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Electronics => Metrology => Topic started by: zlymex on March 10, 2016, 03:11:37 am

Title: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 03:11:37 am
I've been fascinated by standard resistors of their performance, cannot stop thinking of what's on earth inside.

Before teardown, let's look at some of the important factors of a standard resistor, such as specified by esi SR104:
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207289;image)

 - Stability
Specified as ppm/year, It is a long time factor that most important for a standard resistor.
Every Chinese and Japanese resistor has a CLASS, they classify them according to annual drift.

 - Temperature Coefficient, alpha23
This is the slop of the temperature chart at 23 deg C, in ppm/C. Because the temperature chart is curved for most resistors, alpha varies with temperature. That's why it has a subscript specifying at what temperature the alpha is measured. Also, for standard resistors that often used in lab environment, they don't specify or test in large temperature range. Normally 18 to 28 degree C is suffice.

 - Temperature Coefficient, beta
The unit of beta is ppm/C2(per sq deg C), not ppm/C as above spec. The temperature chart can be roughly represented by a quadratic curve, this is especially true for standard resistors where the temperature range is limited. This beta is the coefficient(constant) of the second order equation. The larger the beta, the more the curvature. Most of the metals and resistors have negative beta(parabolic shaped). If a WW made of manganin, the beta is usually -0.6ppm/C2, If made of evanohm the beta usually around -0.028ppm/C2. Foil resistors often have even smaller beta.

 - Power Coefficient
Represent in ppm/Watt. This parameter depends on how heat dissipated and also related to tempco.

 - Adjustment to nominal value, ppm
Its the deviation from nominal value at the time of being made, or may call it initial error, initial accuracy.

One thing also worth noting is that when people measure a standard resistor by a DMM, the standard resistor is superior in most of the cases even the DMM is a 8.5 digits. Most of the imperfection/noise/instability in the test results are probably from the DMM rather than the standard resistor.

ADVANTEST 10k, find no spec, 1 hermetically sealed WW resistor inside.
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207291;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207293;image)

Chinese BZ3, 0.001 Ohm, class 0.01%, manganin.
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207295;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207297;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207299;image)

Remarks: This is one of the nine BZ3 resistor set, 0.001 Ohm, max current 33A, everything is heavy from binding post, thick manganin stripe. There is a small compensation resistor in parallel with the main.


esi SR104, 10k, stability 0.5ppm/a. Oil filled, hermetically sealed evanohm WW in a stainless steel container.
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207301;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207303;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207305;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207307;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207312;image)
What can I say, the best 10k resistor ever made. Pity that no further teardown.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 03:13:46 am
esi SR1, 100 ohm, 50ppm/year
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207314;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207316;image)
Normal wire on mica, the favorite way of esi.


Fluke 742A, 10k
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207318;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207320;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207322;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207324;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207326;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207328;image)

Stability 4ppm/year, tempco is very small. Four 39992 Ohm hermetically sealed evanohm WW resistors in parallel, a 32 ohm adjust resistor is in series with one before parallel. Fluke is probably the largest hermetic WW manufacturer.


Fluke 742A, 1 Ohm
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207330;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207332;image)

Stability specified as 8ppm/year. Twenty 20.01 Ohm hermetically sealed evanohm WW resistors in parallel, parallel another small adjust resistor of about 2k.
The inside photo was by Leicamr of 38hot.net
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 03:15:54 am
IET SRL 1 Ohm
Same specification as Fluke 742A 1 Ohm but different internal construction.
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207334;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207336;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207338;image)
The small resistor on the top is probably the compensation resistor.

IET SRX, 1Ok
I bought this one from IET 11.5 years ago, specified as 10ppm/year, 1ppm/C. One hermetically sealed WW resistor with some compensation/adjustment
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207340;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207342;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207344;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207428;image)

MI 9331, 100 Ohm, Specified as 5ppm/year, 0.1ppm/C
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207346;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207348;image)


Transmille RS3000
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207350;image)

http://www.transmille.com/references-and-standards/precision-references-and-standards/3000rs (http://www.transmille.com/references-and-standards/precision-references-and-standards/3000rs)

Although this is not an actual teardown but I know what's inside.
When this UK standard was first released in 2009, I saw something interesting on their website that must be mistakenly put by someone the manuscript of the resistors they used in the standard. A few days later it's gone but I saved it.
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207352;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207354;image)

Another interesting thing about the script is that they described the tempco of  VSC232Z as 0.05ppm/C, apparently mislead by Visahy's datasheet. Later, they modified this to 0.5ppm/C >:D
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207359;image)
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 03:17:54 am
Wekomm RS9010A, 10k
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207376;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207378;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207380;image)

More photo and info see Dave's blog #834 and xdevs.com
Specified as 1ppm/year, 0.3ppm/C, one hermetically sealed Vishay foil resistor
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207382;image)

I must say this is not up to German standard as the actual tempco of -0.47ppm/C is larger than specified. Wekomm may have misinterpret the datasheet from Vishay like most of us did, and they didn't throw away or compensate ones with large tempco.
Also they are contradictory on those max voltage and max current specs. How can you apply 10mA max current on a 10k without exceed the 20V max voltage. Well, they may say they are on 'which is smaller' basis, but why 10mA max for 10k in the first place?
Another thing is that the resistor is off by as much as 7.72ppm, but the spec says it should be within 2ppm.

Inside VHA518-7, there are seven foil resistor elements.
(https://www.eevblog.com/forum/blog/eevblog-834-wekomm-resistance-standard/?action=dlattach;attach=206257;image)


Yokogawa, 1k, class 50ppm, not hermetically sealed
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207384;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207386;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207388;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207390;image)


Lastly, let's teardown some hermetically sealed WW and see how they are made.
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207392;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207394;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207396;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207402;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207404;image)

Apart from usual bobbin/teflon insulation etc, the special thing about the hermetic resistor is the seal. They have those pre-made glass/ceramic disk with a small tube in the middle and thin layer of metal ring outside to be later soldered to bass tube case.
Although brass has different temp expansion co-efficient with glass, it's flexible and will expand and extract with the hard glass as temperature vary. If the casing is thick, they cut the edge part to make thinner. The inner metal on the hand must be Kovar which expand the same with glass, otherwise, the not-so-easy-compressed 'rod' will soon destroy the seal or even break the glass especially in high temperature when soldering the leads. But, Kovar is notorious for its large thermal EMF that should not be used in precision WW. They solved this dilemma by first implant a Kovar tube(instead of Kovar wire) that bond with glass well, and pass the copper lead through the hole and fill the gap by soldering. Solder is soft that act as cushion if temperature varies and still keep the seal.

The end of the teardown. Sorry for taking too long and split, I had difficulty in uploading images that often stopped in the middle.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on March 10, 2016, 03:46:50 am
Looking forward to the rest. I have a 1k SR1 resistor(I tore it down too).
Title: Re: Teardown: Standard Resistors
Post by: TiN on March 10, 2016, 06:04:44 am
Very nice summary :) Hope will can update it as it evolve.
Title: Re: Teardown: Standard Resistors
Post by: quarks on March 10, 2016, 06:38:31 am
Great post :-+ :-+ :-+

here are some pictures from my Leeds & Northrup 4210 "Thomas Type One Ohm Standard" resistor.
This was advertised by L&N as the "Prime standard for use in maintaining value of the ohm".
Title: Re: Teardown: Standard Resistors
Post by: quantumvolt on March 10, 2016, 08:05:44 am
Very interesting.

I would like to know how the 4 resistors and the trimpot on the compensation board of IET SRX, 1Ok are connected and what values they have (at least for me, they cannot all be seen clearly). Maybe it would be possible to infer if it is all resistance value adjustment, or there also are some temperature coefficient elimination (reduction).

Thanks for a very informative post.
Title: Re: Teardown: Standard Resistors
Post by: nidlaX on March 10, 2016, 08:59:49 am
Wow! :-+ Nice stuff you have access to!
Title: Re: Teardown: Standard Resistors
Post by: daqq on March 10, 2016, 09:21:44 am
Thanks a lot! Great images!
Title: Re: Teardown: Standard Resistors
Post by: NANDBlog on March 10, 2016, 09:49:19 am
Very good stuff.
Quote
Another interesting thing about the script is that they described the tempco of  VSC232Z as 0.05ppm/C, apparently mislead by Visahy's datasheet. Later, they modified this to 0.5ppm/C
Yes, the VishayPG datasheets are very very misleading. They claim insane typical drift on the top of the page, and then you scroll down, and see that while the typical is 0.0005 PPM the actual worst case drift is 0.0005+/-2 ppm. And since it is in the datasheet, it is not even a lie.

If you want to see something stupid, order a few thousand of their precision resistor. Once I saw that they delivered a big order, where the SMD resistors were in trays, not reels. I guess the bending would destroy the accuracy. But that is not the funny part. The tray was tiny, containing 25 resistor. Way to go, production ready!
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 10, 2016, 11:17:03 am

The Chinese standard resistor is a direct copy of the Soviet version down to the smallest details.

Of course the Soviet design wasn't their own either...


Chinese BZ3, 0.001 Ohm, class 0.01%, manganin.

(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207297;image)
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 11:21:29 am

The Chinese standard resistor is a direct copy of the Soviet version down to the smallest details.

Of course the Soviet design wasn't their own either...
You are right, I have a few standards of the Soviet as well.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 11:29:26 am
Very good stuff.
Quote
Another interesting thing about the script is that they described the tempco of  VSC232Z as 0.05ppm/C, apparently mislead by Visahy's datasheet. Later, they modified this to 0.5ppm/C
Yes, the VishayPG datasheets are very very misleading. They claim insane typical drift on the top of the page, and then you scroll down, and see that while the typical is 0.0005 PPM the actual worst case drift is 0.0005+/-2 ppm. And since it is in the datasheet, it is not even a lie.

If you want to see something stupid, order a few thousand of their precision resistor. Once I saw that they delivered a big order, where the SMD resistors were in trays, not reels. I guess the bending would destroy the accuracy. But that is not the funny part. The tray was tiny, containing 25 resistor. Way to go, production ready!
I knew it's true, they have mislead me before. Although didn't  order a few thousand, but a few hundred is more than enough. When my first order of 50 VHP101 came, it arrived in one plastic bag.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 11:38:32 am
Very interesting.

I would like to know how the 4 resistors and the trimpot on the compensation board of IET SRX, 1Ok are connected and what values they have (at least for me, they cannot all be seen clearly). Maybe it would be possible to infer if it is all resistance value adjustment, or there also are some temperature coefficient elimination (reduction).

Thanks for a very informative post.
I've never care about the adjustment part before since I think it is the usual way of trim a resistor for exact value like those in Fluke 720A.
Since you ask, I just teardown it again and it is. There is no tempco related compensation what so ever. If you need something for temco compensation, I myself developed a way of doing that: compensate the alpha tempco and trim the value at the same time. Also, there are ways to compensate the beta as well.
I've update it with the circuit above, there is a 39.2 Ohm resistor on the board but shorted.
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 10, 2016, 11:45:10 am
IET SRL 1 Ohm. Same specification as Fluke 742A 1 Ohm but different internal construction.

The internal construction is actually the same. Multiple resistors connected in parallel with the copper equalizing plates. But in the IET version the whole package was resin potted which allows to use much cheaper non-hermetic resistors. The solution is not perfect but another layer of protection seems to make the humidity time constant long enough.

The "wings" in the equalizing plates are a clever idea, because they allow soldering the adjustment resistor after the potting.

(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207336;image)
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 11:48:16 am
Great post :-+ :-+ :-+

here are some pictures from my Leeds & Northrup 4210 "Thomas Type One Ohm Standard" resistor.
This was advertised by L&N as the "Prime standard for use in maintaining value of the ohm".
Thanks quarks, 4210 is a great resistor. Is that on the bottom red paint? Or there is solder underneath for the double wall to hermetically seal?
Title: Re: Teardown: Standard Resistors
Post by: quarks on March 10, 2016, 11:49:51 am
Although didn't  order a few thousand, but a few hundred is more than enough. When my first order of 50 VHP101 came, it arrived in one plastic bag.

I did order even less than you and received individually packaged resistors, some even in plastic cases (see pic.)
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 11:57:12 am
IET SRL 1 Ohm. Same specification as Fluke 742A 1 Ohm but different internal construction.

The internal construction is actually the same. Multiple resistors connected in parallel with the copper equalizing plates. But in the IET version the whole package was resin potted which allows to use much cheaper non-hermetic resistors. The solution is not perfect but another layer of protection seems to make the humidity time constant long enough.

The "wings" in the equalizing plates are a clever idea, because they allow soldering the adjustment resistor after the potting.
Great info. I'm curiosity about why the spec of the old IET SRL series are exactly the same as Fluke 742A.
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 10, 2016, 12:04:47 pm
Is that on the bottom red paint? Or there is solder underneath for the double wall to hermetically seal?

Solder which is just "tamper sealed" by the red paint.

The construction is very simple. The edges of the inner cylinder are bent so that it tighly fits inside the outer cylinder. The coil is wound on the inner cylinder. After the heat treatment the inner cylinder is slided inside the outer one and soldered together at both ends.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 12:22:56 pm
Is that on the bottom red paint? Or there is solder underneath for the double wall to hermetically seal?

Solder which is just "tamper sealed" by the red paint.

The construction is very simple. The edges of the inner cylinder are bent so that it tighly fits inside the outer cylinder. The coil is wound on the inner cylinder. After the heat treatment the inner cylinder is slided inside the outer one and soldered together at both ends.
Got it. I'm asking this because I saw another teardown of a Cambridge standard where there is those red paint as well, but there is no solder inside the paint.
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 10, 2016, 12:43:49 pm
The construction is very simple. The edges of the inner cylinder are bent so that it tighly fits inside the outer cylinder. The coil is wound on the inner cylinder. After the heat treatment the inner cylinder is slided inside the outer one and soldered together at both ends.

By the way, the Soviet 1 ohm (and higher) standard resistors share the same contruction. Except that the the edge of the outer cylinder bended at the bottom and the inner cylinder at the top. The Chinese version is probably similar.

Unfortunately the stability is not even close to the Thomas. The mechanical construction was easy to copy, but not the art of the heat treatment.


I saw another teardown of a Cambridge standard where there is those red paint as well, but there is no solder inside the paint.

The Cambridge was also sealed by soldering but there is a separate bottom plate between the inner and outer cylinders. Please see the picture attached.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 01:38:47 pm
The construction is very simple. The edges of the inner cylinder are bent so that it tighly fits inside the outer cylinder. The coil is wound on the inner cylinder. After the heat treatment the inner cylinder is slided inside the outer one and soldered together at both ends.

By the way, the Soviet 1 ohm (and higher) standard resistors share the same contruction. Except that the the edge of the outer cylinder bended at the bottom and the inner cylinder at the top. The Chinese version is probably similar.

Unfortunately the stability is not even close to the Thomas. The mechanical construction was easy to copy, but not the art of the heat treatment.


I saw another teardown of a Cambridge standard where there is those red paint as well, but there is no solder inside the paint.

The Cambridge was also sealed by soldering but there is a separate bottom plate between the inner and outer cylinders. Please see the picture attached.
I also teardown the Chinese 1 Ohm, top and bottom all soldered. However, there were many factors that they did not do it correctly as I have pointed out at 38hot times ago, so I did not include the teardown here. As for the average aging of those Chinese resistors, it varies. Here are the distribution of 24 samples, some are good but others not.
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207470;image)

The bottom of the Cambridge is soldered, what about the top?
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 10, 2016, 02:42:59 pm
The bottom of the Cambridge is soldered, what about the top?

The top is soldered. But the connection bar seals are far from hermetic. The Cambridge type is oil filled, not air, so there is also an oil screw at the top plate.

But the ceramic feedthrough of the Soviet type is not perfect either. Many resistors which have spent decades in an oil bath have changed from air filled to oil filled...

As for the average aging of those Chinese resistors, it varies. Here are the distribution of 24 samples, some are good but others not.

Very interesting data of the Chinese BZ3. Large variation (poor quality control) is typical for the Soviet type too.

How did you eliminate the temperature coefficient in your measurements? The TC of the Soviet type is so high that an oil bath is a necessity. And the hysteresis is remarkable which can lead to wrong assumptions if the resistors are not stored in constant temperature between the measurements.

Title: Re: Teardown: Standard Resistors
Post by: doktor pyta on March 10, 2016, 03:41:18 pm
Good job, zlymex, Thanks!
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 10, 2016, 04:07:54 pm
How did you eliminate the temperature coefficient in your measurements? The TC of the Soviet type is so high that an oil bath is a necessity. And the hysteresis is remarkable which can lead to wrong assumptions if the resistors are not stored in constant temperature between the measurements.
I put a mercury thermometer to measure  the temperature and make corrections based on the alpha and beta tempco which are on the certificate.
Those standards was manufactured 25 to 40 years ago, need not measure the value very precisely to determine the average annual drift.
Most of beta are at around -0.6ppm/C2,which are similar for all manganin resistors, right? In China/Soviet, reference temperature is 20 deg C, 3 deg lower than 23C. Since most alpha20 is positive, if changed to alpha23, they will go done by 1.8ppm/C and appear smaller, magic! That is to say, alpha20=5ppm/C is the same as alpha23=3.2ppm/C when beta=-0.6ppm/C2.  I measured some Chinese BZ3 and they show little hysteresis.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on March 10, 2016, 05:03:21 pm
Im intrigued to see how the trim the srx to 10k, as the vishay is 9.995k. I will need to look at the pics,for the possible series resistor.
Title: Re: Teardown: Standard Resistors
Post by: quantumvolt on March 10, 2016, 07:25:15 pm
Very interesting.

I would like to know how the 4 resistors and the trimpot on the compensation board of IET SRX, 1Ok are connected and what values they have (at least for me, they cannot all be seen clearly). Maybe it would be possible to infer if it is all resistance value adjustment, or there also are some temperature coefficient elimination (reduction).

Thanks for a very informative post.
I've never care about the adjustment part before since I think it is the usual way of trim a resistor for exact value like those in Fluke 720A.
Since you ask, I just teardown it again and it is. There is no tempco related compensation what so ever. If you need something for temco compensation, I myself developed a way of doing that: compensate the alpha tempco and trim the value at the same time. Also, there are ways to compensate the beta as well.
I've update it with the circuit above, there is a 39.2 Ohm resistor on the board but shorted.

Thank you very much.

Again - a very interesting thread.
Title: Re: Teardown: Standard Resistors
Post by: Macbeth on March 10, 2016, 09:45:06 pm
Great thread. On the opposite end of the scale this is my standard resistor  :-DD

(http://i.imgur.com/Vntr2eR.jpg)

A military version of the S102 I think.
Title: Re: Teardown: Standard Resistors
Post by: splin on March 10, 2016, 10:48:18 pm

I knew it's true, they have mislead me before. Although didn't  order a few thousand, but a few hundred is more than enough. When my first order of 50 VHP101 came, it arrived in one plastic bag.

Ohh please do tell - what's your experience with respect to the 'typical' 2ppm/6 years claim? Even a few weeks worth of data could be very interesting.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 11, 2016, 11:45:48 am
Im intrigued to see how the trim the srx to 10k, as the vishay is 9.995k. I will need to look at the pics,for the possible series resistor.
I updated to include the schematic of the trim part.



I knew it's true, they have mislead me before. Although didn't  order a few thousand, but a few hundred is more than enough. When my first order of 50 VHP101 came, it arrived in one plastic bag.

Ohh please do tell - what's your experience with respect to the 'typical' 2ppm/6 years claim? Even a few weeks worth of data could be very interesting.
I didn't test the aging in a systematic way for all, but I made a standard resistor out of them in 2008 and the result is superb. Have a look at photos below, the value is virtually unchanged in five and half years time.
(https://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/?action=dlattach;attach=136724;image)
(https://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/?action=dlattach;attach=136732;image)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207782;image)
Title: Re: Teardown: Standard Resistors
Post by: quarks on March 14, 2016, 07:04:24 pm
Hello zlymex,

it is really a pleasure to see, read and learn from your great experience and knowledge!
Your DIY 10k seems to be extremly stable.
I wonder which combination of resistors (parallel, series or comb.) gives the very best resulting TC and stability.
Also I am interest to know how to meassure and use the alpha and beta values.
Thanks a lot for sharing

Bye
quarks
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 15, 2016, 03:02:53 am
Hello zlymex,

it is really a pleasure to see, read and learn from your great experience and knowledge!
Your DIY 10k seems to be extremly stable.
I wonder which combination of resistors (parallel, series or comb.) gives the very best resulting TC and stability.
Also I am interest to know how to meassure and use the alpha and beta values.
Thanks a lot for sharing

Bye
quarks
Thanks quarks,
I can open a new thread for DIY resistors - I made some before and this one is probably my best.
This particular one, made from selected 4 Vishay VHP101 hermetic resistors from a batch of 50, 9.999k, 0.01%.
I first tested those resistors for values and tempco for sometimes and type in the data in Excel, selected 4 best matched base on alpha and beta, then its not necessary to use compensation late, though I do have a spread-sheet way of compensation for tempco and value, which have been used in other of my DIYs.
Connect 2 in series first, and then parallel. This formed something like a bridge, those orange wires are for 'null detector' output.
As far as the performance is concerned, parallel first or series first is exactly the same, provided they are all equally weighted(same power). I believe that 1k to 10k range is the best for Vishay foils resistor as the value is concerned. I may have ordered the value at 2.499k but that will eliminate the option for single-resistor use at 10k.

I didn't design, select or control the stability, it mainly depends on the resistors themselves, just lucky to be this stable.
I did some small range temperature cycle before hand of -18 deg C in a fridge and about 80 deg C hot water bath, just for mental comfort.
Made sure not to introduce any unstable elements into it by some considerations like long-lead, less stress. When soldering use thick tweezers with heat conducting paste to prevent it reaching the body.
Well, the leads is copper, with about +4200ppm/K tempco, had been taken into account during selection and measurement.
No heatsink, thermal equalizer or grease were used because I was thinking those may do more harm than good for stability, and because it only dissipates 10mW, it can be handled well with four elements.
I do use Teflon board and dual case, the inner case is electrically isolated and also is the guard output.
Those small resistor along side were German brand, Czeck made Vitrohm of 0.1%, and also very small in value, in series with VHP101 to facilitate the adjustment to final value. I ordered those VHP101 at slightly less than 10k for that purpose. I do sensitive analysis for each components to make sure they don't affect the end results in an unexpected way.
The binding posts was taken out of my Dataproof scanner(164A), very low thermal EMF according to them.
This particular standard have been traveled in China for about two years among my Ohm-nuts friends and return to me recently.

For tempco measurement of alpha and beta, put them in a car-fridge and run a temperature cycle, record value and temperature. The measurement is always done by my own scanner/switch, where I connect my two SR104 as a reference, data was feed to 3458A direct or indirect(by a Warshawsky bridge), and against one of my SR104, to eliminate the drift of 3458A.
Then, plot the temperature-value scatter diagram in Excel like this:
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=207525;image)

This is an example, but is the actual plot of a BZ3 1k standard resistor, also see the attached spread sheet for how to plot and calculate.
Then make a trend line of second-order polynomial(red line, by right click the data), this is the least-squares regression of the best fit of the scattered data.
Also, there is this 'display equation' and 'R square' option of this trend line in the form of
y = c + bx + ax^2
where y is the resistor value and x is the temperature
the R^2 is the measurement of the fit quality and should be close to 1. It is also the indication for hysteresis.
beta is immediately available: beta = a/c
actually alpha0=b/c but this alpha is at zero degree C, we normally use alpha at 23 degree C, so a little conversion has to be done in spread sheet(enclosed) to transform the equation to the form of
y = c1 + b1*(x-23) + a*(x-23)^2
and finally alpha23=b1/c1
 
In order to make the good result of alpha and beta, use slow temperature cycle to reduce hysteresis, use a good temperature sensor close mounted with the resistor. I use DS18B20 for sensor(part of the data collection system) and checked it by ice-water and mercury thermal meter of the Chinese 2nd grade(to 0.1 degree C).
SR104 is regularly calibrated. Recent is done at Hong Kong HKAS two months ago. I also monitor the thermometer and made small corrections if necessary. As for the measurement of alpha and beta, absolute value of the resistor reference is not critical at all.
I measured alpha/beta of one of my SR104 this way and the procedure/result were on 38hot.net
http://bbs.38hot.net/thread-1352-1-1.html (http://bbs.38hot.net/thread-1352-1-1.html)
(Sorry its in Chinese, may be you can use google translate)

To use the alpha and beta, just measure the temperature and use the formula y = c1 + b1*(x-23) + a*(x-23)^2 to obtain the exact resistance at that temperature. Or better make a temperature chart(like attached) to get the resistance quickly.
The tempr chart in the inner case of SR104 is not good because it does not show the deviation explicitly and is error prone when add it up.
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=208431;image)
Title: Re: Teardown: Standard Resistors
Post by: altaic on March 15, 2016, 05:28:14 am
What a great look at resistance standards! I'm curious-- how did you select the resistors for the one you made? Any special method (Wheatstone bridge or something), or just use a precision ohmmeter?
Title: Re: Teardown: Standard Resistors
Post by: quarks on March 15, 2016, 06:20:33 am
Hello zlymex,

now I will sure need some time to work through all your very good information and try to make use of it.
Many thanks again and please start a new threat on DIY resistors.

Bye
quarks
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 15, 2016, 06:37:39 am
What a great look at resistance standards! I'm curious-- how did you select the resistors for the one you made? Any special method (Wheatstone bridge or something), or just use a precision ohmmeter?
I tested all the 50 VHP101 for alpha and beta according to above method.
I also make rough measurement for values by 3458A but that is not very important, they will be adjust at final stage anyway.
The selection was done on paper(spread sheet) for matched alpha and beta - just chose those that added up to zero.
The final adjustment is by use of different small value resistors in series and in parallel, value aided by spread sheet.
The final measurement of value that the adjustment is based on was performed by this:
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=208456;image)
Center part is the Warshawsky bridge specifically for 10k, capable of compare two 10k standard resistors at 0.05ppm uncertainty.
3458A here is merely as a sensitive voltmeter/null detector, no calibration needed. I use it because it hook up to the system most of the time.
The absolute value of the measurement depend on the reference resistor which is a SR104 in my case.
I use automatic substitute technique by employing a 4-pole double throw switch:
https://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/msg610755/ (https://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/msg610755/)
 
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 15, 2016, 06:55:08 am
Hello zlymex,

now I will sure need some time to work through all your very good information and try to make use of it.
Many thanks again and please start a new threat on DIY resistors.

Bye
quarks
Sure, may be next weekend.
The reason I bought VHP101 is because of 3458A. Although I didn't find a lot of precision parts when I opened the case the day it arrived, I did find two things, one is VHP101, the other is LTZ1000A, and that start my DIY journey.
At that time, Vishay specified VHP101 as 2ppm/10years.
Title: Re: Teardown: Standard Resistors
Post by: altaic on March 15, 2016, 07:30:40 pm
I use automatic substitute technique by employing a 4-pole double throw switch:
https://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/msg610755/ (https://www.eevblog.com/forum/projects/diy-low-thermal-emf-switchscanner-for-comparisons-of-voltage-and-resistor-stand/msg610755/)

Your setup is similar to one I came up with, but what is the automatic substitute technique you mentioned? Is this a way to attach lots of resistors to a test rig, and have it test all permutations of resistors to find a set which matches your desired specification? You mentioned measuring the alpha and beta values and using a spreadsheet to pair resistors, so I'm confused about the automatic substitute w/ the 4-pole double throw switch.

Hello zlymex,

now I will sure need some time to work through all your very good information and try to make use of it.
Many thanks again and please start a new threat on DIY resistors.

Bye
quarks
Sure, may be next weekend.
The reason I bought VHP101 is because of 3458A. Although I didn't find a lot of precision parts when I opened the case the day it arrived, I did find two things, one is VHP101, the other is LTZ1000A, and that start my DIY journey.
At that time, Vishay specified VHP101 as 2ppm/10years.

That would be great! I'm looking to bootstrap some metrology equipment, hopefully to high precision. I'm hoping to figure out how one can get high precision out of low precision equipment, though I suppose one always has to have some sort of standard-- voltage standard, or some such. Some day, room temperature quantum hall devices (graphene looks promising) will be easily available, giving cheap resistance standards to 1ppb, but currently we need some sort of cryogenic cooler (there are tabletop ones [https://en.wikipedia.org/wiki/Cryocooler (https://en.wikipedia.org/wiki/Cryocooler)] which aren't too expensive, all things considered).

Anyway, more on topic, do you know of any good references for types of resistors which can be used to balance the tempo (or if one must just tediously measure it for each one), and techniques for aging resistors? Seems like a lot of resistors only have to be aged for 10-20 days to get them to be fairly level.
Title: Re: Teardown: Standard Resistors
Post by: TiN on March 15, 2016, 11:16:45 pm
Some time ago I got pair of Guildline 9330 resistors, with one being broken (readings jump all over the place).

(https://xdevs.com/doc/Guildline/9330/gr_top_1.jpg) (https://xdevs.com/doc/Guildline/9330/gr_side_1.jpg)

It's very small, compared to most of other resistors of this type, designed for oil bath operation

(https://xdevs.com/doc/Guildline/9330/gr_in_1.jpg) (https://xdevs.com/doc/Guildline/9330/gr_int2_1.jpg)

Inside is just spool of wire, no bifilar winding, no support, just flying in the space.  ???

(https://xdevs.com/doc/Guildline/9330/gr_coil_1.jpg) (https://xdevs.com/doc/Guildline/9330/gr_res_1.jpg)

Problem is with thinner wire spool, which is most of 100K resistance.

(https://xdevs.com/doc/Guildline/9330/gr_windings_1.jpg)

Schematics of resistor network:

(https://xdevs.com/doc/Guildline/9330/g9330_100k.png)

Hi-res photos and test results here in the article (https://xdevs.com/fix/g9330/).

And since it's just a wire element, I'm not sure of repair approach on this one, except replacing wire with new manganin one of correct resistance. Tried to clean wire with IPA bath, did not help.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on March 16, 2016, 01:30:17 am
^^^
Seeing your post, I should tear down my Otto Wolff 10k resistor.
Time to either get medieval, or break out the blowtorch.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 16, 2016, 02:08:35 am
Your setup is similar to one I came up with, but what is the automatic substitute technique you mentioned? Is this a way to attach lots of resistors to a test rig, and have it test all permutations of resistors to find a set which matches your desired specification? You mentioned measuring the alpha and beta values and using a spreadsheet to pair resistors, so I'm confused about the automatic substitute w/ the 4-pole double throw switch.
Well, substitution is a more general term than a specific technique that close related to the term 'transfer'. It may be used together with many existing measuring methods, whether on purpose or unintentional, to achieve a better result with less uncertainty. For example:
1. you have a standard resistor with a calculated deviation of +1.5ppm
2. you measure this standard with a specific method(4-wire), reading is +12.0ppm (which means 10000.120 Ohm if the nominal value is 10k)
3. you substitute your standard with the unknown resistor, either manually by detaching those 4 wires to the standard and attach them to the unknown, or automatically by a scanner with 4-poles to switch to the unknown from the standard for you.
4. then you measure you unknown resistor, with other setup unchanged, reading is +8.0ppm   
5. you calculate the unknows as +1.5ppm +8.0ppm -12.0ppm = -2.5ppm. That is to say, you unknown will be 9999.975 Ohm if the nominal value is 10k, and the uncertainty of you unknown would be the uncertainty of your standard 'plus' the uncertainty of your substitution measurement, and the later depends on what kind of specific method and the equipment used.
6. The above calculation is approximate, I have replaced the multiplications and divisions with additions and subtractions, but it will be accurate enough if all those ppms are small. This means that all the standards, unknowns, the equipment etc should be all close to nominal value in order for this simple calculation to be valid, and that's one of the reasons why we always have this 'close to nominal' desire, we can safely ignore those second order variables.

By meaning of 'a calculated deviation of +1.5ppm', this is how it calculated:
1. your standard resistor is calibrated 6 months ago with deviation of +1.4ppm @23 deg C
2. your standard resistor has a predictable aging rate of +0.4ppm per 12 months
3. your standard resistor has a tempco of +0.5ppm and you do your measurement @ 18 deg C, this will give +0.5/(18-23)=-0.1ppm correction
(for simplicity, I just ignored the beta tempco)
4, then you can calculate the deviation as +1.1ppm +0.4ppm/12*6 -0.1ppm = 1.5ppm

Substitution may be performed in one to one manner as exampled above, or may be performed in one to many manner as I often do by using a 4-pole 17-position scanner.

I measure those resistors first(for value, alpha, beta), then I match them in spread sheet.

  I'm looking to bootstrap some metrology equipment, hopefully to high precision. I'm hoping to figure out how one can get high precision out of low precision equipment,
That's exactly what I'm talking about. I, as an amateur, and I guess many of us here are, keen on to find cheap ways to measures resistance to high degree of uncertainty. I think I've got something, I may start a new thread on this and analysis the uncertainty associated.


Anyway, more on topic, do you know of any good references for types of resistors which can be used to balance the tempo (or if one must just tediously measure it for each one), and techniques for aging resistors? Seems like a lot of resistors only have to be aged for 10-20 days to get them to be fairly level.
Balance the temco? I use a copper resistor if the tempco of the main resistor is negative, as describe in my new thread Yesterday:
https://www.eevblog.com/forum/metrology/spread-sheet-aided-design-of-compensation-for-7v-to-10v-step-up-resistor-set/ (https://www.eevblog.com/forum/metrology/spread-sheet-aided-design-of-compensation-for-7v-to-10v-step-up-resistor-set/)
If the tempco is positive, then it will be troublesome to find the suitable negatively going balancer. I bought some NTC resistors for this purpose but have not tried them out yet, I was worrying about the stability and none linear curve, although the curve is concave and is perfect to balance the beta of most of WW.

As for techniques for aging resistors, I believe there are many discussions already on this forum. Personally, I rely on the design/construction/materiel of the resistor rather than accelerated aging by myself.

To summarize, if the tempco not balanced but known, and there exist aging but predictable, then you can deduct those small values by calculation, therefore no worry about balancing or adjustment.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 16, 2016, 03:32:14 am
Some time ago I got pair of Guildline 9330 resistors, with one being broken (readings jump all over the place).
........
Superb photo!
Is that 'no support' thing only for the small WW? or also for part of the 99.998185k wire?
Any idea for the maker of those two foil-liked hermetic?


^^^
Seeing your post, I should tear down my Otto Wolff 10k resistor.
Time to either get medieval, or break out the blowtorch.
That would be very nice. But hopefully only to the degree of able to reassemble in original precision. I've only seen some photo of Otto Wolff shunt.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on March 16, 2016, 03:57:02 am

^^^
Seeing your post, I should tear down my Otto Wolff 10k resistor.
Time to either get medieval, or break out the blowtorch.
That would be very nice. But hopefully only to the degree of able to reassemble in original precision. I've only seen some photo of Otto Wolff shunt.
Unfortunately it was dropped, so it never went back to its original stability. Wildly drifty,even in a short span.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 16, 2016, 04:01:39 am

^^^
Seeing your post, I should tear down my Otto Wolff 10k resistor.
Time to either get medieval, or break out the blowtorch.
That would be very nice. But hopefully only to the degree of able to reassemble in original precision. I've only seen some photo of Otto Wolff shunt.
Unfortunately it was dropped, so it never went back to its original stability. Wildly drifty,even in a short span.
That‘s sad news, but not too bad from teardown point of view, or may be repairable.
Title: Re: Teardown: Standard Resistors
Post by: TiN on March 16, 2016, 04:06:18 am
Quote
Is that 'no support' thing only for the small WW? or also for part of the 99.998185k wire?
Any idea for the maker of those two foil-liked hermetic?

More meant for wire (both 99K and 1K). It's just in there, not fixed to anything.
Hermetics more or less sturdy hanging with their thick legs. They have no labels except written resistance on them, and can is bit taller than VHPs. Probably Guildline inhouse resistors?
Title: Re: Teardown: Standard Resistors
Post by: zlymex on March 16, 2016, 04:31:21 am
More meant for wire (both 99K and 1K). It's just in there, not fixed to anything.
Hermetics more or less sturdy hanging with their thick legs. They have no labels except written resistance on them, and can is bit taller than VHPs. Probably Guildline inhouse resistors?
Well, I have some photo of AE and TDK hermertics with taller cans, inside, they are plastic foils, not bare chips like VHPs.
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 16, 2016, 11:00:14 am
Quote from: TiN
Some time ago I got pair of Guildline 9330 resistors, with one being broken (readings jump all over the place).

After resin removed, resistive EVANOHM® or Manganin wired elements were revealed. Shiny yellow coil with thinner wire is 99x K? element, and smaller dark wire coil is 1.1K? element.

The main resistor wire is manganin. The smaller one is another alloy with much higher TC. The 9330 relies on compensation instead of adjusting the TC of the main resistor by annealing process. Measuring the TC of the 1K wire would help to deduce the type of it.

The bulk metal foil resistors are used for fine adjustment after the container has been sealed. The 9330 resistors that I have seen had only one BMF adjustment resistor.

And since it's just a wire element, I'm not sure of repair approach on this one, except replacing wire with new manganin one of correct resistance.

That will ruin the temperature compensation made for that specific wire.

Sounds like a bad solder joint or a short between the adjacent turns (or the metal container). The manganin wire itself doesn't behave like that. Carefully rewinding the wire on a large piece of cardboard (mica card resistor style so that the turns don't touch each other) could help to make it stable again. That also helps to locate the possibly damaged wire or insulation using a microscope.

Inside is just spool of wire, no bifilar winding, no support, just flying in the space. ???

That allows almost free thermal expansion, which much reduces the hysteresis and improves the stability in varying temperature environment. The drawback is that a mechanical shock can cause permanent change.

The bifilar construction would have been easy to do by simply double folding the wire before the winding. Are you sure it wasn't made that way?

Title: Re: Teardown: Standard Resistors
Post by: Vgkid on March 17, 2016, 05:04:18 am
Quote
That‘s sad news, but not too bad from teardown point of view, or may be repairable.
Was tempted to not tear it down,since it was kind of stable last night 20ppm p-p over 8 degree delta. Slid the outer case off to see how deep the dent was, and it dropped 9 ohms :(.
What offset voltages should one get for these types of resistors?  I had 8uV last night, and about that, after cleaning.
I will tear it down.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on March 18, 2016, 05:49:22 am
My Otto Wolff 10K resistor, Heat didn't even melt the solder, needed force.
I could not determine what caused the resistance value to changeby 10 ohms...
The top of the unit.
(http://i.imgur.com/2mTYRk7.jpg)
Wires joining the copper terminal block to the resistor. They appear to be silver. I sanded off the paint.
(http://i.imgur.com/Wkwwwv7.jpg)
Getting medieval. Used a chisel, and a large screwdriver to flex the entire cylinder(breaking the solder seal).
(http://i.imgur.com/9FDmSxt.jpg)
Resistor
(http://i.imgur.com/4LOCpAu.jpg)
close ups
(http://i.imgur.com/Y5Q5a2A.jpg)
This almost looks like a metal wire, under the right light.
(http://i.imgur.com/Y5Q5a2A.jpg)
Currently hooked up to my 3456A, and will run it over night. These resistors really do not like offset compensated ohms mode(pulse DC), my others resistors don't mind it.
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 18, 2016, 07:47:02 am
Heat didn't even melt the solder, needed force.

The soldered seam of the container can be opened without brute force by using a heated wire. Sand paper needed first to reveal the bare metal surface.
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 18, 2016, 07:49:00 am

Information about the Otto Wolff NG series:

The standard resistor NG 100 consists of a wire coil which is hermetically sealed between two brass tubes. A nickel-plated brass tube of diameter of 102mm and height of 170mm serves as a protecting device which is locked at the top by an ebonite cover. The sealed coil is connected to the outside terminal through glass. The ebonite cover as well as the terminals on it are of exactly the same design as those of the N 100. The escape of the heat being poorer with the model NG 100, the admissible load is lower than the case of the model N100 and corresponds to the values of the N 85. The model NG 100-2a has an accurary of 0.005 percent; the other models have an accurary of 0.002 percent. Loading in air must be restricted to 0.1 Watt.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on March 18, 2016, 02:44:53 pm
@ Manganin how did you find this information, I looked a few years ago, and found nothing. Were these oil filled, or just air filled? When I opened it up, it smelled of stale gasoline, and noticed that the internal walls of the brass conainer appeared to have corrosion on them.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on March 20, 2016, 05:26:49 am
For those curious, if I killed it. Nope
Ran it on the 3456 over a day, didn't note the temps.
Min: 10.00055k, max:10.0076k, avg: 10.00068, var 4.21988E^-3.
i need to look into a cheap datalogging thermometer.
Title: Re: Teardown: Standard Resistors
Post by: manganin on March 20, 2016, 01:27:21 pm
Manganin how did you find this information, I looked a few years ago, and found nothing.

I have a full Otto Wolff binder somewhere, but all I could find now was a poor one page photocopy which had that short description.

Were these oil filled, or just air filled? When I opened it up, it smelled of stale gasoline, and noticed that the internal walls of the brass conainer appeared to have corrosion on them.

Air filled. But a few decades in an oil bath...

The sealed version is quite rare, probably because it was more expensive and didn't offer much advantage over the open version. The brass cylinder was less rigid than the ceramic and the closed container actually amplified rather than attenuated the pressure coefficient. Same thing with the temperature hysteresis.

I took a photo of one of my N 100 resistors (100 ohm) wound on a ceramic cylinder. No hard laquer, but elastic wax instead which doesn't stress the wire as much.



(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=210012;image)

Title: Re: Teardown: Standard Resistors
Post by: quarks on April 02, 2016, 02:41:47 pm
does anyone know what is inside this "Zero Ohm Standard"

(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=214162;image)



http://www.ohm-labs.com/resistance-standards/100-0-standard.html (http://www.ohm-labs.com/resistance-standards/100-0-standard.html)

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

Title: Re: Teardown: Standard Resistors
Post by: manganin on April 02, 2016, 03:17:20 pm
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 (http://www.google.com/patents/US3252091)

Title: Re: Teardown: Standard Resistors
Post by: zlymex on April 02, 2016, 03:39:31 pm
does anyone know what is inside this "Zero Ohm Standard"

(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=214162;image)



http://www.ohm-labs.com/resistance-standards/100-0-standard.html (http://www.ohm-labs.com/resistance-standards/100-0-standard.html)

and explain the
    BALANCED TETRAJUNCTION DESIGN
    A TRUE ZERO-OHM RESISTOR
   
It's better than those in patent US3252091, all of which are not fully symmetrical. That is, when any two terminals passing thru a current, the other two might have none-zero potential.
A regular tetrahedron will do the trick but is difficult to implement. Another one I know is attached.
 
Title: Re: Teardown: Standard Resistors
Post by: manganin on April 02, 2016, 07:00:24 pm
It's better than those in patent US3252091, all of which are not fully symmetrical. That is, when any two terminals passing thru a current, the other two might have none-zero potential. A regular tetrahedron will do the trick but is difficult to implement. Another one I know is attached.

In real life the simplified versions developed by ESI provide excellent performance. With practical current levels and reasonable copper thickness the connector thermal EMFs are a bigger problem than the error caused by the current distribution. And the shape can be fine tuned afterwards based on the measurements to compensate the limited metalwork accurary.

Title: Re: Teardown: Standard Resistors
Post by: quarks on April 02, 2016, 07:03:34 pm
http://www.google.com/patents/US3252091 (http://www.google.com/patents/US3252091)

Looks very much like inside my ESI SR1010s
(https://www.eevblog.com/forum/metrology/esi-resitance-standard-sr1010-and-standard-resistor-sr104/?action=dlattach;attach=194043;image)
Title: Re: Teardown: Standard Resistors
Post by: manganin on April 02, 2016, 07:16:26 pm
Looks very much like inside my ESI SR1010s

And if I remember correctly, there is even a brief junction error analysis in the SR1010 manual.

Title: Re: Teardown: Standard Resistors
Post by: babysitter on April 02, 2016, 07:54:01 pm
Yes, there is. Giving approx. numbers for the junctions, iirc in the 50-150µOhm range depending on the used "ports".
Title: Re: Teardown: Standard Resistors
Post by: zlymex on April 02, 2016, 10:52:58 pm
It's better than those in patent US3252091, all of which are not fully symmetrical. That is, when any two terminals passing thru a current, the other two might have none-zero potential. A regular tetrahedron will do the trick but is difficult to implement. Another one I know is attached.

In real life the simplified versions developed by ESI provide excellent performance. With practical current levels and reasonable copper thickness the connector thermal EMFs are a bigger problem than the error caused by the current distribution. And the shape can be fine tuned afterwards based on the measurements to compensate the limited metalwork accurary.
I've never in doubt the performance of those ESI simplified versions within their Hamons. It is the universal zero ohm that people may connect 4 terminals in anyway which requires the use of full symmetrical version.

A 2D fully symmetrical version(electrical sense) can be made like this.
Title: Re: Teardown: Standard Resistors
Post by: quarks on April 03, 2016, 03:08:31 pm
@zlymex,

the 4 hole symmetry makes very much sense, but I wonder why they made all posts inline and not just use the same pattern outside of the box. At least that would avoid cabeling inside.

Also is there a reason to go for the triangle shape of the plate?
Im asking because a round disc with the same 4 hole symmetry pattern would be my first idea to build it

Thanks
quarks
Title: Re: Teardown: Standard Resistors
Post by: zlymex on April 03, 2016, 03:40:33 pm
@zlymex,

the 4 hole symmetry makes very much sense, but I wonder why they made all posts inline and not just use the same pattern outside of the box. At least that would avoid cabeling inside.

Also is there a reason to go for the triangle shape of the plate?
Im asking because a round disc with the same 4 hole symmetry pattern would be my first idea to build it

Thanks
quarks
I didn't quite get the question, did you mean why they use a metal box?

It just because I draw the triangle easy, it's thinner than a round disc and will save material. The thinnest would be down to just 4 wires. Be careful though, a cross won't do.
Title: Re: Teardown: Standard Resistors
Post by: quarks on April 03, 2016, 04:19:56 pm
I didn't quite get the question, did you mean why they use a metal box?

No my question was not about the metal box but about the arrangement of the connectors.

It just because I draw the triangle easy, it's thinner than a round disc and will save material.

if the triangle plate is not for a technical reason, I think with my limited lathe/mill skills, it should be easier to use round stock and achieve near perfect symmetry (also there are no plates in CuTe but only round stock afaik).
Title: Re: Teardown: Standard Resistors
Post by: Kleinstein on April 03, 2016, 04:29:47 pm
The triangle shape should be a little less sensitive on how well the wire is connected / soldered. It could also make soldering more easy, as heat is not conducted away so fast.
Still I see the advantages in machining for the round form.

Title: Re: Teardown: Standard Resistors
Post by: quarks on April 03, 2016, 04:37:30 pm
The triangle shape should be a little less sensitive on how well the wire is connected / soldered. It could also make soldering more easy, as heat is not conducted away so fast.

when I build it, I plan not to use any wire or solder and directly screw on the binding posts
Title: Re: Teardown: Standard Resistors
Post by: zlymex on April 04, 2016, 03:28:01 am
The triangle shape should be a little less sensitive on how well the wire is connected / soldered. It could also make soldering more easy, as heat is not conducted away so fast.

when I build it, I plan not to use any wire or solder and directly screw on the binding posts
I made this purely by hand: hand cut, hand drill, hand soldering, without any measurement of geometry when make, symmetry done by eyeball observation only, no adjustment/trim of any kind afterwards.
Thickness of the triangle copper is 1.5mm, length of each side is aprox. 21mm, diameter of the copper bar is 2.2mm, diameter of the wires is 0.8mm.
When I run thru a current of 6.2A into 2 wires of any of the 6 combinations(excluding reversal), I measure the other two wires with less than +-0.3uV voltage variation with my 34401A.
This means that I have achieved the kind of zero that OHM-LABS claimed in their specification just by this simple DIY.
 
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on April 04, 2016, 04:10:30 am
Before reading through the last few post I assumed that either a sphere, or diamond would be needed to make a zeroe ohm resistor.
Title: Re: Teardown: Standard Resistors
Post by: quarks on April 04, 2016, 06:43:21 am
I made this purely by hand: hand cut, hand drill, hand soldering, without any measurement of geometry when make, symmetry done by eyeball observation only, no adjustment/trim of any kind afterwards.
Thickness of the triangle copper is 1.5mm, length of each side is aprox. 21mm, diameter of the copper bar is 2.2mm, diameter of the wires is 0.8mm.
When I run thru a current of 6.2A into 2 wires of any of the 6 combinations(excluding reversal), I measure the other two wires with less than +-0.3uV voltage variation with my 34401A.
This means that I have achieved the kind of zero that OHM-LABS claimed in their specification just by this simple DIY.

my guess was, that a perfect symmetry is the most importand part, but if it is that easy, I am even more interested to see what is inside the Ohmlabs product
Title: Re: Teardown: Standard Resistors
Post by: zlymex on April 04, 2016, 08:00:26 am
I made this purely by hand: hand cut, hand drill, hand soldering, without any measurement of geometry when make, symmetry done by eyeball observation only, no adjustment/trim of any kind afterwards.
Thickness of the triangle copper is 1.5mm, length of each side is aprox. 21mm, diameter of the copper bar is 2.2mm, diameter of the wires is 0.8mm.
When I run thru a current of 6.2A into 2 wires of any of the 6 combinations(excluding reversal), I measure the other two wires with less than +-0.3uV voltage variation with my 34401A.
This means that I have achieved the kind of zero that OHM-LABS claimed in their specification just by this simple DIY.

my guess was, that a perfect symmetry is the most importand part, but if it is that easy, I am even more interested to see what is inside the Ohmlabs product
Agreed that symmetry is the key. The bulky copper also plays an important role if not perfectly balanced. And you always have the option if trimming if all fails.
Title: Re: Teardown: Standard Resistors
Post by: lowimpedance on April 06, 2016, 02:07:24 am
Here is a PDF (pt1 and 2, split to fit the forums upload conditions!!) which you resistance 'tinkerers' might find an interesting read.
Its a scan from the ESI Engineering bulletins; this one being the Traceability of Resistance Measurements no.30.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on April 06, 2016, 03:23:09 am
Thanks for those, I wish IET Labs hosted the esi documents.
Title: Re: Teardown: Standard Resistors
Post by: quarks on April 06, 2016, 06:40:44 am
lowimpedance thanks very much for the "Traceability of Resistance Measurements no.30" document


I just looked through my ESI documents to see if I overlooked the details about 4-terminal junction like Figure 27 in your document
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=215104;image)

but only found this (which also shows patent from manganins post)
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=215106;image)

 
Title: Re: Teardown: Standard Resistors
Post by: zlymex on July 14, 2016, 01:54:27 pm
IET SRL 1 Ohm. Same specification as Fluke 742A 1 Ohm but different internal construction.

The internal construction is actually the same. Multiple resistors connected in parallel with the copper equalizing plates. But in the IET version the whole package was resin potted which allows to use much cheaper non-hermetic resistors.

Here is a new photo showing the oil leakage from one of the SRL-1. It seems that the pot is oil filled.
Title: Re: Teardown: Standard Resistors
Post by: quarks on August 04, 2016, 02:58:52 pm
just in case anyone is still interested, here are pictures of my prototype and the final product
Title: Re: Teardown: Standard Resistors
Post by: Dr. Frank on August 04, 2016, 06:45:30 pm
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
Title: Re: Teardown: Standard Resistors
Post by: lowimpedance on August 05, 2016, 04:45:57 am
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!)
Title: Re: Teardown: Standard Resistors
Post by: quarks on August 05, 2016, 08:05:17 am
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
Title: Re: Teardown: Standard Resistors
Post by: guenthert on August 07, 2016, 06:42:37 pm
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 (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, (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/ (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. :-//
Title: Re: Teardown: Standard Resistors
Post by: Macbeth on August 07, 2016, 09:17:21 pm
guenthert, you will be saying it is nothing more than an AY-O fingerbox  :palm:

(http://cromwell-intl.com/fun/fingerbox/pictures/fingerbox-ay-o.jpg)

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.  :-DD
Title: Re: Teardown: Standard Resistors
Post by: chickenHeadKnob on August 08, 2016, 03:21:47 am

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.
Title: Re: Teardown: Standard Resistors
Post by: zlymex on August 11, 2016, 03:02:09 pm
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.
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on March 19, 2017, 01:58:11 pm
*CalMachine casts a resurrection spell* :-/O  :horse:

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.
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on March 19, 2017, 02:05:48 pm
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.
Title: Re: Teardown: Standard Resistors
Post by: TiN on March 19, 2017, 02:09:30 pm
I thought it was you who snagged stash of recent 742A's.  :)
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on March 19, 2017, 02:18:00 pm
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. |O


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.
Title: Re: Teardown: Standard Resistors
Post by: TiN on March 19, 2017, 02:19:30 pm
No, on ebay for 9k :)
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on March 19, 2017, 02:25:07 pm
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.
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on March 19, 2017, 02:35:13 pm
Another goodie I acquired! This one is a Resistive voltage divider (or a Kelvin Varley Divider to be precise).  The ESI RV722!  :scared:

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

Title: Re: Teardown: Standard Resistors
Post by: Assafl on March 19, 2017, 08:10:19 pm
That's a Mylar card millefeuille. Impressive.
Title: Re: Teardown: Standard Resistors
Post by: Pipelie on March 20, 2017, 02:24:59 am
 :-+ :-+
Thanks for sharing, looks like the MTB have a oil tan? like his brother( SR1010 MTA).
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on March 25, 2017, 05:30:37 pm
Do you know the differences between the MTA and MTB?  I need to find a SB103 too.
Title: Re: Teardown: Standard Resistors
Post by: VintageNut on March 26, 2017, 04:02:56 am
@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.

Title: Re: Teardown: Standard Resistors
Post by: CalMachine on March 26, 2017, 06:34:00 am
@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.
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on March 26, 2017, 01:46:18 pm
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.
Title: Re: Teardown: Standard Resistors Leeds&Northrup 4323
Post by: Henrik_V on April 08, 2017, 03:23:47 pm
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 (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  :scared:

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.
Title: Re: Teardown: Standard Resistors
Post by: Henrik_V on April 08, 2017, 03:28:25 pm
part II  some more pics
Nice to see the realization of the Zero Ohm junctions
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on April 08, 2017, 04:09:44 pm
Very Cool. The more I see old L&N gear, the more I like it. >:D
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.
Title: Re: Teardown: Standard Resistors Leeds&Northrup 4323
Post by: guenthert on April 08, 2017, 08:21:27 pm
[..]
I got it because the former owner soiled it with mercury, so it's hazardous waste now  :scared:

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.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on April 08, 2017, 08:59:27 pm
I believe that up until the 80's standard resistors were supposed to be used with mercury wetted contacts. After all, they sold mercury cups/posts for that purpose.
Title: Re: Teardown: Standard Resistors
Post by: e61_phil on April 08, 2017, 09:08:22 pm
Iih! :(

I was only afraid of cadmium solder until now...
Title: Re: Teardown: Standard Resistors
Post by: Henrik_V on April 09, 2017, 11:54:03 am
When you hunt for the next digit in metrology, physics don't care human biology :-//
Cd in solder, Hg on contacts , my amatures are Be  ...   

Title: Re: Teardown: Standard Resistors
Post by: e61_phil on April 09, 2017, 12:28:39 pm
When you hunt for the next digit in metrology, physics don't care human biology :-//
Cd in solder, Hg on contacts , my amatures are Be  ...

Pure Be oder BeCu?

If you don't inhale Be dust it is quite safe, isn't it?
Title: Re: Teardown: Standard Resistors
Post by: Henrik_V on April 09, 2017, 04:40:50 pm
I calibrate accelerometers and the amarture of the shaker is ceramic or mostly pure berillium. No problem unless you lick it for cleaning  ;)
Even our workshop got used to it, because after some years you need to replolish the armature, and you don't what to inhale the dust.  (Primary calibration with laser doppler interferrometers) And these workshop guys are awesome.  :-+ They also polish the Si-'orange' for the new representation of the kilogram. Different story...

From Wikipedia: https://en.wikipedia.org/wiki/Ohm (https://en.wikipedia.org/wiki/Ohm)
The "international" ohm was defined as a mercury column 106.3 cm long of mass 14.4521 grams and 0 °C at the International Electrical Conference 1893 in Chicago.
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 05, 2017, 03:31:40 am
Well... I'm back at it :-+  This time the magical RS925D!   :scared:

This was purchased, for pretty cheap, in an attempt to get an ESI 242D system up and going.  I opened her up to reapply a new foam seal as well as make sure there are no obvious issues that needed to be addressed.  After some quick preliminary tests, it looked like some of the lower decades had slight a hysteresis.   The issue seemed to have disappeared after letting the decade, and the K2002 I was using, thermally stabilize together for over 24 hours.

(http://i.imgur.com/QPh2Rbt.jpg?1)

(http://i.imgur.com/TX6B48D.jpg)

Let's open her up!
(http://i.imgur.com/VwzwtLw.jpg?1)

100 kOhm decade
(http://i.imgur.com/LRg2uCP.jpg)

10 kOhm decade
(http://i.imgur.com/mrHvkiP.jpg)

1 kOhm decade
(http://i.imgur.com/iC9mddR.jpg)

100 Ohm decade
(http://i.imgur.com/8vqZK5I.jpg)

Top and Insides of trim pot assembly PCBs and WW resistors for the 100 kOhm, 10 kOhm, 1 kOhm, and 100 Ohm decades
(http://i.imgur.com/UFUwcyg.jpg)

(http://i.imgur.com/G38QyxN.jpg)

(http://i.imgur.com/Oosthcy.jpg)

(http://i.imgur.com/O44uXeP.jpg)

(http://i.imgur.com/qDhTqiT.jpg)


10 Ohm decade
(http://i.imgur.com/ewxyyap.jpg)

1 Ohm Decade
(http://i.imgur.com/BC4cnyH.jpg)
(http://i.imgur.com/0Fpf9va.jpg)
(http://i.imgur.com/GnKVw61.jpg)

100 mOhm decade
(http://i.imgur.com/TjjLkME.jpg)
(http://i.imgur.com/rRNsSWO.jpg)

10 mOhm decade.  These units have a fixed minimum resistance of 10 mOhms.  Because of this implementation there is no 'zero ohm', similar to insertion loss, measurements need to be taken into consideration.  This allows for the displayed resistance value to actually be the absolute value.
(http://i.imgur.com/3GCeuHD.jpg)
(http://i.imgur.com/eXY4qbF.jpg)

100 µOhm Decade fine trim pot
(http://i.imgur.com/035OCmM.jpg)

More Goodies!

100 kOhm and 10 kOhm decades

(http://i.imgur.com/2XZW0SZ.jpg)


10 Ohm and 1 Ohm decades
(http://i.imgur.com/e6y6cPN.jpg)


1k and 10 kOhm decades
(http://i.imgur.com/noomGJj.jpg)
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on May 05, 2017, 03:41:25 am
Thanks for sharing. It looks like it in great shape.
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 05, 2017, 03:45:15 am
Thanks for sharing. It looks like it in great shape.

You're are very welcome!  This is my first RS925D I've seen, so I wasn't 100% positive on the condition.  It seems as if there is a decent amount of flux residue still on some of the connections... is that normal? 
Title: Re: Teardown: Standard Resistors
Post by: TiN on May 05, 2017, 04:12:49 am
Auch, purple wire resistor on 10K decade looks damaged to me. I have some Fluke PWWs, and those edges are real easy to get damaged and open wires, due to very fine gauge.
Thanks for sharing.
Title: Re: Teardown: Standard Resistors
Post by: quarks on May 05, 2017, 07:42:10 am
here are pictures from my RS925A for comparison to the RS925D above
(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=313147)

(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=313149)
Title: Re: Teardown: Standard Resistors
Post by: manganin on May 05, 2017, 09:31:52 am
This time the magical RS925D!

That is a late one, seems to be from the mid 1980s.

Switches are the weak point, inferior compared with the General Radio counterparts. ESI solved the problem by paralleling several switch wafers. Which actually works fine, until dirty or totally worn out.

It would be a good idea to clean all the switches with a rough paper simulating the movement of the switch blade. You are ready when there is no dirt in the paper. Not easy to access and takes a lot of time, but worth the effort. Absolutely no switch cleaner chemicals!

Another thing worth checking are the screw connections of the slide wire. That is the 4-wire node so the possible change can only be seen in a 2-wire measurement. Open the screws, clean the surfaces and bend the spring washer teeth if required.

The trimmers are better that you would expect, but still the obvious reason for any high decade instability. That specific type is still available but very expensive. Turn back and forth a few times as a preventive measure.

Title: Re: Teardown: Standard Resistors
Post by: Assafl on May 05, 2017, 10:13:39 am
Why not use a switch cleaner (like Caig stuff)?

For electrometers and the like one has to ensure that any cleaner does not touch any isolators such as Teflon, but if done extremely sparingly (e.g. Just on the wiping metal surface) then it does do away with oxidation and the like.

Does it affect calibration if it does not touch insulation?

(By sparingly I mean with a syringe or a wipe, and watch oilers do work well to dispense tiny drops into leaf contacts. )
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 05, 2017, 12:22:27 pm
Auch, purple wire resistor on 10K decade looks damaged to me. I have some Fluke PWWs, and those edges are real easy to get damaged and open wires, due to very fine gauge.
Thanks for sharing.

I didn't really notice that at first, Good Eye!  Is the only coarse of action to repair said damage, to replace the resistor?


This time the magical RS925D!

That is a late one, seems to be from the mid 1980s.

Switches are the weak point, inferior compared with the General Radio counterparts. ESI solved the problem by paralleling several switch wafers. Which actually works fine, until dirty or totally worn out.

It would be a good idea to clean all the switches with a rough paper simulating the movement of the switch blade. You are ready when there is no dirt in the paper. Not easy to access and takes a lot of time, but worth the effort. Absolutely no switch cleaner chemicals!

Another thing worth checking are the screw connections of the slide wire. That is the 4-wire node so the possible change can only be seen in a 2-wire measurement. Open the screws, clean the surfaces and bend the spring washer teeth if required.

The trimmers are better that you would expect, but still the obvious reason for any high decade instability. That specific type is still available but very expensive. Turn back and forth a few times as a preventive measure.



Thank you for the advice!  :-+  I'll work on this here in the future.  Will probably post some before/after pictures, when I get to opening her back up.
Title: Re: Teardown: Standard Resistors
Post by: 0.01C on May 16, 2017, 05:38:44 pm
I love 925D ,it is a great resistance stanard :-+
Title: Re: Teardown: Standard Resistors
Post by: Edwin G. Pettis on May 17, 2017, 04:52:12 pm
That discoloration on the 10K may be an indication of overload or a chemical spill, the coating on these resistors are not very resistant, even isopropyl will soften it up and if you get any on it, it will have to dry out thoroughly but has no lasting effects.  You'll have to check the resistor with a high accuracy measurement to see if it is out of tolerance.  You can use a contact cleaner like deoxit but do not spray it on the resistors, use a lint-less wipe.  Yes there is always some rosin residue left on the solder joints, it is of no consequence.  Usually these units require very little maintenance.

I have both a RS925D (part of my 242D) and a RS925A (part of a 242B) which I am going through and giving it a once over.  The connections on the rheostat are very important and should be snug (do not over tighten), the resistance element/wiper can be gently redressed with crocus cloth and cleaned.  I have found some units with some kind of gooey grease on the rheostat, that attracts dirt, I prefer to keep them clean and dry.  These units are more or less sealed in their case, there should be little to no contamination getting in there.

These resistors are wound on a mica card and therefor is somewhat easily damaged, not only the fine wire but the mica so be very careful around them.
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 19, 2017, 06:54:09 pm
She's Alive!!!!   :scared:

Title: Re: Teardown: Standard Resistors
Post by: e61_phil on May 19, 2017, 07:04:14 pm
Is there a Helmut Singer Sticker?
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 19, 2017, 07:12:56 pm
Is there a Helmut Singer Sticker?

Correct!
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on May 19, 2017, 08:10:51 pm
I remember seeing one on ebay for $1500 obo, it sat on there for years. I think it was a dealer based on the West Coast.
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on May 19, 2017, 09:56:02 pm
The black monolith is alive. Now the race is on to see which one of us can figure it out first. Mine keeps looking at me wondering when I will stop fixing stuff and start measuring my SR1010 and SR104 resistors.
I think there will be some projects to do soon involving resistance bridges.
Title: Re: Teardown: Standard Resistors
Post by: 0.01C on May 20, 2017, 12:37:26 am
She's Alive!!!!   :scared:

How do you calibrate this black monolith? I have a 242C still sleeping on the floor. :palm:
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on May 20, 2017, 01:27:25 am
According to the manual you need a 10k reference resistor with 1ppm calibration accuracy (SR-104) and a trimmable 10k/step transfer standard like the hard to find SR 1010 MTx.
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 20, 2017, 01:34:19 am
The black monolith is alive. Now the race is on to see which one of us can figure it out first. Mine keeps looking at me wondering when I will stop fixing stuff and start measuring my SR1010 and SR104 resistors.
I think there will be some projects to do soon involving resistance bridges.

You're on!   >:D I don't have any of the connectors or adapters so I ended up making my own.  We'll see how they turn out, as I have not put everything to the test yet.  I spent most of the day cleaning everything up on the outside, getting her looking good, as well as calibrating the 801.  The 801 performed very well and needed no adjustments coming from Helmut Singer. 

According to the manual you need a 10k reference resistor with 1ppm calibration accuracy (SR-104) and a trimmable 10k/step transfer standard like the hard to find SR 1010 MTx.

Done and done!   :popcorn:
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on May 20, 2017, 01:56:30 am
Ok. Let's communicate offline and get some details worked out.

We can start a new thread and post any results if you want to do some detailed comparisons of portable standards.
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 20, 2017, 02:14:46 am
Ok. Let's communicate offline and get some details worked out.

We can start a new thread and post any results if you want to do some detailed comparisons of portable standards.

Sounds good! And yes, I would like that very much. :-+
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on May 20, 2017, 02:30:26 am
I look forward to reading about your 242 endeavors.
I have a feeling E.G. Pettis will chime in. ;D  :popcorn:
Title: Re: Teardown: Standard Resistors
Post by: Edwin G. Pettis on May 20, 2017, 02:34:36 am
The SR-1010 10K does not need to be trimmable, it is directly compared to the SR-104 for each step and the readings noted, the trimmable SR-1010 is optional.

Okay, I chimed in......
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 20, 2017, 02:46:44 am
The SR1010 I picked up a few months ago is the MTS version, and I've already trimmed each step to our Ohm Labs 10k standard resistor.  If I remember correctly (I'm not at the lab), but I think our Ohm Labs 10k standard has drifted about 2ppm over the last 5 years.  So it's holding pretty strong!   I plan on shifting it to our working standard once I can get a SR104 in our hands with sufficient data to use as our lab's primary standard.

I tore it down, slightly, and posted pics on page 4 for those interested!   ;D
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on May 20, 2017, 03:09:57 am
I thought you partially tore down your Ohm Labs 10k standard. I was disappointed they weren't there.   :-DD

Which model do you have? Is it the 104 or 204?
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on May 20, 2017, 03:16:00 am
I thought you partially tore down your Ohm Labs 10k standard. I was disappointed they weren't there.   :-DD


:-DD   No way I'm opening up our current, freshly cal'd, 10k standard.

Which model do you have? Is it the 104 or 204?

We have the 100 (1 amp version) and 104.  I wish we had the 200 series!  We were really small back then when they picked them up, before I was around. 
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on May 20, 2017, 03:28:17 am
A couple of years ago I got a quote on the 200 1 ohm model and the price was $3400.00
Title: Re: Teardown: Standard Resistors
Post by: MasterTech on August 25, 2017, 12:00:11 pm
Very interesting thread.

However I noticed that very few resistance standards use an oil bath ( the Leeds Northrup and another potted resistor If I recall did use it), and none have heated ovens, something common in voltage standards.
Why is that? any guesses?
Title: Re: Teardown: Standard Resistors
Post by: TiN on August 25, 2017, 12:04:08 pm
Elevated temperature accelerate aging drift.
Same apply to voltage references, but with them it's "lesser evil" and in the end result is better. Not so much for passive resistor though.
Title: Re: Teardown: Standard Resistors
Post by: MasterTech on August 25, 2017, 12:36:53 pm
Elevated temperature accelerate aging drift.
Same apply to voltage references, but with them it's "lesser evil" and in the end result is better. Not so much for passive resistor though.

Hmm, well since voltage standards use resistors too, to set currents, and as voltage dividers, heat would be evil too in that sense.
I've been reading for example about the HP 735A, its basically a selected and ovenized (at 80ºC) 6.3V zener, whose output is divided to 1V via resistors, ie no op-amp feedback or similar. Two
of those resistors are inside the oven. If those resistors drift fast its game over for it. But these little things were pretty stable over time.

More about it here https://www.eevblog.com/forum/testgear/hp-735a-dc-transfer-standard/ (https://www.eevblog.com/forum/testgear/hp-735a-dc-transfer-standard/)


(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=344652;image)

Title: Re: Teardown: Standard Resistors
Post by: MasterTech on August 25, 2017, 07:18:00 pm
Earlier this year I was too busy and missed this one, how is it not referenced here??

https://www.eevblog.com/forum/metrology/fsl-project/ (https://www.eevblog.com/forum/metrology/fsl-project/)
https://xdevs.com/article/fsl935/ (https://xdevs.com/article/fsl935/)
Title: Re: Teardown: Standard Resistors
Post by: Echo88 on August 25, 2017, 07:49:27 pm
Well, its a prototype, not a standard resistor. Regarding the HP 735A-post: The necessary resistors have to be inside the ovenized compartment together with the voltage reference, otherwise the temperature difference between voltage ref and resistor junctions would create drifting parasitic thermal emf voltages.
Title: Re: Teardown: Standard Resistors
Post by: MasterTech on August 25, 2017, 08:17:04 pm
Regarding the HP 735A-post: The necessary resistors have to be inside the ovenized compartment together with the voltage reference, otherwise the temperature difference between voltage ref and resistor junctions would create drifting parasitic thermal emf voltages.

Oh, the HP735A was just an example to see that resistors are heated in voltage standards. The Fluke 732B also does the same. Thus my question of why we see no resistance standards with heating, but well Fluke also thought of that in the SL935 :)
Title: Re: Teardown: Standard Resistors
Post by: ap on August 25, 2017, 09:47:57 pm
There absolutely are resistance standards that are heated. E.g. Measurements International offers them. Price is steep though.
You can also diy for your labs, using oild filled precision resistors and a precision heater device.
Title: Re: Teardown: Standard Resistors
Post by: schmitt trigger on August 26, 2017, 02:18:14 am
Well... I'm back at it :-+  This time the magical RS925D!   :scared:


Watching these images, I'm completely in awe, no, actually speechless, at the top-level workmanship of these units.

I'm pretty sure that this level of craftsmanship was obtained in a shop which employed only a very few, very skilled workers.
Ran by managers which were technically very competent.

Back then when the label: MADE IN USA actually meant something special.
Title: Re: Teardown: Standard Resistors
Post by: Echo88 on August 26, 2017, 09:38:28 am
Interesting ap! A few standard resistors to check your equipment? Are they more suitable for some jobs than your 5720A?
Title: Re: Teardown: Standard Resistors
Post by: ap on August 26, 2017, 10:20:09 am
Actually I use 4808s as sources (which, btw, in many areas have better uncertainty specs than a 5720), but resistors uncertainties of calibrators are usually pretty high. The 5720 10kOhms spec is e.g. 9ppm for 90 days, +/-5K and 3ppm at +/-1K (plus factory calibration). A hermetic, thermo-regulated resistor has <0.5ppm/a uncertainty (plus calibration uncertainty). The temperature stability can easily be made better than 0.1K.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on August 26, 2017, 10:29:30 am
There absolutely are resistance standards that are heated. E.g. Measurements International offers them. Price is steep though.
You can also diy for your labs, using oild filled precision resistors and a precision heater device.
Do you have a build thread for your resistance standard. I feel like I have seen it before.
Title: Re: Teardown: Standard Resistors
Post by: ap on August 26, 2017, 11:28:29 am
There was some mentioning earlier, but no real build thread, just one or two more pictures.
Title: Re: Teardown: Standard Resistors
Post by: TiN on September 04, 2017, 03:32:05 pm
It was unavoidable, at rate I'm lurking and buying stuff of evilbay. RS925D ESI arrived today. Great deal at 600$ huh?

Hmm, what is that rattling sound...  :wtf:

(https://xdevs.com/doc/ESI/RS925D_t/esi_deada_1.jpg) (https://xdevs.com/doc/ESI/RS925D_t/esi_deada.jpg) (https://xdevs.com/doc/ESI/RS925D_t/esi_dead2_1.jpg) (https://xdevs.com/doc/ESI/RS925D_t/esi_dead2.jpg)

(https://xdevs.com/doc/ESI/RS925D_t/esi_dead3_1.jpg) (https://xdevs.com/doc/ESI/RS925D_t/esi_dead3.jpg) (https://xdevs.com/doc/ESI/RS925D_t/esi_dead4_1.jpg) (https://xdevs.com/doc/ESI/RS925D_t/esi_dead4.jpg)

Ah... those are bits of coal from the switch... ...  :-BROKE

0.1 ohm decade is cooked to coal condition. Other decades "seem" to work, but I'd be very surprised if whole box is any good other than metal enclosure and binding posts.
Oh well, don't go shoppin unprepared, dear precision-nuts.  :scared:

P.S. was listed as "used".
Title: Re: Teardown: Standard Resistors
Post by: cellularmitosis on September 04, 2017, 03:45:55 pm
Thanks for the cautionary tale!  That's a bummer.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on September 04, 2017, 04:03:06 pm
Damn, interesting things always happen when TiN spends money... :scared:
Title: Re: Teardown: Standard Resistors
Post by: CalMachine on September 04, 2017, 06:01:27 pm
That is most unfortunate =(  I was hoping the RS925 you picked up was going to be a good one, so we can get some international transfers going  :popcorn:   

We will have to resort to other plans.

Perhaps, now, you might have a donor unit for fellow precision-nutt hobbyists who might have faulty parts. (I don't know.. perhaps $50 or so per dial?  :-X) 

How does the µOhm vernier feel as you make complete revolutions?
Title: Re: Teardown: Standard Resistors
Post by: alm on September 04, 2017, 06:52:46 pm
P.S. was listed as "used".
At least that gives you a shot at returning and/or receiving a (partial) refund. Ebay's description of used is "fully functional, but possibly some sings of wear that are described in the pictures and/or item description". So based on that, any non-described defect is a reason to consider the object not as described. Severe undisclosed defects make it significantly not as described.
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on September 04, 2017, 07:14:31 pm
The initial accuracy of 20ppm on the untrimmed decades would be difficult to match. The 0.1 ohm decade on my RS925D has signs of filing/sanding where they adjusted each step by hand. Not sure about the 0.01 decade but it was probably done the same way.
Title: Re: Teardown: Standard Resistors
Post by: TheSteve on September 04, 2017, 07:36:33 pm
It was unavoidable, at rate I'm lurking and buying stuff of evilbay. RS925D ESI arrived today. Great deal at 600$ huh?

Hmm, what is that rattling sound...  :wtf:


Crispy sadness.
Title: Re: Teardown: Standard Resistors
Post by: plesa on September 04, 2017, 08:44:34 pm
The initial accuracy of 20ppm on the untrimmed decades would be difficult to match. The 0.1 ohm decade on my RS925D has signs of filing/sanding where they adjusted each step by hand. Not sure about the 0.01 decade but it was probably done the same way.

In HARSX series the 0,01 and 0,1 Ohm ranges looks like trimmed by solder joints inside bend area. I can post some pictures. On TiN picture the solder has been evaporated :-)
I like the shadows on front panel. RIP \$\Omega\$
Title: Re: Teardown: Standard Resistors
Post by: manganin on September 05, 2017, 08:40:20 am
0.1 ohm decade is cooked to coal condition. Other decades "seem" to work, but I'd be very surprised if whole box is any good other than metal enclosure and binding posts.

Luckily the lowest decade resistive elements are identical to the ESI DB series decade boxes, which are very cheap. Especially the low resistance ones.

Note that the DB series has only two parallel switch sections while the 924D has four.

By extending the spindle you can parallel all six sections, there is plenty of space. Better than the original...

Title: Re: Teardown: Standard Resistors
Post by: Edwin G. Pettis on September 05, 2017, 05:20:36 pm
Hello TiN,

It is really aggravating when someone abuses precision equipment like this, I hope they got fired for it, no excuse.  You could have a case for a refund given the condition it is in, definitely not in working condition by any definition.  That decade was severely overloaded, the resistors are definitely ruined, the switch might be recoverable hard to tell from the photo.  The blackening on the panel indicates severe stupidity.  If the switch could be recovered, it would be possible to rebuild the resistor chain since it is of Manganin alloy.  However, given the design of the 925D, the 0.1? decade has to calibrated to the 925D's 'zero' ohm value which is different for every unit, just 'plugging in' another decade will result in higher error.
Title: Re: Teardown: Standard Resistors
Post by: TiN on September 05, 2017, 06:55:08 pm
Just got the message from seller, with promise to honor my partial refund requestGot the agreed partial refund, leaving me which what it is.
So eventually I'll be looking on ways to restore this unit, however at this point it likely to collect dust on the shelf, until I get decade element for replacement.

In the end whole thing must be calibrated, so I'd expect current "zero ohm value" doesn't mean anything anymore. What puzzles me a bit, how the other decades are not damaged (at least visually) as per my understanding they all in series? Maybe operator had all higher decades set to zero, and was trying to use RS925D as a 0.x ohm shunt?? That would be the only possible explanation.
Title: Re: Teardown: Standard Resistors
Post by: Edwin G. Pettis on September 05, 2017, 07:51:38 pm
The .01? minimum value consists of the interconnect wiring between the decades (at 'zero' setting of course) plus the minimal error contributed by the vernier resistance which is not quite 'zero' either.  The 1st decade setting of the .01? bank is adjusted to correct (as best possible) for that total 'zero' resistance, the subsequent settings on the .01? decade are accordingly adjusted at each step and so on.  The 0.1? decade resistors are adjusted to the .01? bank.  The 1? and 10? banks are wound and either selected or adjusted to also account for the lower bank's error to stay within the required accuracy spec.

Since your 0.1? decade is destroyed and possibly the switch as well, the only compensation required to the total 'zero ohm' net resistance is if a new switch has a significantly different 'zero' resistance that the original switch if replaced.  If the resistance of the new switch is sufficiently different to throw the accuracy of the other low ohm banks off of spec, then you would indeed have to re-calibrate the lower decks.  This is a cascade failure in that one low end bank could cause the entire low end to require re-calibration and the upper adjustable banks need to be re-calibrated anyhow after traveling and obviously being mishandled, its accuracy/calibration is unknown.  I would also verify that the .01? resistors are okay, that black on them may be just blow back from the 0.1? resistors but then....maybe not.  There is no public copy of the calibration procedure for a newly made RSxxx standard.

When time permits, I would first remove the damaged resistors and then clean up the switch decks and see what condition they are in before doing anything else,  the question of whether or not the switch requires replacement is the first step, we already know the resistors are toast (literally!).

Personally I have never seen an RS925D is such bad condition, sometimes I've seen dec boxes with damaged resistors (DB series or even SR-1010s) but usually standards of the RS725 or RS925 series are treated with kid glove care, they are worth too much for such tomfoolery.

May I inquire what country this came from?
Title: Re: Teardown: Standard Resistors
Post by: TiN on September 06, 2017, 12:35:11 am
I've also got a word that decade from new IET RS925 are not compatible with this older ESI unit. It came from USA as most of my stuff :)
Title: Re: Teardown: Standard Resistors
Post by: Edwin G. Pettis on September 06, 2017, 01:42:33 am
Well, I'm not too surprised, IET has been busy trying to cut costs some as those older ESI switch decks were of very high quality and weren't too cheap back when ESI  was buying them.  I'd say if you want to try and save this unit, start by cleaning and checking the switch, if that is still in good shape, that is one less hurdle, next would be replacing the resistors and re-calibrating it, could be worth the trouble.

Argh, it appears that this website doesn't support standard special character coding, it changed my Omegas into '?'....tsk, tsk.
Title: Re: Teardown: Standard Resistors
Post by: TiN on September 06, 2017, 04:54:28 am
Will do, Edwin, thanks for suggestions. I might also first test higher decades by bypassing the lower side connection, just to check if whole thing worth the efforts.
Based on smoke marks it would look like there was open fire of spacer at 0.1 decade, which could very well caused PWW's above it to be cooked as well.
I'd expect resistance wire stability may be affected by that.

And yea, none of &Omega; &deg; &plusmn; stuff working here. Another reason why I maintain own site :D.
Title: Re: Teardown: Standard Resistors
Post by: alm on September 06, 2017, 06:08:44 am
\$ 1 \Omega \$ (Mathjax) works on the desktop version.
Title: Re: Teardown: Standard Resistors
Post by: sarel.wagner on September 06, 2017, 09:53:39 am
My lesson also learned on the DB788, burnt  :palm:  but not quite as bad as Tin's unit.... Managed to get some NOS resistors to repair. Also talking to Edwin about that first decade resistors.

Rgrds
Title: Re: Teardown: Standard Resistors
Post by: manganin on September 06, 2017, 10:15:38 am
What puzzles me a bit, how the other decades are not damaged (at least visually) as per my understanding they all in series?

I = U/R and P = U*I

Low voltage / high current supply will damage the lower decades. In case of high voltage / low current supply the higher decades will suffer.

Higher decade switches are probably just fine. The switch current carrying capacity is much larger than the switching capacity.

The ESI 801 source is not able to damage the 925D, even if directly connected. Must have been something with output current much higher than 2A.

Title: Re: Teardown: Standard Resistors
Post by: manganin on September 06, 2017, 10:21:14 am
IET has been busy trying to cut costs some as those older ESI switch decks were of very high quality and weren't too cheap back when ESI was buying them.

GenRad 1433 by General Radio:

(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=348397;image)


Genrad 1433 by IET Labs:

(https://www.eevblog.com/forum/metrology/teardown-standard-resistors/?action=dlattach;attach=348399;image)


More IET photos:
http://www.edn.com/design/components-and-packaging/4421782/When-wires-become-components (http://www.edn.com/design/components-and-packaging/4421782/When-wires-become-components)

Title: Re: Teardown: Standard Resistors
Post by: CalMachine on September 06, 2017, 03:47:13 pm
Quality and craftsmanship has hit a rock bottom, it seems...  Thanks IET!  :--
Title: Re: Teardown: Standard Resistors
Post by: Macbeth on September 06, 2017, 08:11:35 pm
Just look at the ludicrously overpriced relabeled IET DE-5000/6000 debacle compared with the Taiwan DER EE DE-5000 and all the bullshit that goes with it.

I've always wondered why Dave gave a glowing review and never used it since, he always uses his Agilent LCR like with the $7 AVR 328 Transistor Tester review that is so recent.

Title: Re: Teardown: Standard Resistors
Post by: cellularmitosis on April 12, 2018, 04:03:11 pm
Just came across this powerpoint presentation about the history of the Ohm and resistance standards.  Great intro to the subject!

https://pdfs.semanticscholar.org/presentation/7395/d0272221da51ebe5b45970a3bb55c29d0f30.pdf
Title: Re: Teardown: Standard Resistors
Post by: ManateeMafia on April 12, 2018, 04:19:54 pm
nice find.  :-+

It is good to see some of my own standards covered and their history. There is an article out there that describes the method used to build a 4210 resistor and how the wire was annealed including temperatures. Have you come across that one?
Title: Re: Teardown: Standard Resistors
Post by: Dr. Frank on April 12, 2018, 05:48:16 pm
Very nice presentation, thank you!

Resistance  \$\Omega\$ seems to be a typical German affair: Georg Ohm, Werner von Siemens, Wilhelm Eduard Weber, Otto Wolff, Reichsanstalt Ohm, von Klitzing QHR... great evolution story.

Next year, 20th May, this story will come to a finish, as the Ohm will have a zero definition uncertainty, and an extremely small realization uncertainty, due to being a quantum standard, finally.

Frank
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on April 12, 2018, 06:09:20 pm
nice find.  :-+

It is good to see some of my own standards covered and their history. There is an article out there that describes the method used to build a 4210 resistor and how the wire was annealed including temperatures. Have you come across that one?
Here you go
Stability of double-walled manganin resistors - Nvlpubs.nist.gov…
PDFhttps://nvlpubs.nist.gov › nistpubs › jres

Another good one:

A new design of precision resistance standard - Nvlpubs.nist.gov…
PDFnvlpubs.nist.gov › jresv5n2p295_A2b


Title: Re: Teardown: Standard Resistors
Post by: alm on April 13, 2018, 06:04:42 pm
The above two articles as links:
Stability of double-walled manganin resistors (http://nvlpubs.nist.gov/nistpubs/jres/36/jresv36n1p107_A1b.pdf)
A new design of precision resistance standard (https://nvlpubs.nist.gov/nistpubs/jres/5/jresv5n2p295_A2b.pdf)
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on April 13, 2018, 07:00:39 pm
Thanks , my phone doesn't like to copy certain links for some reason.
Title: Re: Teardown: Standard Resistors
Post by: ian.ameline on April 23, 2018, 05:02:22 pm
I have recently acquired a General Radio 1433-M in very clean condition. I've tested it (as well as I can with an HP34401A with kelvin probes, and using recommended metrology practises.) All of the values on all of the decades are within 0.01% +- 2mOhms, with the exception of 3 of the values in the 100 Ohm/div decade -- 500 Ohms is high by 0.012% and 600 and 700 are high by 0.011%. Several other values in this decade are at 0.01% high.

The other decades are all closer -- the 1k/div has all values within 0.001% !!!. The highest decade is about 0.005% low, and the low three decades are between 0.004% and 0.009% high, with the exception of the 100 ohm/div decade which is 0.009% to 0.012% high.

Other than cleaning the contacts with deoxit (as recommended by IET Labs) is there anything else to be done? I don't think I can say with any confidence that the unit is in or out of spec without something with more precision and less uncertainty than an HP34401A.

The IET documentation says to lubricate using Synco Super-Lube with PTFE -- would not the PTFE particles suspended in the synthetic grease increase contact resistance? This unit at 0 measures at under 2.5 mOhm using kelvin probes on my HP34401A. The General Radio specs for these switches was  < 0.5 milli-Ohms of contact resistance. With the exception of the three values above, it is so precise, I'm reluctant to fuck with it.

Any advice?


Title: Re: Teardown: Standard Resistors
Post by: Edwin G. Pettis on April 23, 2018, 05:44:13 pm
According to original General Radio specs, the 1433-M accuracy is ±0.01% + 2m \$\Omega\$, so it appears that most of the resistors are within tolerance, with a few of them close to the limits and some of the 100 ohm units a bit on the high side possibly.  The newer IET versions are using significantly lower quality switches and they appear to have began replacing mica card resistors with film/foil resulting in lessor specifications.  This is probably due to their inability to manufacture the mica card resistors.  Given the accuracy of the 34401A on low ohms range, a fair number of your readings are on the 'ragged' edge of being out of tolerance.

In my opinion, the older genuine GR units are of higher value than the new units.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on April 23, 2018, 06:45:25 pm
Thr new IET 1433's appear to use the same switches as the ESI DB(the old ones , and probably new as well) series boxes.
Title: Re: Teardown: Standard Resistors
Post by: ian.ameline on April 23, 2018, 07:18:28 pm
According to original General Radio specs, the 1433-M accuracy is ±0.01% + 2m \$\Omega\$, so it appears that most of the resistors are within tolerance, with a few of them close to the limits and some of the 100 ohm units a bit on the high side possibly.  The newer IET versions are using significantly lower quality switches and they appear to have began replacing mica card resistors with film/foil resulting in lessor specifications.  This is probably due to their inability to manufacture the mica card resistors.  Given the accuracy of the 34401A on low ohms range, a fair number of your readings are on the 'ragged' edge of being out of tolerance.

In my opinion, the older genuine GR units are of higher value than the new units.

On the 1 Ohm/division all but one reading was within the 2 milliOhm uncertainty, and the single one that was more than 2 milliOhms was 2.2 milliOhms out. So I think those ranges are ok (within what a 34401 can say). Its the 100 Ohm/step decade that is on the "ragged edge".

I'm attaching the readings (the 0 offset has been subtracted from all readings on each scale of the 34401) The "corrected" column is the actual readings with up to 2 milliOhms of error subtracted. (The 34401 had been on and connected to the unit with kelvin probes for 24 hours no movement or touching other than turning the knobs and waiting for 30 seconds, temp is a constant 22C, with no gradients or breezes) The readings are very stable and very reproducible - to within 1 digit in the least place every time.

I agree that the older units seem to be much better built. I've ordered some deoxit -- I wonder if it can trim 10 milliOhms off the resistance of the 100 Ohm/Step decade...

Still, for $140, not too bad. IET wants $2300 for a new one.
Title: Re: Teardown: Standard Resistors
Post by: ian.ameline on April 23, 2018, 07:31:02 pm
Given the accuracy of the 34401A on low ohms range, a fair number of your readings are on the 'ragged' edge of being out of tolerance.

For the low ohms range, the 34401 is 0.01% of reading + 0.004% of range (which is 100 Ohms.) For the 1K range it is 0.01% of reading + 0.001% of range.

So for 500 Ohms, it would be 50 milliOhms + 10 milliOhm -- 60 milliOhms of uncertainty. My reading for the 500 Ohm setting on the 1433-M is 500.062 Ohms. Just outside of the uncertainty of the meter -- So without a more accurate & precise meter, I don't know that I can say that the 1433 is out of spec. (Which should be +- 52 milliOhms for a setting of 500 Ohms.)

Title: Re: Teardown: Standard Resistors
Post by: Conrad Hoffman on April 24, 2018, 05:50:45 pm
...
The IET documentation says to lubricate using Synco Super-Lube with PTFE -- would not the PTFE particles suspended in the synthetic grease increase contact resistance? This unit at 0 measures at under 2.5 mOhm using kelvin probes on my HP34401A. The General Radio specs for these switches was  < 0.5 milli-Ohms of contact resistance. With the exception of the three values above, it is so precise, I'm reluctant to fuck with it.

Any advice?

AFAIK, the PTFE shouldn't be a problem. The Super Lube products are a PAO oil, supposedly an excellent lube for electrical contacts. The thickener is fumed silica rather than the usual soaps. It would be interesting to re-grease it and run the resistance test again just to be sure. I think the old GR literature suggested Vaseline for lube, and maybe some other grease, depending on the vintage. One has to remember that the GR resistance boxes are very good, but they were never intended as metrology grade calibration standards.
Title: Re: Teardown: Standard Resistors
Post by: ian.ameline on April 24, 2018, 09:59:18 pm
...
The IET documentation says to lubricate using Synco Super-Lube with PTFE -- would not the PTFE particles suspended in the synthetic grease increase contact resistance? This unit at 0 measures at under 2.5 mOhm using kelvin probes on my HP34401A. The General Radio specs for these switches was  < 0.5 milli-Ohms of contact resistance. With the exception of the three values above, it is so precise, I'm reluctant to fuck with it.

Any advice?

AFAIK, the PTFE shouldn't be a problem. The Super Lube products are a PAO oil, supposedly an excellent lube for electrical contacts. The thickener is fumed silica rather than the usual soaps. It would be interesting to re-grease it and run the resistance test again just to be sure. I think the old GR literature suggested Vaseline for lube, and maybe some other grease, depending on the vintage. One has to remember that the GR resistance boxes are very good, but they were never intended as metrology grade calibration standards.

I also have some deoxit lithium based grease (L260Np), I'll give that a try on the 100Ohm decade along with the deoxit cleaner and see what effect that has.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on October 20, 2018, 04:33:47 am
A quick impromptu teardown. L&N 4221-B
Title: Re: Teardown: Standard Resistors
Post by: Conrad Hoffman on October 20, 2018, 02:05:24 pm
With all the concern about spot welding and wire fastening in other threads, and the impossibility of it being done well enough my mere mortals and DIYers, it's hard to believe the crude construction of the 4221 yields as good performance as it does.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on October 20, 2018, 05:51:49 pm
With all the concern about spot welding and wire fastening in other threads, and the impossibility of it being done well enough my mere mortals and DIYers, it's hard to believe the crude construction of the 4221 yields as good performance as it does.
Very true , especially since it was still getting calibrated until 2006. Then again, I wonder what the ultra precision low ohms resistors look like(ohm-labs , Measurements International). I'm think not much different.
Title: Re: Teardown: Standard Resistors
Post by: Edwin G. Pettis on October 21, 2018, 01:16:39 am
You are comparing apples and oranges here, these resistors such as the L&N 42xx series are made with Manganin and are soldered, PWW resistors such as I make are made with Evanohm alloys which are not solder-able and must be welded.  It is not the 'crude' construction as much as the processes used to make them stable.

These resistors require entirely different methods to produce the end result, using the same methods on Evanohm resistors wouldn't even bother them.  Some of the Soviet style resistors similar to the L&Ns were actually made with a relatively thick sheet of Manganin with heavy copper leads soldered to the sheet.  Others such as L&N used heavy gauge wire instead with smaller gauge wire being used for higher values.  On the whole, the techniques were not that different between the Manganin type standards.  None the less, it does take considerable care and handling to produce such stable Manganin resistors, it isn't an off-the-shelf type of thing.  Manganin does remain very sensitive to handling and its environment unlike the Evanohm standards such as the SR-104.
Title: Re: Teardown: Standard Resistors
Post by: HighVoltage on October 21, 2018, 08:59:55 am
With all the concern about spot welding and wire fastening in other threads, and the impossibility of it being done well enough my mere mortals and DIYers, it's hard to believe the crude construction of the 4221 yields as good performance as it does.

Yes, I expected somehow a "much better", whatever that means.
By the look of it, we all could have built something like this L&N 4221-B ourselfs


Title: Re: Teardown: Standard Resistors
Post by: Vgkid on October 22, 2018, 01:19:03 am
Here is some reading material:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.dtic.mil/dtic/tr/fulltext/u2/a284623.pdf&ved=2ahUKEwiT5MGh8JjeAhVBnOAKHVgUA_4QFjADegQICRAB&usg=AOvVaw1gjJqlrXjH1vYJwjzwvhrI (https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.dtic.mil/dtic/tr/fulltext/u2/a284623.pdf&ved=2ahUKEwiT5MGh8JjeAhVBnOAKHVgUA_4QFjADegQICRAB&usg=AOvVaw1gjJqlrXjH1vYJwjzwvhrI)
Title: Re: Teardown: Standard Resistors
Post by: BradC on October 22, 2018, 01:47:19 am
By the look of it, we all could have built something like this L&N 4221-B ourselfs

I will just say that years of hard won experience (across many different disciplines) will indicate that looks can often be deceiving. I'm sure there is an awful lot more to it than grabbing a spool of manganin and soldering on some binding posts when it comes to any post assembly treatment to manage long term accuracy and drift.

Of course I could be wrong.
Title: Re: Teardown: Standard Resistors
Post by: Vgkid on October 22, 2018, 01:54:08 am
By the look of it, we all could have built something like this L&N 4221-B ourselfs

I will just say that years of hard won experience (across many different disciplines) will indicate that looks can often be deceiving. I'm sure there is an awful lot more to it than grabbing a spool of manganin and soldering on some binding posts when it comes to any post assembly treatment to manage long term accuracy and drift.

Of course I could be wrong.
The link I posted goes into some of the processes involved.
Title: Re: Teardown: Standard Resistors
Post by: Mr. Scram on February 17, 2019, 11:58:10 pm
I remember from some of Dave's videos that high grade decade boxes tend to look similar, but that they appear to be trimmed after assembly. Crude looking isn't necessarily crude.
Title: Re: Teardown: Standard Resistors
Post by: calija on February 24, 2020, 02:01:04 pm
Dear all,

I am new and I got resistor fluke 742A-1.
One of the pin starts to moving on - can you help me to show how I can open this type of resistor.

Best regards!!!!
Title: Re: Teardown: Standard Resistors
Post by: MegaVolt on February 24, 2020, 02:06:40 pm
help me to show how I can open this type of resistor.
https://www.eevblog.com/forum/metrology/teardown-standard-resistors/msg891672/#msg891672 (https://www.eevblog.com/forum/metrology/teardown-standard-resistors/msg891672/#msg891672)
Title: Re: Teardown: Standard Resistors
Post by: calija on February 24, 2020, 02:12:06 pm
yes I find this pictures but I can t find screws  |O !!!
Title: Re: Teardown: Standard Resistors
Post by: MegaVolt on February 24, 2020, 02:14:57 pm
yes I find this pictures but I can t find screws  |O !!!
It looks like they are under the sticker on the front panel.
Title: Re: Teardown: Standard Resistors
Post by: MegaVolt on February 24, 2020, 02:18:52 pm
Or, back under the black elements there are just 4 of them.
Title: Re: Teardown: Standard Resistors
Post by: calija on February 24, 2020, 02:20:38 pm
Yes, you are right  :-+!!!!

 :palm: what a stupid solution!!!!

Thanks!!!!
Title: Re: Teardown: Standard Resistors
Post by: calija on February 24, 2020, 02:22:29 pm
Under sticker  :-DD!!!!
Title: Re: Teardown: Standard Resistors
Post by: HighVoltage on February 24, 2020, 03:33:27 pm
Under sticker  :-DD!!!!
Can you post some pictures?
Title: Re: Teardown: Standard Resistors
Post by: calija on February 25, 2020, 08:22:59 am
here it is!!!!
Title: Re: Teardown: Standard Resistors
Post by: Dr. Frank on February 25, 2020, 08:51:42 am
Hello and welcome, calija!

You're really new here.. we all would like to see pictures of the interior, of course  :popcorn:
Would you mind taking some of the interior construction and post them here, please?

Frank
Title: Re: Teardown: Standard Resistors
Post by: calija on February 25, 2020, 08:52:47 am
that's all folks!!!!
Title: Re: Teardown: Standard Resistors
Post by: calija on February 25, 2020, 08:57:19 am
I see internal picture in this blog
https://www.eevblog.com/forum/metrology/teardown-standard-resistors/ (https://www.eevblog.com/forum/metrology/teardown-standard-resistors/)
first page!!!!
Title: Re: Teardown: Standard Resistors
Post by: HighVoltage on February 25, 2020, 09:31:38 am
Thank you for the pictures calija!

I am surprised to find the screws under the metallic label.
The is not an easy production step, since the label is squeezed to the housing by the binding posts.
Very interesting.