Author Topic: Low thermal EMF binding posts - a quality warning.  (Read 13373 times)

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Offline MiDi

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #25 on: September 06, 2019, 07:48:01 pm »
Could you recommend a reliable source for plain, pure copper binding posts?

Seems you missed the group buy.
 

Offline dietert1

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #26 on: September 06, 2019, 08:48:08 pm »
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
 

Offline FriedLogic

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #27 on: September 10, 2019, 12:02:15 pm »
I see that Pomona also does a tin plated brass version. Are there any particular issues with tin as a plating?
 

Offline klimm

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #28 on: May 20, 2020, 03:47:08 pm »
Yeah, I know it is an old thread but to keep the things about low EMF  connected...
 
... 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

With 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. 
 

Offline Lesolee

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #29 on: May 21, 2020, 09:42:38 am »
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?

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.
Quote
With 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.

Our suppliers won't plate gold directly on brass for this same reason. They insist on a 10nm nickel 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.  |O
 

Offline TimFox

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #30 on: May 21, 2020, 02:15:24 pm »
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.
 

Online leighcorrigall

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #31 on: May 27, 2021, 01:15:41 pm »
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')
-appearance

Disadvantages:
-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 insulation

Disadvantages:
-looks cheap
-comes with inferior nuts and washers that should not be used for metrology grade applications

Does 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!
« Last Edit: May 27, 2021, 01:37:53 pm by leighcorrigall »
 

Offline exe

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #32 on: May 27, 2021, 08:52:14 pm »
-insulation is Nylon (not as good as polycarbonate)

In which situation that would be an issue?
 

Offline Dr. Frank

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #33 on: May 27, 2021, 09:36:52 pm »
-insulation is Nylon (not as good as polycarbonate)

In which situation that would be an issue?

For 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 > 1011 Ohm 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
« Last Edit: May 27, 2021, 10:21:16 pm by Dr. Frank »
 
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Online leighcorrigall

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #34 on: May 27, 2021, 09:57:40 pm »

For 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 > 1011 Ohm insulation from each of the binding posts.

...


Exactly. 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.
 
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Offline branadic

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #35 on: May 27, 2021, 10:00:49 pm »
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-
Computers exist to solve problems that we wouldn't have without them. AI exists to answers questions, we wouldn't ask without it.
 
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Online BU508A

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #36 on: May 27, 2021, 10:26:33 pm »
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=12

A bit more expensive: ESI SR1030 series:
https://www.ebay.com/sch/i.html?_nkw=esi+sr1030&_sop=12

Example for a 100kOhm steps unit:


« Last Edit: May 27, 2021, 10:31:34 pm by BU508A »
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 
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Online leighcorrigall

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #37 on: May 27, 2021, 11:08:21 pm »
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=12

A bit more expensive: ESI SR1030 series:
https://www.ebay.com/sch/i.html?_nkw=esi+sr1030&_sop=12

Example for a 100kOhm steps unit:


Great 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.html

They use polycarbonate insulators and have stood up to the test of time.

Thank you, BU508A.
 
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Online BU508A

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #38 on: May 28, 2021, 01:46:25 pm »
Just for entertainment reasons I've requested a quote for 10 red and 10 black binding posts.

“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 

Online Kosmic

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #39 on: May 28, 2021, 02:27:51 pm »
Just for entertainment reasons I've requested a quote for 10 red and 10 black binding posts.



Probably better to live with the fact that the Pomona binding post might break  :)
 

Online leighcorrigall

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #40 on: May 28, 2021, 02:31:37 pm »
Just for entertainment reasons I've requested a quote for 10 red and 10 black binding posts.



Probably better to live with the fact that the Pomona binding post might break  :)

Better 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.  :-DD

[attachimg=1]
 

Offline martinr33

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #41 on: May 28, 2021, 05:59:59 pm »
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.

 
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Offline Robert763

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #42 on: May 31, 2021, 04:42:30 pm »

For 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 > 1011 Ohm insulation from each of the binding posts.

...


Exactly. 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.

Kelvin 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.
 
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Offline TimFox

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #43 on: May 31, 2021, 04:57:15 pm »
Also, the bulk resistivity of an insulating material allows you to estimate the leakage resistance through the insulator, but often the leakage is dominated by surface "creepage" along the insulator.  Guarding is effective against surface effects.
 
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Online leighcorrigall

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #44 on: June 22, 2021, 05:44:24 pm »
I was really hoping that my research into binding post alternatives would pay off when I spoke with Guildline https://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.  :palm:

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 posts http://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.  :-+
« Last Edit: June 22, 2021, 05:48:44 pm by leighcorrigall »
 
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Offline mawyatt

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #45 on: June 23, 2021, 01:16:09 am »
Also, the bulk resistivity of an insulating material allows you to estimate the leakage resistance through the insulator, but often the leakage is dominated by surface "creepage" along the insulator.  Guarding is effective against surface effects.

Guarding 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,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Wyatt Labs by Mike~
 
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Offline TimFox

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #46 on: June 23, 2021, 03:14:00 am »
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
 

Offline RaymondMack

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #47 on: July 02, 2021, 03:10:54 am »
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.

It 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.
« Last Edit: July 02, 2021, 03:16:28 am by RaymondMack »
 
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Online leighcorrigall

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #48 on: July 09, 2021, 05:27:47 pm »

...

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 posts http://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.  :-+

According 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.  :'(
 

Offline martinr33

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Re: Low thermal EMF binding posts - a quality warning.
« Reply #49 on: July 18, 2021, 09:47:09 pm »
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=1


Gold 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.














 
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