4 Wire (kelvin) probes - Page 1
Forum section: electronics / projects

author: misho
author_rank: Newbie
timestamp: March 18, 2015, 05:11:59 pm
content: Hello everyone,I am currently in the R&D stage of a project of mine involving a 4 wire resistance measurement instrument for milliohm range resistances. In the end I would like to sell it as a consumer product and currently the projected net cost is <$50. However I hit a snag when it came to selecting the probes. I looked at a lot of places and the prices IMO are outrageous. For example:http://www.digikey.com/product-search/en?mpart=6303&vendor=501orhttp://www.keithley.com/products/accessories/testleadsprobes/?mn=5805orhttp://www.digikey.com/product-detail/en/6730/501-1102-ND/603918I understand that someone who owns a DMM worth >$1k would not mind spending this much money on probes, especially considering they are from a reputable manufacturer but these don't cut it for me.I am looking for something low cost but still at a reasonable quality that I can include with my product. I may be wrong but there is nothing much to these probes (like exotic metals - gold, platinum) to make them this expensive apart from the fact that they are a specialised piece of equipment that come together with an expensive multimeter. Am I wrong and if so, please correct me.Can anyone give me an idea, where I can find this sort of probe at a quantity of lets say between 100 and 1000. Is there an alternative to this which I can use (not talking about individually soldering wires to connectors and then the board/resistor, as I need it in bigger quantities).If not, should I just abandon the project, or try to sell it without the probes and let the consumer figure it out (that might be a bit of a d*ck move on my part).

author: georges80
author_rank: Frequent Contributor
timestamp: March 18, 2015, 05:48:36 pm
content: My Fluke 8845A has a 4 wire mode that uses a 2 conductor banana jack (somewhat specialised I guess). So, it can do 4 wire using what "appears" to be a 2 wire banana cable (that actually provides 2 wires EACH).TL2X4W is the series of 4 wire probes that work with the meter family. Cost is <$70 shopping around.One reason for the cost premium is volume - not many folk buy a 4 wire probe set or a 4 wire capable meter. The other is that it does require some engineering design to create a decent kelvin connection/path.For my power supply I made my own 4 wire setup (the PS I use can run with sense leads). I just purchased kelvin croc clips on ebay and ran a thick/thin silicone wire pair to each clip (heatshrink to pair them), functional but not commercially 'pretty'.cheers,george.

author: rdl
author_rank: Super Contributor
timestamp: March 18, 2015, 08:14:27 pm
content: There was a thread a while back about low cost Kelvin clips. Maybe if you read through it and check some of the links, you'll find something that would work for you.https://www.eevblog.com/forum/testgear/inexpensive-kelvin-clips-on-ebay/

author: MK
author_rank: Regular Contributor
timestamp: March 18, 2015, 09:25:08 pm
content: Be shure to check that those cheap ones are not just plated brass... caveat emptor.

author: electr_peter
author_rank: Unknown
timestamp: March 18, 2015, 10:52:03 pm
content: For low quantities, see here:http://www.ebay.com/itm/231245383567http://www.ebay.com/itm/231343581989