Chinese Kelvin clips, Banana plugs and Posts. - Page 1
Forum section: electronics / testgear

author: henas
author_rank: Contributor
timestamp: July 21, 2015, 01:49:15 am
content: I would be interested what experience others have had with these products out of China.Maybe some did some testing to compare them to some reputable brands or even determined what material are they made off. Anyone bought a real gold over copper from China?I ordered two sets most common Kelvin clips on Ebay. Both were advertised as gold plated over copper.After filing some material off I found silver coloured alloy underneath. No copper whatsoever.The metal is not magnetic. What material is this?I learned gold plated banana plugs and banana posts are made out of steal alloy. Both attract magnet.It is possible to buy more expensive "copper"(no magnetic) with this silver alloy material inside but still no copper.What about gold plating? Are they really gold plated? I have no way to establish this one way or another.

author: Monkeh
author_rank: Super Contributor
timestamp: July 21, 2015, 01:56:37 am
content: File further, that's probably nickel over the copper.

author: henas
author_rank: Contributor
timestamp: July 21, 2015, 02:01:11 am
content: Initially I thought that too but I filled pretty deep and no copper. I would expect nickel layer to be very thin??

author: Monkeh
author_rank: Super Contributor
timestamp: July 21, 2015, 02:02:47 am
content: It would be, but it's fairly hard.. but seeing as you've gone deep.. Could be aluminium or something else. See if it solders.

author: thefamilyman
author_rank: Regular Contributor
timestamp: July 21, 2015, 05:55:54 am
content: If they're the same ones as mine they would be gold anodized aluminum.the banana plugs on them is a joke, its just poorly screwed down, not soldered at all.I complained to the seller and got my money back then bought some Hirschmann banana plugs and soldered them in.

author: henas
author_rank: Contributor
timestamp: July 22, 2015, 03:27:20 am
content: I bought only two pairs of kelvin clips and made my own set. More expensive pair looks exactly like one on your picture.How gold over aluminium compare to gold over copper or brass ?Anyone did any comparison ??

author: edavid
author_rank: Super Contributor
timestamp: July 22, 2015, 03:51:04 am
content: The ones I bought were brass.You can tell from the color that there is no gold in the platiing.

author: henas
author_rank: Contributor
timestamp: July 23, 2015, 01:01:43 am
content: These picture is not giving justice. The plating on these clips is definitely gold coloured.This brings me to my second question so far unanswered. Is this real gold plating on all these products from china?I have no doubt some are but is there other process available which can fake gold plating???

author: sburrell
author_rank: Newbie
timestamp: July 23, 2015, 01:54:46 am
content: If you are talking about the 4 wire kelvin's the chinese clips work equally as well. 4 wire setups eliminate the leads and contact points so it doesn't matter what they are made of as long as everything is connected. All my 4 wire meters give identical readings with "real" 4 wire clips vs Chinese.

author: henas
author_rank: Contributor
timestamp: July 23, 2015, 04:51:49 am
content: I understand, for 4 wire measurement that OK but this is not just about kelvin clips and 4 wire measurement.Other application require low EMF contacts and gold over copper is hard to beat.I started this thread because I received kelvin clips/banana plugs/binding posts claimed to be gold plated copper made from other material but copper.Since I learned some are made from aluminium others are steel alloy.Now I have serious doubts if the plating is gold too so I asked is there any other process which could fake gold plating.

author: eas
author_rank: Frequent Contributor
timestamp: July 23, 2015, 05:51:41 am
content: I have some ofthese binding posts, some ofthese adapters, and thesebanana plugs. They all came from the listings I linked to. I didn't have high-expectations, and so I'm not too surprised or disappointed to say that I doubt that they have any gold on them, of if they do, not enough. They didn't look genuine gold plate when they arrived, the color to them was off, sort of brassy. The ones that have been handled are starting to discolor a bit.I've had some other stuff that seems genuine, but who knows. It's a crap-shoot. If you just need a few, your best bet is probably to pay the overhead of getting something from digikey or similar, that or check with Franky (iloveelectronics). That's probably what I'm going to do.

author: TMM
author_rank: Frequent Contributor
timestamp: July 23, 2015, 07:53:32 am
content: Those type of cheap banana plugs with the 'birdcage' springy part loosely crimped over the solid pole piece are trouble if you want a low resistance connection. Often they arrive with contamination between the cage part and the solid part forming a poor connection. Even if you clean them, eventually they oxidise and you get a high impedance condition again. Quick fix is to solder the two pieces together. Just be careful because now twisting the connector can mutilate the jack, particularly multimeter ones with split connections.Personally I run these Hirschmann banana plugs on all my test leads now, super reliable:

author: BurningTantalum
author_rank: Frequent Contributor
timestamp: July 24, 2015, 11:59:34 am
content: These plugs were always known and sold as 'Bunch Pins' when I were a lad. Banana Plugs had a solid pin with a banana spring part on one side.I wonder when this changed, or was it just a UK thing?BT

author: Stray Electron
author_rank: Super Contributor
timestamp: July 24, 2015, 01:53:15 pm
content: Quote from: Monkeh on July 21, 2015, 01:56:37 amI very much doubt it. I haven't seen anybody do that in decades. I've replaced hundreds if not thousands of battery contacts in Hewlett Packard (and other) products ranging from 1973 production to current production and even they don't use nickel or even copper. Just gold plate over steel. Also keep in mind that battery contacts, banana plugs etc need to be springy and copper isn't stiff enough or springy enough so most things use a steel core. Also FYI gold is very porous and the purpose of a layer of nickel is to prevent corrosion from reaching the steel below. You'll notice that in many products, the batteries release electrolyte with age and it goes through the gold layer and corrodes the steel and the gold (or chrome) outer layer falls off in sheets. Thebestpractice is a copper layer over steel and then nickel over that and then gold or chrome on the top. But I haven't seen anything made like that since the 1950s. Ironically the last time that I saw that used was on a MG TD that I used to have.

author: Stray Electron
author_rank: Super Contributor
timestamp: July 24, 2015, 02:02:22 pm
content: Quote from: henas on July 23, 2015, 04:51:49 amYes, there absolutely is. It's been done for centuries. That's why people started using touchstones over 5000 years ago.https://en.wikipedia.org/wiki/Touchstone_%28assaying_tool%29You rub a piece of "gold" across one and the color of the streak will tell you how pure it is. There are much more sophisticated tests today but a touchstone is quick and easy and it works! Mostly likely, your items are gold plated but only VERY thinly. Also pure gold is to0 soft for most uses so more than likely than likely that they're plated with a gold alloy.

author: fqahmad66
author_rank: Regular Contributor
timestamp: July 24, 2015, 05:06:50 pm
content: Well I made my own. shield must be close to tip

author: Gyro
author_rank: Super Contributor
timestamp: July 24, 2015, 07:17:18 pm
content: QuoteJust curious, how durable are those elastomer sleeves, they look like an obvious point of failure. Does anyone have experience of this? Do they come with spares?

author: splin
author_rank: Frequent Contributor
timestamp: July 26, 2015, 12:54:04 am
content: It wouldn't be difficult to make your own from copper sheet, plastic pivots and some elastic bands, but how feasible, and how expensive would it be to gold plate the tips using one of the many gold-plating kits on the market? Alternatively how expensive would it be to get a few home made clips, connectors and spade lugs gold plated professionly?Would it be essential to nickel plate first to prevent the copper diffusing into the gold and subsequently oxidising at the surface which would be disastrous for thermal EMFs. This company for examplehttp://www.lowthermal.com/cables-and-connectors.phpdoesn't use nickel claiming reduced thermal EMFs but I'd have thought the difference would be negligible for such a thin layer - the temperature gradient across a few microns of plating must be extremely small surely?

author: edavid
author_rank: Super Contributor
timestamp: July 26, 2015, 02:39:31 am
content: Quote from: splin on July 26, 2015, 12:54:04 amAt least for home plating, if you don't have a nickel barrier, it doesn't work - the gold diffuses into the copper as you try to plate it.

author: dadler
author_rank: Unknown
timestamp: July 26, 2015, 03:21:47 am
content: Quote from: Gyro on July 24, 2015, 07:17:18 pmI have a set of these. Have not used them a lot, but I suspect they will weaken with time. No spare bands, although I am sure you could fashion something out surgical tubing.

author: splin
author_rank: Frequent Contributor
timestamp: July 26, 2015, 04:23:59 pm
content: Quote from: edavid on July 26, 2015, 02:39:31 amDo you end up with a 50:50 (or whatever) copper-gold alloy? You can get nickel and gold plating kits for around £60 so is this likely to be feasible? 24K gold would be too soft for contacts so I guess the problem would be getting a suitable gold alloy plating solution as these kits are primarily for jewellery/cosmetic purposes.

author: edavid
author_rank: Super Contributor
timestamp: July 26, 2015, 04:34:30 pm
content: Quote from: splin on July 26, 2015, 04:23:59 pmI don't know, I think most people would stop before they wasted $1000 worth of gold to find out.QuoteI don't see why not, but I don't understand the purpose of gold plated Kelvin clips in the first place, since contact resistance doesn't matter, and you have plenty of pressure.

author: splin
author_rank: Frequent Contributor
timestamp: July 26, 2015, 06:03:52 pm
content: Quote from: edavid on July 26, 2015, 04:34:30 pmThermal EMFs when measuring microvolt signals. Copper to copper has low thermal EMF, < 0.3uV/C, but copper oxide to copper is terrible at around 1000uV/C. Gold plating stops the copper oxidising and only increases the thermal EMF slightly to .5uV/C

author: Gyro
author_rank: Super Contributor
timestamp: July 26, 2015, 06:22:32 pm
content: QuoteThanks, that's what I suspected. As you say, replacements could be fairly easily fashioned with the right material, would need to be silicone (as you suggest) or maybe butyl. Elastic bands at a pinch

author: henas
author_rank: Contributor
timestamp: July 27, 2015, 11:07:35 am
content: After reading about all these possible problems with gold plated copper when not done properly,why not having copper tinned with solder instead. This will stop oxidation and the EMF is only slightly higher then gold plating.For Kelvin clips this doesn't matter anyway. This can be nulled out in most cases.Am I missing something here??

author: Gyro
author_rank: Super Contributor
timestamp: July 27, 2015, 11:28:28 am
content: Copper - Tin/Lead solder 1 - 3uV/'C Can't find a figure for unleaded.

author: henas
author_rank: Contributor
timestamp: July 27, 2015, 10:21:04 pm
content: For gold/copper EMF is 0.5uV. I believe this is for 24 carat gold.In case the plating is not pure gold and there is nickel barrier used underneath I would expect EMF will exceeds 0.5uV by substantial amount. This leads me back to the same conclusion the difference is not that great when the solder is carefully chosen.Any thoughts???