Small Kelvin clips that actually grab?

[precaud]

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?

[precaud]

Bump...

[Stray Electron]

  I bought these and I'm happy with them https://www.amazon.com/gp/product/B071SL6PQS/ref=ppx_yo_dt_b_asin_title_o00_s01?ie=UTF8&psc=1 They'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.

[precaud]

Thanks, but that wouldn't work for me. I need a Kelvin clip arrangement with small contact area, not separate leads.

[tautech]

Dremel mods time ?

[Martin72]

Hi,

You could use these ones:

https://www.distrelec.de/Web/Downloads/_t/ds/BU-30C_eng_tds.pdf

And solder/crimp two leads at the same point of the clip.

[precaud]

Dremel mods time ?

Yeah, I've considered that and similar, but didn't want to bugger the plating.

You could use these ones:

https://www.distrelec.de/Web/Downloads/_t/ds/BU-30C_eng_tds.pdf

And solder/crimp two leads at the same point of the clip.

Not a true Kelvin, but a fallback...

[Martin72]

Not a true Kelvin

Here they did the same I suggested and call it kelvin clamps:

https://www.sourcetronic.com/shop/de/kelvin-test-clips-st26027a.html

You get the "best" results, when you´re measuring the voltage as near as possible to the point you feed in the current.

[Electro Fan]

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_BwE

Others 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/#msg3227316

Experience 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

[precaud]

Those are the large clips, of which I have several. I want the small ones for this.

[Electro Fan]

Those are the large clips, of which I have several. I want the small ones for this.

Oh, that's what 2" or less means in length means 
I should have read your post more closely

None 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 grabbers are 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.

[precaud]

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.

[precaud]

Here they did the same I suggested and call it kelvin clamps:

https://www.sourcetronic.com/shop/de/kelvin-test-clips-st26027a.html

Those 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.

[tautech]

Dremel mods time ?

Yeah, I've considered that and similar, but didn't want to bugger the plating.

File a little of the metal off where it doesn't matter to check what's under the plating.

[Martin72]

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.

[Electro Fan]

Ascel are just about 4”, OP is looking for 2” or less.  Kind of hard to find such mini Kelvins so far....

[precaud]

File a little of the metal off where it doesn't matter to check what's under the plating.

I 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/283109177832

They 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.

[Electro Fan]

File a little of the metal off where it doesn't matter to check what's under the plating.

I 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/283109177832

They 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.

Hard to beat that price with free shipping.

[precaud]

Hard to beat that price with free shipping.

I 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

[tautech]

File a little of the metal off where it doesn't matter to check what's under the plating.

I 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/283109177832

They 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.

Don'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.

[Electro Fan]

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?

Why all the wires with these clips?  What is the wiring strategy?

[precaud]

You'll need a small mechanics pickup magnet to find which bits are and which bits aren't.

That's what I used. My hamhandedness requires that I keep it handy...

Why all the wires with these clips?  What is the wiring strategy?

That 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.

[Electro Fan]

You'll need a small mechanics pickup magnet to find which bits are and which bits aren't.

That's what I used. My hamhandedness requires that I keep it handy...

Why all the wires with these clips?  What is the wiring strategy?

That 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.

http://www.testequipmenthq.com/datasheets/Keysight-4328A-Datasheet.pdf
cool!

[precaud]

http://www.testequipmenthq.com/datasheets/Keysight-4328A-Datasheet.pdf
cool!

Yes, I like it. Fixed 1kHz, so not useful for capacitor ESR, though...

[Electro Fan]

http://www.testequipmenthq.com/datasheets/Keysight-4328A-Datasheet.pdf
cool!

Yes, I like it. Fixed 1kHz, so not useful for capacitor ESR, though...

Not as cool as the 4328A but for that there is this...
https://www.peakelec.co.uk/acatalog/esr70-capacitor-esr-meter.html

[graybeard]

The smallest one I have seen is this homemade clip.

[precaud]

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.

[precaud]

These ones are new since I last looked:
https://www.ebay.com/itm/283109177832

They 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.

I 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.

[pope]

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.

[Phil1977]

These ones are not too bad, but in total they are around 4" / 10cm:

https://de.aliexpress.com/item/1005004587014590.html



If it needs to be smaller, 3D-printing may be a literally scalable option:

https://www.thingiverse.com/thing:5606311

[pope]

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 1

Link 2

Link 3

[Phil1977]

Sorry, I hope this link is better:

https://de.aliexpress.com/item/1005004587014590.html

[TopQuark]

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.

[pope]

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 

[TopQuark]

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 

Well 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. 

[pope]

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 

Well 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. 

Well, 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...

[TopQuark]

Well, 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...

Well 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. 

[pope]

Well, 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...

Well 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. 

Haha, OK fair enough

[shabaz]

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.