP16034E on eBay last week. The outside looks just like the low-cost SMD fixture shown in reply #33 earlier in this thread. Here's a picture of what's inside. The terminals are shorted in pairs very close to the BNC connectors. I could believe this will allow reasonable performance at higher frequencies than the technique used in the low-cost fixture, but it probably doesn't matter at 100 kHz and below.As one might expect, the sheet metal work and build quality of the HP unit is much better than the eBay copy.

author: mawyatt
author_rank: Super Contributor
timestamp: February 12, 2022, 03:18:53 am
content: That's not how the inside of ours looks, it has separate wires from each BNC to the plunger, no shorting bar!! Suspect the wires terminate at the plunger metal shaft and form a somewhat Kelvin type connection. There's also a ground wire across each BNC which has the solder lug terminal and goes to the center shield.Edit: Just took a quick picture of the inside, the black wires on each end we added to ground to the brackets which the back lid mounts to. We were just characterizing some COG capacitors and checking some 0805 small caps, these were from Venkel. Recall a 0.5pF that measured 0.51444pF with the fixture, then removed and later remeasured at 0.515pf something (we recorded the initial value but not the remeasured). All the other measured caps were very close to the Venkel specified value.BTW I did a crude experiment to see if my hand touching around the fixture would influence the reading of the 0.5pF cap, recall it did have an effect before we modified the fixture by cleaning the paint from the various mounting holes and added the two black ground wires. My hand had no influence in the measurement, even at 0.5pF the readings were very stable.Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 12, 2022, 09:39:09 am
content: The Electrician, if you need to measure the last mili ohm of smd parts, maybe an idea to make all wires as close as possible to what Mawyatt shows ?specially the red wires are importent for sub mili ohm performance.i got the same TH fixture and mine dont seems to be affected by hands on the outside,i also use it to very small pFand down to sub mili ohms internal resistance on some of the caps i use right now.

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 12, 2022, 01:50:08 pm
content: Quote from: mawyatt on February 12, 2022, 03:18:53 amYou can see that the HP fixture has the internal paint masked off where the BNC connectors are bolted to the sheet metal. There is also some paint masked off where the wires penetrate the sheet metal, and where the little brackets at the end are riveted on.

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 12, 2022, 02:12:07 pm
content: Quote from: oz2cpu on February 12, 2022, 09:39:09 amAre these MLCC large value caps? Who is the manufacturer? Can you give a link to a spec sheet?

author: nctnico
author_rank: Super Contributor
timestamp: February 12, 2022, 02:28:58 pm
content: Quote from: mawyatt on February 12, 2022, 03:18:53 amThis looks much better than the HP 16334A fixture The Electrician showed. The closer you get the Kelvin connection to the DUT, the better.Below the recommended connection to a DUT from the manual for the HP4274 LCR meter:I have made a set of Kelvin clips using this schematic and it allows accurate readings over the entire frequency range (not with the HP4274 though; got rid of it a long time ago).

author: mawyatt
author_rank: Super Contributor
timestamp: February 12, 2022, 04:05:01 pm
content: Quote from: The Electrician on February 12, 2022, 01:50:08 pmThe 3rd party fixture we have didn't do the masking and the entire case and lid were powder coat painted after all the machining. So we had to selectively remove the paint in areas where ground contact was required.Evidently the TH fixture that oz2cpu has is properly prepared regarding grounding, which isn't surprising since Tonghui seems to be a 1st class equipment supplier, certainly so with the 3 Tonghui devices we have.Best,

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 13, 2022, 04:00:46 am
content: There was some question earlier in this thread as to the frequency capability of the SMD fixture. I found a manual for the HP 16034E version:https://www.keysight.com/us/en/assets/9018-01396/user-manuals/9018-01396.pdf?success=trueThe spec says max 40 MHz, but on page 9, figure 1-5 shows the error vs. frequency; 25% error at 40 MHz!!I suspect the low-cost eBay version without the shorting bars can't do as well.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 13, 2022, 09:16:10 am
content: news : i just opened my TH26008A smd fixtureit is not with paint on any alu surfaces inside anymore,this means all parts have good connection, and this also explain the good shielding on my unit,>Are these MLCC large value caps? Who is the manufacturer? Can you give a link to a spec sheet?AVX 22201C106KAT2A10uF 100V 2220 sizeXC is 170mOhm at 100kHzESR is 0.9mOhm (yes, this meter can measure both XC and ESR)SRF is 1.4MHzattached is my DC voltage tests also.and also my component test pcb for SRF using SA, this way i can test from kHz to GHz

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 13, 2022, 09:27:58 am
content: PICTURES of the latest version TH28008A fixture internal parts

author: nctnico
author_rank: Super Contributor
timestamp: February 13, 2022, 12:36:39 pm
content: Quote from: oz2cpu on February 13, 2022, 09:16:10 amThat looks very interesting. Can you share more about the design? I noticed you included an attenuator at the in & outputs; I guess to get a better impedance match.

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 13, 2022, 01:06:36 pm
content: > Can you share more about the design? I noticed you included an attenuator at the in & outputs; I guess to get a better impedance match.sure can, if you send me your email, i send you the gerber zip, so you can order this design,here is a youtube link to a detailed explainer about this :https://youtu.be/y79nOd8GLWIi keep one with 0R on the centre, and then use that to calibrate the analyzer tracking generator, for a flat line,now swap to the tester one, where an inductor or capacitor is mounted,you can also use this to trim filter designs for best performance, see how different caps in parallel behave (parallel resonance)the two 5dB attenuators each side of the DUT, is to keep the NA / SA-TG tester in good match,and to feed the test area with a resistive load from both sides,else you create resonance problems with the cable length, different cables would then create different results,this methode is much better :-)this PCB is flat to over 3GHz. i also design RF stuff, so i need to see how my parts perform.

author: mawyatt
author_rank: Super Contributor
timestamp: February 13, 2022, 04:03:10 pm
content: Quote from: The Electrician on February 13, 2022, 04:00:46 amFrankly wouldn't consider a 25% error specification a measurement at all, more like a "wing it" attemptThe fixtures by Tonghui (TH26008B) are specified to 120MHz, although not sure I would put much faith in a measurement at 40MHz much less 120MHz with these either. Of course the eBay clones have no specifications, but the construction is similar to the TH26008B, so infer as you wish.If you look at the construction of these fixtures, experience dictates that achieving accurate and repeatable measurements at frequencies like 40 or 120MHz is questionable, specs or not we wouldn't rely on these fixtures at these frequencies which are better served with a VNA or Impedance Analyzer with proper fixtures, connectors and cables to support higher frequency component measurements.Anyway, our LCR meter (TH2830) only supports 100KHz , so that's where we are interested in accurate and repeatable measurements with this LCR meter at this time, and these fixtures serve this frequency range well.Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 20, 2022, 12:42:07 pm
content: NEW REPAIRED VIDEO HERE :https://youtu.be/y79nOd8GLWII am so sorry the first one contained a few missing pictures, i used a bad video editor,now it is repaired, and a new video is uploaded,with this design you can measure impedance of parts, caps, inductors, filter performance,up to what ever frequency your spectrum / network analyzer can handleEDIT : this call for a new seperate thread :https://www.eevblog.com/forum/projects/component-tester-board-for-sa-na-impedance-caps-inductors-filters/

author: mawyatt
author_rank: Super Contributor
timestamp: February 21, 2022, 06:11:21 pm
content: Those are nice test PCBs.Where did you get those, or did you design yourself?Best,

author: oz2cpu
author_rank: Frequent Contributor
timestamp: February 21, 2022, 06:13:24 pm
content: yes my design, all you have to do email me, as ask for the gerber set,bom is included, then order at jlc,my email is my username at gmail dot comNEW thread for this.. please jump here, so we dont jam up the KS34465 / TH2830 threadall files are now shared for free, just goto thread and pick it up..https://www.eevblog.com/forum/projects/component-tester-board-for-sa-na-impedance-caps-inductors-filters/