Video's of making the Ultimate Kelvin connection(major hacking of a Pomona clip) - Page 1
Forum section: electronics / projects

author: robrenz
author_rank: Super Contributor
timestamp: July 27, 2012, 12:20:37 pm
content: This is the first video of two that show my quest for the ultimate (IMO) Kelvin connector system. Sorry for the long length but I tried to keep it very concise while still showing all the techniques used. I am not nearly as dynamic and entertaining as Dave so try to stay awakeThis is very mechanically oriented but many forum members seem to like Dave's fixture related stuff so I hope you find this interesting as opposed to boring.This first video covers the modification of a Pomona 5418 pincer clip into a Kelvin clip. This clip is the basis of a system that will allow any combination of clip, probe, soldered-on wires, clamps, etc. to be used instantly. The second video will cover the making of all those attachments of the system.

author: JuiceKing
author_rank: Regular Contributor
timestamp: July 27, 2012, 06:31:05 pm
content: Great idea and fascinating video. I see you made a pile of these. Are you planning to make a business of this?

author: robrenz
author_rank: Super Contributor
timestamp: July 27, 2012, 06:57:49 pm
content: If there is a lot of interest I would run another batch of them. But as you can see they won't be cheap as there is a lot of work in them. I don't expect to get paid for the development and fixturing time I consider that playtime. I will post what I think they will sell for when I figure that out.That is not my main purpose though. I just want to contribute to the forum in the areas I feel I have something worthwhile to post.

author: JuiceKing
author_rank: Regular Contributor
timestamp: July 27, 2012, 07:23:18 pm
content: Thanks for posting it. It's a world I know nothing about. My only other experience observing machine tools was at the Paul E. Garber Preservation, Restoration, and Storage Facility in Maryland, where the Smithsonian works on military aircraft restoration projects. This was many years ago, and I was a production assistant in a TV crew doing a documentary on the restoration of a WW2 Japanese airplane. They had some 30 gigantic warehouses full of aircraft and a small team of restoration experts that would take these planes apart down to the individual part, clean them up, and put them back together again...restored in flying condition. Parts that were missing or unusable were machined from scratch. After they put it all back together again, they would coat the finished work in some kind of preservative resin that would keep them from rusting but would ground them permanently. Like mummies, I thought. This was around 1989, I think, and they were working on the Enola Gay at the time, and many years later, I saw an announcement that they finally finished it. Needless to say, the guys who worked on these things thought they had the best jobs on the planet. Very cool.Can't wait to see your kelvin probe and the ingenuity that goes into that.Thanks again for sharing this.

author: PedroDiogo
author_rank: Regular Contributor
timestamp: July 27, 2012, 07:27:20 pm
content: I was delighted watching this video. I didn't even know that was possible to machine something so small with such precision, great workSubscribed the channel also.

author: almoehi
author_rank: Contributor
timestamp: July 27, 2012, 08:21:24 pm
content: Hi robrenz,thank you for the very informative and fascinating video. Big thumbs up!!!Cheers,Armin

author: DmitryL
author_rank: Regular Contributor
timestamp: July 27, 2012, 10:17:15 pm
content: Great video, nice to watch!But is there anything wrong with things like this: ?http://www.dealextreme.com/p/test-clip-probes-for-lcr-meter-with-bnc-wires-pair-34214?item=8And Open-Short-Load probes calibration as well ?

author: JackOfVA
author_rank: Unknown
timestamp: July 27, 2012, 11:57:53 pm
content: Quote from: DmitryL on July 27, 2012, 10:17:15 pmI've bought a couple sets of these and find them acceptable considering the modest price. However, with extended use the RG-174 coax fatigue fails at the clip end. It's not difficult to repair the failure, however.

author: digsys
author_rank: Unknown
timestamp: July 28, 2012, 12:17:50 am
content: Holly snapping duck shit !! That is awesome work !! I'd have drilled and machined off MOST my fingers trying that !!Put me down as a potential customer. Thank you for showing us what can be achieved.

author: Chasm
author_rank: Regular Contributor
timestamp: July 28, 2012, 01:41:14 am
content: Very nice!The machining work I've seen so far was much coarser.

author: nanofrog
author_rank: Super Contributor
timestamp: July 28, 2012, 01:45:51 am
content: Absolutely beautiful work IMHO.I'd dearly love to learn machining at that skill level. Huge Thumbs up!

author: robrenz
author_rank: Super Contributor
timestamp: July 28, 2012, 01:56:12 am
content: Thanks guys, I have lots more to come.

author: IanB
author_rank: Super Contributor
timestamp: July 28, 2012, 04:54:18 am
content: I think having an electronics workbench in your garage is one thing. But having a high precision machine shop in your garage is crazy!

author: M. András
author_rank: Super Contributor
timestamp: July 28, 2012, 03:03:03 pm
content: wow, nice tools and very good workmanship. you dont have problems with thigs you cant buy. just simply make them

author: SeanB
author_rank: Super Contributor
timestamp: July 28, 2012, 04:11:29 pm
content: I think if i show this to a toolmaker I know he will cry, you have a very nice setup there that he cannot even dream of having.

author: dcel
author_rank: Regular Contributor
timestamp: July 29, 2012, 02:36:26 am
content: I will say sir you have indeed constructed theultimatekelvin clip! Congrats. Great video!My father was a machinst for 30 yrs and the skill is slowly becoming a lost art. There was a job fair here in West Michigan where a company from Wisconsin was hiring and moving machinist to their state to work and teach the next generation of machinist. They were paying the "teachers" and students well for the "education" because they could no longer find people there with your skillset. It was such a big deal here that it made the evening news for a few nights.Back on topic.... Have you thought about the actual contact resistance? Get yourself a can of Caig DeoxIT and ProGold. You own a microOhm meter, you can prove it to yourself and members here that it actually works. ( No affiliation, just a long time user. ) It will preserve the silver in your expensive looking connectors from tarnishing and improve the conductivity of the connection. I just thought you might be intrested in something that would help your quest for accurate microOhm measurements.Chris

author: dda
author_rank: Contributor
timestamp: July 29, 2012, 09:38:58 am
content: I find this so amazing. Such a beautiful piece of equipment you have made.

author: robrenz
author_rank: Super Contributor
timestamp: July 29, 2012, 01:59:42 pm
content: Quote from: dcel on July 29, 2012, 02:36:26 am

author: nanofrog
author_rank: Super Contributor
timestamp: July 29, 2012, 05:56:22 pm
content: Quote from: robrenz on July 29, 2012, 01:59:42 pmRob, where would someone even learn this skill these days?I ask, as taking a quick look at the local Technical/Trade Schools in my area, there's no machinist program at all. So I'm wondering how many still offer it, or where it might be learned outside of the military (I'm too old for this one).Thanks.

author: robrenz
author_rank: Super Contributor
timestamp: July 29, 2012, 07:10:10 pm
content: There are still Technical/trade schools that have machining programs but as in most occupations you only learn enough to not hurt yourself in school. The real practical learning starts on the job. There are many companies that have very good internal training programs because that is the only way they can develop the skilled help necessary for the level of work they do.

author: chrome
author_rank: Regular Contributor
timestamp: July 29, 2012, 07:29:41 pm
content: Here in Belgium the school I went too definitely taught machining, we had a large machining area with tons of lathe's, mills, drill, cnc's etc etc.I kind of wanted to also do that but it was either electricity, mechanical+electricity or mechanical and to me it seemed like mechanical+electricity was basically both but you didn't see enough of either.

author: SeanB
author_rank: Super Contributor
timestamp: July 29, 2012, 07:31:56 pm
content: I have seen some young apprentices, they are goo, but the results vary. John is a good trainer, and he will at least have taught all his prospective apprentices something more than what they came in with. You have got to admire a guy who does rough work to 0.1mm accuracy. Fine work comes out with a near mirror finish, only place you find tool marks are in screw holes and under welds.

author: chrome
author_rank: Regular Contributor
timestamp: July 29, 2012, 07:45:01 pm
content: I would also say that it's not as easy to get into machining yourself since the equipment is pretty expensive compared to other hobbies.

author: IanB
author_rank: Super Contributor
timestamp: July 29, 2012, 07:54:16 pm
content: Quote from: chrome on July 29, 2012, 07:45:01 pmNot necessarily. You need a good space for a workshop, but there are plenty of less expensive ways to get tools, either new or second hand. Part of the learning exercise is starting with a tool of average quality and tuning it up to have less play, better tolerances, smoother action and so on. Once you have a few tools you can use them to make new and better parts to upgrade what you have.There are many hobbyists out there who make model steam engines and other mechanical devices in their home workshop. If you're really enthusiastic you can have a home foundry to complement your machine shop and then you can make almost anything.

author: robrenz
author_rank: Super Contributor
timestamp: July 29, 2012, 07:58:41 pm
content: @ chrome ; Very true. Fortunately I make my living out of my home shop. I would not be able to justify all this equipment for a hobby.

author: Greate
author_rank: Contributor
timestamp: July 29, 2012, 08:31:17 pm
content: That is an awsome work! Can you let us kow how much would it cost? I bet developers would be interested I might recomend your products to my friends.Sent from my A100 using Tapatalk

author: chrome
author_rank: Regular Contributor
timestamp: July 29, 2012, 08:35:04 pm
content: Quote from: IanB on July 29, 2012, 07:54:16 pmOK lets say you want a lathe and a mill, how are you gonna find that for say sub 1k$? You almost aren't gonna find that and even then you still need the cutters for the mill and other tools.Now say you wanna start learning electronics, for <10$ you can get one of those cheap multimeter and for a few dollars you can find some basic parts to start out with.

author: dcel
author_rank: Regular Contributor
timestamp: July 29, 2012, 09:07:21 pm
content: Quote from: robrenz on July 27, 2012, 06:57:49 pmCalculations complete yet?Chris

author: tramjoe
author_rank: Regular Contributor
timestamp: July 29, 2012, 10:59:34 pm
content: This is amazing to watch for a guy like me who dreams of machining equipment.Please keep on sharing that kind of videos, I spent a very inspiring hour watching this one, and I'm sure it's the same for others.Thank you :-)

author: IanB
author_rank: Super Contributor
timestamp: July 30, 2012, 02:06:07 am
content: If you like that kind of video you should check out Mattiaswandel's channel on YouTube. He does the same kind of precision construction with wood.

author: tramjoe
author_rank: Regular Contributor
timestamp: July 30, 2012, 06:47:15 am
content: Thanks for the pointer, seems very interesting too

author: robrenz
author_rank: Super Contributor
timestamp: July 30, 2012, 05:25:11 pm
content: For those that asked about availability and price, If there is enough interest to do at least 10 sets they would be $195.00 US That would be two Kelvin pincers each with a 36" lead with a double Pomona banana plug and a shield lead with stackable banana plug. That setup will allow connecting both shields to the low of the input or to whatever you want to connect the shield to. The Kelvin probes or the universal adapters that can attach to these pincers will be separate items. (still finishing them and the corresponding video).That may sound expensive but a mass produced Pomona 5940 kelvin clip set is roughly $194.00 My purpose in posting was not to sell these but there seems to be enough interest to consider it.

author: Monkeh
author_rank: Super Contributor
timestamp: July 30, 2012, 05:33:47 pm
content: Sell the design to Pomona.

author: dcel
author_rank: Regular Contributor
timestamp: July 31, 2012, 04:58:00 am
content: Quote from: Monkeh on July 30, 2012, 05:33:47 pmThen Pomona would want to sell the perfectly redesigned kelvin clips for $388.00 each!I kinda figured about $150 would have been the price I was willing to jump at, but I didn't add in the cable, bananas and assembly costs. I don't have a meter capable of milli/microOhms (4 wire) yet, but I'm in negotiations to obtain one, haggling over price. I know he does not have kelvin leads for the meter, so that is why I am intrested.I never priced kelvin clips before and didn't know they were sooooo expensive.Have to think about it...Chris

author: nukie
author_rank: Frequent Contributor
timestamp: August 02, 2012, 12:41:53 am
content: I was cringing when you took out the slitting saw at around 30 min mark, it was hard to imagine, how a tiny mistake can ruin all the work done. Then you talk about the jig that holds it, you made it look so safe. It was excellent. Also, you have hands of steel. May I ask what lathe / mill was that.

author: robrenz
author_rank: Super Contributor
timestamp: August 02, 2012, 12:53:58 am
content: Quote from: nukie on August 02, 2012, 12:41:53 am

author: nukie
author_rank: Frequent Contributor
timestamp: August 02, 2012, 01:22:51 am
content: Quite true, the tooling will quickly add up $$$. The cheap machines need a lot of work to perform and it requires a wealth of knowledge to tune them. Second hand machines come with problems of their own. Machining is a lot of practical work where EE is half maths and theory. The best way to learn machining is at school or a job at a machining shop then graduate to owning your own machines. If you have the money you can start off buying the best you can afford and learn slowly. I started off buying cheap Chinese lathe and boy it was a steep road ahead.Rob is extremely lucky to be able to own a mill when he was 17. I had to wait till I was able to own a house with a tiny shed to start with machining.Nowadays there's another solution, that is to learn Solidworks, then send off the drawing to a machining shop where the CNC machines do their job. This is similar to home DIY etch PCB vs professionally shop made PCB.Quote from: chrome on July 29, 2012, 08:35:04 pm

author: robrenz
author_rank: Super Contributor
timestamp: August 02, 2012, 01:47:27 am
content: [quote author=nukie link=topic=9807.msg134247#msg134247 date=1343870571Rob is extremely lucky to be able to own a mill when he was 17. I had to wait till I was able to own a house with a tiny shed to start with machining.QuoteNowadays there's another solution, that is to learn Solidworks, then send off the drawing to a machining shop where the CNC machines do their job. This is similar to home DIY etch PCB vs professionally shop made PCB.QuoteEdit: I just sent off to "firstcut prototype services" the nose piece and the brass inner piece you saw in the video to be quoted for 10 pieces of each. I will report back what type of prices I get if any. I suspect they will balk at the rectangular broached holes in both pieces.

author: robrenz
author_rank: Super Contributor
timestamp: August 02, 2012, 03:56:42 pm
content: Quote from: robrenz on August 02, 2012, 01:47:27 amEdit: I just sent off to "firstcut prototype services" the nose piece and the brass inner piece you saw in the video to be quoted for 10 pieces of each. I will report back what type of prices I get if any. I suspect they will balk at the rectangular broached holes in both pieces.As I suspected Firstcut (machining) and protomold (molding) would not quote the parts because of being below their 1/4" size limit. And the rectangular broached holes were a problem anyhow.Email from them:Thank you for sending us your parts to quote.Due to the thin walls on the parts listed below, they are not a good fit with the Firstcut manufacturing process. If the walls can be thickened to at least 0.040 (1mm), please send revised 3D files. We will provide a quote as quickly as possible. If you have any questions, please feel free to contact me.General machining is a different animal than PCB's or things that will be rapid prototyped by any of the current methods. The latter two don't need much specialist input beyond what is defined in the files sent to the service. Machining does need a lot of human decision making based on what machines/processes are available even when using a CAM system for the programming of the CNC machines.

author: M. András
author_rank: Super Contributor
timestamp: August 02, 2012, 04:43:47 pm
content: some machine shop especially here only do fairly large runs if even do it for a single person not for a corporation. not even talking about 1 off prototypes for bigger metal pieaces/parts.as for solidworks. i like the software, i dont have any traning for machining(dont ask how i get it).so i can say that i find it easy to learn to use the software. i wish i could buy a lathe+mill combo even if its manual. finally i could statisfy my creativity while creating things for myself which i can use.question for you Robrenz, can you say some info about the endmills or any kinds of mills what they use for cutting slots into metal, i would like to know what are the milling depths for them at sub 5mm diameter. even on oldish manual/cnc controlled ones, or on a cnc machining centres/mill centers

author: robrenz
author_rank: Super Contributor
timestamp: August 02, 2012, 04:58:17 pm
content: Quote from: M. András on August 02, 2012, 04:43:47 pmThese charts will give you a general idea. Most plastics can be cut at aluminum speeds. I use mostly solid carbide end mills.Side milling with end millhttp://www.microcutusa.com/cuttingcond.phpSlot milling with end millhttp://www.microcutusa.com/slotcuttingcond.phpGoogle "miniature end mill feeds and speeds" and you will get this and lots more.Everything I made could be done on machines from here.http://www.sherline.com/

author: M. András
author_rank: Super Contributor
timestamp: August 02, 2012, 05:26:47 pm
content: i forgot to write the material i want to get my idea made from is copper. thanks for the help

author: robrenz
author_rank: Super Contributor
timestamp: August 02, 2012, 05:41:45 pm
content: Quote from: M. András on August 02, 2012, 05:26:47 pmCopper is not fun to machine unless you are using C145 or C147 . The other grades are very gummy and tend to push and smear if you dont have very sharp cutters and a good lubricant. This is evidenced by their machineabilty rating of only 20% as good as C360 free machining brass (what I used in the video). I suggest using C145 Tellurium Copperif its electrical properties will allow in your application.See properties herehttp://www.onlinemetals.com/copperguide.cfm

author: Unknown
author_rank: Unknown
timestamp: August 11, 2012, 10:21:50 am
content: The second video is even more interesting than the first. True mastery and pride throughout! I must thank you for making these, they are very interesting to watch. The end product is definitely worthy of its own display case and maker's signature.

author: robrenz
author_rank: Super Contributor
timestamp: August 11, 2012, 11:38:17 am
content: Thanks HAL_42b, very kind words.Here is part 2 which covers design and making of the probes and universal adapters. This completes the whole system. There is a lot of content I left out because I am concerned about exceeding an hour and I don't know how many are interested in mechanically oriented stuff. I hope many find this interesting and informative.

author: IanB
author_rank: Super Contributor
timestamp: August 11, 2012, 06:54:36 pm
content: Mechanical stuff is very interesting. I think you have reached a level of fascination similar to Claude Paillard's video of making vacuum tubes

author: chrome
author_rank: Regular Contributor
timestamp: August 11, 2012, 07:14:44 pm
content: Quote from: robrenz on August 11, 2012, 11:38:17 amFor me it wouldn't be a problem if it was longer.You had very good shots, clear and to the point and well edited in a way that didn't make me lose interest.So well done.

author: tramjoe
author_rank: Regular Contributor
timestamp: August 11, 2012, 08:26:40 pm
content: I would watch it if it were 3 hours long. This stuff is most interesting, and you are making such a great job ! Thanks again for sharing :-)

author: robrenz
author_rank: Super Contributor
timestamp: August 12, 2012, 10:47:25 pm
content: Thanks everyone for the encouragement. Lots more to come on other topics.

author: digsys
author_rank: Unknown
timestamp: August 13, 2012, 12:23:09 am
content: Your first video was faultlessly awesome, I really appreciate seeing engineering (of any field) done well.Your second video ... now I hate you :-)

author: robrenz
author_rank: Super Contributor
timestamp: August 16, 2012, 03:10:52 pm
content: I sent a complete set to IET Labs to evaluate as an addition to their probe lineup. We will see what happens.

author: dcel
author_rank: Regular Contributor
timestamp: August 16, 2012, 04:13:52 pm
content: Quote from: robrenz on August 16, 2012, 03:10:52 pmWow! That's great. Did they contact you after seeing your Videos?Your first video was over the top, and the second, well, it is satisfying to see real genius at work.May I ask where your 'obsession' of accurately measuring ultra low Ohms stems from?Chris

author: Unknown
author_rank: Unknown
timestamp: August 16, 2012, 04:20:51 pm
content: I don't know if it plays any role in this type of measurement but thermal EMF might be an interesting aspect to look into, given that there are many junctions between dissimilar metals.

author: robrenz
author_rank: Super Contributor
timestamp: August 16, 2012, 04:58:19 pm
content: Quote from: dcel on August 16, 2012, 04:13:52 pm

author: dcel
author_rank: Regular Contributor
timestamp: August 16, 2012, 05:21:22 pm
content: Quote from: robrenz on August 16, 2012, 03:10:52 pmSo you contacted them to analyse the system and calibrate?Quote from: robrenz on August 16, 2012, 03:10:52 pmCant wait to see it, I know I cannot afford IET's products, but maybe could afford yours.Good luck.Chris

author: robrenz
author_rank: Super Contributor
timestamp: August 16, 2012, 05:28:58 pm
content: Quote from: dcel on August 16, 2012, 05:21:22 pmI sent my Cambridge/IET LOM510A Micro ohmmeter to do a full before and after calibration so I have traceable accuracy for the low ranges of the decade box. They will separately look at the probe system to see if they want to include it in their lineup of accessories.

author: robrenz
author_rank: Super Contributor
timestamp: August 16, 2012, 06:11:56 pm
content: Quote from: HAL-42b on August 16, 2012, 04:20:51 pmYes HAL-42b Thermal emfs are a huge place for errors at this level. These probes just like any probes will have thermal emfs that need to be eliminated by either using offset compensated ohms or current reversal techniques to eliminate thermal emf errors.My Cambridge/IET LOM510A does offset compensated ohms and removes thermal emfs automatically.My post on it herehttps://www.eevblog.com/forum/product-reviews-photos-and-discussion/ie/msg96311/#msg96311Here is a post of mine with description of offset compensated ohms defined and how I made a offset attachment for meters that don't have it.https://www.eevblog.com/forum/projects-designs-and-technical-stuff/offset-compensated-ohms-adaptor/msg121362/#msg121362Here is my post on a current reversal switch to eliminate thermal emfshttps://www.eevblog.com/forum/blog-specific/gaussian-resistors/msg71215/#msg71215

author: Unknown
author_rank: Unknown
timestamp: August 16, 2012, 07:33:22 pm
content: Quote from: robrenz on August 16, 2012, 06:11:56 pmOops, seems like I should concern myself with reading more, instead of throwing half-thoughts aroundSorry if I made you repeat yourself.

author: robrenz
author_rank: Super Contributor
timestamp: August 16, 2012, 07:35:31 pm
content: Quote from: HAL-42b on August 16, 2012, 07:33:22 pmNo problem, glad to help out.

author: Unknown
author_rank: Unknown
timestamp: August 26, 2012, 10:32:52 pm
content: Amazing!! I really enjoyed that video.

author: robrenz
author_rank: Super Contributor
timestamp: August 27, 2012, 12:50:21 am
content: Thanks, there are 2 parts, did you see both?

author: Unknown
author_rank: Unknown
timestamp: August 27, 2012, 09:51:24 am
content: Quote from: robrenz on August 27, 2012, 12:50:21 amhave now! thanks for the heads-up.I especially like the way you clearly describe each step in the process; and your dedication to precision is just inspirational to watch!I have to ask though; how did you get the nasty finger cut between video 1 and 2? and do you or the camera person have a watch that goes "beep-beep" on the hour? :-)

author: robrenz
author_rank: Super Contributor
timestamp: August 27, 2012, 12:47:47 pm
content: Quote from: jucole on August 27, 2012, 09:51:24 am

author: robrenz
author_rank: Super Contributor
timestamp: November 29, 2012, 01:03:50 pm
content: Wow the part 1 video went viral (for me) in Germany. 79 views in one day on 11-27-12 with only one other view for the whole month world wide.Watch out dave

author: saturation
author_rank: Super Contributor
timestamp: November 29, 2012, 01:16:45 pm
content: It must have been a machinists conventionGerman audiences and precision tools seem very synonymous. The video is a tour de force in machining, the cuts are not just precision, but minimal waste and movement, then in tiny parts, so the smallest error makes a BIG difference! I don't think there is much of that around that is as clear as your video. Also close up of your fingers show you've been at this for a while.Quote from: robrenz on November 29, 2012, 01:03:50 pm

author: quarks
author_rank: Frequent Contributor
timestamp: November 29, 2012, 03:59:48 pm
content: Quote from: robrenz on November 29, 2012, 01:03:50 pmThat's great!!! There must be some more Germans who know what is really good.Because I enjoyed it so much I even watched some of your videos at least twice already and told friends about your art.I am looking forward for more to come.Thx again for showing your great work.