Teardown: Standard Resistors

[quarks]

just in case anyone is still interested, here are pictures of my prototype and the final product

[Dr. Frank]

Very nice, quarks!

That's physically worthwhile and esthetically appealing.

Did you already check its Symmetrie, i.e. its zero value to best possible resolution?

Frank

[lowimpedance]

Neat, any pics of the inside of final build ?.
 Interested at the mounting of the binding posts through the diecast lid then to the copper plate !. I assume there is suitable mechanical isolation from lid to the plate. (eg nut holding post to lid then a few turns down the thread a nut/washer either side of the copper plate ?... just guessing hence any inside photos!)

[quarks]

here is a inside picture

my construction is made with 5mm copper plate and Pomona 3770 posts directly screwed in, because I did not want any other metal involved
(not even the screw nuts provided with the pomona binding posts) 
my main focus was "perfect" symmetry
(and it came out very well: mechan. it is within about 0.01mm in any dimension and el. so far it shows less than 1µOhm change in any plug combination I tried)
only the screw thread gave me trouble, because the binding posts have more than expected tolerances
because of that, the screws are very close fitting (and one of my 3770 broke off), but becuase of very fast oxidation I like the fact that the screws are most probably gas tight and therefore hopefully no need to have it gold plated

[guenthert]

does anyone know what is inside this "Zero Ohm Standard"

and explain the BALANCED TETRAJUNCTION DESIGN A TRUE ZERO-OHM RESISTOR

http://www.google.com/patents/US3252091

I glanced over that patent, but need another hint on what's it's purpose.  I read through https://www.google.com/patents/US5867018, can't claim that I understood that, but believe I grasp the advantage of using a four junction terminal as part of haman resistors and similar.  But what on earth is a single 0 Ohm resistance 'standard' for?  That question was asked in https://www.eevblog.com/forum/chat/a-precision-zero-ohm-resistor/ before and there were (naturally) some more or less funny replies, but I didn't see an serious attempt to answer it.

[Macbeth]

guenthert, you will be saying it is nothing more than an AY-O fingerbox 



There are many many practical uses for a fingerbox, everyone knows that. But there are many fakes or poor designs too. Some you can't even waggle the full finger but just the knuckle finger. Very poor design, but it doesn't disprove that a perfect fingerbox is out there somewhere. 

[chickenHeadKnob]

my main focus was "perfect" symmetry
(and it came out very well: mechan. it is within about 0.01mm in any dimension and el. so far it shows less than 1µOhm change in any plug combination I tried)
only the screw thread gave me trouble, because the binding posts have more than expected tolerances
because of that, the screws are very close fitting (and one of my 3770 broke off), but becuase of very fast oxidation I like the fact that the screws are most probably gas tight and therefore hopefully no need to have it gold plated

A thread will never be air-tight by itself. OK, there are some exceptions like stainless steel on stainless steel which can  gall and self weld shut. With solid gold or completely annealed dead soft copper you will still have the spiral leak. However you might be able to seal by peening  the exits I wouldn't trust such a seal for long term integrity. Thin flash gold on gold plating in the thread might work better. I would be tempted to do the simplest and cheapest: assemble as you have with the threads as clean as possible and then coat or dip the outside with paraffin wax. Leaving  the contact areas of the pomonas uncoated of course.

[zlymex]

just in case anyone is still interested, here are pictures of my prototype and the final product

Very nice mechanical construction and finish. However, frankly speaking, I think the binding posts should be soldered to the copper triangle to ensure even electrical contact. Otherwise, the screw force cannot be guaranteed the uniform distribution of contact resistant on all directions especially when the binding post are used.

[CalMachine]

*CalMachine casts a resurrection spell*  

Over the past few months I have been accumulating some test gear to get my own home lab up and running.  A few of the things I purchased were some resistance standards.  I snagged the ESI SR1010 because it was pretty cheap and it was the first one that I had seen with cal trim pots.  I was amazed when I opened this guy up.  I wasn't sure exactly what to expect...   Each trimmer has got a set of wire wrapped resistors with it!  I took these pictures a week or so ago...  I should have gotten a better one of the back trim pot PCB.

[ManateeMafia]

Ahhh. It took me a while to find one of those. It looks like you are in your way to getting the full set plus ESI 242D/E. The 10k version is called out in the 242 manual and is initially adjusted to match a higher standard like the SR-104. Then you can build up/down to the other SR-1010 using the series-parallel adapters.

I have the full set but need to set aside time to step through the manual. The SR-1030 are also nice but are more expensive.

[TiN]

I thought it was you who snagged stash of recent 742A's. 

[CalMachine]

I thought it was you who snagged stash of recent 742A's. 

If you're referring to the big lot on Equipnet, unfortunately not.    Someone over in Europe swooped up $200k+ test equipment for 0.pennies on the dollar before I even got a chance at bidding.

Ahhh. It took me a while to find one of those. It looks like you are in your way to getting the full set plus ESI 242D/E. The 10k version is called out in the 242 manual and is initially adjusted to match a higher standard like the SR-104. Then you can build up/down to the other SR-1010 using the series-parallel adapters.

I have the full set but need to set aside time to step through the manual. The SR-1030 are also nice but are more expensive.

It will probably be awhile before I accumulate an entire set and the bridge.  I just had to jump on this one because it was the first time I had seen one.

[TiN]

No, on ebay for 9k

[CalMachine]

No, on ebay for 9k

Ahh,  I must have missed that!

On Equipnet there was a lot of like 12 742As going for like 2 or 3k.  They had an 8508 going for 250, a 740A going for 1k, A40B shunt sent for 1k, 5720 for 7k, 5790 for 8k, 792 for 9k, 720A for 250... They had some triple point of water cells as well as some other pretty cool metrology gear.

[CalMachine]

Another goodie I acquired! This one is a Resistive voltage divider (or a Kelvin Varley Divider to be precise).  The ESI RV722! 

I'm sure pictures of the insides of one of these have been passed around already... well here are some more.

[Assafl]

That's a Mylar card millefeuille. Impressive.

[Pipelie]

 
Thanks for sharing, looks like the MTB have a oil tan? like his brother( SR1010 MTA).

[CalMachine]

Do you know the differences between the MTA and MTB?  I need to find a SB103 too.

[VintageNut]

@Calmachine   did you buy the KVD from eBay? I saw the 7-decade KVD for $500 or thereabouts. It was tempting, but I already have two Gen Res KVDs.

Do you have a lead compensator?  I bought a Fluke 721A to use with the KVD.

[CalMachine]

@Calmachine   did you buy the KVD from eBay? I saw the 7-decade KVD for $500 or thereabouts. It was tempting, but I already have two Gen Res KVDs.

Do you have a lead compensator?  I bought a Fluke 721A to use with the KVD.

I did!  I offered him $375 and he took it.  There was an RS925 up very recently that I was thinking about picking up.  I had my reservations as it was a non-A model.

I do not have a lead compensator yet.

[ManateeMafia]

If you go for a ESI 925, I would recommend the C or D models. They have the ability to trim the upper four ranges. Just look for the removable plate on the front of the case.

A few ESI 242 have popped up in the last couple of months. The D version is nice and I have one I assembled in pieces over a couple of years and mounted in a case. The E version is basically the same but the null meter is a Keithley 155 vs the HP design.
You can tell by the control knobs on the meter which model is installed.

[Henrik_V]

Hi,
I got my hand on a Leeds & Northrup Hammon Transfer Standard Resistor Type 4323. That 10x 1K  and according to
http://www.ohm-labs.com/resistance-standards/hamon-transfer-standards.html
it's good for 0.01ppm for a 1:100 transfer 

I got it because the former owner soiled it with mercury, so it's hazardous waste now 

However, I took some risc in the name of science ... well ... my curiosity...  and made a small tear down:

What looks like solder on the contacs and the bar is visible pure mercury, so nothing for my home lab.

[Henrik_V]

part II  some more pics
Nice to see the realization of the Zero Ohm junctions

[Vgkid]

Very Cool. The more I see old L&N gear, the more I like it.
It will safe to handle, just remember to wash your hands after touching those posts, after all it forms a mercury amalgam( they were used as fillings, for a very long time)
Here are the specs.

[guenthert]

[..]
I got it because the former owner soiled it with mercury, so it's hazardous waste now 

However, I took some risc in the name of science ... well ... my curiosity...  and made a small tear down:

What looks like solder on the contacs and the bar is visible pure mercury, so nothing for my home lab.

Actually Leeds&Northrup specifies for their standard resistors that the contacts need to be mercury wetted.  So such 'soiled' resistors shouldn't be all that rare.  And yes, thanks, but no thanks.  You can keep it.