| Products > Test Equipment |
| Kelvin leads for DMM |
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| mawyatt:
--- Quote from: tooki on March 09, 2022, 08:50:25 pm --- --- End quote --- Please use the screenshot features of your operating system to take screenshots. Photographs of the display suck in so many ways. [/quote] Will do!! --- Quote ---As for the plating: you do realize the whole point of Kelvin measurement is to eliminate the effects of test lead and contact resistance? --- End quote --- Actually in reality it doesn't "eliminate the effects" of test lead and contact resistance, it attempts to reduce these effects. There are many different types of "Kelvin" type fixtures/clips/tweezers available, and not all fit the same measurement situation. ;) Best, |
| Hydron:
--- Quote from: Kean on March 09, 2022, 08:08:23 pm ---I also have some of the Tonghui measurement sets for my LCR meter - SMD fixture, tweezers, and Kelvin clips. They are pretty good but in my opinion not as nicely constructed as the 11059A set. I haven't tried the Pomona Kelvin leads but generally Pomona quality is reasonable. --- End quote --- I think there is a chance that all of these are made by pomona (with small differences between runs - they seem to have been around a while), in which case you have tried the pomona ones :P https://uk.farnell.com/pomona/5940/test-lead-set-kelvin-clip/dp/4136020 ~= https://uk.farnell.com/keysight-technologies/11059a/kelvin-probe-set-0-8m-42v/dp/2853359 ~= https://uk.farnell.com/keithley/5809/set-clip-lead-kelvin/dp/2131248 edit: missed these too! https://www.warwickts.com/1311/PJP-440-Kelvin-Clips-Lead-Set @Kean - have you specifically tried the BK precision/Tonghui clip style from the following link vs the Keysight ones? https://www.tequipment.net/BK/TLDK1/Kelvin-Test-Leads/ It looks like the TLDK1 would have an advantage in ease of use, only needed to plug in 2 connections vs 4 or 5. |
| Traceless:
Thanks to everyone for the feedback. So far the TL;DR I get from all the responses is: "Expensive probes are kinda nice and can make a difference but probably are not really worth the money, cheap or diy ones do the job at a fraction of the cost." @mawyatt that is a nice collection of probes you have there, also thank you for posting your test measurements, the probes you tested all seem to be pretty good. The most impressive were of course the single shielded ones tested on the DMM6500. It would be interesting to see a comparison where you swap one of the probes you tested with the KS with those tested on the Keithley just to see if the probes are that good or if it is the DMM or a combination of both. --- Quote from: alm on March 07, 2022, 10:54:59 pm ---You may already know this, but you don't need Kelvin clips to do a four-wire (Kelvin) measurement. It works pretty much as well if you use four separate wires. The only downside is the extra hassle of having to attach four clips, and possibly extra noise pickup unless you twist the wire together (sense with sense, force with force). --- End quote --- Yes thats a good point using four seperate clips/grabbers and not touching the probes is surely the best way to go in many cases. There is at least one case where Kelvin probes, especially @JohnGs Pomona probes are really useful (IMO): Following the lowest resistance path to trace a short. With regular two wire probes your test leads keep influencing the measurements and may send you on a goose chase, but with these 4-wire-2-point probes you pretty much eliminate the effect of your leads. Tracing shorts with 4 seperate wires especially when SMD components involved is cumbersome . In the past I used my "poor man's version" of the Pomona 6303 probes, with varying degree of success. Here is a picture for the amusement of everyone around ;) While they don't perform actual 4-point measurements and thus may not give the most accurate absolute value they give pretty good relative measurements and eliminate any influence of the test leads. If anyone knows cheaper alternatives to the Pomona 6303 let me know. @Electro Fan I was also looking at the BK TLDK1 and liked them but they are also rather expensive here. You can expect to pay 100€ in Germany. @TomWinTejas, @duckduck: The AST probes look nice but don't seem to be easily available in Germany. Importing them from the US will make them a lot more expensive due to shipping + import fees. @alm: I did a quick search on ebay for the Keithleys, the cheapest 5805s currently available are 172,93€ + shipping ;D. Maybe there pops up a bargain at some point. @SHTechnics: I do like the banggood ones you linked a lot, are affordable and also look like they are less bulky and more flexible than the ebay-GW-Instek ones I posted. I think I might buy a pair of these to give them a try. @Hydron: Thanks for reporting back on your experience the GW-Instek ones I linked in my original post. Before you and alm mentioned it i didn't recognize how wide the clip-tips are. Indeed I was looking for something more filigree. |
| Hydron:
Thought this might be useful for reference: |
| Electro Fan:
fwiw, I've found that where the BK TLDK1 Kelvin clips and leads will measure my reference DUT (45 cm of 18 gauge copper wire) as being approx 9.5 milliohms (depends on ambient temp, settling time, etc.) I can get a very similar reading (within about 0.1 milliohms, ie about 100 microohms) by using four separate just plain old every day nothing special leads with banana to alligator clips and banana to minigrabber clips. I am very happy with the TLDK1 Kelvins (they provide convenience and confidence inspiring measurements) as companions to the 34465A but unless you are going deep(er) into metrology 4 regular separate clips and leads can probably suffice. |
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