Soviet standard resistors?

[dmmguy]

Hi there...

How they performs?

https://www.ebay.com/itm/271930151419



Thanks

[alm]

There are some comments within the first 26 posts here: https://www.eevblog.com/forum/metrology/teardown-standard-resistors/. Seems quality is somewhat variable. User HighVoltage seems to like them.

[dmmguy]

There are some comments within the first 26 posts here: https://www.eevblog.com/forum/metrology/teardown-standard-resistors/. Seems quality is somewhat variable. User HighVoltage seems to like them.

I couldn't fine anything on the first link to posted. The second one has some references. Thank you so much!

[alm]

Look more closely:

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.

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.

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.