Author Topic: Teardown: Standard Resistors  (Read 75829 times)

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Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #25 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.
« Last Edit: March 10, 2016, 04:12:08 pm by zlymex »
 
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Offline Vgkid

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Re: Teardown: Standard Resistors
« Reply #26 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.
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Offline quantumvolt

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Re: Teardown: Standard Resistors
« Reply #27 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.
 

Offline Macbeth

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Re: Teardown: Standard Resistors
« Reply #28 on: March 10, 2016, 09:45:06 pm »
Great thread. On the opposite end of the scale this is my standard resistor  :-DD



A military version of the S102 I think.
 

Offline splin

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Re: Teardown: Standard Resistors
« Reply #29 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.
 

Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #30 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.


« Last Edit: March 11, 2016, 12:02:22 pm by zlymex »
 
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Offline quarks

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Re: Teardown: Standard Resistors
« Reply #31 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
« Last Edit: March 14, 2016, 07:06:38 pm by quarks »
 

Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #32 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:


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
(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.
« Last Edit: March 15, 2016, 07:32:47 am by zlymex »
 
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Offline altaic

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Re: Teardown: Standard Resistors
« Reply #33 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?
 

Offline quarks

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Re: Teardown: Standard Resistors
« Reply #34 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
 

Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #35 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:

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/
 
« Last Edit: March 15, 2016, 06:44:49 am by zlymex »
 
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Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #36 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.
 
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Offline altaic

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Re: Teardown: Standard Resistors
« Reply #37 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/

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] 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.
« Last Edit: March 15, 2016, 11:51:33 pm by altaic »
 

Offline TiN

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Re: Teardown: Standard Resistors
« Reply #38 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).



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



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



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



Schematics of resistor network:



Hi-res photos and test results here in the article.

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.
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Offline Vgkid

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Re: Teardown: Standard Resistors
« Reply #39 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.
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Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #40 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/
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.
« Last Edit: March 16, 2016, 02:39:43 am by zlymex »
 
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Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #41 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.
 

Offline Vgkid

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Re: Teardown: Standard Resistors
« Reply #42 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.
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Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #43 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.
 

Offline TiN

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Re: Teardown: Standard Resistors
« Reply #44 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?
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Offline zlymex

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Re: Teardown: Standard Resistors
« Reply #45 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.
 
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Offline manganin

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Re: Teardown: Standard Resistors
« Reply #46 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?

 
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Offline Vgkid

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Re: Teardown: Standard Resistors
« Reply #47 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.
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Offline Vgkid

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Re: Teardown: Standard Resistors
« Reply #48 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.

Wires joining the copper terminal block to the resistor. They appear to be silver. I sanded off the paint.

Getting medieval. Used a chisel, and a large screwdriver to flex the entire cylinder(breaking the solder seal).

Resistor

close ups

This almost looks like a metal wire, under the right light.

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.
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Offline manganin

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Re: Teardown: Standard Resistors
« Reply #49 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.
 


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