Small Kelvin clips that actually grab? - Page 1
Forum section: electronics / testgear

author: precaud
author_rank: Frequent Contributor
timestamp: November 19, 2020, 01:49:58 pm
content: All of the small (2" or less in length) Kelvin clips I have tried are practically useless, their contact surfaces don't have serrations deep enough to hold onto anything. Most larger clips are pretty good in this respect. But the small ones for some reason are all very smooth.I've tried generics from China (see pic below), and domestic-branded ones. No difference. Except price...Does anyone know of a small Kelvin clip that actually has usable teeth?

author: precaud
author_rank: Frequent Contributor
timestamp: November 20, 2020, 03:40:52 pm
content: Bump...

author: Stray Electron
author_rank: Super Contributor
timestamp: November 20, 2020, 05:25:21 pm
content: I bought these and I'm happy with themhttps://www.amazon.com/gp/product/B071SL6PQS/ref=ppx_yo_dt_b_asin_title_o00_s01?ie=UTF8&psc=1They're not Kelvin clips but they can be used in a Kelvin arrangement. Just clip the two leads from the voltage sense circuit as close to the body of the DUT as possible and connect the two leads from the current source out beyond those two.

author: precaud
author_rank: Frequent Contributor
timestamp: November 20, 2020, 09:14:48 pm
content: Thanks, but that wouldn't work for me. I need a Kelvin clip arrangement with small contact area, not separate leads.

author: tautech
author_rank: Super Contributor
timestamp: November 20, 2020, 09:23:42 pm
content: Dremel mods time ?

author: Martin72
author_rank: Super Contributor
timestamp: November 20, 2020, 09:41:47 pm
content: Hi,You could use these ones:https://www.distrelec.de/Web/Downloads/_t/ds/BU-30C_eng_tds.pdfAnd solder/crimp two leads at the same point of the clip.

author: precaud
author_rank: Frequent Contributor
timestamp: November 20, 2020, 09:53:25 pm
content: Quote from: tautech on November 20, 2020, 09:23:42 pmYeah, I've considered that and similar, but didn't want to bugger the plating.Quote from: Martin72 on November 20, 2020, 09:41:47 pmNot a true Kelvin, but a fallback...

author: Martin72
author_rank: Super Contributor
timestamp: November 20, 2020, 09:57:37 pm
content: QuoteHere they did the same I suggested and call it kelvin clamps:https://www.sourcetronic.com/shop/de/kelvin-test-clips-st26027a.htmlYou get the "best" results, when you´re measuring the voltage as near as possible to the point you feed in the current.

author: Electro Fan
author_rank: Super Contributor
timestamp: November 20, 2020, 09:59:32 pm
content: I tried a few inexpensive Kelvin clips - these grab ok and seem to measure reliably:https://www.tequipment.net/BK/TLDK1/Kelvin-Test-Leads/?Source=googleshopping&gclid=EAIaIQobChMIubrx_Y326wIVDb7ACh3bAQs_EAQYAyABEgLdZ_D_BwEOthers might grab ok but didn’t seem to measure as reliably:https://www.eevblog.com/forum/testgear/4-wire-2-wire-resistance-tests-various-cheap-kelvin-clips-various-meters/msg3227316/#msg3227316Experience with BK Precision Kelvin Clips:https://www.eevblog.com/forum/testgear/4-wire-2-wire-resistance-tests-various-cheap-kelvin-clips-various-meters/msg3240888/#msg3240888

author: precaud
author_rank: Frequent Contributor
timestamp: November 20, 2020, 11:21:28 pm
content: Those are the large clips, of which I have several. I want the small ones for this.

author: Electro Fan
author_rank: Super Contributor
timestamp: November 20, 2020, 11:43:41 pm
content: Quote from: precaud on November 20, 2020, 11:21:28 pmOh, that's what 2" or less means in length meansI should have read your post more closelyNone of the ones I tried were close to 2"; all were about 3.5" in length. Only other idea is to try 4 small (~2") Pomona or Pomona-like (E-Z Hook) mini grabbers - just not sure how much "grab" you need.These E-Z Hook grabbersare the shortest (~2.25") single mini-grabber types I've seen that have some sorta/kinda semi-decent (but not real great) "grab", and the molded housings on the stackable banana plugs are better than the screw on plastic cover version. They come in various lead lengths.If you find small, good grabbing, reliable measuring Kelvin clips let us know.

author: precaud
author_rank: Frequent Contributor
timestamp: November 21, 2020, 03:49:18 am
content: I definitely will post if I find something. I don't wanna mess with individual grabbers. Sometimes there woudn't be enuf room for them anyway. The 2" clips I have would be fine if they didn't slip off so easily.

author: precaud
author_rank: Frequent Contributor
timestamp: November 21, 2020, 03:53:11 am
content: Quote from: Martin72 on November 20, 2020, 09:57:37 pmThose look real enough. The sense terminals are probably on the other side of the insertions. GenRad and Wayne Kerr made clip sets that attached like that.

author: tautech
author_rank: Super Contributor
timestamp: November 21, 2020, 04:41:13 am
content: Quote from: precaud on November 20, 2020, 09:53:25 pmFile a little of the metal off where it doesn't matter to check what's under the plating.

author: Martin72
author_rank: Super Contributor
timestamp: November 21, 2020, 10:32:31 am
content: Well.....I´ve totally forgot that I´ve already got small clips with good grip...They came with my Ascel milliohm meter and got a nice building quality.Grip is good, a small resistor with 0.8mm diameter leads they can handle it with no problems.

author: Electro Fan
author_rank: Super Contributor
timestamp: November 21, 2020, 03:54:50 pm
content: Ascel are just about 4”, OP is looking for 2” or less. Kind of hard to find such mini Kelvins so far....

author: precaud
author_rank: Frequent Contributor
timestamp: November 21, 2020, 04:31:10 pm
content: Quote from: tautech on November 21, 2020, 04:41:13 amI bought them a couple years ago from China via eBay. IIRC, they were advertised as "solid brass" with gold plating. But since a magnet picks them up, it's obvious what they really are...These ones are new since I last looked:https://www.ebay.com/itm/283109177832They are described as "pure copper", gold-plated. The teeth actually look like they could bite. So I ordered a couple sets. If they're steel, he can eat them.

author: Electro Fan
author_rank: Super Contributor
timestamp: November 21, 2020, 04:38:56 pm
content: Quote from: precaud on November 21, 2020, 04:31:10 pmHard to beat that price with free shipping.

author: precaud
author_rank: Frequent Contributor
timestamp: November 21, 2020, 06:17:22 pm
content: Quote from: Electro Fan on November 21, 2020, 04:38:56 pmI think they both may be an error. But then, this seller looks like he sells closeouts/overstocks, or just about anything he can get his hands on

author: tautech
author_rank: Super Contributor
timestamp: November 21, 2020, 06:35:38 pm
content: Quote from: precaud on November 21, 2020, 04:31:10 pmDon't be too judgemental until you pull one completely apart.The spring of course should be steel as too the pivot and any fastenings.You'll need a small mechanics pickup magnet to find which bits are and which bits aren't.Then just to throw another apanner in any conclusions, some stainless is magnetic too.

author: Electro Fan
author_rank: Super Contributor
timestamp: November 21, 2020, 07:30:02 pm
content: Quote from: precaud on November 19, 2020, 01:49:58 pmWhy all the wires with these clips? What is the wiring strategy?

author: precaud
author_rank: Frequent Contributor
timestamp: November 21, 2020, 08:02:37 pm
content: Quote from: tautech on November 21, 2020, 06:35:38 pmThat's what I used. My hamhandedness requires that I keep it handy...Quote from: Electro Fan on November 21, 2020, 07:30:02 pmThat particular set was for an HP 4328A. Using multiple wires to lower the inductance allowed me to use a longer lead length than they specified. I have a similar setup that I use for HP 4800A. But it's not a 4-wire setup.

author: Electro Fan
author_rank: Super Contributor
timestamp: November 21, 2020, 09:05:50 pm
content: Quote from: precaud on November 21, 2020, 08:02:37 pmhttp://www.testequipmenthq.com/datasheets/Keysight-4328A-Datasheet.pdfcool!

author: precaud
author_rank: Frequent Contributor
timestamp: November 21, 2020, 10:39:29 pm
content: Quote from: Electro Fan on November 21, 2020, 09:05:50 pmYes, I like it. Fixed 1kHz, so not useful for capacitor ESR, though...

author: Electro Fan
author_rank: Super Contributor
timestamp: November 22, 2020, 04:03:59 am
content: Quote from: precaud on November 21, 2020, 10:39:29 pmNot as cool as the 4328A but for that there is this...https://www.peakelec.co.uk/acatalog/esr70-capacitor-esr-meter.html

author: graybeard
author_rank: Frequent Contributor
timestamp: November 22, 2020, 10:48:03 am
content: The smallest one I have seen is this homemade clip.

author: precaud
author_rank: Frequent Contributor
timestamp: November 22, 2020, 02:17:42 pm
content: Yeah, those are awesome. I remember when Rob was doing that project, the hope was some manufacturer would pick up on it and make them... sadly one hasn't.

author: precaud
author_rank: Frequent Contributor
timestamp: January 02, 2021, 06:01:53 pm
content: Quote from: precaud on November 21, 2020, 04:31:10 pmI just got the mini-Kelvin clips referred to above. About 45 days from order to receipt. They are definitely better than previous similar ones I've bought. The contacts are indeed non-ferrous and gold-plated. And the teeth grooves actually are deep enough. Not as deep as I'd like to see but deep enough to grab fairly well. They are still available so I'll be ordering a few more sets just to have around. At this price they're a great deal.

author: pope
author_rank: Frequent Contributor
timestamp: April 07, 2024, 05:43:14 pm
content: Hey, sorry to resurrect this topic but I've also been looking for some good mini kelvin clips with no great success so I'm wondering whether there are more option in 2024.Unfortunately the ebay links don't work.

author: Phil1977
author_rank: Frequent Contributor
timestamp: April 08, 2024, 08:18:23 am
content: These ones are not too bad, but in total they are around 4" / 10cm:https://de.aliexpress.com/item/1005004587014590.htmlIf it needs to be smaller, 3D-printing may be a literally scalable option:https://www.thingiverse.com/thing:5606311

author: pope
author_rank: Frequent Contributor
timestamp: April 08, 2024, 10:14:33 am
content: Thank you Phil,Unfortunately your aliexpress link doesn't work.I also found these and I'm tempted to try them out but I found 2-3 sellers but all of them without great feedback, which is weird. So, I hesitate...Link 1Link 2Link 3

author: Phil1977
author_rank: Frequent Contributor
timestamp: April 08, 2024, 10:33:50 am
content: Sorry, I hope this link is better:https://de.aliexpress.com/item/1005004587014590.html

author: TopQuark
author_rank: Frequent Contributor
timestamp: April 08, 2024, 02:04:05 pm
content: I got this set of Kelvin clips to go with my DMM6500. They are made by ETA (ETA4552) and are of high quality.The cable junctions are over moulded and the spring action of the clips is smooth without being overly strong. The clip tips are serrated reasonably well, and are thin enough to be useful in tight places (e.g. 4 leaded TO-220 precision resistors).The banana plugs has "SENSE" and "SOURCE" moulded into it, the the sense side of the tip has a small triangle presses into it. Though I still scribbled "SEN" on the sense side of the clip to make things obvious.Not cheap at 490 RMB (roughly 68 USD), but if you care about making 4-wire measurements with clips, I don't think it gets much better than this. I got mine through taobao (https://item.taobao.com/item.htm?id=40686646352) , so I'm not sure about availability outside of the site's service area.

author: pope
author_rank: Frequent Contributor
timestamp: April 08, 2024, 02:58:13 pm
content: Thanks for the recommendation Topquark!In fact, I'm looking for BNC ends so I can use them with my RLC meter. I measure L of small coils like the ones shown below and it's a bitch to do it with the normal kelvin clips

author: TopQuark
author_rank: Frequent Contributor
timestamp: April 08, 2024, 03:09:01 pm
content: Quote from: pope on April 08, 2024, 02:58:13 pmWell if you already have a LCR meter, then you'll need the BNC type for sure.But playing the devil's advocate here, LCR tweezers are definitely the easiest way to go for winding transformers. Bonus points for ease of taking it to the drill press / grinder when grinding the air gap iteratively for flyback coupled inductors.

author: pope
author_rank: Frequent Contributor
timestamp: April 08, 2024, 03:20:20 pm
content: Quote from: TopQuark on April 08, 2024, 03:09:01 pmWell, yeah I thought about tweezers but I need to use the first pin as a reference and then measure the L from pin1 to every other pin. I don't see it happening without a fair amount of swearing... Plus I need to have free hands to go through the menus, etc...

author: TopQuark
author_rank: Frequent Contributor
timestamp: April 08, 2024, 03:27:30 pm
content: Quote from: pope on April 08, 2024, 03:20:20 pmWell I was trained to use chopsticks before learning how to walk, so as not to starve. So the fact that it is a pair of tweezers but not two metal sticks as probes is an absolute luxury.But for real, it is actually quite easy to test different coil pairs with tweezers, but YMMV.

author: pope
author_rank: Frequent Contributor
timestamp: April 08, 2024, 03:28:49 pm
content: Quote from: TopQuark on April 08, 2024, 03:27:30 pmHaha, OK fair enough

author: shabaz
author_rank: Frequent Contributor
timestamp: April 08, 2024, 04:05:26 pm
content: Some of the AliExpress Kelvin clips I've tried seem pretty good, not super-robust if accidentally crushed e.g. stepped on! but definitely usable, although there's no real cable strain relief, but that's easy to work around with things like heat-shrink, etc. The ends are not heavily grooved, only lightly, but they stay on unless the cable is tugged. Some LCR meters come with such Kelvin clips, and they work fine.In terms of physical size, the Mueller Electric BU-75K Kelvin clips are smaller, but more expensive : (They come with screws (for using with small ring terminals I guess), but it's possible to quickly solder instead (the plastic will melt a bit if not careful), if that's preferred. Main downside is that the screws are still required, because they secure the terminals in place. My solution was to remove the screws, solder the wires, and then put the screws back. The bulge where the wire insulator passes over the screw heads, provides a nice grippy area to hold the clips. That explanation was probably not very good, but hopefully the photo makes it clearer.The contact ends are pretty flat, not really grooved much, but can stay clipped if no tugging on the leads.