Can 4 wire probe be made at home? And making your own DMM probe? - Page 1
Forum section: electronics / beginners

author: romhunter
author_rank: Regular Contributor
timestamp: May 31, 2017, 03:56:42 pm
content: Yeah I apologize about the title, can't think of something else more appropriateAnyway, I got a lot of question about probe, which is kinda holding me back. First of all, is there anything more complicated about a DMM probe? Other than the fact it's just a normal wire? Cause some people tell me that's it's specially designed and stuff like that so it's the reason their Fluke probe is so damn expensive!Second, can I made my own probe? And especially 4 wire Kevin probe? I have an Advantest R6781E (nice DMM) but I have no kevin probe (and no money for it too), so I want to make my own.and if it can be made then where should I start? (buy what wire? what connector? can I trust china stuff like gold plated banana plug?)Many thanks in advance.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: May 31, 2017, 04:26:58 pm
content: Yes, they can be simple to make. They won't be safety qualified but for many purposes, perhaps yours included, that doesn't matter. People tend to like very flexible probe wire so that tends to get a bit expensive since it's special purpose.One very handy resource we have is Frankie:http://stores.ebay.com/99centhobbiesHe tests out cheap stuff and lists the good cheap stuff. Between his items and a few expensive (example Ponoma, Mueller) parts from Digikey I now have some very nice and very useful test leads.EDIT: Forgot to link this. This is for a pretty extreme set of Kelvin clips, but shows what you can do to make things better than what's available:

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: May 31, 2017, 04:50:03 pm
content: You can make your own probes .The problem is having a meter that you can plug them into ?I just got playing with a new to me meter , a battery conductance meter , I do solar and automotive work so looking at anything that helps to checkout batteries .While going through the manual and a mixed stack of lead acid batteries , a closer look & later some internet research on the meter , found that the clamps were Kelvin clamps .This unit is a Midtronic Midtron 3200 .What meter do your have and what do your want to use it for ?

author: ebclr
author_rank: Super Contributor
timestamp: May 31, 2017, 05:13:25 pm
content: Are you sure you have no money for that ?https://www.aliexpress.com/item/UNI-T-Accessories-Durable-Kelvin-Test-Leads-Probes-Clip-LCR-Meter-Test-Line-for-UT612-UT611/32696015716.html?spm=2114.01010208.3.18.mbReU4&ws_ab_test=searchweb0_0,searchweb201602_2_10152_10065_10151_10068_10136_10137_10157_10060_10138_10155_10062_10156_437_10154_5010020_10056_10055_10054_10059_303_100031_10099_10103_10102_10096_10147_10052_10053_10142_10107_10050_10051_10173_10084_10083_10080_10082_10081_10110_519_10111_10112_10113_10114_10182_5020020_10185_10078_10079_10073_10123_142-10102,searchweb201603_1,ppcSwitch_5&btsid=0301a923-5712-4386-9a7b-915017399715&algo_expid=80163bf9-65cb-4698-8a8c-8a04d7767bb8-2&algo_pvid=80163bf9-65cb-4698-8a8c-8a04d7767bb8

author: romhunter
author_rank: Regular Contributor
timestamp: May 31, 2017, 05:21:37 pm
content: Quote from: Paul Moir on May 31, 2017, 04:26:58 pmThanks for the reply. It's very helpful indeedQuote from: KD0CAC John on May 31, 2017, 04:50:03 pmAs I said above I think I just need a kevin probe for my Advantest R6871E to measure resistance at most. And maybe making some normal DMM probe, gotta get away from the cheap chinese crappy DMM zone. Maybe later on I'll need some to measure picoamp and milivolt and stuff like that. Jeez, can it all really be homemade?Quote from: ebclr on May 31, 2017, 05:13:25 pmI kinda have a biased opinion about chinese stuff... Got a few DMM probe from china before and they kinda fall apart before I can even use them. Get back to the seller and he changed it but meh... Depend though, opinion can be change at anytime.Anyway, that's just me mumbling. Should I buy it?P/s: forgot to say, my DMM have binding post at it's input

author: jeroen79
author_rank: Frequent Contributor
timestamp: May 31, 2017, 05:25:33 pm
content: A basic DMM probe is hust a wire with a bananaplug on one end and a pointy metal rod on the other end.Oscilloscope probes are a bit more complicated.A kelvinprobeis just two pointy rods in one casing or two cables connected to one short pointy rod.A kelivincliphas both jaws of the clips isolated.The main thing with kelvin clips/probes is to keep the sense and current lines separated from eachother all the way to the end so that the DUT makes the connection.You could get away with having a single probetip or alligatorclip as the connection for some applications but these would not be true kelvin clips/probes.If you want to use the probes with mains or other high voltage applications the you should properly isolate the probes.What is your motivation for building them yourself?If the big brand stuff is too expensive then China will offer many cheap alternatives. Just don't go too cheap.Otherwise there is nothing wrong with building things yourself for the experience and pride.Don't be intimidated by the stuff in the video, it is way beyond entry level.

author: romhunter
author_rank: Regular Contributor
timestamp: May 31, 2017, 05:33:45 pm
content: Quote from: jeroen79 on May 31, 2017, 05:25:33 pmYeah I think I'll just buy a normal probe set for voltage and current measurement. You got any good suggestion?Quote from: jeroen79 on May 31, 2017, 05:25:33 pmIt's just because a friend of mine bet, he said that DMM probe is "specially engineered" and I wouldn't even be able to make one.Quote from: jeroen79 on May 31, 2017, 05:25:33 pmGotta learn them all!

author: jeroen79
author_rank: Frequent Contributor
timestamp: May 31, 2017, 05:42:34 pm
content: The aforementioned Frankie has a Brymen set in his store for $18:http://www.ebay.com/itm/Brymen-Silicone-Gold-Plated-Test-Leads-Probes-for-Multimeters-CAT-IV-1000V-/171162377470The biggest hurdle to make something comparable (IMO) would be not having injection moulding equipment and suitable 'rubber' to make the nice probe handles of the commercial gear.That would leave you with constructing the handles from other materials. (ie hard plastic tubing)

author: ebclr
author_rank: Super Contributor
timestamp: May 31, 2017, 05:43:03 pm
content: You told 2 things to measure Resistance and have no money, per my knowledge resistance measurement have very low voltages involved when talking about low ohms range ( otherwise no sense to use Kelvin).If you want a cheap solution based on low budget that's it, Otherwise be prepared to pay 100 times more to complain to Standards that you may not need to complain, since you are evaluating the possibility to make yourself

author: whitevamp
author_rank: Regular Contributor
timestamp: May 31, 2017, 09:05:18 pm
content: this might be of some use.and this one

author: ebclr
author_rank: Super Contributor
timestamp: June 01, 2017, 04:13:07 am
content: How realistic are this test on a real life use of a probeFor a hypothetic set of random measurements, made with different customers who bought a multimeter on a real life lab, how much this test will fit the real life test?Do the multimeter itself can hold this current for this time?How often a multimeter/probe have this kind of specs"Maximum amps, 10 A (20 A for 30 seconds maximum) "Why they set a maximum time on the spec?Did we prove the ohms law is valid, is that the point?

author: romhunter
author_rank: Regular Contributor
timestamp: June 01, 2017, 06:29:53 am
content: anyway my DMM have binding post as it's input terminal. Can I just cut the insulation around the plug and then be able to plug it in or something else? Non-standard connector for DMM, I know

author: Shock
author_rank: Super Contributor
timestamp: June 01, 2017, 08:17:02 am
content: Depends how far you go but you have 2 wire, 4 wire, then shielded wire and or a guard connection which people call the 5th wire.For kelvin leads these ones are cheap, not used them though. Downside is no shielding in the cable.http://www.ebay.com/itm/332008183641These ones I have.http://www.ebay.com/itm/142267585778I was able to insert shrouded banana plugs into these (tight fit) and the lugs can be removed for soldering wire. You can add whatever cabling you like or experiment. Ideally for precision the less contact resistances the better.For the cheapest ghetto home made pair my idea is to use the best quality cheap shielded cable I could find and a simple wooden peg as a clip where you can mount the contacts variety of ways, or create a custom test fixture. You could add needle type probes and a set screw in the peg end and have adjustable width micro probes for measuring smd components or IC legs. Cost could be as little as a few dollars plus the connections to your instrument.

author: Shock
author_rank: Super Contributor
timestamp: June 01, 2017, 08:35:12 am
content: Old or unused multimeter leads make great cheap hookup leads as well, cut the probes off and solder some hook or croc clips on. The shrouding on the banana plugs can be cut away if needed. It's a good idea to inspect the banana plugs anyway as if corroded they go to the bin, I've been surprised and found probes falling to bits and really nice banana plugs.

author: romhunter
author_rank: Regular Contributor
timestamp: June 01, 2017, 09:43:00 am
content: Quote from: Shock on June 01, 2017, 08:17:02 amI can spare somewhere like 20$ or 30$ for a Kelvin probe though, but not something like 150$, I just want to make sure my 0.005% resistor is in tolerance. I mean, I got an Agilent N9230B working and calibrated for 200$, and the kevin probe cost is 3/4 of that. Not really worth itFor normal probe I'm thinking about the Brymen probe which Frankie are selling right now and the Probemaster 8010S. First one for portable VOM and the later one is for the benchmeter when I need to measure voltage and current. I just want some opinion on my choice, is it fair enough?

author: GreyWoolfe
author_rank: Unknown
timestamp: June 01, 2017, 11:53:29 am
content: Quote from: romhunter on June 01, 2017, 09:43:00 amI have 2 sets of the Brymen probes that Frankie sells and I like them. They also come with screw on banana plug adapters.

author: macboy
author_rank: Super Contributor
timestamp: June 01, 2017, 12:37:41 pm
content: Quote from: romhunter on June 01, 2017, 06:29:53 amYes, you can cut the shroud off from around the banana plug, then you have a normal (less safe) unshrouded plug. I also have a couple of meters with binding posts (both older Fluke). I recently bought a set of probes from Probemaster.com with the retractable shroud. This way they are safer but also fit any normal binding post or banana jack. I also like having a set of probes that fit power supply output binding posts.

author: Shock
author_rank: Super Contributor
timestamp: June 01, 2017, 12:48:30 pm
content: Quote from: romhunter on June 01, 2017, 09:43:00 amWhat brand and value and is it through hole?QuoteI've got Fluke TL71s so nothing special there. I'd probably go with the Probemaster if I needed more sets. I don't need gold contacts on everything though and it makes very little difference to me for in circuit measurements, considering tin and leads conductivity. You can go overboard with gold, beryllium copper, silver soldering.Lantern style banana plugs to me are not a great idea either, people have reported problems with them especially on cheaper cables. In my mind a one piece plug is the way to go. So I'm really suspicious of whats inside the shroud on cheap multimeter probes.I did buy some gold plated dual banana plug to screw terminals, you can make cheap 2 wire testers and with some copper clad PCB make cheap 4 wire component testers and little circuits that you can run straight on your multimeter sockets in a similar style to theHalf ohm milliohm adapter.

author: romhunter
author_rank: Regular Contributor
timestamp: June 01, 2017, 04:25:44 pm
content: Quote from: Shock on June 01, 2017, 12:48:30 pmVishay Z series, 10K 0.005%, it's a beautyQuoteWell, I think I'll go with Probemaster 8044SK with retractable shroud. My meter really is a beast of it's own time, 6 1/2 digit (can display 7 1/2 digit though) with pretty high accuracy but why do they have to make the input binding post?Well, at least the only other thing I can plug into it (beside the bare wire) is a banana plugAnyway should I get the "master set" with all the different option or should I just go with the test lead only? Quite a difference in price and I don't know if I'm gonna need those accesories or not in the future. And also I'm quite running out on budget here

author: ebclr
author_rank: Super Contributor
timestamp: June 01, 2017, 04:59:17 pm
content: This probe master is a nice probe but does not fit "I have little money", and "I want 4 wire", For general use is a nice probe. If you plan to measure SMD things is a little big

author: romhunter
author_rank: Regular Contributor
timestamp: June 01, 2017, 05:08:18 pm
content: Quote from: ebclr on June 01, 2017, 04:59:17 pmI didn't say I want to buy a 4 wire probemasterJust want it as a general purpose probe. Still wondering what I should buy for 4 wire though, since shielding is a thing

author: Shock
author_rank: Super Contributor
timestamp: June 01, 2017, 09:05:23 pm
content: The only probe accessory I find useful are croc clips and the fine probe tips. The screw on clips in my opinion are a pain, which is why I like the standard Fluke probe design as you can just push clips on and only takes a second.I have a set of probes with the banana plug tips but it's just as fast to pull out the multimeter leads. I'll also use a pair of banana to hook grabbers and clip them onto the probes if in a hurry.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: June 01, 2017, 10:18:36 pm
content: Basically yes, as stated above. Where the difference lies, is how long the test leads stay usable and how much abuse they will stand. I still have some BBC Metrawatt test leads that came with my Metravo 2H in about 1982. They hav lots of accessories which lock onto the wide safety collar and i have converted the instrument side to spring-shrouded safety plugs at some time.The point about using only VERY fine stranded leads is not only about ease of use, but it has a big influence on the lifetime. Imagine that some strands will break inevitably by the repeated bending and flexing that make up a test leads life. So a finer stranding will result in less severe deterioration. Another criterium that is often cited is to use silicone rubber insulated leads, because they are proof against inadvertent contact with a soldering iron or other hot surfaces, especially when compared to PVC.http://ec.staubli.com/products/cableline/1(formerly Multi-Contact) has a nice line of test lead stranded wire. I especially like their TPE insulated variants. Look at their stranding and you will understand the difference. For example, I have used their PLAST-1V 0,50 SN, which is 0.5mm² made up as 129x0,07mm²!Those make nice Voltage-mode test leads. I used Hirschmann/SKS 2mm cable receptacles with receptacles for ATE-type spring needle probes hard soldered into them. The are far superior to the spring-loaded probes sold by SKS, as they are able to pierce through the various coatings found on pcb's. Also, I can use different tip types and replace them when worn.