Author Topic: V7-49 electrometer produced in Minsk, Belarus. (Read 26179 times)

bsw_m · « **on:** June 25, 2020, 02:06:35 pm »

Some weeks ago I'm bought new 30 year old-stock electrometer V7-49. This instrument designed by MNIPI and produced by BELVAR. Start production year is 1986. End production - I don't known.
This instrument is lowest end electrometer by MNIPI, but not bad at all.
This instrument has all sapphire insulation in input circuits.
By official documentation this instrument can measure current range 1fA - 10mA and voltage range 10uV - 200V with input impedance greater than 100TOhm (Measured by me input impedance has 1.3POhm, but I think this is can be more. At this time I'm don't have methanol to properly wash the insulators).

After some repair (replace all electrolytic capacitors, cleaning insulators and some other work) I'm take the performance verification. (I'm not calibrate instrument)
For voltage I'm use V1-18 as source and cannot calculate error in all ranges (in relation to V1-18)
For current verification I'm use V1-18 as voltage source and 1TOhm resistor.

Rated current 500aA:
0.0005pA.JPEG на ixbt.photo:

Rated current 1fA:
0.001pA.JPEG на ixbt.photo:

Rated current 1pA:
1pa.jpg на ixbt.photo:

And rated current 10pA:
10pa.jpg на ixbt.photo:

Do you accept me to the ampnuts club?

P.S. Teardown of this instrument: https://yadi.sk/d/uUZoiU154grgFg

For 1TOhm resistor, big thanks to Shodan_x

ramon · « **Reply #1 on:** June 25, 2020, 02:38:13 pm »

accepted !

Is that a KPC104A with Voskhod/Kaluga logo?
Who has datasheet? Generic FET or secret weapon component from cold war?

(Saving part number on ebay in case it someday it pops there.)

schmitt trigger · « **Reply #2 on:** June 25, 2020, 02:44:44 pm »

I Attempted to open the provided hyperlink, and while it opens a Yandex website, all of the image links are broken.

https://yadi.sk/d/uUZoiU154grgFg

bsw_m · « **Reply #3 on:** June 25, 2020, 02:47:22 pm »

From home I'm do reload photos to other hosting.

bsw_m · « **Reply #4 on:** June 25, 2020, 03:37:34 pm »

Quote from: schmitt trigger on June 25, 2020, 02:44:44 pm

I Attempted to open the provided hyperlink, and while it opens a Yandex website, all of the image links are broken.

So, I'm reloaded photos to google drive: https://drive.google.com/drive/folders/1XB6oVjcwRhqEmF3nmEniEFkNRFCoNIB6?usp=sharing

bsw_m · « **Reply #5 on:** June 25, 2020, 03:39:23 pm »

Quote from: ramon on June 25, 2020, 02:38:13 pm

accepted !

Is that a KPC104A with Voskhod/Kaluga logo?
Who has datasheet? Generic FET or secret weapon component from cold war?

(Saving part number on ebay in case it someday it pops there.)

Here is

guenthert · « **Reply #6 on:** June 25, 2020, 04:11:56 pm »

Neat pictures of an outstanding instrument, thanks for sharing.

I'm a bit puzzled by the large number of what I presume are TTL logic chips and even some very specialized chips on the (again, I presume) logic board. I guess those were due to constraints of the market in soviet times. The analogue board is (of course) just magic -- are circuit diagrams still available?

Kudos on the calibration. Creating a stable current of precisely 1pA is no small feat.

bsw_m · « **Reply #7 on:** June 25, 2020, 04:17:40 pm »

Upper board is digital board, based on 580VM80 cpu (Russian analog to i8080)
Lower board is analog board, and power supply regulators.
Schematic is here, but sorry for low quality.

Big metal case IC on center of analog board - is high voltage hybride ampifier IC. In schematic is DA15.

TimFox · « **Reply #8 on:** June 25, 2020, 05:09:57 pm »

I can see the pdf file for the schematic, but I can't open the jpg file for the specs.
I assume VT8, the dual FET, is the critical component--do you know any details about it?
In the close-up photo of the hybrid IC, the socket resembles a ceramic socket for a transmitting tube. How large is the IC?

RoGeorge · « **Reply #9 on:** June 25, 2020, 05:26:54 pm »

Quote from: ramon on June 25, 2020, 02:38:13 pm

accepted !

Is that a KPC104A with Voskhod/Kaluga logo?
Who has datasheet? Generic FET or secret weapon component from cold war?

(Saving part number on ebay in case it someday it pops there.)

What's that 8 petals component?

bsw_m · « **Reply #10 on:** June 25, 2020, 05:33:56 pm »

Quote from: TimFox on June 25, 2020, 05:09:57 pm

I can see the pdf file for the schematic, but I can't open the jpg file for the specs.
I assume VT8, the dual FET, is the critical component--do you know any details about it?

This is selected KPS104A dual jfet (very old from 197x). Selection procedure present in instrument manual.

Quote from: TimFox on June 25, 2020, 05:09:57 pm

In the close-up photo of the hybrid IC, the socket resembles a ceramic socket for a transmitting tube. How large is the IC?

In this instrument socket is plastic. Ic have long side is about 40-45mm.

bsw_m · « **Reply #11 on:** June 25, 2020, 05:37:40 pm »

Quote from: RoGeorge on June 25, 2020, 05:26:54 pm

What's that 8 petals component?

This is heart of this instrument - electrometric commutator (8 relays). Sapphire insulators and AuNi alloy for contacts with percentage 95Au 5Ni.

schmitt trigger · « **Reply #12 on:** June 25, 2020, 05:43:53 pm »

Quote from: bsw_m on June 25, 2020, 04:17:40 pm

Upper board is digital board, based on 580VM80 cpu (Russian analog to i8080)
Lower board is analog board, and power supply regulators.

The board material for the digital and analog boards appears to be different?
Or perhaps the digital board does not have a solder mask? That would explain the color difference.

Quite a beauty!

bsw_m · « **Reply #13 on:** June 25, 2020, 05:51:04 pm »

Quote from: schmitt trigger on June 25, 2020, 05:43:53 pm

Or perhaps the digital board does not have a solder mask? That would explain the color difference.

Right!

jaromir · « **Reply #14 on:** June 25, 2020, 07:02:49 pm »

Thank you for sharing the pictures and schematics, very intriguing! It's refreshing to take a look at this instrument, totally unknown to me

The schematics has no part numbers, I can mostly guess the ICs functions, but there is mysterious DA21, in two logical blocks DA21.1 and DA21.2 Could you tell me what is this part, please, or perhaps share datasheet?
Also, what parts are DA11-DA13 and DA5/DA7? That looks like a part of integrating or mark-space ADC, along with DA21.2 (I guess resistor network?) and DA5/DA7 (reference switches).
Reference circuit looks to be build around DA6 and DA10 and resistor network (?) in DA21.1. What part is VD29?

bsw_m · « **Reply #15 on:** June 25, 2020, 07:21:29 pm »

Quote from: jaromir on June 25, 2020, 07:02:49 pm

Thank you for sharing the pictures and schematics, very intriguing! It's refreshing to take a look at this instrument, totally unknown to me

The schematics has no part numbers, I can mostly guess the ICs functions, but there is mysterious DA21, in two logical blocks DA21.1 and DA21.2 Could you tell me what is this part, please, or perhaps share datasheet?
Also, what parts are DA11-DA13 and DA5/DA7? That looks like a part of integrating or mark-space ADC, along with DA21.2 (I guess resistor network?) and DA5/DA7 (reference switches).
Reference circuit looks to be build around DA6 and DA10 and resistor network (?) in DA21.1. What part is VD29?

You right DA21- this is resistor network 313NR220 http://www.155la3.ru/datafiles/k313nr2xx.pdf
DA11 - KR140UD1408A (Lm308)
DA12,13 - comparators - K554SA3A (LM311)
DA5 - KR590KN4 (HI5043)
DA6 - KR140UD1408A
VD29 - KS190D 9V at 10mA Temperature coefficient ±0,0005% / degree and 0,02% / 5000h

bsw_m · « **Reply #16 on:** June 26, 2020, 05:51:16 am »

I'm reloaded specs for KPS104. The first time, for unknown reasons, the file was attached with an error.
Now all it's ok.

coppercone2 · « **Reply #17 on:** July 05, 2020, 05:24:51 am »

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exe · « **Reply #18 on:** July 05, 2020, 10:37:16 am »

Wow, that's impressive. How much does it cost? I found it on sale in one place, they want ~$1200 or thereabout... Other shops don't tell the price, or don't work with individuals.

HighVoltage · « **Reply #19 on:** July 05, 2020, 10:43:57 am »

Interesting comparison with the Keysight electrometer.

Echo88 · « **Reply #20 on:** July 05, 2020, 11:38:21 am »

The following document contains B2985A current reversal settling time measurements/noise. Maybe its of interest in regard to comparison against other electrometers.
https://arxiv.org/pdf/1808.08881 Page 3

bsw_m · « **Reply #21 on:** July 05, 2020, 12:01:05 pm »

Real cost is about 450$. If attempt deep searching (waste time), can buy this instrument about 300$ "NOS" condition.
Used unit without kit can buy 100$

RoGeorge · « **Reply #22 on:** July 05, 2020, 01:24:35 pm »

Quote from: shodan@micron on July 05, 2020, 01:19:05 pm

I've scanned books. Unfortunately quality of paper is too bad.

After some post processing i create more reliability images, but it's still bad...

V7-49 user manual: https://ampnuts.com/data_pub/V7-49_book1.djvu
V7-49 Schematic, Bill of material, diagnostics procedures: https://ampnuts.com/data_pub/V7-49_sch_bom.djvu

Djvu reader: https://windjview.sourceforge.io
Raw data from scanner: https://ampnuts.com/data_pub/V7-49_books_source.rar

Thank you!

I was just looking for specs, because the first pic from the OP is so intriguing.
500 attoamps will mean slightly less than 10 electrons each millisecond.

TimFox · « **Reply #23 on:** July 05, 2020, 03:12:55 pm »

When measuring such low currents, the bandwidth of the electrometer will be correspondingly low, far below 1 kHz.
Of course, current in a conductor is not discrete flow of discrete electrons as in a vacuum tube (current in a conductor does not exhibit shot noise).
However, if we were measuring the shot current in a "saturated" diode (no space-charge limit), and wanted 1% statistical error, (Poisson statistics) we would need 10,000 electrons per measurement.
At 500 x 10^-18 A = 3125 Q_e/sec, that would require a measurement time of 3.2 sec, which seems reasonable for an electrometer at such a miniscule current.
Another poster here quoted a settling time of 12 to 15 sec for 1 fA full-scale on a Keysight electrometer, while another measured about 1 sec at 0.1 to 1 fA on a Russian unit.

TimFox · « **Reply #24 on:** July 05, 2020, 03:53:55 pm »

Oops, my typo! The Keysight measurement was done at 1 pA, not 1 fA, and that was not full-scale. The settling-time values quoted for the Russian unit are surprisingly short.


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Author Topic: V7-49 electrometer produced in Minsk, Belarus. (Read 26179 times)

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