Low thermal EMF binding posts - a quality warning. - Page 1
Forum section: electronics / general

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 16, 2016, 11:11:03 am
content: I've used Pomona 3770 gold plated Tellurium Copper posts with good results for a while, however recently I've ordered a somewhat cheaper "Mueller" posts from Digikey, and found these to be a Chinese copy of Pomona ones, of inferior quality (cracks in the plastic, not as accurate shape) and - most important difference - Pomona posts are gold plated over copper directly, but Mueller ones have a Nickel layer as well (and still the gold layer peels off easily). Pomona posts cost only about 30% more.Pomona 3770-0/2 - Digikey p/n 501-1612-ND, 501-1699-NDMueller BU-P3770-0/2 - Digikey p/n 314-1200-ND, 314-1196-NDCheersAlex

author: d-smes
author_rank: Regular Contributor
timestamp: August 16, 2016, 06:40:10 pm
content: Did you call Digi-Key about this? They should have traceability of the parts they stock to the manufacturer and I bet they would like to know of the quality difference. Maybe it's Mueller that decided to outsource the part instead of manufacture them...

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: August 17, 2016, 12:24:52 am
content: This is a very timely warning for me as I was just about to order the mueller posts. The plating layers should not come off, that is an indication there was a contaminant on the surface. Is the base metal on the mueller really copper? I would think one way to cheap out is to use brass and simply claim copper which what I suspect most of the ebay sellers do as they think no one will check.

author: KE5FX
author_rank: Super Contributor
timestamp: August 17, 2016, 12:46:00 am
content: Tellurium, huh? I don't want to be around when they test those things for thermal EMF...

author: Alex Nikitin
author_rank: Super Contributor
timestamp: August 17, 2016, 07:27:05 am
content: Quote from: chickenHeadKnob on August 17, 2016, 12:24:52 amNo, the main body on Mueller posts appears to be copper, I've checked by cutting a bit off.CheersAlex

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 17, 2016, 09:19:07 am
content: I also would suggest Pomona, for use with high precision standard resistors:The Pomona 3770 jacks have superior insulator material, it's made from PC, poly carbonate.This material has electrical parameters of about 10^13 Ohm * m for bulk, and 10^15 Ohm for surface resistanceI also bought the equivalent high quality jacks from mc, multi-contact, PK4-TS (also CuTe alloy). These use PA, poly amid, which is mechanically better, but its resistance parameters are an order of magnitude worse, i.e. 10^12 Ohm *m / 10^14 Ohm .For voltage references, that makes no difference, but for a 10kOhm resistor, that already yields a possible error of up to 1 ppm.Frank

author: TiN
author_rank: Super Contributor
timestamp: August 17, 2016, 12:59:32 pm
content: There are alsothese. They are very similar to ones used in Fluke gear.

author: splin
author_rank: Frequent Contributor
timestamp: August 17, 2016, 01:39:33 pm
content: Quote from: Alex Nikitin on August 16, 2016, 11:11:03 amPoor quality plating is not acceptable of course but is a Nickel layer a few microns thick going to make any difference to thermal EMFs? Unless you have a *great* deal of heat flowing through the connector, I doubt that the temperature difference across the Nickel layer could be more than a few micro Kelvins which translates to a few tens of pico volts. The Nickel is supposed to help avoid corrosion due to pinholes which can ocurr when the gold is plated directly onto copper.Does anyone have any objective measurements which demonstrate that Nickel plating has any significant effect on thermal EMFs?

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 17, 2016, 03:19:26 pm
content: Quote from: TiN on August 17, 2016, 12:59:32 pmThese are made from nylon, which is the trademark for PA.. so not the best insulator.. or they made some improvements.Look like the jacks, which WEEKOM is using. Expensive.Frank

author: BU508A
author_rank: Super Contributor
timestamp: August 18, 2016, 05:03:31 am
content: Quote from: Dr. Frank on August 17, 2016, 03:19:26 pmI've requested some weeks ago a quote from LowThermal. This is what I got:sales@lowthermal.com wrote:10 2758-00 (black) $23 USD each10 2758-02 (red) $23 USD each10 2758-Fork $2.99 USD each10 2758-Ring $2.99 USD eachPlus shipping, VAT, customs fee etc. of course.Andreas

author: orin
author_rank: Frequent Contributor
timestamp: August 18, 2016, 06:06:17 am
content: Quote from: Dr. Frank on August 17, 2016, 09:19:07 amI like the 3770s, but only available in Red or Black from the usual suspects at the moment.I replaced the binding posts on my Fluke 731B with them, but I think I had to go with the 3750 which is brass/gold plating for the guard terminal.Orin.

author: wiss
author_rank: Frequent Contributor
timestamp: August 18, 2016, 08:38:44 pm
content: Quote from: Alex Nikitin on August 16, 2016, 11:11:03 amIs it gold then? Or titaniumnitride?

author: MisterDiodes
author_rank: Frequent Contributor
timestamp: August 19, 2016, 11:51:13 pm
content: I feel like I stumbled onto an Audiophool thread: If the connectors are expensive, they MUST be good!!Seriously, be aware: I have had the opposite experience: I have some Pomona jacks that are gold over nickle (and lousy mechanical quality), and the Mueller posts that are gold over Te-CU (104 alloy). Ordered probably a few years ago. Of course generally you don't use TeCu wire, so regular 110 copper works also...when it's clean.The "Low Thermal" jacks are suspect also - I'm holding one in my hands, and its gold over what looks to be thin electroless nickle. I contacted the owner, who confirmed that he didn't think they are actually TeCu, and couldn't confirm the exact coating process. I thinks it's a replacement part for whatever instruments he reps. They aren't worth the price IMHO. We tested them at the lab and they don't work 25 times better than our self-built $1 posts. They work about the same, actually.He's also got spade lugs which are garden variety spades that are gold plated. They aren't TeCU either. You can send any crimp lugs to a plating house for gold plating, it's cheap and common. They don't work any different than the 12 cent spade lug without the plating.We just machine our own posts from TeCu or regular 110 copper, keep them clean and skip the gold. The gold only adds a few uV noise - maybe a little more convenient to keep clean but we never use it. Use a ceramic or teflon insulator, and regular nuts / washers in copper. Use colored nylon washers at the base for color coding. Skip the expensive "Low Thermal" leads - clean copper works fine. The silver-coated stuff is stiff and hard to get a repeatable compression on. Sometime on finicky setups we use teflon - insulated wire - but watch out for how that material cold-flows and creeps into crimped connections. Use guard circuits well, and then the wire type is even less important.For resistor standards under 10k you'll be using 4 wire anyway - and if designed right the binding posts won't matter much.The bottom line: Mount your binding posts on a good thermal conductor, keep the copper connections clean, and use a small, precision torque wrench on spring-loaded nuts to make a repeatable compression force on the wire - that will make more difference than thermal volatge anyway. The thermal voltage will generally not be an issue if both binding post are at about same temperature, so keep them covered and draft-free.SKIP the BANANA plugs if you want repeatable readings. Those really have no place in precision measurements, usually.This is how its done at our cal lab, and is by far the most cost-effective way to get repeatable results even into sub ppm range. We ditched the expensive low thermal connector baloney years ago, and never looked back.If your binding post system costs more than a few dollars per post, it's maybe not the best way.. at least that's what we've found out during testing.

author: onemilimeter
author_rank: Frequent Contributor
timestamp: August 22, 2017, 03:41:09 am
content: Recently I ordered Mueller (BU-P3770-0 & BU-P3770-2) and Pomona (3770-0 and 3770-2) binding posts from element14 and Digi-Key. I just received those from element14. The quality of the Mueller parts is quite poor compared to the Pomona parts. For example, the gold-plating layer of the Mueller parts looks inconsistent - some look golden-shinny while other look faded-shinny. Besides, as written on the package, the Mueller parts are all made in China. Still waiting for the parts from Digi-Key, not sure the Mueller parts from Digi-Key will have the same problem.After inspection the Mueller parts (BU-P3770-0 & BU-P3770-2) ordered from element14, I also found "crack" in the plastic of one of the binding posts.Today, I received the Mueller (BU-P3770-0 & BU-P3770-2) from Digi-Key. After inspection, I again also found "crack" in the plastic of one of the binding posts ordered from Digi-Key.By the way, can we consider or still consider Mueller a branded name or trusted brand in the connector industry? (I think the answer is NO)P/S: Just found this thread after I ordered the binding posts

author: TechnicsHiFiFan
author_rank: Newbie
timestamp: August 30, 2019, 03:23:48 am
content: Hello AlexThat is interesting,. I got Mueller TE coppper posts and the plastic has broken on some. I didnt think the Pomoma would be any different. Also the gold has gone on my posts also.Ive used them on my speakers and amplifer terminals

author: MiDi
author_rank: Frequent Contributor
timestamp: August 30, 2019, 05:07:11 am
content: This Pomona 3770 are ~1 year old and still looking good.It seems that the Mueller P3770 are not the same as the Pomonas - even though one would think.I am not convinced of the quality at that price-point - I would expect better.In comparison to the Mueller, which are not cheap either, the Pomonas seem to be better.There are not many options for TeCu posts, so one has to accept the bad bang-for-the-buck.

author: dietert1
author_rank: Super Contributor
timestamp: September 06, 2019, 09:55:54 am
content: During the last days i got two offers on copper binding posts which were 30 $ per piece and 66 $ per piece. I also got two different kinds of chinese "pure copper" binding posts, that were all white metal inside (gold plated iron). Multi-contact parts that used to be made from copper, are now brass. So i bought some Pomona 3770.Their body is copper, yet i noticed that the insulated thumb nut is brass. Don't know why they are doing that. Spade lugs will be sitting between the brass nut and the copper body. Maybe one can use some kind of nylon washer to keep the brass part off.Regards, Dieter

author: wraper
author_rank: Unknown
timestamp: September 06, 2019, 10:03:25 am
content: Quote from: Alex Nikitin on August 16, 2016, 11:11:03 amNonsense. Nobody will plate gold on copper directly if there is no intention to make short lasting crap.Quote

author: MiDi
author_rank: Frequent Contributor
timestamp: September 06, 2019, 10:46:47 am
content: Quote from: wraper on September 06, 2019, 10:03:25 amIf done properly (with the help of black magic) this makes sense: e.g.LowThermal, Fluke

author: branadic
author_rank: Super Contributor
timestamp: September 06, 2019, 02:09:07 pm
content: I'm sure you need an intermediate layer in any case, be it nickel or silver, otherwise the gold will diffuse into the copper. There is no black magic going on, it's simply chemistry.-branadic-

author: wraper
author_rank: Unknown
timestamp: September 06, 2019, 02:19:10 pm
content: Quote from: branadic on September 06, 2019, 02:09:07 pmSilver won't do as intermediate layer. It has the same problem with gold as copper but to even worse extent.

author: wraper
author_rank: Unknown
timestamp: September 06, 2019, 02:26:24 pm
content: Quote from: MiDi on September 06, 2019, 10:46:47 amIt says no nickel. But does not say something like 'no intermediate layer' or 'direct plating'. So I have doubts about that.

author: Magnificent Bastard
author_rank: Regular Contributor
timestamp: September 06, 2019, 03:57:13 pm
content: The best binding post for low thermal EMF's is solid copper without any plating at all. That's why quality nanovoltmeters only use pure copper in the input circuitry, including the connectors and cabling. This does mean that you are expected to keep these connections clean and clear of any copper oxide before making any measurements. The gold plating is for lazy people that don't want to keep their connections clean, and it comes with "issues". In my experience, a freshly stripped hunk of plain old cheap Bell telephone wire on freshly cleaned (with DeOxit) solid copper binding posts has performed the best with regard to thermal EMF's. Try not to "over think" the problem.

author: dietert1
author_rank: Super Contributor
timestamp: September 06, 2019, 04:22:29 pm
content: Could you recommend a reliable source for plain, pure copper binding posts? I tried to buy something labeled "pure copper" from china and they sent gold plated iron. Appears like they didn't know any better.Regards, Dieter

author: MiDi
author_rank: Frequent Contributor
timestamp: September 06, 2019, 06:03:27 pm
content: Quote from: wraper on September 06, 2019, 02:26:24 pmHow would you interpret:Quote

author: MiDi
author_rank: Frequent Contributor
timestamp: September 06, 2019, 07:48:01 pm
content: Quote from: dietert1 on September 06, 2019, 04:22:29 pmSeems youmissed the group buy.

author: dietert1
author_rank: Super Contributor
timestamp: September 06, 2019, 08:48:08 pm
content: Yes, and i think some of the remarks in this discussion are pretty academic. How about the advantages of implementing a complete metrology lab with silver instead of copper. Conductivity of silver is better than copper, isn't it? If you can't find silver binding posts, make them!Regards, Dieter

author: FriedLogic
author_rank: Regular Contributor
timestamp: September 10, 2019, 12:02:15 pm
content: I see that Pomona also does a tin plated brass version. Are there any particular issues with tin as a plating?

author: klimm
author_rank: Contributor
timestamp: May 20, 2020, 03:47:08 pm
content: Yeah, I know it is an old thread but to keep the things about low EMF connected...Quote from: dietert1 on September 06, 2019, 08:48:08 pmWith respect to silver, having some silver connectors I am considering this my self but seemingly, the silver connectors tend to develop an oxide layer as I find in a paper. Now, copper does this too.

author: Lesolee
author_rank: Regular Contributor
timestamp: May 21, 2020, 09:42:38 am
content: Quote from: splin on August 17, 2016, 01:39:33 pmQuote from: wraper on September 06, 2019, 10:03:25 amOur suppliers won't plate gold directly on brass for this same reason. They insist on a10nmnickel flash. Other interlayers are probably available.I know this is an old thread, but Mouser just started selling the Mueller ones, and I bought one.

author: TimFox
author_rank: Super Contributor
timestamp: May 21, 2020, 02:15:24 pm
content: Ag vs Cu: look it up! The conductivity of silver is only 5% higher than copper. In normal conditions, Cu oxidizes, forming a copper oxide semiconductor, but Ag reacts with sulfur in the atmosphere to form the black tarnish you see on silverware. The advantage of gold is that the surface will remain untarnished in normal conditions.

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: May 27, 2021, 01:15:41 pm
content: There seems to be only two commercially available options that I am aware of for Copper-Tellurium:LowThermal 2758(33 USD, quoted May 26 2021 ; 30 USD each in quantities 1-9 & 28.50 USD each to quantities of 99, quoted November 12 2020)Advantages:-Au plated Cu-Te (for 'lazy people')-appearanceDisadvantages:-insulation is Nylon (not as good as polycarbonate)-cost keeps rising-often backordered (next availability, mid-July)Pomona 3770(12 USD, price from Mouser on May 27 2021)Advantages:-cheap-Au plated Cu-Te (for 'lazy people')-superior polycarbonate insulationDisadvantages:-looks cheap-comes with inferior nuts and washers that should not be used for metrology grade applicationsDoes anyone have other suggestions for Binding Posts? Keep in mind that most of us do not have a machine shop to make our own. I love the new Fluke and Advantest posts, but I doubt they sell them to us plebeians. If anyone has some LowThermal posts that they don't mind parting with, please PM me. Thanks!

author: exe
author_rank: Unknown
timestamp: May 27, 2021, 08:52:14 pm
content: Quote from: leighcorrigall on May 27, 2021, 01:15:41 pmIn which situation that would be an issue?

author: Dr. Frank
author_rank: Super Contributor
timestamp: May 27, 2021, 09:36:52 pm
content: Quote from: exe on May 27, 2021, 08:52:14 pmFor building high precision resistance standards and dividers!Taking a 10kOhm resistor in a metal shielding box and to ensure <= 0.5ppm error from the insulation would require > 1011Ohm insulation from each of the binding posts.I have used the obsolete CuTe binding posts from multi contact, PK4-TS, I think the plastic was PA, and you could easily measure too high leakage currents of ~ nA @ 100V test voltage, (don't remember the exact measurements any more) leading to nearly 1ppm error..If you realize a precision divider like 720A, or the 752A, there's the very same situation, even worse, as the resistance values used are orders of magnitude higher.Therefore PC of the Pomonas 3770 is superior for these use cases.Another disadvantage is that latter might be more brittle.. I have had no problem so far.Frank

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: May 27, 2021, 09:57:40 pm
content: Quote from: Dr. Frank on May 27, 2021, 09:36:52 pmExactly. I am in the process of ordering a NIST Calibrated Vishay Y473310K0000S0L (HZ Series) 4-wire resistor with PMO and I am concerned about the quality of binding posts for the job. Hence, my inquiry of binding post options. I suppose there will be less interference because of the kelvin connections, but I don't want to risk anything unnecessarily. I am not exactly an expert, but I understand the importance of materials selection. Pomona 3770 binding posts seem to be the best option unless I can get my hands on something better. Still considering the LowThermal option and mounting the posts on something with higher electrical resistance and a layer of shielding. Tricky business.

author: branadic
author_rank: Super Contributor
timestamp: May 27, 2021, 10:00:49 pm
content: Pomona 3770 are quite brittle and I also had some of them broken, because they were delivered with obvious strain cracks inside the plastic, but BU-P3770 by Mueller Electric are even worse.-branadic-

author: BU508A
author_rank: Super Contributor
timestamp: May 27, 2021, 10:26:33 pm
content: I don't know your timeline, but from time to time,some broken (for parts, not working) ESI SR1010 resistor boxes are showing up on ebay.If you could get one of those, then you can get some very high quality low-thermal EMF binding posts (and some good resistors too).Examples:ESI SR1010 series:https://www.ebay.com/sch/i.html?_nkw=esi+sr1010&_sop=12A bit more expensive: ESI SR1030 series:https://www.ebay.com/sch/i.html?_nkw=esi+sr1030&_sop=12Example for a 100kOhm steps unit:

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: May 27, 2021, 11:08:21 pm
content: Quote from: BU508A on May 27, 2021, 10:26:33 pmGreat suggestion!I notice that there are subtle differences between the two types of binding posts used on the SR1010 Series. See the lower resistance range. The SR1030 seems to be using all the same type.My guess is that ESI is still using the same recipe as what they are listing today:https://www.ietlabs.com/binding-posts-bp-1000.htmlThey use polycarbonate insulators and have stood up to the test of time.Thank you, BU508A.

author: BU508A
author_rank: Super Contributor
timestamp: May 28, 2021, 01:46:25 pm
content: Just for entertainment reasons I've requested a quote for 10 red and 10 black binding posts.

author: Kosmic
author_rank: Super Contributor
timestamp: May 28, 2021, 02:27:51 pm
content: Quote from: BU508A on May 28, 2021, 01:46:25 pmProbably better to live with the fact that the Pomona binding post might break

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: May 28, 2021, 02:31:37 pm
content: Quote from: Kosmic on May 28, 2021, 02:27:51 pmBetter to live in a country that has a lower relative currency to the USD. Apparently, they are making so much money from these binding posts that they can charge the same magnitude in any country.

author: martinr33
author_rank: Frequent Contributor
timestamp: May 28, 2021, 05:59:59 pm
content: I sort of like the idea of stripping a cheap 1010 for sockets. I'd feel better about if there was a busted, broken one up for sale.However, for $300, a little labor, and maybe a crisis of conscience you get 26 battle-tested black nut gold-plated banana jacks (the metallic nuts don't have the panel insulator).On the down side, no colors, and the obsession as to what to do with a stack of wafer resistors.

author: Robert763
author_rank: Super Contributor
timestamp: May 31, 2021, 04:42:30 pm
content: Quote from: leighcorrigall on May 27, 2021, 09:57:40 pmKelvin connections will not help with leakage resistance. In fact with all else being equal a 4 terminal resistor will have more leakage then a two terminal because there are more insulators to leak.A guarded connection will compensate for leakage.It can also be misleadng to just consider the bulk resistivity of the raw plastic used for insulators to compare different terminals. While it obviously has an influence, so does the shape and size of the insulator. Additives such as dyes can also have a big influence.

author: TimFox
author_rank: Super Contributor
timestamp: May 31, 2021, 04:57:15 pm
content: Also, the bulk resistivity of an insulating material allows you to estimate the leakage resistancethroughthe insulator, but often the leakage is dominated by surface "creepage"alongthe insulator. Guarding is effective against surface effects.

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: June 22, 2021, 05:44:24 pm
content: I was really hoping that my research into binding post alternatives would pay off when I spoke with Guildlinehttps://guildline.com/primary-electrical-metrology/resistance-standards/precision-dc-air-standard-resistors. Apparently, this international metrology company with a branch in Canada are now switching over to LowThermal 2758 Series binding posts too. According to a representative, they used to make their own binding posts from beryllium-copper and are phasing these parts out for something readily available.My current lead is JP FineChem (E&C)https://www.jfine.co.jp/eng/e_c/resistorbox/, who manufacture ultra-high voltage precision resistors and enclosures with Miyama Electric Co binding postshttp://www.miyama.co.jp/products/category/miyama_cat-202011G.pdf. See the MT-122,123,124, and 129 Series binding posts. Some of the JP FineChem product illustrations that appear in colour show the conductors as gold plated (see attached). Maybe they haven't cheaped out on the base metal? When I find out if they are really copper (with either beryllium or tellurium alloying elements) I will let people know.

author: mawyatt
author_rank: Super Contributor
timestamp: June 23, 2021, 01:16:09 am
content: Quote from: TimFox on May 31, 2021, 04:57:15 pmGuarding can be a very effective technique. We utilizing "Guarding" to reduce surface contamination leakage effects to electron/seconds levels with specialized high sensitivity Night Vision Imaging chips (patent 8102452 Electron Imaging Pixel Leakage Reduction), where every electron mattered. The technique was "borrowed" from the 1960s (maybe earlier) concept of reducing cable capacitance by driving the cable inter-shield with a replica of the analog signal on the center conductor. Since the displacement current (capacitive current) is proportional to capacitance times voltage rate of change (I=C*dv/dt), the voltage rate of change was significantly reduced because the differential voltage between the center conductor and shield was reduced, thus dv/dt ~ 0. Since there is no dv/dt, the signal experiences no displacement current, thus no capacitance! This works well if the center and shield voltages don't deviate from each other, or in other words the center and shield voltages have the same phase change (and voltage level) along the cable. Very clever technique from the old analog days, wouldn't be surprised if the old Tektronix didn't have a hand in this "Guarding" development way back then.Best,

author: TimFox
author_rank: Super Contributor
timestamp: June 23, 2021, 03:14:00 am
content: Actually, guarding goes back to the very old days of electrical bridges. A reasonably modern version is the Keithley 515A:http://doc.xdevs.com/doc/Keithley/515/515A%28Model515A%29.pdf

author: RaymondMack
author_rank: Regular Contributor
timestamp: July 02, 2021, 03:10:54 am
content: Quote from: TimFox on May 21, 2020, 02:15:24 pmIt depends on the trace gases present, but Silver generally does not oxidize as fast as copper. If you have a natural gas heating system, then you will have much higher trace compounds that will react with silver and cause it to oxidize at an accelerated rate.I have many silver plated RF connectors that still look white and (mostly) oxide free that are well over 10 years old. On the other hand, I have bought random lots of vintage RF connectors from eBay that had some silver connectors that were black as sin (though they cleaned up nicely using the aluminum foil and sodium bicarbonate trick). I also have some stripped copper wire that has turned brown in just over a week (which can be removed with citric or ascorbic acid when tin or zinc is not present).As for earlier comments about direct gold plating: Gold will readily diffuse into copper without a diffusion barrier like nickel present. However, if the plating is thick enough, then you can get away without using the diffusion barrier. Commercially speaking, this requires much more gold than manufacturers would like to use. With the exception of audio fools, you really only see this approach done on older test/calibration equipment. For example, this is the plating process HP used on the 419A DC Null Voltmeter's input terminals. Leeds and Northrup's binding posts (for bare copper wire connections) also use gold flash directly on copper. They also chose to save costs with a brass nut since the copper wire would directly touch the gold-on-copper terminal.A diffusion barrier is really just a way to cut costs (and use a thinner plating). It is not a set-in-stone requirement.Personally, I hate cleaning bare copper. So I tend to avoid using it outside of critical short term applications. Unfortunately, most modern gold platings (i.e., economically thin platings) aren't that great either. I've seen 40 micron or less platings of gold literally peel off due to holes in the gold surface coat that allow chemical attack of the underlying nickel to take place. Older stuff that had over 40 micron coatings seem to last forever under minimal connect/disconnect cycles. So there is some optimal thickness here.From what I've seen firsthand, the "heavy" gold flash platings (usually having a dull sheen) have the highest wear characteristic since the plating is so thick. Thin platings of gold in high friction environments (i.e., a 4mm banana plug or cable) do not last long and the nickel under coat becomes visible after a while.

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: July 09, 2021, 05:27:47 pm
content: Quote from: leighcorrigall on June 22, 2021, 05:44:24 pmAccording to the manufacturer, MT-123/MT-124 conductor material is nickel-plated brass. The HVR10000 resistance standard conductor material is gold plated.JP FineChem must request customized binding posts from Miyama in a bulk order.Sorry friends. Looks like there are Pomona, LowThermal, and ESI that can be purchased new in low quantities.

author: martinr33
author_rank: Frequent Contributor
timestamp: July 18, 2021, 09:47:09 pm
content: Viborrg has some pricey, but well built, products with high-grade copper. These products are built as audio exotica, but have decent materials.http://www.viborgaudio.com/en/Product/SDFFASD/However - they seem a lot more expensve than can be justified over the Pomonas.Bananas are harder to find. Vibor spring bananas are about $8 each, and I found some tubular bananas for $20 each.https://www.amazon.com/gp/product/B01KTBBVNO/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1Gold over silver spades are about $4 each.On eBay, I have come to the conclusion that " pure copper" means "brass".If they are not brass, they are pot metal (low grade zinc alloy). Pot metal connectors appear to be used in that infamous 10V reference.The low cost Pomona TeCu banana sockets have zinck plated hardware. You would have to source copper nuts and washers or solder to the terminals.

author: notfaded1
author_rank: Frequent Contributor
timestamp: July 23, 2021, 04:54:35 pm
content: Quote from: martinr33 on July 18, 2021, 09:47:09 pmWhat's the infamous 10V reference?Thanks,Bill

author: Gyro
author_rank: Super Contributor
timestamp: July 23, 2021, 05:25:39 pm
content: Quote from: notfaded1 on July 23, 2021, 04:54:35 pmhttps://www.eevblog.com/forum/metrology/precision-dc-votage-source/msg3601830/#msg3601830

author: GWL
author_rank: Newbie
timestamp: August 10, 2021, 10:07:06 am
content: I have built a 1% high resistance box, for internal insulation/megger testing, for which i had used a brass-gold plated multi-comp binding post (SPC15203 and SPC15208). They were pretty cheap USD 4 each. The values i recorded had a good repeatability. I had tested only till 1 gig ohms at 1000 volt. I was thinking of upgrading the box with 1 tera ohms resistors and binding post that can withstand 10kV. Not sure if i can use the same binding post and test 1 tera ohms at 10kV. The multi-comp datasheet does not have any technical details other than max 15Amps. Any leads for upgrade will be helpful.

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: August 10, 2021, 12:02:36 pm
content: Quote from: GWL on August 10, 2021, 10:07:06 amWelcome GWL,As I mentioned previously, JP Fine Chem designs and manufacturers ultra-high voltage resistance references:https://www.eevblog.com/forum/metrology/low-thermal-emf-binding-posts-a-quality-warning/msg3592418/#msg3592418https://www.eevblog.com/forum/metrology/low-thermal-emf-binding-posts-a-quality-warning/msg3604042/#msg3604042JP Fine Chem (also known as E&C) uses custom-made Miyama binding posts. You might not be able to acquire these binding posts as a consumer, but you could ask anyways. I spoke to a representative at DMTL from the UK (https://www.dmtl.co.uk/) and they were very helpful in answering my questions.The JP Fine company also makes high voltage measuring equipment:https://www.jfine.co.jp/eng/e_c/voltage/index.htmlBy the way, what brand are your tera-ohm resistors? I would love to know your experience with them in the precision resistors general thread:https://www.eevblog.com/forum/metrology/precision-resistors-general-thread/

author: e61_phil
author_rank: Frequent Contributor
timestamp: August 13, 2021, 10:31:13 pm
content: Quote from: GWL on August 10, 2021, 10:07:06 amNice box!I'm interested in your 10kV setup: Do you have 10kV with such low uncertainties that it make sense to measure with 10kV instead of 1kV?I can generate 10kV with <10ppm uncertainty, but that is a lot of effort.

author: martinr33
author_rank: Frequent Contributor
timestamp: August 24, 2021, 12:00:20 am
content: Unpleasant discovery.When installing copper binding posts - make sure that the front terminal nuts are loose, several turns or so.Otherwise, when you tighten the rear nut, you will hear the snap of your post breaking at the wire holes. It doesn't take much, you can do it with a nut driver.Low thermal copper is not as strong as brass.

author: dietert1
author_rank: Super Contributor
timestamp: August 24, 2021, 05:16:49 am
content: If you want something stronger, you can try EIZZ EZ-303. Those are speaker terminals made from CuTe (!) and they are about 15 € per piece. I got some atwww.audiophonics.fr.They look like having about twice as much copper than a Pomona 3770.Regards, Dieter

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: August 24, 2021, 08:42:31 am
content: Quote from: dietert1 on August 24, 2021, 05:16:49 amNice find, Dieter.It would be nice to know what insulating material they use if they have not already said so. If you can, see if there is a thin nickel coating or something else suspicious hiding under that 'gold' coating with a strong magnet. Sometimes they will gold coat iron.I love how it is blatantly obvious that these posts came from China. When I get back from vacation I am going to see if my friend can identify the manufacturer so we can avoid the middle man.

author: dietert1
author_rank: Super Contributor
timestamp: August 24, 2021, 10:02:51 am
content: Yes, when they arrived, the first thing i did was look at the inside, and it had a similar reddish shine like the Pomonas. Nothing silvery. The body doesn't react at all with a strong magnet, including the set screw. The gold plated decoration of the knob and the back nut show a minute, hardly detectable attraction.I bought from France to save time, they had some stock.Meanwhile we also have a second SR1010 with 100 Ohm steps and with copper binding posts while the first one with 1 KOhm steps has binding posts made of white, non-magnetic metal.Regards, Dieter

author: Vgkid
author_rank: Super Contributor
timestamp: August 24, 2021, 10:05:54 am
content: Quote from: leighcorrigall on August 24, 2021, 08:42:31 amHere you go:http://eizz.cn/en-us/x23.html

author: martinr33
author_rank: Frequent Contributor
timestamp: August 27, 2021, 03:09:51 am
content: They do look nice, and that is a good price.However - the Aliexpress ones call out brass, but also mention no nickel plate, which I have only seen on copper terminals. No nickel plate is consistent with the lack of magnetic attraction.We may need some filing to see.https://www.aliexpress.com/item/32722111716.html

author: dietert1
author_rank: Super Contributor
timestamp: August 27, 2021, 08:25:06 am
content: I would not trust that aliexpress any more than the EIZZ web page.As far as i understand they have them in brass and CuTe (different product IDs). If i buy from a french company selling it as CuTe, i can insist. As i wrote above, i did the filing as soon as they arrived and it looked like the CuTe of the Pomonas, and softer than brass.Recently we got a FLIR camara, and one day i will buy one of those handheld X-Ray analyzers they use for metallurgy (garbage recycling). As far as i understand it discovers traces of Pb in RoHS products and many other metals, depending on the setup.Or make a thermal EMF voltage setup to do a real measurement.Regards, Dieter

author: OscarM
author_rank: Newbie
timestamp: January 12, 2023, 07:38:09 pm
content: This seems as good as place as any (even if it is old) to post this picture.I received these from Digi-key last week.When is a 3770-0 not a 3770-0 ?Its not obvious but they are still in the original packaging.It isn't a trick of the lighting.

author: sahko123
author_rank: Frequent Contributor
timestamp: January 12, 2023, 10:28:35 pm
content: one of those is the 3760 which is tin plated. So pomona must have screwed up the packaging

author: Rax
author_rank: Super Contributor
timestamp: March 30, 2025, 09:45:45 pm
content: Old thread, but I haven't been able to satisfactorily figure this out.Quote from: martinr33 on July 18, 2021, 09:47:09 pmWhat have others done with the 3770 binding posts? I've been digging deep trying to source some copper nuts and washers, without much success. On the other hand, soldering on the terminals would be easy enough, but it'd "lock in place" the binding posts (They'd no longer be easily detachable from the panel I have them placed on).

author: Overspeed
author_rank: Frequent Contributor
timestamp: April 01, 2025, 12:06:06 pm
content: HelloFirst problem is the cross drilled hole in the body , which limit the metal aeraI have traced banana cut away with 1 mm and 2 mm drilled holesRegardsOS