Author Topic: V7-45 electrometer made in Belarus (welcome in attoamps world)  (Read 22174 times)

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Offline lukier

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #50 on: September 06, 2020, 02:37:12 pm »
Ah sorry, I misunderstood your post.
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #51 on: September 08, 2020, 11:03:40 pm »
I tried to estimate the input impedance of my B7-45 in voltmeter mode. The first attempt to do this using a 1T resistor was unsuccessful.
The second attempt I made using a 1pF air capacitor with sapphire insulator.
Its discharge rate turned out to be 1mV / 10min.
If I am not wrong  that the input impedance is about 6E+17 ohms.
 
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Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #52 on: September 09, 2020, 08:39:49 pm »
Noise and stability of my V7-45. Capped input. 1E-15A range. About 8 hours data collection.
First image - Allan variance.
Second - raw data, big spikes from integrator/differentiator reset.
« Last Edit: September 09, 2020, 09:22:27 pm by bsw_m »
 
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Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #53 on: September 10, 2020, 11:02:46 am »
Further investigation of my instrument revealed 2 problems.

One - long settling after integrator reset, but this is not very big issue.

The second is the change in the measured current readings over time, which in fact makes the last discharge insignificant. Despite the gradual increase in the instrument readings from the beginning of the cycle, after the establishment and until the end of the cycle, the instrument error is within the specification.

I think this effect may be due to the DA of the integrating capacitors.
I will investigate this effect in more detail and may be able to improve it.

On first graph, big spikes is integrator reset. And start new measurement cycle.
Second graph - more detailed one measurement cycle.

« Last Edit: September 10, 2020, 11:12:58 am by bsw_m »
 
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Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #54 on: September 10, 2020, 11:23:35 am »
Thank You for your confirmation.
 

Offline Vgkid

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #55 on: September 12, 2020, 12:03:46 am »
That rust is not good.
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline TiN

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #56 on: September 12, 2020, 03:03:28 am »
Little rusty, makes project 10 times more fun to repair  :)
YouTube | Metrology IRC Chat room | Let's share T&M documentation? Upload! No upload limits for firmwares, photos, files.
 
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Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #57 on: September 12, 2020, 03:07:17 pm »
This is real pain.
Time will tell if this DRC-6 can work again.
According to some insider information, tuning the DRK-6 was very difficult and could only be done by one person. The design of the DRK-6 looks quite simple, but alas, there are a lot of nuances. And alas, they are no longer recognizable, the documentation was destroyed, and the developer of this capacitor is no longer alive. And there is no one to ask.
As far as I know, 6 original measuring devices were developed for tuning and checking the characteristics of this capacitor. But what they measured, what they were, and how the DRK-6 was tuning / checked - there is no information.
I will also try to restore my second killed DRK-6, but I have no illusion of success.

And our sellers are really not good people, under the guise of a normal product they try to deceive and sell complete trash. (
It is very difficult to find such a device in an adequate condition. And into which they did not climb with crooked hands and totally did not kill him.
« Last Edit: September 12, 2020, 03:09:31 pm by bsw_m »
 
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Online Kleinstein

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #58 on: September 12, 2020, 05:31:40 pm »
There are probably a few tricky points with the vibrating capacitor part. Target should be getting a stable amplitude and about the same amplitude on both sides. If everything is symmetric there should be 2 modes of vibration, the wanted one with the opposite phase on both sides and one at a slightly lower frequency with same phase on both sides. The magnetic excitation should mainly excite the wanted mode, but if not fully centered, the other mode could be excited too. The 2 modes are probably very close in frequency(e.g. ~ 1 Hz) , so it may be not so easy to separate them. This can interfere with amplitude regulation.
Best chance would probably be to make sure the excitation is symmetric, likely coarse tune mechanical and than maybe fine tune with a resistor in parallel to one of the coils.

Another tricky point could be that an external magnetic field would lower the frequency of the wanted mode and possibly bring them even closer together. However I am not sure how strong this effect is. In the extreme case one may be able to run it as a parametric oscillator. The force would be proportional to the square of the field.
The detection part may also couple magnetically and the square law would require some bias field.

The next higher modes would than be at some 6.6 times the frequency, so high enough that they should not interfere.

I have some experience with smaller similar resonators.

I don't like the resonator construction very much, I would have used some extra common part to make it more like a classical tuning fork and this way get more frequency separation and less coupling to the fixed end.
 
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Online doktor pyta

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #59 on: September 12, 2020, 07:09:05 pm »
Interesting article about MEMS reed electrometer: 'Room-Temperature Sensing of Single Electrons Using Vibrating-Reed Electrometer in Silicon-on-Glass Technology'
DOI: 10.1109/LED.2018.2876506
+ paste DOI number here: https://sci-hub.st/

Contains coparision with Keysight B2987A.
 
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Offline RoGeorge

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #60 on: September 13, 2020, 06:27:53 am »
Interesting, I didn't expect to see sharp metal edges, including a sharp tip left from the wire snipping (can be seen in the pic, the sharp tip at the end of the horizontal gold wire).   :o

Seems interesting to me because I always thought electrons tend to fly away through sharp tips/edges, and leave the boundary.

Shouldn't be better (in terms of charge leakage) with all the parts rounded?

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #61 on: September 13, 2020, 06:25:03 pm »
Interesting, I didn't expect to see sharp metal edges, including a sharp tip left from the wire snipping (can be seen in the pic, the sharp tip at the end of the horizontal gold wire).   :o

Seems interesting to me because I always thought electrons tend to fly away through sharp tips/edges, and leave the boundary.

Shouldn't be better (in terms of charge leakage) with all the parts rounded?

If you can read in Russian. There is patent for that electrometric unit.
 

Offline RoGeorge

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #62 on: September 13, 2020, 07:58:44 pm »
Sorry, I don't speak Russian, I can at most recognize a few letters, simply because some decades ago I (and many others here, in Romania) happened to use Russian IC's for TTL equivalent chips, memories, EEPROMS, etc.  I was into Z80 Spectrum "business" back then.   :)

Not saying that the manufacturing with those sharp edges is bad, or that the sharp terminations is impacting the performances.  Just genuinely asking why there is no rounding of the sharp edges, and trying to learn more.

As a non Russian speaking is hard for me to translate those pics, is there any particular key passage or thing I should know in order to learn more, please?

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #63 on: September 13, 2020, 08:30:54 pm »
In fact, these points do not affect the noise level of the instrument. Moreover, taking into account the size of these elements, it is very difficult to make rounding on them.
For reference, the wire diameter of the contact block is 0.16mm.
 
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Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #64 on: September 16, 2020, 01:11:03 pm »
Commutator in this instrument have very clean and nice construction!
 

Offline exe

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #65 on: September 17, 2020, 06:58:55 pm »
Production of new Sapphire insulators.... negotiations are underway with the plant[/li][/list]

What's the price approximately?
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #66 on: September 17, 2020, 11:31:40 pm »
I think price is probably comparable to the price at which the sapphire is bought by MNIPI.
I know the prices for sapphire at which MNIPI buys, but I don't want to share it on public.
« Last Edit: September 18, 2020, 02:47:11 am by bsw_m »
 

Offline Vgkid

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #67 on: September 18, 2020, 05:29:45 am »
Thanks for those, looking forward to the restoration.
If you own any North Hills Electronics gear, message me. L&N Fan
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #68 on: September 18, 2020, 01:06:52 pm »
Hmmm... Sapphire in ultrasonic.
At the end, you might end up with a battery, not an insulator.  :)  And it may take some time for the parasitic current to stop generating.
 

Online doktor pyta

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #69 on: September 18, 2020, 03:08:59 pm »
It seems that there are two kinds of sapphire used by the manufacturer: both are transparent but one is colorless and one is violet.
Am I right?
Does anyone know what are differences between them in terms of resistance, other properties?

Online Kleinstein

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #70 on: September 18, 2020, 04:21:52 pm »
The colors are from minute impurities. Likely no big effect on the conductivity, though chances are it does not get better.

Sapphire wafers are actually no very expensive - I found them as low as $15 for a 1 in (25 mm) diameter, though only thin. Also optical window are not all that expensive. With a laser they can also make precise holes and get you odd Mickey mouse shape parts.  So I don't think the Sapphire is the difficult or very expensive part any more.
 
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Online TimFox

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #71 on: September 19, 2020, 02:07:47 pm »
Is this parasitic current due to chemical reactions, or piezo-electric effects in the stressed Al2O3 crystalline sapphire?
 

Online Kleinstein

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #72 on: September 19, 2020, 03:41:26 pm »
Pure sapphire should not be piezoelectric . I would more expect things like dielectric absorption and maybe surface effects, where the surface layer changes to a new equilibrium. There is also a chance to have surface charge on isolators that can persist for a long time. The slow decay can cause a background current.
 

Online TimFox

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #73 on: September 19, 2020, 04:16:04 pm »
Bulk crystalline sapphire is not piezoelectric, but the broken symmetry at the surface can have piezoelectric effects.
 

Offline bsw_m

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Re: V7-45 electrometer made in Belarus (welcome in attoamps world)
« Reply #74 on: September 19, 2020, 06:34:11 pm »
it need more time... 1-3 days or so...
Or some weeks for settling to 0 aA ;)
 


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