V7-45 electrometer made in Belarus (welcome in attoamps world)

[Kleinstein]

The bi-morphs are probably quite brittle. I would prefer the full metal core tuning fork like resonator with added piezos at the outside and close to the fixed (lower) end. This would provide some initial shielding. There can still be some coupling through the resistance and ground side current - so there may be a kind of offset. The cross coupling could be measured off resonance.

The magnet version would also have some electrical coupling: there are eddy currents in the reeds and thus a variable voltage. In the ideal case this would likely be zero on average, but no longer if not perfectly parallel or symmetric.

[MadTux]

What's the reason for gold wire on those relays?
Thermoelectric effects doesn't matter on electrometer, AFAIK and I don't see much reason why gold is better for low leakage either.

[bsw_m]

What's the reason for gold wire on those relays?
Thermoelectric effects doesn't matter on electrometer, AFAIK and I don't see much reason why gold is better for low leakage either.

Reliable contact for ultra-low currents.

[MK]

Lets continue cleanAmp-porn hour!!!

Be careful with atto-amps! When i measure femto-amps with my B2985A i use not too much cleanser, but atto-amps need a TONS cleanser....

High purity grade Methyl-alcohol pack

I hope your lab is well ventilated, dont want you needing a white stick.

[doktor pyta]

"За здоровье"

[exe]

Looks better to me. Lighter background better matches the front panel.

[Vgkid]

Agreed on the display looking better.

[Echo88]

  Sexy

[chekhov]

Is there any proof that this device is indeed going to provide metrology-grade pure sinus ?
I'd expect some electro-mechanical stabilizer if of course input voltage it less-polluted.

[Vgkid]

Looking forward to seeing if there is any affect, nice job so far.

[bsw_m]

For those who can read in Russian. Interesting article.

[bsw_m]

Measuring the noise shelf V7-45 after rebuild DRK-6, but, this is not end of reworking my V7-45.
I have some plans for modification of this device.

[tchicago]

My V7-45 awaiting delivery a new modding stuff: 

Where did you order those? I want a similar set K580xx or 580xx and РФ2/5's too, for my РАДИО-86РК that I recently made. I have a bunch of leftover blank PCBs, so I'd make another one fully original ceramic. I checked ebay and olx.ua and did not find anyone selling those

[tchicago]

Where did you order those? I want a similar set K580xx or 580xx and РФ2/5's too, for my РАДИО-86РК that I recently made. I have a bunch of leftover blank PCBs, so I'd make another one fully original ceramic. I checked ebay and olx.ua and did not find anyone selling those

On avito.ru trade platform.
But most seller don't speak english.


Link to my preferred seller: https://www.avito.ru/moskva/kollektsionirovanie/mikroprotsessory_sssr_serii_580_1672307644 (slow response, high price, but high IC's quality)

Thanks! Language will not be a problem. The shipping might be...

[drghl]

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 have a question to the B7-45 unit: Can you tell the capacitance value of the current sensor?

[drghl]

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)?

[bsw_m]

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.

[drghl]

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?

[bsw_m]

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.

[bsw_m]

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/

[TimFox]

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.

[drghl]

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.

[TimFox]

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

[bsw_m]

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.

[drghl]

... 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.