Agreed.
The whole idea of a Kelvin connection is making the measurement accurate even when the resistance of the leads and connectors is questionable.
It is usually accomplished with a meter and leads that has 4 independent conductors. Basicaly, you separate the stimulus for the measurement from the voltage that is being sensed. I don't see any of that here, so I don't how the word Kelvin got associated with the hardware shown, except in error.
Oh it is very real, I know how you role and the games you play. As for the price, $23 shipped for the banana plugs, wire and clips.
I already explained the reasoning behind the 14AWG wire. As I have already said, it offers no electrical benefit, but it does offer some structural and tactile benefit as well as some durability benefits over the bare minimum amount of copper required. This was on the first page of posts.
As for being Kelvin or not: you are in error, check the photos again. Four isolated leads going into the clips (two black, two red): High Force, High Sense, Low Force, Low sense. This is by definition a Kelvin setup. The force wires carry what you call the stimulus and the sense wires measure the voltage. If you want to be truly pedantic, they are by definition a pair of Kelvin Clips.
To quote Wikipedia:
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Hi Arny, and Pedro,
I'm not taking sides in this, but rather asking for clarification.
Arny, this might be a good learning example for us.
Can you provide us with a link that shows what you are discussing.
Can you scan or take a pic of a book reference page that shows what
you are discussing as a Kelvin Connection or Kelvin Sensing Connection?
And, is this in error with the connections and measurement
that Pedro has shown?
Please, for those following along and other DIYers let show
some references other than just statements.
Thank you,
Sync
Nothing new here.
Nothing new here. The 4 wire “Kelvin” test leads are a standard accessory to the HP 6 ½ digit DMM shown in the photos. The theory and application instructions are in the manual that comes on the DVD that ship with the meter. Call TestEquity they will be glad to sell you a new Keysight DMM, Kelvin clips included,
DT
Nothing new here. The 4 wire “Kelvin” test leads are a standard accessory to the HP 6 ½ digit DMM shown in the photos. The theory and application instructions are in the manual that comes on the DVD that ship with the meter. Call TestEquity they will be glad to sell you a new Keysight DMM, Kelvin clips included,
DT
Kelvin (4-wire) Resistance Measurement : DC Metering Circuits - Electronics Textbook
It includes explanation and relevant pictures.
The short answer from the cited article is that the Kelvin clips are different from conventional alligator clips in that each contact is electrically isolated from all the rest and connected to a wire and multi-meter terminal that is dedicated solely to it. A look-nearly-alike Kelvin clip electrically isolates each side of the clip. That provides the needed functionality.
If used with a conventional 2 lead meter, the benefit of the special clip and wiring is lost. If all you have is a 2 lead meter, then you need a current source to drive the other pair of leads and clip contacts.
It shows that I was wrong because I did not get any explanation of why the clips that were shown can work. Instead, the usual "you are wrong" demeaning reply was given and some irrelevant comments about the 14 gauge wire (an issue that was irrelevant to my post - I never mentioned it).
This is a good example why these forums are often diminished by threads such as the resistor sound thread - the quality of the answers and responses is poor and often shows more defensiveness than actual engagement with the topic.
Pedrodagr8, thanks for sharing.
I use kelvin clips on my HP meters especially for low resistance readings and I am looking for better replacements. One of the drawbacks I encountered with some eBay kelvin clips (like the ones you linked to) was the lack of gripping strength due to weak springs. How well do these clips grip?
I use kelvin clips on my HP meters especially for low resistance readings and I am looking for better replacements. One of the drawbacks I encountered with some eBay kelvin clips (like the ones you linked to) was the lack of gripping strength due to weak springs. How well do these clips grip?
Using Mini Gators for Kelvin Measurements?
Well the good news is that we figured
out that the measurement was okay and it worked out.
Thank you for providing reference.
Thank you for showing how to build one.
Maybe someone can answer with the discussion.
Does it matter which clips are used?
I have the mini clips (mini gators [B. Pease]) with
single clip one end, single banana other end, got
about 20 of them. Any issues using them for
Kelvin measurements?
Cheers,
Sync
Well the good news is that we figured
out that the measurement was okay and it worked out.
Thank you for providing reference.
Thank you for showing how to build one.
Maybe someone can answer with the discussion.
Does it matter which clips are used?
I have the mini clips (mini gators [B. Pease]) with
single clip one end, single banana other end, got
about 20 of them. Any issues using them for
Kelvin measurements?
Cheers,
Sync
That why I use the term "4 wire" instead of bowing to royalty. I'm n merican damit
save Kelvin when discussing temp. probes.
save Kelvin when discussing temp. probes.
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It wasn't like you cached your interaction either, you didn't say that you don't think that these are Kelvin clips. You gave a definition of Kelvin clips and said that I was wrong in calling them Kelvin clips. That being said, I did let me interaction with Kiriakos shade my interaction with yours. He only comes around to start trouble.
These clips are electrically isolated, I figured that this was clear in the images showing their construction (let alone my discussion of the labels that go on each side). The images in reference that show their construction:
[url=http://imgur.com/Jqf2Wjm]
Putting it all together, large screws attach the connector to the kelvin clip.
The screw covers are a very nice touch. There is one for High Force, High Sense, Low Force and Low Sense.
The only thing I did not do is explicitly breakdown each individual cable but I did pretty much everything except that.
When I get home this evening I will try to think of a way to describe the grip if I can.
These CAN work but you would need to use four different lines. Additionally, ideally you would need to have the force lines on the outside of the sense lines. This is because you don't want the resistance between the two clips coming into play. This only would occur on VERY low resistances and for the most part shouldn't be an issue otherwise. That being said, doing something right is always a good idea. There might be some other issues that I can't think of right now but I am not coming up with any.
High Force-->High Sense-->DUT-->Low Sense-->Low Force
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Tomorrow I am going to order one pack of three of those 3 Pcs Alligator Kelvin Test Copper Gold Plated Electrical Clips Black Red Grey | eBay
An Christmas gift to my DE-5000.
Who knows I might cut my fingers and die, and the world this will become a better place with out me. 😀
An Christmas gift to my DE-5000.
Who knows I might cut my fingers and die, and the world this will become a better place with out me. 😀
Sorry PedroDaGr8,
I just realized when I asked "How well do these clips grip" that my question was vague.
Looking again at the pictures, it appears the spring is stout and these clips should grip fairly well. I will be interested when these clips become available and thanks again for sharing.
I just realized when I asked "How well do these clips grip" that my question was vague.
Looking again at the pictures, it appears the spring is stout and these clips should grip fairly well. I will be interested when these clips become available and thanks again for sharing.
Haha, no worries. The best description I can give is that I have a big wire wound resitor with spade terminals. I hung the clips from the spade terminals and I could swing it around relatively well, with the leads dangling, and they didn't come off. To me they are sufficiently tight enough for my uses. Additionally, if you find they aren't quite tight enough they do come apart and you can easily insert a stiffer spring if you wish.
Hi PedroDaGr8,
Did you link to your sellers store? I may have missed it between all the back and forth.
I use the HP Kelvin leads, but those look good. Mine are over 20 years old now and they don't last forever.
-Chris
Did you link to your sellers store? I may have missed it between all the back and forth.
I use the HP Kelvin leads, but those look good. Mine are over 20 years old now and they don't last forever.
-Chris
I did not because he's currently out of stock at this time. I'll PM you his contact info.
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"When is 2 wire not close enough?"
If you are measuring extremely low resistance like connections on a 800 amp welder where a .06 ohm loss can cause problems. Another use is trying to find a shorted capacitor on a large circuit board. With kelvin clips, you can pinpoint the failed component.
It appears your meter has a "Zero" option on the ohm scale, so you are fortunate. None of my portable Fluke meters have that option and they read .5 to .7 ohm when the leads are shorted.
If you are measuring extremely low resistance like connections on a 800 amp welder where a .06 ohm loss can cause problems. Another use is trying to find a shorted capacitor on a large circuit board. With kelvin clips, you can pinpoint the failed component.
It appears your meter has a "Zero" option on the ohm scale, so you are fortunate. None of my portable Fluke meters have that option and they read .5 to .7 ohm when the leads are shorted.
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agreed but the smallish clips shown above are not that useful for welding / batt cable apps. besides you want to use the force current across a string of connections and use the sense to trouble shoot a cable run.
I guess my point is those clips are more specialized for a general purpose capability like 4 wire, E.g. use 4 "separate connectors / wires appropriate for the test. don't get me wrong I think the cables that Pedro built are very nice for what his use is. (IDK maybe a production environment for testing current shunts etc ) DIY don't need em , unless I got cash to burn
>indeed a very useful option I use it on every thing resistors, caps, voltage, and current!, Im lovin' it!
I just used it to measure a low value precision 150 pF cap, seems very accurate with high resolution
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When you want better than 10% accuracy. Zeroing out your leads helps, but even then your reads are susceptible to contact resistance. Depending on how accurate your reads need to be, a four wire setup is either necessary or overkill.
In your case, with that meter, there is no use for Kelvin leads. I have two of that meter, is not a bad meter though it's very fragile to voltage spikes, reverse batteries (found that out the hard way) and drifting over time. I still use it commonly. It actually does pretty well on resistance, other than for high inductance resistors. For example, if you try to measure the dcr of a transformer, not gonna happen. The meter freaks out with inductive loads. Truthfully, you are lucky if your meter is truly that accurate at that low, I know mine is not. It would read somewhere between 0.08 and 0.12 for that one. Both numbers are within spec but not as accurate as you showed.
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