Teardown: Standard Resistors

[HighVoltage]

Measurement results for these standard resistors (See attached photos).
All standard resistors are out of tolerance.
They also have a very high TCR (about 10ppm/K)
Conclusions - these standard resistors are interesting artifacts from the past, but nothing more.

What instrument is it that you using to measure these resistors in your pictures?

[bsw_m]

What instrument is it that you using to measure these resistors in your pictures?

Measurement International 6242B Resistance bridge.

[manganin]

All standard resistors are out of tolerance.

The marked "Class" should be considered as an initial adjustment accurary rather than the long term stability. The tight tolerance comes from the very easy trimming of the bulk metal foil element - compared to the Krasnodar wire wound standards, which were generally more stable.

I think the resistors have performed surprisingly well, age considered.

Also the direct measured value doesn't tell the whole truth, you need to include the change of the Ohm as well as the original calibration uncertainty in your calculations.

[Victorman222]

Might be a bit off topic but here is a teardown of a soviet hermetic metal foil resistor S5-61 (С5-61 Cyrillic). There resistors were made with tolerances up to 0.005% and TCR grades 30/20/10/5 ppm/℃ in temperature range from 20℃ to 125℃.
This resistor had two chips but the second "trim" chip was cracked and not bonded. It's a 340R 0.05% 30ppm/C resistor.
The last photo is of a S5-62 resistor, that one is the caseless version, but the ones i got were destroyed by moisture and decomposing foam. The value is 6.42K 0.05%.

[TUMEMBER]

What instrument is it that you using to measure these resistors in your pictures?

Measurement International 6242B Resistance bridge.

Respect if you operate such a machine.
A question like this: do you "check the entrusted material"?
I recently came across something like this on Aliexpress
https://pl.aliexpress.com/item/1005005989851239.html?spm=a2g0o.cart.0.0.11c5452cIMCvgC&mp=1&gatewayAdapt=glo2pol

but I have no way to verify whether what they declare is reality or marketing.
It looks cheaper than the famous Vishay and I am tempted by the 200 ohm, 2 kohm, 20 k ohm, 200 kohm series.

[bsw_m]

but I have no way to verify whether what they declare is reality or marketing.

I don't have these resistors and can't say anything about their performance.

[TUMEMBER]

but I have no way to verify whether what they declare is reality or marketing.

I don't have these resistors and can't say anything about their performance.

Thank you for your answer 

[Kosmic]

What instrument is it that you using to measure these resistors in your pictures?

Measurement International 6242B Resistance bridge.

Respect if you operate such a machine.
A question like this: do you "check the entrusted material"?
I recently came across something like this on Aliexpress
https://pl.aliexpress.com/item/1005005989851239.html?spm=a2g0o.cart.0.0.11c5452cIMCvgC&mp=1&gatewayAdapt=glo2pol

but I have no way to verify whether what they declare is reality or marketing.
It looks cheaper than the famous Vishay and I am tempted by the 200 ohm, 2 kohm, 20 k ohm, 200 kohm series.

Check out this article: "Temperature drift test results of RJ711 and other plastic metal foil resistors" https://www.kechuang.org/t/89682

[TUMEMBER]

What instrument is it that you using to measure these resistors in your pictures?

Measurement International 6242B Resistance bridge.

Respect if you operate such a machine.
A question like this: do you "check the entrusted material"?
I recently came across something like this on Aliexpress
https://pl.aliexpress.com/item/1005005989851239.html?spm=a2g0o.cart.0.0.11c5452cIMCvgC&mp=1&gatewayAdapt=glo2pol

but I have no way to verify whether what they declare is reality or marketing.
It looks cheaper than the famous Vishay and I am tempted by the 200 ohm, 2 kohm, 20 k ohm, 200 kohm series.

Check out this article: "Temperature drift test results of RJ711 and other plastic metal foil resistors" https://www.kechuang.org/t/89682

And thank you, I probably would never have found it on my own. After all the effort of Google translate, his - is it kenji?

Fortunately, there are pictures and it's somehow easier to "understand" 

[Kosmic]

What instrument is it that you using to measure these resistors in your pictures?

Measurement International 6242B Resistance bridge.

Respect if you operate such a machine.
A question like this: do you "check the entrusted material"?
I recently came across something like this on Aliexpress
https://pl.aliexpress.com/item/1005005989851239.html?spm=a2g0o.cart.0.0.11c5452cIMCvgC&mp=1&gatewayAdapt=glo2pol

but I have no way to verify whether what they declare is reality or marketing.
It looks cheaper than the famous Vishay and I am tempted by the 200 ohm, 2 kohm, 20 k ohm, 200 kohm series.

Check out this article: "Temperature drift test results of RJ711 and other plastic metal foil resistors" https://www.kechuang.org/t/89682

And thank you, I probably would never have found it on my own. After all the effort of Google translate, his - is it kenji?

Fortunately, there are pictures and it's somehow easier to "understand" 

The auto translater in Edge says it's "Simplified Chinese". Try this link instead: https://www.eevblog.com/forum/metrology/rj711-foil-resistors-from-china/?action=dlattach;attach=1946766

[C-47]

Adding a recent acquisition to this post, a J.L William 1 Ohm after it made a journey across Australia, where unfortunately it lost quite a bit of oil, question is, which is better, Paraffin or White Mineral Oil (food grade), as both of these are locally available and to what level should it be refilled.
After opening up to inspect the internals as the readings obtained were not stable, it was noted that winding #2 (from top) has been replaced at some time, noticeable due no varnish and newer looking twine, should varnish be applied considering its already oil soaked, if so, any leads on cleaning.
After the coil unit has been out of the body housing for a couple of days the readings have somewhat stabilised using a 4 wire setup into a calibrated HP34401A.
Any advise appreciated. Thanks, Alan.




 

[trobbins]

I would have thought that a transformer grade mineral oil would have been used, due to its high resistance and stable performance and general use in other standard resistor metrology devices (even though a 1 ohm resistance is unlikely to be affected by distributed oil resistance like say a 100k device).

Imho the repair looks like it was done by the manufacturer, given the same wiring foldback technique and some obvious trimming.  I wouldn't think varnishing are the use of non-standard transformer oils is a good path to follow. 

The instability may be more related to the busbar bolting, and soldering of the wire elements to busbaring, but the photos don't really show that continuity region.  What variation were you seeing with the 34401A ?

[C-47]

Thanks for the input, the variation was initially in +/- 100th of an Ohm, but this has since reduced back considerably just using the alligator clips of the leads, probably should be using proper terminal spades. The photo shows the connections, while #2 coil lead looks like its not as good as the others. Will look into transformer oil.

[trobbins]

Ta - that's a better photo for awareness of the electrical joints.

Maybe the variation was thermal EMF related - was it drift or fluctuating ?  You would have 1mA test current, so 1mV FS reading.  Can you confirm acceptable shorted measurement value using test leads to one of the device terminals?  You may be able to log over a day to get a feel for the tempco, given it is now in free air.

It's not easy to get a small commercial quantity of transformer oil in oz - I looked last year.  Perhaps ring around any remaining transformer manufacturer/service/recyclers in your area - they may have a drum out the back.

[C-47]

Ok thanks, will see what I can find re power supply and getting readings, they were fluctuating rather than drifting, I'll see if I can get better connection setup at the end of the 4 wires. Have to be tomorrow as work intervenes.

[guenthert]

Thanks for the input, the variation was initially in +/- 100th of an Ohm, but this has since reduced back considerably just using the alligator clips of the leads, probably should be using proper terminal spades. The photo shows the connections, while #2 coil lead looks like its not as good as the others. Will look into transformer oil.

    The -hp-34401A is a fine bench multimeter, but it's not ideally suited to measure low value resistors.  It's lowest resistance range is 100Ohm, so 100th of an Ohm is only 100ppm of its range which is outside of its comfort zone.  You might get more consistent results with a Kelvin bridge configuration or if you happen to have a stable current source (some 10 to 100mA), use that and measure the voltage drop across the resistor instead.

    And yes, copper spades or bare solid wire should get better connections than alligator clips (which might also introduce fairly high thermal EMF).

[HighVoltage]

If it was really transformer oil inside this resistor, be careful. Old transformer oil can contain polychlorinated biphenyls (PCBs) and other toxic chemicals that can be harmful to human health. If possible, stay away from transformer oil, which is also not needed here at all.

[Gyro]

Here's the definitive standard resistor filling thread, well as definitive as it's got on here anyway...  https://www.eevblog.com/forum/metrology/oil-for-a-leaking-tinsley-standard-resistor/

[Kosmic]

In Fluke Calibration Philosophy in Practice, page 14, they mention "light mineral oil" when describing NBS style resistor:



You're going to laugh, but a cheap source of good quality mineral oil is actually horse laxative 

[C-47]

Thank you to all for input and suggestions, indicates that I have a bit to learn when dealing with low value Ohms, but as this is a hobby to keep me out of the pub at night, wife reckons the pub maybe cheaper.
Anyway a quick reading shows its now in the ballpark of 1 Ohm, will pickup some White Mineral Oil on Monday, any left over I can use to clean the horse out  . Thanks to all, including beanflying, useful input.

[beanflying]

Sweating for the cause. 36C 'outside' and topping 40C in the shack and climbing 

My Williams 0.1 Standard plugged into my 34461A on 4W is there or thereabouts. To hot to move the Quadtech milliohm meter to the bench or to pull mine down for a comparison.

Motivation ceases to the rest of the day.....

[C-47]

Crikey, didn't think it got so hot there, more amber liquid refreshment needed !!