Author Topic: V7-45 electrometer made in Belarus (welcome in attoamps world)  (Read 21638 times)

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Offline drghl

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #100 on: November 16, 2020, 03:26:08 pm »
Hello Sir, special greetings to little town in Russia from little village in Germany. This answer is already very helpful. I will try to make a spice model of the DRK-6 with it. For clarity I translated your document into English. Maybe you have a minute to check if it is correct?

By the way, what is exactly the DC (ДК)?
« Last Edit: November 16, 2020, 03:33:39 pm by drghl »
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #101 on: November 16, 2020, 04:36:53 pm »
Hello!
Maybe you have a minute to check if it is correct?
By the way, what is exactly the DC (ДК)?
All good. But "ДК" is Dynamic Capacitor. where I read this document in English and seeing "DC" I think about direct current.

I have a question to the B7-45 unit: Can you tell the capacitance value of the current sensor?
If you mean capacitance in feedback. Feedback air capacitor that used in most sensitive ranges (1E-12 and less) is 11.5pF typically.
Own capacity of DRK-6 is 15pF typically.
« Last Edit: November 16, 2020, 04:43:30 pm by bsw_m »
 
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Offline drghl

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #102 on: November 16, 2020, 04:49:16 pm »

All good. But "ДК" is Dynamic Capacitor. where I read this document in English and seeing "DC" I think about direct current.
[/quote]
Yes, first I thought of dynamic capacitance ("Dynamische Kapazität") but now as we talk about it I think the author means the "chopper capacitor", the center stripe with the mechanically resonating ground stripes in the DRK-6.

Is this document available somewhere in completeness?
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #103 on: November 16, 2020, 04:54:31 pm »
Is this document available somewhere in completeness?
Unfortunately, datasheet for DRK-6 is not available in any form.
Some little info present in internet and patents for previous DRK-2....DRK-5.
« Last Edit: November 16, 2020, 04:58:39 pm by bsw_m »
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #104 on: November 16, 2020, 06:14:32 pm »
Greetings to the Forists. I am investigating current metrology since more than a year now with enhanced intensity and only a few weeks ago found this forum here after seeing a youtube video of the B7-45 aA meter.

I also recommend looking at my topic about probably the first electrometer from MNIPI. Which is also built on a dynamic capacitor (DRK-3)
https://www.eevblog.com/forum/metrology/vk2-16-very-old-analog-electrometer-from-minsk/
« Last Edit: November 16, 2020, 08:23:30 pm by bsw_m »
 

Offline TimFox

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #105 on: November 16, 2020, 06:49:04 pm »
An old American term for a vibrating capacitor is “wobbulator”, often used to frequency-modulate a VHF oscillator at a constant modulation frequency.  Usually, “chopper” refers to a switch (mechanical or solid-state) used for DC stability.  The Cary electrometers used the term "vibrating reed" for their capacitor.
« Last Edit: November 16, 2020, 07:35:18 pm by TimFox »
 
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Offline drghl

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #106 on: November 16, 2020, 08:59:27 pm »
An old American term for a vibrating capacitor is “wobbulator”, often used to frequency-modulate a VHF oscillator at a constant modulation frequency.  Usually, “chopper” refers to a switch (mechanical or solid-state) used for DC stability.  The Cary electrometers used the term "vibrating reed" for their capacitor.
In this old PHILBRICK article they call it "vibrating capacitor" too. Nowhere a chopper. thanks for clarification.
 
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Offline TimFox

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #107 on: November 16, 2020, 10:17:52 pm »
Philbrick made amplifiers using varactor diodes for modulated capacitors, and they compare that technique with mechanically vibrated capacitors in that article.  At the time of the article, I believe the most popular mechanically vibrating capacitor units on the American market were the Cary "vibrating reed" electrometers.  Here is an advertisement for a later version of the Cary unit:  https://pubs.acs.org/doi/pdf/10.1021/ac60304a744
« Last Edit: November 16, 2020, 10:19:28 pm by TimFox »
 
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Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #108 on: November 16, 2020, 10:40:04 pm »
I see the sensitivity of the Cary 401 and VK2-16 is comparable and is in the range of tens of attoamperes. As well as all other specifications are comparable. Moreover, both devices are built on dynamic capacitors, and as I understand it, they were developed at about the same time.
 

Offline drghl

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #109 on: November 17, 2020, 08:49:06 am »
... I believe the most popular mechanically vibrating capacitor units on the American market were the Cary "vibrating reed" electrometers.  ...
The Cary (then later VARIAN) 401 was introduced in 1967 - check it out here: https://worldradiohistory.com/Archive-Electronics-World/60s/1967/Electronics-World-1967-05.pdf
Some people in the Netherlands later worked on a successor https://www.researchgate.net/publication/288839878_ACCURATE_VIBRATING_REED_ELECTROMETER
Obviously there have also been ideas to make the vibrating capacitor in MEMS Technology https://core.ac.uk/download/pdf/143890037.pdf
Among all attempts elsewhere, it seems the B7-45 unit still has its nose ahead. Respect to the developers.

For conveniance, I have attached the PDFs to this post below.
« Last Edit: November 17, 2020, 08:51:44 am by drghl »
 
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Offline drghl

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #110 on: November 17, 2020, 03:14:47 pm »
...
No problem, see here:
http://offtop.ru/dustyattic/v20_686383_8.php
Page 25
I loaded the document down. These are 190+ pages of a manual. Plenty of stuff to read and I am slow. The last time Iwas reading russian texts is 40 years ago. Will take some time. Thanks for the link.
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #111 on: November 17, 2020, 07:50:19 pm »
...
No problem, see here:
http://offtop.ru/dustyattic/v20_686383_8.php
Page 25
I loaded the document down. These are 190+ pages of a manual. Plenty of stuff to read and I am slow. The last time Iwas reading russian texts is 40 years ago. Will take some time. Thanks for the link.
So, if You have big interest, You may fun by read manual and schematics diagrams for predecessor of V7-45.
This metter is V7-29 which was developed in 1976. https://yadi.sk/d/y5kjpVAvJyrNkQ (sorry for poor quality for this manual).
This device comparable to V7-45 in sensitivity, but had an upper range of 1E-13A
This device is digital, but build on logic, and don't have GPIB.
« Last Edit: May 11, 2021, 01:40:26 pm by bsw_m »
 

Offline drghl

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #112 on: November 17, 2020, 09:01:51 pm »
...
Earlier  i'm say here: "Atto-amps - good chance to start learn Russian. It's very exciting!"
It's true  >:D
Russian is the 4th of the most common languages in Europe. In Germany there live around 3 million Russian speakers. In my village maybe 300.
I volunteered in Russian classes in Gymnasium (High school) because my parents spoke Checkish and Polish fluently (refugees from Checkoslovakia) but I decided to rather study the language of the "big brother". With a background in Latin the Russian systematics was not a challenge. However to find a native language speaker for conversation practicing was impossible. During a trip to Berlin I tried to chat with a Russian soldier who was standing there not far from the "Brandenburger Tor" but he refused to talk to me. Later during trips to Japan with Aeroflot I had the opportunity to talk to plane and hotel personnel but they were quite repelling, maybe because I belonged to the class enemy. Cold war was dominating the scenery.
Today, it is much easier because the civil society no longer experiences the pressure of politics, which is good. Nontheless my Russian knowledge got very rusty and I am now enjoying freshing it up.
 
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Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #113 on: November 18, 2020, 06:52:10 am »
Keithley and Keysight need not worry, MNIPI & BELVAR will no longer release such electrometry monsters as V7-45 or V7-57/2. The workshops where DRK and electrometers were produced were finally destroyed in 1997. All documentation, as far as I know, has also been destroyed.
I still managed to find some scraps of documentation for 5 years of searching, but this is no more than 0.1% on the topic discussed here.
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #114 on: June 06, 2021, 02:15:29 pm »
Some upgrade and tuning for my V7-45.
First, i'm replaced the S5-50 100Meg 0.1% resistor, that out of spec (+0.29%) in electrometric module to precision microwire resistor MRH 100Meg tolerance 0.1%
In fact they have resistance 100Meg -0.04%, I'm compensate this with S2-29V in series resistor 42KOhm.
As result, TIA ranges (1E-7 and 1E-9) tight aligned. And also tight aligned higher bands for integrator. Where this resistor using to calibrate integrating capacitors.
TIA ranges check:

Higher integrating range check:


Second. Where I'm restored with a complete disassembly and assembly the dynamic resonance capacitor DRK-6. The integration capacitor which is installed on it was changed their capacitance, and meter need calibrate this capacitance. The calibration of this capacitor is carried out by the method of supplying a charge 1E-10C and setting the switches in the instrument. For supply a charge I used differentiator from my NK4-1.
As a result, checking with the NK4-1 lower ranges wich using this capacitor showed full compliance with the specification with a good margin.

Lower integrating ranges check:


And last point check, where readings should correspond to 20 ±8 lsb.


Third.
As you can see, my instrument has been replaced with a new backlit display. The display was purchased from the Display Unitary Enterprise.
But backlit module is DIY. To build backlit module I'm use the light guide and leds from cracked "slim" notebook display.
DIY backlit module with new display

For powering this backlit module I'm build the voltage multiplier and constant current drive based on jfet. That mounted on outguard powersupply board.


Now the project for the modification and study of this wonderful instrument can be considered closed and I started work on the next interesting project. Soon I will start publishing results on it.
(Spoiler: this is very hard restoration projects for V7-57/1 and V7-57/2 electrometers)
« Last Edit: June 06, 2021, 03:12:58 pm by bsw_m »
 
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