Inexpensive Kelvin clips on Ebay - Page 1
Forum section: electronics / testgear

author: BillWojo
author_rank: Regular Contributor
timestamp: September 24, 2014, 04:51:01 am
content: Found these just after ordering up all the parts I need to make a set of kelvin clips for my HP 3456A. I'm using the same clips, 14GA silicone test lead wire and some better grade banana plugs.Here is the listing number 181379888365. About $22.00 shipped for the set.BillWojo

author: salbayeng
author_rank: Frequent Contributor
timestamp: September 24, 2014, 05:11:08 am
content: Yep , I've bought nearly identical bare clips on ebay , I bought a couple of pairs of red and of black (rather then the grey you have), and soldered my own 4sqmm silicone leads and good banana clips.They work OK (they have a plastic pivot for the hinge, but it looks OK (unlike some of the cheap plastic clippy things on EBAY)) , great for measuring SMD parts and you can measure 4wire milliohms on SMD ferrite beads and inductors!

author: BravoV
author_rank: Super Contributor
timestamp: September 24, 2014, 05:30:38 am
content: Quote from: salbayeng on September 24, 2014, 05:11:08 amI believe this kind of clip is not very suitable for smd component, especially you have to use them in pairs, having 4 contact points at a small smd cap is not that easy. Its more for through hole components, example here the same clip used on small plastic polystyrene cap. Imagine the clip's tips grabbing small smd, it will easily slip out.There is other type that is more suitable for smd.

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 24, 2014, 12:38:02 pm
content: I bought a set of these Chinese specials for about $18.00 to the door to use with the 4 wire ohms multimeters I have. They have gold plated clips and banana jacks, and use pure copper wire. I figured I could barely make these myself with the same materials for that price. My Applent LCR meter uses the same clips on its kelvin fixture and they are decent, which made for a strong selling point- the clip springs are very strong as they should be. The main purpose of 4 wire low ohms measurements is to eliminate test lead and contact resistance. At the low resistances where 4 wire measurements can play a factor, shielding of the leads is not necessary. For all sense and purpose the Chinese vendors make these the way they should be made to do the job properly.-Mark-

author: edavid
author_rank: Super Contributor
timestamp: September 24, 2014, 03:12:00 pm
content: What I don't understand is why it costs less to buy them with BNC connectors than banana plugs

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 24, 2014, 03:35:26 pm
content: Quote from: edavid on September 24, 2014, 03:12:00 pmThat I'm not sure of. Maybe they can get BNC male connectors at less cost than gold plated bananas.-Mark-

author: timb
author_rank: Super Contributor
timestamp: September 24, 2014, 04:09:13 pm
content: Quote from: MarkPalmer on September 24, 2014, 12:38:02 pmShouldn't one cable be going into each jaw instead of both to the same jaw, in a true kelvin clip?Sent from my Smartphone

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 24, 2014, 04:18:49 pm
content: "Shouldn't one cable be going into each jaw instead of both to the same jaw, in a true kelvin clip?"Yes, they do. It's hard to see in the picture, but the wire overlaps to the opposing jaw just above the pivot inside each clip. Doing it that way makes the clips less cumbersome to use.-Mark-

author: timb
author_rank: Super Contributor
timestamp: September 24, 2014, 04:24:38 pm
content: Quote from: MarkPalmer on September 24, 2014, 04:18:49 pmAwesome, that's perfect then. Do yours seem durable? Have a link to the vendor you got yours from? I'd like to pickup a pair.Sent from my Smartphone

author: timb
author_rank: Super Contributor
timestamp: September 24, 2014, 04:31:34 pm
content: On a related note, my main multimeter is a Tektronix 4020 which has 2x4 wire capability.Does anyone know where I can get the split banana plugs like Tek uses in their OEM cables? I'd like to roll my own.Here's a PDF explaining 2x4 Wire if anyone doesn't know what I'm talking about:http://download.tek.com/secure/3MW_24469_0_MR_8.25x11.pdf?nvb=20140924162706&nva=20140924163206&token=0a284032bec428e17625cSent from my Smartphone

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 24, 2014, 04:38:57 pm
content: Quote from: timb on September 24, 2014, 04:24:38 pmLink to the Fleabay site I got the clips at:http://www.ebay.com/itm/Kelvin-Test-line-LCR-Meter-Low-Resistance-Test-Leads-test-Clip-Terminal-/291203411964?pt=US_Cabling_Tools&hash=item43cd136ffcPlug-and-play for any multimeter with 4 wire ohms capability that uses banana jack inputs.-Mark-

author: edavid
author_rank: Super Contributor
timestamp: September 24, 2014, 04:44:28 pm
content: Quote from: MarkPalmer on September 24, 2014, 03:35:26 pmIf you believe that's gold, I have a Wheatstone bridge to sell you

author: Orange
author_rank: Frequent Contributor
timestamp: September 24, 2014, 05:07:38 pm
content: With all these clips; check if the spring inside is not puncture the thin isolation tape on both jaws. If they do, (mine did) your kelvin principle is gone.So yes they are cheap, but check them, and or fix them.

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 24, 2014, 05:20:48 pm
content: Quote from: edavid on September 24, 2014, 04:44:28 pmI'm (so to say) familiar enough with it where I can say that it probably is real gold plating. But that is nothing all too special or uncommon in electronics. It's the most un-pure industrial gold there is, and the plating is extremely thin. Anyone familiar with legacy HP and Tektronix circuit boards has come across it as trace plating.-Mark-

author: edavid
author_rank: Super Contributor
timestamp: September 24, 2014, 05:47:45 pm
content: Quote from: MarkPalmer on September 24, 2014, 05:20:48 pmWhy do you say that? I have some of these clips and plugs, and they are not at all the same color as real gold plating. They look like brass to me.

author: edpalmer42
author_rank: Super Contributor
timestamp: September 24, 2014, 05:56:39 pm
content: I used the same clips to make my own cables. The only thing I did that hasn't been mentioned is that I used dual banana plugs to make it a bit easier to connect to my milliohmeter. My meter has a resolution of 0.01 ohms and that's what I measure when I short the leads together. Good enough for me.By the way, if you search this forum for 'kelvin clips' you'll find at least one old thread about these connectors.Ed

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 24, 2014, 06:11:46 pm
content: Quote from: edavid on September 24, 2014, 05:47:45 pmBrass is not generally used as a conductor, and it definitely shouldn't be used for a low ohms wire application. Even aluminum has better conductivity than brass or a brass/zinc alloy and would have been cheaper to use than brass. Gold has one of the most stable and lowest contact resistances of all metals. However I am not a metallurgist, so if anyone knows of some type of easy to perform test I could do on these clips to see what the plating actually is please let me know. In any event I don't think it matters much as far as the performance of the clips.-Mark-

author: G0HZU
author_rank: Super Contributor
timestamp: September 24, 2014, 06:29:06 pm
content: Because I rarely need to do 4 wire measurements and I don't need great accuracy I just made my own using cheap wire, cheap banana plugs and a couple of bits of copper shim.They seem to work very well although they are not true Kelvin leads because of the simplistic construction method.However, for tiny SMD stuff I think my (compromised) leads may well outperform the ones in this thread because the croc tips look so big and clumsy. But for classic measurements of stuff like wire or leaded components my cheapo leads will not be as good.

author: G0HZU
author_rank: Super Contributor
timestamp: September 24, 2014, 06:36:24 pm
content: If you had to measure something like one of these:http://uk.farnell.com/te-connectivity-cgs/cgssl1r01j/resistor-smd-0-01r/dp/11742430.01R 5% SMD resistorWhat results do you get with the croc style leads?With my crude lashup leads I can get 0.010R with maybe +/- 0.001R of wavering uncertainty (because my cheap and nasty leads can't properly compensate for contact resistance)If I measure two in series I get an averaged reading of 0.0196R.

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 24, 2014, 06:50:20 pm
content: Surprisingly the croc clips aren't clumsy, they are much better than meets the eye IMHO. I don't know how they would work on SMD components because that is not my personal application for them, I suppose they would be OK. But there are 4 wire Kelvin tweezers made specifically for SMD applications, however they are considerably more expensive than the ideas mentioned here. The ones I mention are an $18.00 poor man's plug-and-play, not necessarily intended for precision rocket launching applications. They are more to be able to easily take advantage of multimeters with 4 wire ohms capability in a convenient manner by not having to factor in or zero out lead resistance or worry about poor contact from standard test leads when measuring low resistance.-Mark-

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2014, 07:08:11 pm
content: If you want the split banana pins it would be best to look at the videos from Robrenz here, where he has made some.

author: robrenz
author_rank: Super Contributor
timestamp: September 24, 2014, 07:21:22 pm
content: Quote from: MarkPalmer on September 24, 2014, 06:11:46 pmIMO when doing low ohms kelvin measurements the materials and contact resistances of your leads and plugs is not an issue. At these levels you must be using some form thermal emf error removal either offset compensated ohms or current reversal technique. The nature of 4 wire Kelvin measurement inherently removes lead resistances from the measurement process.

author: G0HZU
author_rank: Super Contributor
timestamp: September 24, 2014, 08:54:02 pm
content: QuoteAgreed. However, my homemade leads aren't (quite) arranged like a classic Kelvin connection and so therefore can't compenstate for contact resistance in the same way the $18 croc leads on this thread can do. I've compromised this against simplicity of construction and also the ability to measure SMD parts and PCB traces that are very small.So to get good performance from mine I have to make sure I get a very good contact.I'd be interested in what (4wire tweezers?) people use for measuring fine PCB traces and very small SMD parts with sub 0.05R resistance. I'm tempted to buy the $18 leads for measuring stuff like wires and leaded parts but I'm much more likely to want to measure SMD parts or PCB traces.

author: BillWojo
author_rank: Regular Contributor
timestamp: September 24, 2014, 10:42:23 pm
content: Mark Palmer, I looked at those leads before I purchased the stuff to make my own and thought that both leads went to one jaw. I actually spent a few more dollars than they cost to get the parts to make my own. I wish they had shown a picture of the insides of the jaws. Oh well. I purchased 1 meter of 14Ga red and black silicone insulated wire. Any reason to cut them down to 20" as that seems to be a popular lead length for Kelvin clips.BillWojo

author: AlfBaz
author_rank: Super Contributor
timestamp: September 24, 2014, 11:08:37 pm
content: When buying these leads from ebay just be aware of some of the issues with themhttps://www.eevblog.com/forum/testgear/kelvin-clips/msg383643/#msg383643

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 25, 2014, 12:37:20 am
content: Handled normally the Chinese clip set holds up fine. If it breaks, no differential calculus is needed for repair. It is not a $200.00 set from Pomona but an $18.00 set from China that is functional. You can't expect sun, moon, and stars for 18 bucks.-Mark-

author: salbayeng
author_rank: Frequent Contributor
timestamp: September 25, 2014, 03:56:58 am
content: Thanks tohttps://www.eevblog.com/forum/testgear/kelvin-clips/msg383643/#msg383643I now have figured out what's wrong with my fleabay "power supply leads" = red/black dual croc clips to dual bananas ,same deal with the screw going into insulation, I'll fix them with some ferrules.

author: AlfBaz
author_rank: Super Contributor
timestamp: September 25, 2014, 05:36:16 am
content: Quote from: MarkPalmer on September 25, 2014, 12:37:20 amPerhaps not but the rate of change of my mood certainly warranted a rate of change in the dose of my meds

author: DanielS
author_rank: Frequent Contributor
timestamp: September 25, 2014, 06:48:02 am
content: Quote from: MarkPalmer on September 24, 2014, 05:20:48 pmNo need to look at fancy equipment since gold plating is quite common in PCs and consumer electronics in general - nearly all high-speed connectors are gold-plated to make contacts less vulnerable to contamination and oxidation.

author: MarkPalmer
author_rank: Regular Contributor
timestamp: September 25, 2014, 12:33:03 pm
content: Quote from: AlfBaz on September 25, 2014, 05:36:16 amI have shared your frustration many times with some of this crap that falls apart the very first time I go to use it. I’ll take my blood pressure meds, than remind myself that I’ve wasted money on a lot stupider things as I pull out my tools to try to cobble the piece of Chinese garbage back together. Many times you can vastly improve upon the design on your own, and still be many dollars ahead and only out a little of your time. We know the Pomona equivalent to this cable is $200.00. It’s a professional set that would probably last several human lifetimes but price wise likely well out of reach of the hobbyist. It’s that, deal with China-cha-loo, or you, “roll your own,” cable set.-Mark-

author: MarkL
author_rank: Unknown
timestamp: September 25, 2014, 06:55:51 pm
content: These Pomona 5143-K SMD tweezer leads are pretty handy:http://www.pomonaelectronics.com/pdf/d5143_101.pdfYou need two of them to do Kelvin measurements, but unlike Kelvin tweezers you can separate the 2 measurement endpoints. I've found them useful for tracking down PCB shorts and I think they're easier to maneuver on a crowded board than Kelvin alligator clips. If you need one hand free you could use one tweezer and one alligator.They're not super cheap, about US$30 each.Pomona has a couple of other similar models with BNC (5142-K) or shrouded banana (5678-K) termination.Hint: If you get these, don't try to bend the probe tips so they can be closer together. The tips are very brittle. It cost me $30 to learn that.

author: BillWojo
author_rank: Regular Contributor
timestamp: September 25, 2014, 10:39:29 pm
content: The first components of my Kelvin clips came in today. I ordered banana jacks from a hobby shop on Ebay as Franky (Iloveelectronis) from this board didn't have the ones I was looking for. I purchased item number 331284031622 They have gold plated machined pins with solder sockets. Looks like nice heavy duty banana plugs. Not really cheap at 3.50 a set but you get what you pay for.I have a question, seems like most of the ready made Kelvin clips have rather short leads. Is there a reason for that? I ordered 2 meters of 14GA silicon lead wire from Franky. I was going to make the leads 20" but that seems really short. Is 30 or 36" OK?ThanksBillWojo

author: robrenz
author_rank: Super Contributor
timestamp: September 26, 2014, 12:40:43 am
content: You should have no problems with 36" leads with 14Ga wire with Kelvin connections as long as your meters input impedance on the sense circuit is 10Meg or higher.

author: timb
author_rank: Super Contributor
timestamp: September 29, 2014, 10:04:29 pm
content: So, for a few dollars more ($23 vs $18) I ended up getting these:http://r.ebay.com/xelEVTI like the fact they’ve got real molded strain relief on the banana plug ends and use decent quality silicon cable. They’re clearly using the same clips as the cheaper versions; they also have wires going into each handle, which is a bit more cumbersome, I suppose. Anyway, I’ve bought from her before and it’s always been quality stuff.BTW, I did a “Best Offer” of $15 and she came back with $23 and Free Shipping, so that’s how I got them lower than the $25 list price, saving a couple of bucks.

author: VK5RC
author_rank: Unknown
timestamp: September 30, 2014, 07:58:02 am
content: I put a bit of heatshrink over the spring to help insulation.

author: MK
author_rank: Regular Contributor
timestamp: September 30, 2014, 05:25:36 pm
content: I bought some other "gold plated Copper" Kelvin clips, they had inserts for the jaw contact so the spring shorting will not be an issue. It was real gold plate over nickel, over copper, over brass, so the insert will be changed before use, but those look quite good to me.I took a file to the soldering area at the back of the insert to check...

author: mzzj
author_rank: Super Contributor
timestamp: October 01, 2014, 07:39:06 am
content: My favorite so far:http://www.ebay.com/itm/NEW-Mueller-BU-75K-10-amp-electric-kelvin-test-clip-/130946949354?pt=LH_DefaultDomain_0&hash=item1e7d0be0ea