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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-ND
Mueller BU-P3770-0/2 - Digikey p/n 314-1200-ND, 314-1196-ND
Cheers
Alex -
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...
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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.
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Tellurium, huh? I don't want to be around when they test those things for thermal EMF...
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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.
No, the main body on Mueller posts appears to be copper, I've checked by cutting a bit off.
Cheers
Alex -
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 resistance
I 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 -
There are also these. They are very similar to ones used in Fluke gear.
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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.
Poor 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?
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There are also these. They are very similar to ones used in Fluke gear.
These 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 -
There are also these. They are very similar to ones used in Fluke gear.
These 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.
I've requested some weeks ago a quote from LowThermal. This is what I got:
sales@lowthermal.com wrote:
10 2758-00 (black) $23 USD each
10 2758-02 (red) $23 USD each
10 2758-Fork $2.99 USD each
10 2758-Ring $2.99 USD each
Plus shipping, VAT, customs fee etc. of course.
Andreas -
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 resistance
I 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. -
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.
Is it gold then? Or titaniumnitride? -
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.
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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
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Hello Alex
That 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 -
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.
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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 -
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).
Nonsense. Nobody will plate gold on copper directly if there is no intention to make short lasting crap.QuoteWith direct gold-on-copper plating, the copper atoms tend to diffuse through the gold layer, causing tarnishing of its surface and formation of an oxide and/or sulphide layer.
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Nonsense. Nobody will plate gold on copper directly if there is no intention to make short lasting crap.
If done properly (with the help of black magic) this makes sense: e.g. LowThermal, Fluke -
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- -
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.
Silver won't do as intermediate layer. It has the same problem with gold as copper but to even worse extent.
-branadic- -
It says no nickel. But does not say something like 'no intermediate layer' or 'direct plating'. So I have doubts about that.Nonsense. Nobody will plate gold on copper directly if there is no intention to make short lasting crap.
If done properly (with the help of black magic) this makes sense: e.g. LowThermal, Fluke -
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.
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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 -
It says no nickel. But does not say something like 'no intermediate layer' or 'direct plating'. So I have doubts about that.
How would you interpret:Quotetellurium copper and are direct plated with gold