Author Topic: Shopping help: What's a good set of Kelvin probes?  (Read 4435 times)

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Offline cvanc

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Shopping help: What's a good set of Kelvin probes?
« on: October 09, 2015, 01:58:39 pm »
So I want to get a set of good, but not crazy expensive, probes for 4-wire resistance measuring.  Meter has banana plug inputs.

I've found the Extech 380580 http://www.tequipment.net/Extech/380565/Alligator-Test-Leads/?search=true

...and the Pomona 5940 http://www.tequipment.net/Pomona5940.asp?search=true (sadly, these are just too expensive - they look nice though)

Are there others I might be looking at?  Any comments on these Extechs?  Thanks in advance...


 

Offline BravoV

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #1 on: October 09, 2015, 02:05:06 pm »
If you don't mind doing diy, Franky (iloveelectronics ) sells kelvin clips in kit form, bought one and very happy with it.

Shared a testimony -> Here

Note : The 4 mini banana connectors on the right (gold pins) are separate purchase, also the shrink tubings are not pictured here.

Offline ekeppel

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #2 on: October 09, 2015, 02:46:04 pm »
It sounds like the Extech or Pamona would be higher on the quality scale, but I'll share this, since others may have a lower budget.  I was on a tight budget myself, and purchased a set similar to these listed on eBay:

http://www.ebay.com/itm/LCR-Meter-Test-Leads-Lead-Clip-Cable-Terminal-Kelvin-Probe-Wires-w-4-Banana-/261721902334

The ones I received came wired correctly and work well, but your mileage / kilometreage may vary. :-)

I have heard that sometimes these cheap probes need to be double checked to make sure that each probe has its two wires correctly separated clear to the tips of the probes rather than connected further up the handle, etc.  Other than that, the quality is good enough for my uses,and they have held up.

There are also tweezer style available at similar prices if that is something you consider useful.

Hope you find something that works for you.  I'll be watching this thread to see what others have to say.  Perhaps there is a better value out there, but for $15USD paid, I think these basic probes are a bargain.

Best Regards,
Eric
 

Offline thefamilyman

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #3 on: October 09, 2015, 02:58:42 pm »
It sounds like the Extech or Pamona would be higher on the quality scale, but I'll share this, since others may have a lower budget.  I was on a tight budget myself, and purchased a set similar to these listed on eBay:

http://www.ebay.com/itm/LCR-Meter-Test-Leads-Lead-Clip-Cable-Terminal-Kelvin-Probe-Wires-w-4-Banana-/261721902334

The ones I received came wired correctly and work well, but your mileage / kilometreage may vary. :-)

I have heard that sometimes these cheap probes need to be double checked to make sure that each probe has its two wires correctly separated clear to the tips of the probes rather than connected further up the handle, etc.  Other than that, the quality is good enough for my uses,and they have held up.

There are also tweezer style available at similar prices if that is something you consider useful.

Hope you find something that works for you.  I'll be watching this thread to see what others have to say.  Perhaps there is a better value out there, but for $15USD paid, I think these basic probes are a bargain.

Best Regards,
Eric

I also purchased those probes, I feel that they are pretty good for $15 EXCEPT that the wire is only crapply screwed into the banana plug with the tiniest bit of wire stripped. They just pull out.
I bought some nice hirschmann banana plugs and soldered in onto the cable, problem solved.
 

Offline ekeppel

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #4 on: October 09, 2015, 03:09:30 pm »
Quote
I also purchased those probes, I feel that they are pretty good for $15 EXCEPT that the wire is only crapply screwed into the banana plug with the tiniest bit of wire stripped. They just pull out.
I bought some nice hirschmann banana plugs and soldered in onto the cable, problem solved.

Ahh, yes!  You are correct about the poor connection to the banana plugs.  I had purchased these to replace the overly short ones that originally came with my DER EE-5000 ESR meter.  For that use, I actually removed the banana plugs and soldered them to the existing probe module that came with the meter.  I do recall now that the banana plug connection could have used some beefing up.  Thanks for the reminder! :-)

Eric
 

Offline edavid

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #5 on: October 09, 2015, 03:20:57 pm »
If you are not going to use the banana plugs, you might was well buy the $11 version that comes with BNC connectors: http://www.ebay.com/itm/LCR-Meter-Test-Leads-Lead-Clip-Cable-Terminal-Kelvin-Clip-Wires-with-4-BNC-/181391981262
 

Offline Gyro

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #6 on: October 09, 2015, 05:46:39 pm »
Quote
If you are not going to use the banana plugs, you might was well buy the $11 version that comes with BNC connectors: http://www.ebay.com/itm/LCR-Meter-Test-Leads-Lead-Clip-Cable-Terminal-Kelvin-Clip-Wires-with-4-BNC-/181391981262

Good idea, I've found that the clips are actually rather good but the banana plugs are lousy. The spring 'lanterns' on the plugs are very loose and don't make good enough contact with the plug itself when inserted into a socket (they can still spin). The bits you're wanting are the clips, so it makes sense to get them the cheapest way you can and fit your own plugs.

P.S. If you want to go the whole hog you can buy just the clips themselves on ebay even cheaper. Depends if you want to go to the effort of fitting your own leads and heatshrink.
« Last Edit: October 09, 2015, 05:53:39 pm by Gyro »
Chris

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Offline eas

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #7 on: October 09, 2015, 06:19:07 pm »
I made my own for ~10-15 bucks with some eBay clips.



A few construction details.
  • I don't know if the clips are plated with real gold, but it isn't discoloring like some of the other cheap "gold" plated connectors I've purchased on eBay.
  • Elsewhere on the forum, people investigated and found the base metal is actually aluminum. In theory, aluminum/gold junctions will have a fairly high seebek effect. In practice, the junction should quickly become isothermal and also, the effect at the positive and negative leads should cancel each other.
  • Both sense and force leads are routed to one side of the clip, then the sense lead is looped back to connect to the opposite side of the clip for a proper Kelvin connection.
  • I used heat shrink over the solder points to provide strain relief.
  • The spring is electrically isolated from the metal halves of the clip by some heavy, fiber reinforced tape, but I think I'll probably add some heatshrink to decrease the chances of the tape wearing through.
  • My banana plugs are stackable, which isn't useful in this application, but it's what I had on hand.

I haven't considered their performance in any great detail, but they work, and give better readings in 4-wire mode than in 2-wire.

I'm considering making up a nicer, more anal-retentive, set using the clips from Franky linked above, and going all out with shielded sense leads, but I have no urgent need for it.
 

Offline BravoV

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #8 on: October 09, 2015, 06:55:38 pm »
I'm considering making up a nicer, more anal-retentive, set using the clips from Franky linked above, and going all out with shielded sense leads, but I have no urgent need for it.

The Franky's kelvin clips as I shown above, actually is the clone of Mueller BU-78K.  :P

But the genuine Mueller clip cost $50 a piece, not even a pair at Digikey -> http://www.digikey.com/product-detail/en/BU-78K/314-1135-ND/304402

Offline Gyro

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #9 on: October 09, 2015, 07:15:01 pm »
Quote
I don't know if the clips are plated with real gold, but it isn't discoloring like some of the other cheap "gold" plated connectors I've purchased on eBay.
Elsewhere on the forum, people investigated and found the base metal is actually aluminum. In theory, aluminum/gold junctions will have a fairly high seebek effect. In practice, the junction should quickly become isothermal and also, the effect at the positive and negative leads should cancel each other.

This is a different type that has appeared on ebay since I last looked (mine are like eas's). I haven't seen the screw fixed jaws. They claim to be gold plated copper for what it's worth (but I suspect the others probably did too), I just wondered if the screws would hold if they were Aluminium. Non-serrated jaws for a change too. It's tempting to take a punt at that price anyway.

http://www.ebay.co.uk/itm/3-Pcs-Alligator-Kelvin-Test-Copper-Gold-Plate-Electrical-Clip-Clamp-Insulated-/381234892490?hash=item58c35ececa
« Last Edit: October 09, 2015, 07:16:48 pm by Gyro »
Chris

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Online GreyWoolfe

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #10 on: October 09, 2015, 11:04:20 pm »
Quote
I also purchased those probes, I feel that they are pretty good for $15 EXCEPT that the wire is only crapply screwed into the banana plug with the tiniest bit of wire stripped. They just pull out.
I bought some nice hirschmann banana plugs and soldered in onto the cable, problem solved.

Ahh, yes!  You are correct about the poor connection to the banana plugs.  I had purchased these to replace the overly short ones that originally came with my DER EE-5000 ESR meter.  For that use, I actually removed the banana plugs and soldered them to the existing probe module that came with the meter.  I do recall now that the banana plug connection could have used some beefing up.  Thanks for the reminder! :-)

Eric

What are you doing for the shielding in the wires?  There is the 3rd solder point for each wire that goes to the connection for the guard wire.  Or are you not bothering with it and will that affect readings.

If you are not going to use the banana plugs, you might was well buy the $11 version that comes with BNC connectors: http://www.ebay.com/itm/LCR-Meter-Test-Leads-Lead-Clip-Cable-Terminal-Kelvin-Clip-Wires-with-4-BNC-/181391981262


Does anyone know if these have the shielding?  I would like to duplicate what the DER EE has.  I can always get the clips and use 2 conductor shielded microphone wire, which I have around.  Come to think of it, that might be the better way to go.  I can get (fake?) Mueller BU-75K clips for $9 US http://www.ebay.com/itm/130946949354?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT and use the above mentioned wire.
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Offline ekeppel

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #11 on: October 10, 2015, 11:36:41 am »
Quote
What are you doing for the shielding in the wires?  There is the 3rd solder point for each wire that goes to the connection for the guard wire.  Or are you not bothering with it and will that affect readings.

The ones on mine are shielded, and I have the shield soldered to the same solder points on my DER meter probe module as it was with the stock probes.

Edit: Incidentally, the eBay probes I have do not look exactly like the ones in the link I posted at the outset, but close.  The ones I purchased have each wire attached to one side of the probe handle, as opposed to both going to one side.  I went back in my purchase history to find the link for the exact ones I purchased:

http://www.ebay.com/itm/381103472166?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Unfortunately, they appear to be out of stock at the moment.

Eric
« Last Edit: October 10, 2015, 11:44:58 am by ekeppel »
 

Offline cvanc

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #12 on: October 13, 2015, 12:08:31 pm »
Thanks to all for the suggestions.  I got lucky and scored a set of Pomona 5940 off eBay for a decent price.  Should do the trick!
 

Offline JackOfVA

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #13 on: October 13, 2015, 01:32:42 pm »
Kelvin clips using rubber tubing to provide clamping force instead of a spring will fail over time as the tubing cracks from exposure to the environment.  You can replace the tubing, of course.
 

Offline eas

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #14 on: October 13, 2015, 07:48:26 pm »
BTW, while I think Franky may still sell his kits if you contact him through the forum, they aren't listed on his eBay store. There are two other sellers who list what look to be the same clips. One of them has had them for a while, priced at about $9/clip. Yesterday though I noticed that another seller, who I've purchased banana plugs/jacks from in the past, is selling them for $5.60/clip. I ordered a pair and will post my impressions when they arrive. Same seller also has some "Gwinstek" Kelvin clips I haven't seen before.
 

Offline johnh

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Re: Shopping help: What's a good set of Kelvin probes?
« Reply #15 on: October 13, 2015, 08:50:40 pm »
I recently purchased a set from Franky, he couldn't supply the heat shrink but that wasn't a problem for me. As I have a small stock of various sizes.
 


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