Reference for LCR or ESR meters - Page 1
Forum section: electronics / projects

author: The Electrician
author_rank: Frequent Contributor
timestamp: December 30, 2013, 07:03:21 pm
content: A continuing problem for builders and buyers of LCR and ESR meters is how to check the performance and accuracy of the meter.Precision capacitors are expensive. An alternative is to have an ordinary capacitor that has been measured with a precision instrument.I want to help. I will measure some capacitors with a Wayne-Kerr 6440B and mail them to forum members. The 6440B:http://www.waynekerrtest.com/global/html/products/LCR/6430%206440.htmis specified to have a basic accuracy of .02%, but that's marketing hype; it applies only to resistors. For reactive components, the basic accuracy is .05% in the instrument's sweet spot.I have a bunch of polystyrene caps that are old enough to have become reasonably stable. Their temperature coefficient is good enough that a user at normal room temperature can probably count on .2% accuracy. These would not be good ESR references because they're rather small--.01uF, but they would be excellent capacitance standards. I can also supply some polycarbonates which also are reasonably stable, and larger at 2.2uF.It might be useful to include an electrolytic or two with known ESR at room temp, although they wouldn't be very stable.If anyone is interested, PM me. I will bear the cost of mailing, so no one need send money.I'm also interested to hear what thoughts people have about this. I could also include some small inductors, but they would have ferromagnetic cores, and a .05% measurement of a not so stable component won't yield a .2% reference component.

author: dannyf
author_rank: Super Contributor
timestamp: December 30, 2013, 07:30:14 pm
content: Having calibrated parts is helpful but not absolutely necessary to determine if a meter is accurate (sufficiently).Let's say that you have a resistor of known value, and a capacitor of unknown value.Put the capacitor on the meter and it should give a reading of C + ESR; Now, put the resistor in serial with the capacitor. You should have a reading of C + (ESR + R). Otherwise, the meter is faulty.If you don't have a known resistor, pick a wire, and mark the middle point on the wire. Measure the resistance from one end point to the next end point, you should have a reading of R; measure the resistance from one end point to the middle, you should have a resistance of R/2.Alternatively, you can combine the two techniques to see if a meter can measure small resistance on a capacitor.

author: mrkev
author_rank: Regular Contributor
timestamp: December 30, 2013, 07:52:07 pm
content: Great idea

author: SeanB
author_rank: Super Contributor
timestamp: December 30, 2013, 10:18:01 pm
content: Good idea, I like that as a reference component for checking, I generally use known values to check, often used components that have aged well. Resistors and good quality film capacitors generally age well and stay accurate if not run hot or at high voltage relative to max ratings.

author: DL8RI
author_rank: Regular Contributor
timestamp: December 30, 2013, 10:35:15 pm
content: Hi,i have an ESI 2110 Video Bridge with basically the same specs.Maybe it's interesting for you to cross-check.And we could look at stability after shipping and so on...

author: plesa
author_rank: Frequent Contributor
timestamp: December 30, 2013, 10:39:51 pm
content: I can made the measurement on my Agilent E4980, preffered only for EU countries.

author: Co6aka
author_rank: Unknown
timestamp: December 30, 2013, 11:59:43 pm
content: But what about stability; temperature, humidity, mechanical stress, gravity, cosmic rays, alignment of the planets, government intervention, etc?

author: robrenz
author_rank: Super Contributor
timestamp: December 31, 2013, 12:12:19 am
content: Quote from: mrkev on December 30, 2013, 07:52:07 pmexample here

author: The Electrician
author_rank: Frequent Contributor
timestamp: December 31, 2013, 05:01:51 am
content: Quote from: plesa on December 30, 2013, 10:39:51 pmI think it would be great if somebody like you could provide for the EU. I can mail to the EU and it's not too expensive for just a few capacitors, but even better if mailing from there.I ran some tests on the polystyrene caps I have. I measured at room temperature (15C) and then put the cap in the refrigerator (0C) for a couple of hours. The capacitance changed by .1% for a 15C decrease in temperature. I don't think it would be unreasonable to expect one of these capacitors to be within .2% of the value I measure for a normal range of room temperatures. Humidity won't be a problem with polystyrene and as far as mechanical shock goes, well, be gentle.We're not trying for metrology lab precision here, after all! Anybody who wants better can get some of these:http://www.ebay.com/sch/i.html?_odkw=standard+capacitor&_osacat=92074&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.Xstandard+capacitor+genrad&_nkw=standard+capacitor+genrad&_sacat=92074and pay for them!

author: The Electrician
author_rank: Frequent Contributor
timestamp: December 31, 2013, 07:42:17 am
content: I'll be sending out the first batch next week. I've gotten 2 requests so far.Something that would help me would be this--in your PM request, please type your mailing info, name and address, in exactly the form it should be on the package. That way I can just print it, cut out the text and tape it on the package.Thanks

author: BravoV
author_rank: Super Contributor
timestamp: December 31, 2013, 08:44:34 am
content: Quote from: The Electrician on December 30, 2013, 07:03:21 pmNoob question, about tempco stability, does an air core inductor better than the one with ferromagnetic core ?If it does, I'm thinking of using like one of these below that are easy to find, and use a hammer to whack out the ferrite part since they're brittle and easy to break, and will leave out only the bobbin with the winding but air core one.

author: The Electrician
author_rank: Frequent Contributor
timestamp: December 31, 2013, 09:22:36 am
content: I would think it would be more stable without the ferrite, but the inductance will be much lower. There are magnetic materials that have been formulated to have a low tempco of permeability.

author: cellularmitosis
author_rank: Unknown
timestamp: December 31, 2013, 09:22:41 am
content: Electrician, this is a great idea. Have you thought about setting up a small store on tindie.com and offering a small assortment of calibrated capacitors as a product? Might be the most convenient way to handle the ordering process, and also give you some more publicity!

author: The Electrician
author_rank: Frequent Contributor
timestamp: December 31, 2013, 10:22:53 am
content: I'm not interested in taking it that far. I just want help those people on this forum who need a reference for checking their meters.But, if somebody else wants to turn it into a small business, more power to them.

author: SeanB
author_rank: Super Contributor
timestamp: December 31, 2013, 04:39:46 pm
content: I think Frankie is starting that, or at least he is supplying check components for sale. Just ask him Iloveelectronics on the forum.

author: plesa
author_rank: Frequent Contributor
timestamp: December 31, 2013, 04:51:05 pm
content: Quote from: The Electrician on December 31, 2013, 05:01:51 amSend me PM if someone is interested. Also what about finding some standartd components kit e.g from Farnell and measure them? It will make it more consistent.

author: Rufus
author_rank: Super Contributor
timestamp: December 31, 2013, 05:33:06 pm
content: It is worth remembering that most 'real' LCR meters measure everything ratiometrically against precision resistance standard(s).There isn't anything to calibrate so there is no calibration to 'go off'.Subtle measurement system faults which don't result in no or completely garbage measurements tend to just introduce noise.

author: The Electrician
author_rank: Frequent Contributor
timestamp: January 10, 2014, 12:06:38 am
content: Quote from: Rufus on December 31, 2013, 05:33:06 pmThose with access to "real" LCR meters don't need the simple references I'm offering; I'm aiming at beginner/hobbyist folks.Now that the holiday season is over, I'm making the measurements needed. I'll be mailing out the caps in the next few days. I will probably include some inductors as well.I'm going to include a polystyrene cap and a polycarbonate cap; I've measured the temperature coefficient of these two caps. I'll also include an OSCON electrolytic. The OSCON has much better low temperature performance than a regular aluminum electrolytic, so the variation in capacitance for a +- 15 degree C variation in measurement temperature is less than 1%. However, I can't say how the OSCON stability with aging is going to be; that would be an experiment I could perform.All the measurements have been made at an ambient temperature of about 15 degrees C. If the user makes no compensation for his different ambient, an accuracy of about .2% (for the film caps) can be expected for an ambient up to perhaps 30 degrees.

author: Rufus
author_rank: Super Contributor
timestamp: January 10, 2014, 12:21:25 am
content: Quote from: The Electrician on January 10, 2014, 12:06:38 amBy 'real' I meant not multimeters that measure capacitors by timing charging ramps or the variety of crude capacitor ESR meters. The cheap Mastech etc hand held LCR meters are 'real'.

author: The Electrician
author_rank: Frequent Contributor
timestamp: January 10, 2014, 05:43:18 am
content: Quote from: Rufus on January 10, 2014, 12:21:25 amThanks for the clarification; I thought you meant high end professional meters. But those "real" meters, costing maybe a few hundred bucks, will have "precision" reference resistances that may not be as good as the ones found in the multi-tens-of-thousand dollar Agilent and other high end instruments. I have no idea how good they may be; I've seen no comprehensive test data. And there may be other error effects. I think it's good to have around a known cap standard to verify that the phase sensitive detector is still working. I haven't noticed a tear-down where the reference was pointed out, and its apparent quality was wondered about.Your point is well taken, though. With that style of instrument one can do a fairly good check on calibration by just measuring a very high precision resistor. I used to keep a .01% 1k ohm resistor around to check my early Digibridge. The manual mentioned that there was no calibration adjustment. Calibration consisted of checking accuracy; if it was off, the reference resistor was replaced.Does anybody know if the owners manual for any of the new LCR meters based of the Cyrustek chip suggest a reasonable cal check would be to simply measure a high precision fixed resistor?I'm going to do a long post on the deficiencies of meters that use a shortcut method that may fail under certain circumstances. I'm hoping some of the people I'm sending these caps to will report their measurement experiences. Then we may see that those meters don't always work so well.

author: bingo600
author_rank: Super Contributor
timestamp: January 10, 2014, 08:46:46 am
content: Quote from: The Electrician on December 31, 2013, 05:01:51 amThank you for the nice offer(s)I might send some "Red Wima" Caps to SwedenI was lucky to grab a HP 4440B decade cap , for 67€/88$http://www.ebay.com/itm/Aglient-Hewlett-Packard-HP-4440B-Precision-Decade-Capacitor-40pF-1-2-F-0-25-/310825818187Was told that it prob. was more precise than my Mastech 5308.I goofed on the pics , as i forgot to calibrate the meter when using the Kelvin probe.The result is better after calibration./Bingo

author: BravoV
author_rank: Super Contributor
timestamp: January 10, 2014, 08:50:23 am
content: Quote from: bingo600 on January 10, 2014, 08:46:46 amWhat is so special about this particular type of cap ?Compared to silver mica type ?

author: bingo600
author_rank: Super Contributor
timestamp: January 10, 2014, 01:21:42 pm
content: Quote from: BravoV on January 10, 2014, 08:50:23 am1: It's a very well behaved cap (for the price)2: I have a lot of them/Bingo

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: January 10, 2014, 08:48:48 pm
content: Hi group,You can search for General Radio 1419 decade capacitor. The 1419K is mica and is a 0.5% decade box. The 1419A and B are polystyrene and are 1% The 1419-M are 1.5% on the higher decades and 1% on the lower decades.The General Radio 1412BC is also 0.5% but these are more expensive.Probably more expensive than the LCR metersRegards,Jay_Diddy_B

author: The Electrician
author_rank: Frequent Contributor
timestamp: January 15, 2014, 04:01:57 am
content: I mailed the capacitors today.I wrote the cap values directly on the caps themselves, where possible, so they don't get lost.There is a list of 4 values; they are measured at 4 different frequencies, 100Hz, 1kHz, 10kHz and 100kHz, in that order.The silvery, cylindrical capacitor is a polystyrene, the red rectangular cap is a polycarbonate, the one electrolytic is an OSCON cap.There's a small inductor, about 27 mH. This component varies quite a bit with temperature. If I just hold it with my fingers, I can see the value drift as it warms up.All these components were measured at a nominal 15 degrees C. The polystyrene and polycarbonate caps have measured temperature coefficients of about -.008%/degree C, so you can compensate for your own ambient temperature. I don't think it will be necessary. Those caps have such low tempco, the error just from different room temps should typically be less than .2%.The measured tempco of the OSCON electrolytic is about .3%/degree C.

author: BravoV
author_rank: Super Contributor
timestamp: January 18, 2014, 05:37:20 pm
content: How is silver mica performs compared to polystyrene in tempco and long term stability ?

author: ivaylo
author_rank: Frequent Contributor
timestamp: January 19, 2014, 06:36:56 am
content: QuoteGot mine. Thanks again for doing this!

author: linux-works
author_rank: Super Contributor
timestamp: January 24, 2014, 05:42:45 am
content: this sounds like a good idea.I wonder if taking it further would be reasonable; mailing a decade box for cap or resistors and having -that- be given measured values for each of the steps.I can see it could be time consuming, so maybe a fee for your time (at that point) would be fair.its surprising that no one is selling sets of R, C, L components in a nice marked plastic tray, all ready to go.

author: BravoV
author_rank: Super Contributor
timestamp: February 22, 2014, 08:10:58 pm
content: Bumping to thank The Electrician, these "reference" caps & inductors are definitely improving my confident on the cheap Cyrustek based LCR. Sorry, just had time to play with them recently, already received them for quite a while.The Mastech MS5308 is proven quite accurate within it's specification ranging from 0.5% up to 5%, just can't complain too much since it cost me < $100.Btw, the esr at the polycarbonate (red box) are quite off, others like polypropylene, polystyrene and the electrolytic are spot on, don't have any idea why is that.Again, thank you so much.Few results while I was testing at approx. 25 C room temp, 10 C hotter when they were profiled.

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 23, 2014, 12:29:31 am
content: Added in edit: I wouldn't have expected the inductors to be measured very accurately because the measured value depends on the level of the voltage applied to them and the temperature.I also see that I made a mistake in the ESR of the little blue 26 mH inductor. The ESRs should be in k ohms, not ohms. In other words, the ESR at 1 kHz is not .109 ohms, but rather 109 ohms.You could add a k on the tape.The measurement of the capacitance of the red box cap looks to me to be about .1%, not .5%I think the problem with the red cap is that I forgot to mention that the ESR numbers are in milliohms, not ohms.Looking at your images, I see that at 1 kHz, you got .04 ohms for ESR, which is pretty close to the .057 ohms I got.At 100 kHz, you got .200 ohms for ESR, whereas I got .0055 ohms. I don't have a ready explanation for that except that polycarbonate caps have a very low ESR at high frequency for their capacitance. It's a difficult measurement to make. Why don't you try making the measurement at 100 kHz with your meter in Rs mode?Here's an image of a frequency sweep showing Z and ESR for another of those red box caps:You can see that the ESR gets quite low at high frequencies.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: February 23, 2014, 03:58:12 am
content: @The ElectricianThanks for clarifying where the decimal points should be in your hand written ESR values for the small inductor that you kindly supplied me. Now I know why my ESR meter wouldn't display any measurement reading when I checked the inductor... the value wasn't 0.192 ohms, but actually 192 ohms (@100KHz) and my vintage Bob Parker ESR meter can unfortunately only display up to 99 ohms. Small mystery solved.I too had a polycarbonate ESR measurement that was pretty far off. My ESR meter measured 60 milliohms (@100KHz) when the side of the part was marked 10 milliohm (I do not expect to see too many other polycarbonate capacitors cross my test bench).Luckily, with the help of your supplied reference components, my AADE L/C MeterIIb and Tenma 72-960 LCR meter (BK Precision 828) gave me measurement results that I can have a fair bit of faith in. I must add that my original Bob Parker ESR meter also works very well indeed when used for its intended purpose when repairing equipment on my bench.Regards

author: BravoV
author_rank: Super Contributor
timestamp: February 23, 2014, 05:25:17 am
content: Quote from: The Electrician on February 23, 2014, 12:29:31 amYeah, I was quite surprised how accurate it is on inductor, remember, it was at 25 C room temp, 10 C hotter.Quote from: The Electrician on February 23, 2014, 12:29:31 amI meant the LCR meter's specification is rated only with 0.5 - 5% accuracy depends on the test frequency, and the red box cap result is at 0.15% which is pretty good considering it's price.Quote from: The Electrician on February 23, 2014, 12:29:31 amAt the 3rd and 4th pictures, the LCR meter was not measuring at 100KHz, its only 100 Hz and the result is 0.2 Ohm vs yours at 0.395 Ohm, while at 1 KHz, its 40 mili Ohm vs yours at 57 mili Ohm.If I have a chance today, I will post all measured results from all test frequencies for these cap & inductor references, already had all of them written in paper.

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 23, 2014, 12:08:07 pm
content: Quote from: fpliuzzi on February 23, 2014, 03:58:12 amSorry about that.Quote from: fpliuzzi on February 23, 2014, 03:58:12 amI'm going to check the red polycarbonate on a couple of other instruments to verify the result I got on the Wayne-Kerr.BravoV, that's really great that the MS5308 is so accurate on capacitance. I have gotten the impression that the Cyrustek chip set is quite capable. It's amazing that you can buy a true LCR meter that goes up to 100 kHz for well under US$200 with that kind of performance.

author: BravoV
author_rank: Super Contributor
timestamp: February 23, 2014, 12:34:46 pm
content: Here are the measurement results ...The items :At the Sanyo OSCON electrolytic cap, it failed at 100 KHz with OL (Over Load) error message, don't know why is that ?<Edit: Fixed with resistance series mode>Also at the capacitance error results is bigger than other plastic caps, I guess its mostly caused by the larger temp co ?About these reference caps & inductors, apart from the electrolytic, I guess if they never used, and stored in dry & temperature stable storage, they must be good enough for next few 5 or even 10 years ?Over all, looks like this el-cheapo LCR meter performs above its rated accuracy, again, many thanks.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 23, 2014, 05:11:26 pm
content: Good stuff! That confirms my suspicion that Oscon caps are a pretty good standard if you need a high value. IMO, it's also a good idea to add a precision resistor to a very low esr cap to check higher readings. For my bridges I do dissipation factor standards consisting of a silver-mica in series with a small metal film to get dial calibration points like .01, .05, .1 and such. Naturally such combinations are good only at the single frequency they're designed for.Polystyrene is said to have a predictable temperature coefficient. Silver-mica maybe not as much, but I think GR took advantage of the combination to create near zero tempco reference caps by making up a total value with a certain percentage of polystyrene and the balance from mica.There's a calculation utility on my site that will give you most of the different forms of impedance for whatever input value you might have, or at least many of 'em.

author: dr.diesel
author_rank: Super Contributor
timestamp: February 23, 2014, 05:15:31 pm
content: I have an in-cal HM8118, 0.05% base, if it helps any US/Midwest folks.

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 23, 2014, 06:41:50 pm
content: Quote from: Conrad Hoffman on February 23, 2014, 05:11:26 pmHi, Conrad,I put the film caps and the OSCON in the refrigerator, which I keep just a degree or so above 0 C, and them measured them quickly to get at idea of the actual tempco of the caps I sent out. I was astounded by the low tempco of the OSCON. Ordinary aluminum electrolytics are terrible.I have several of the classic GR standard caps that I got from Boeing surplus. They still have the cal stickers on them from 40 years ago; they're well aged now. I measured them about 10 years ago, and just recently they have hardly drifted at all.

author: BravoV
author_rank: Super Contributor
timestamp: February 24, 2014, 01:46:48 am
content: Quote from: The Electrician on February 23, 2014, 06:41:50 pmWonder what type of dielectric cap they used inside ? Have you ever take a peek ?Btw, fixed the measurement results and updated the previous spreadsheet, for oscon and other caps. Used series resistance mode which has better resolution at 1 mili Ohm than in cap mode, and measured all without problem. Below OSCON cap measured in Series Resistance Mode @ 100 KHz.

author: BravoV
author_rank: Super Contributor
timestamp: February 24, 2014, 03:15:48 am
content: While observing The Electrician's sweep chart above, I noticed at the circled area is not smooth, and has very rough results and full with crazy fluctuations. As my cheap LCR doesn't have the freq sweep feature and only with certain fixed frequency points like 100,120,1K,10K,100KHz.Just want to ask you guys if this area has something to do with my experience, that it was so difficult to get a stable reading if it happened that the test frequency was in that region ?I imagine a tiny drift or instability at the test frequency will change the measured value erratically.Correct me if I'm wrong.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: February 24, 2014, 03:47:55 am
content: BravoV,The challenge with this measurement is that the resistive portion is 4 orders of magnitude 10,000 times smaller the impedance at these frequencies.Jay_Diddy_B

author: Vgkid
author_rank: Super Contributor
timestamp: February 24, 2014, 06:04:36 am
content: Quote from: BravoV on February 24, 2014, 01:46:48 amMost likely mica, as the really old 505 series used them, along with the 1409 series(though the larger values are polyprop).

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 24, 2014, 10:00:42 pm
content: Yes, the typical GR cap is mica. It's actually an assembled stack of big mica plates and (lead?) electrode foils crammed together by a big mechanical clamp. The cover of the housing is potted, but the cap is in air, not potted itself. A desiccant pack is included next to the cap. I believe the combo mica and polystyrene cap was used in the 1608 bridge. Not sure if they did that with any others, as the 1608 was the most accurate traditional bridge they (or anybody) made. They were bettered by the 1615 type that used a ratio transformer and nitrogen filled invar plate capacitors.

author: The Electrician
author_rank: Frequent Contributor
timestamp: February 25, 2014, 01:38:52 pm
content: Quote from: BravoV on February 24, 2014, 03:15:48 amThe noise in the curve you noted is due to the high quality (Q) of the polycarbonate capacitor. The ESR is so much smaller than the reactance of the capacitor that the meter has difficulty making the measurement. Increasing the applied voltage from .5 volt to 1.0 volt and changing the sweep speed to a slower setting allows a better measurement as can be seen in the following image:I suspect this high Q of the capacitor is the reason your ESR measurements of this capacitor at low frequencies are so much different from mine; this is undoubtedly the reason for the instability of your measurement in that region. The Wayne-Kerr is designed to be able to measure high Q components, whereas your meter is probably not as capable in that regard.I am impressed by the overall performance of the MS5308; one can't complain about it very much.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: March 23, 2014, 11:20:56 pm
content: Hello all,Quite some time ago I sent my measurement results directly to The Electrician for the four reference components that he kindly mailed to me. I had to hold off supplying results in this thread because I was waiting for a new DER EE DE-5000 to be sent from Japan. I wanted to include its results, along with those of my Tenma 72-960 handheld LCR meter that I've been relying on for about 12 years.I didn't include any measurement results here from my AADE L/C IIB inductance and capacitance meter (which I like) because its applied test frequency of approximately 10KHz to 750KHz isn't user adjustable and the measurement results won't fit neatly into this four test frequency reporting format.Also, since BravoV had such a nice layout for his test results above, I just went with that.On a related side note; when I first received the DE-5000, the displayed measurement results seemed to be a bit unstable (unlike the demonstration by robrenz in one of his videos). Opening the meter I found some poor solder wetting on a couple of the joints where the split banana jacks and component insertion slot blades attach to the PCB. There was a visible ridge in the solder. Adding a bit of flux and retouching the joints improved the stability of the meter's readings. I also slipped a piece of thin plastic into the bottom area of the 9V battery to force it a bit more toward the two battery compartment contacts. Those two contacts didn't seem to deflect backwards at all when the battery was installed without the added plastic shim (i.e., a small piece of an old plastic gift card).Regards

author: robrenz
author_rank: Super Contributor
timestamp: March 24, 2014, 12:28:39 am
content: Quote from: fpliuzzi on March 23, 2014, 11:20:56 pmI am using kelvin connections that are separate all the way to the component leads in the video. They seem to perform a little more consistently than the standard crock clips.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: March 24, 2014, 01:08:44 am
content: Quote from: robrenz on March 24, 2014, 12:28:39 amHello robrenz. I was aware that your meter's impressive measurement repeatability was because of your very nicely made custom 4-wire mod to the crock accessory, but my DER DE-5000 was originally making some fairly big swings when I was measuring down to the lower milliohm range. I expected it to be closer to, but certainly not exactly like, the excellent results that you showed in your video.My DER DE-5000 acts better now, but I'll attempt to do some version of your 4-wire crock accessory mod to gain as much stability and repeatability as I can. Your four mini-grabber version looks doable. Thanks for your thought provoking videos.Regards

author: BravoV
author_rank: Super Contributor
timestamp: March 24, 2014, 07:23:38 am
content: Frank, I believe these Cyrustek based LCR meters will only give a stable reading when using 4 wires measurement mode.My MS5308 results were rock solid without even flickering at the least significant digit once the 4 wires alligator clips clamped or bit firmly at the dut pins as shown at my previous photos.All this time I thought DER DE-5000 came with standard 4 wires alligator clips.

author: robrenz
author_rank: Super Contributor
timestamp: March 24, 2014, 11:39:37 am
content: The standard crock clips are 4 wire but only to one leg of the crock clip. The crock clip is not a Kelvin type clip that has the two halves insulated from each other to keep the force and sense leads separate all the way to the component lead.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: March 24, 2014, 12:25:44 pm
content: BravoV, robrenz,I think I'll just substitute a pair of MUELLER BU-75K Kelvin Test Clips in place of the standard crock clips on the TL-21 accessory. This would probably be the quickest path to a more stable and repeatable measurement. As you've both stated, a true 4-wire measurement is the way to go.Thanks for the feedbackwww.ebay.com/itm/2-pcs-MUELLER-Electric-Kelvin-Test-Clip-10-amp-BU-75K-Blakc-NEW-/191109195279?pt=LH_DefaultDomain_0&hash=item2c7efee60f

author: robrenz
author_rank: Super Contributor
timestamp: March 24, 2014, 12:42:19 pm
content: I have some of those clips and they are ok but they tend to slip off the leads rather easily. I would look for some that have actual serrations in the jaws that will grip a lead better.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: March 24, 2014, 04:08:49 pm
content: I see what you mean about the need for the test clips to bite into the component under test's leads to get a stable measurement reading. Just as a very quick test I modified a pair of standard grabbers to make them into makeshift "kelvin clips" for my TL-21. In theory, I think that these things should work better than the standard TL-21 croc clips, but they didn't... (see update)I'll keep my eye out for a true kelvin clip that can supply the needed solid grip onto component leads to get the result that I am looking for when measuring low milliohm values.My Rube Goldberg "kelvin clips" are at least good for a chuckle...---------------------------------------------------------------------------------UPDATE:I only made this rudimentary set of "kelvin clips" from two standard grabbers I had on hand so I could see if the slight instability in my low milliohm measurements was the DE-5000 itself or because of the TL-21 crock assembly. I also made a simple adapter out of a piece of double sided copper-clad material and a bit of lexan so I could plug these "kelvin clips" into the LCR meter without modifying my TL-21 accessory (added two photos below). The copper-clad material has the four required isolated zones cut into it for doing true four wire measurements.To my surprise the readings are very steady now. At least I know now that the LCR meter itself is fine. I'll modify my TL-21 when I purchase a pair of proper kelvin clips, using shielded cable.

author: robrenz
author_rank: Super Contributor
timestamp: March 24, 2014, 04:52:18 pm
content: Quote from: fpliuzzi on March 24, 2014, 04:08:49 pmNothing wrong with that designI am sure the residual on that is smaller than the meter can detect.

author: BravoV
author_rank: Super Contributor
timestamp: March 24, 2014, 05:37:19 pm
content: Agree with Robrenz on a non serrated jaws, apart from the slippery, the "sharp teeth" of the serrations also good for biting into oxidized surface at the pins to have better contacts.Anyway, that Rube Goldberg kelvin clips look awesome, pretty sure it will work just fine.Just for your reference, pictures of the Kelvin clips from the MS5308 standard accessories attached below, not the same league as Agilent'sor worst compared to the ones made by Robrenz, but I think these clips are decent enough to do the job well.

author: fpliuzzi
author_rank: Regular Contributor
timestamp: March 25, 2014, 03:37:22 am
content: robrenz & BravoV... thanks for the kind words. I added an update with two additional photos to reply #50 above. My temporary "kelvin clips" enable very solid low milliohms readings now. At least I know now that the DE-5000 itself is fine. Also, I like the look of those kelvin clips from the MS5308.Regards