V7-45 electrometer made in Belarus (welcome in attoamps world) - Page 1
Forum section: electronics / general

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 09, 2020, 10:16:41 am
content: I bought this tool and am waiting for delivery.This is a very rare device. According to my calculations, only about 600-1000 of these devices were produced. And it's great luck that I was able to find this device. Even if not complete.I may be wrong, but I think this is the most sensitive instrument on Earth that can be put on a table. And which does not require vacuum, low temperatures and other things for operation.Datasheet says, that this instrument can measure 1E-17A, with resolution 1E-18. Tests show that this device is really capable of measuring currents 1E-18A, and have sensitivity in 3E-19A...1E-19A range.This instrument have first production date is 1986 year. Design of this instrument was carried out by MNIPI (Minsk Research Institute of Instrument Construction).Before this instrument MNIPI also have other old instrument that can measure 1E-17A: V7-29, that have start production in 1972 year.Some information about architecture of this instrument.The current measurement in this instrument is based on current integration. Amplifier in current integrator is chopper stabilized.All other info: restoration, photo, tests and others is coming soon. After delivery this instrument.Historical:This device became possible thanks to the work of such a person as Konstantin Sergeevich Shuklin. The electrometric unit and DRK-6 were developed by him. The appearance of the DRK-6 was preceded by almost 30 years of work.The chief designer of this device is Glubokiy Iosif Andreevich.

author: Vgkid
author_rank: Super Contributor
timestamp: August 09, 2020, 11:00:55 am
content: Looking forward to this.

author: TimFox
author_rank: Super Contributor
timestamp: August 09, 2020, 04:09:46 pm
content: I do not read Russian, but from the technical article I assume that this uses the same basic idea as the American classic Cary vibrating-reed electrometers. According to a Varian advertisement from 1971https://pubs.acs.org/doi/pdf/10.1021/ac60304a744it could "detect" currents down to 10 aA.

author: TiN
author_rank: Super Contributor
timestamp: August 09, 2020, 04:41:38 pm
content: Not quite, it's using PMT for current integration (or rather charge, with conversion). So it does require vacuum and have a tube inside

author: TimFox
author_rank: Super Contributor
timestamp: August 09, 2020, 06:01:24 pm
content: In the article, is that a photo-multiplier (with photocathode) or an electron-multiplier in the envelope with the vibrating structure? The Cary had an external head for the vibrating reed, but not connected to an external vacuum chamber. Besides construction quality, these devices need a low-noise amplifier after the reed, but can exploit a phase-sensitive detector at a frequency above the 1/f noise corner of the amplifier.

author: NWerner
author_rank: Contributor
timestamp: August 09, 2020, 08:34:21 pm
content: electron multiplier.

author: MadTux
author_rank: Frequent Contributor
timestamp: August 09, 2020, 09:12:07 pm
content: InterestingBut then it probably can only measure current at a certain voltage drop, since it needs a certain voltage potential to strip electrons off the cathode in electron multiplier tube?Not like Keithley with transimpedance amplifier that has essentially zero voltage drop.Also, how good is the linearity of a electron multiplier tube? A few % at best, I guess?Vibrating-reed electrometers are the coolest, IMO ;-)

author: Bud
author_rank: Super Contributor
timestamp: August 09, 2020, 09:38:30 pm
content: What are the practical applications for this sort of test gear?

author: MadTux
author_rank: Frequent Contributor
timestamp: August 09, 2020, 09:42:29 pm
content: Anything with ions/electrons, like measure beam current in mass spectrometer, electron microscope....Also nice to select low leakage JFETs for repairs, leakage and material resistance in general...Probably also chemistry, pH elctrodes and other electrochemical stuff works best with no current...

author: TimFox
author_rank: Super Contributor
timestamp: August 09, 2020, 09:58:19 pm
content: Electron multipliers are useful for detection of various charged particles, including electrons and ions. The linearity is good at low levels, until the increased output current disturbs the voltage distribution along the channel or in the discrete voltage divider network.

author: exe
author_rank: Unknown
timestamp: August 10, 2020, 02:50:04 pm
content: Waiting for tear down

author: RoGeorge
author_rank: Super Contributor
timestamp: August 16, 2020, 08:35:01 am
content: Quote from: shodan@micron on August 16, 2020, 04:12:07 am- To clean small items against residual charge leaks, for example a very low current IC, does the order matters? Whater with soap first, then alcohol, or alcohol followed by water with soap cleaning, which order do you use, please?- Another question, can a normal pressured air can (gas duster) be used instead of high pressure nitrogen?

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 17, 2020, 11:16:44 am
content: Simplified work principle the amplifier in external integrating unit:Amplifier use chopper topology: as input modulator work DRK-6 (dynamic resonance capacitor model 6, or a more familiar term in English vibrating resonance capacitor), after the AC amplifier, demodulator on jfet and DC amplifier.For highest range this amplifier work as classical TIA, and use in their feedback 100MOhm microwire precise resistor.On other ranges amplifier work as integrator with capacitors in their feedback. This solution improved the thermal stability of the amplifier and eliminated Josephson noise.At all this amplifier have low noise (not more 3aA p-p, typically 1aA p-p), low offset - typically 3aA, and have "rock-solid" temperature and long-therm stability.

author: MadTux
author_rank: Frequent Contributor
timestamp: August 17, 2020, 12:01:21 pm
content: Quote from: shodan@micron on August 17, 2020, 01:03:47 amLike a beta source with 600 decays/s. Or alpha with 150 decays/s

author: guenthert
author_rank: Frequent Contributor
timestamp: August 20, 2020, 01:00:07 am
content: Quote from: shodan@micron on August 17, 2020, 01:03:47 amThose sapphire insulatorwithinthe space restricted triax connectors were nice (thanks for sharing), but if I understand correctly the magic happens in those external blocks. Is there a schematic of those available on-line?

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 20, 2020, 06:34:19 am
content: Quote from: guenthert on August 20, 2020, 01:00:07 amYou right! Schematic is not available on-line, but some posts ago I describe the principles of work.

author: NWerner
author_rank: Contributor
timestamp: August 21, 2020, 03:52:48 pm
content: Athttps://ampnuts.com/you mention the possibility of MEMS vibrating caps.When I first learned about vibrating capacitor the same thought occured to me.As the technology for MEMS vibrating capacitor should be fairly mature since >10yearsI wonder why we dont see any MEMS based electrometers. There are some scientificpapers - but thats it. A vibrating caps electrometer has the potential for- lower input current- robust input protection- reasonable costWhere is the catch?Does anyone has any insight about what might be the obstacles to the realization of such an instrument?

author: Kleinstein
author_rank: Super Contributor
timestamp: August 21, 2020, 04:47:31 pm
content: One tricky part is the surface potential: The capacitor will show some offset voltage that can depend on the temperature an gas composition. So while there is some input chopping action, there can still be some offset-drift.I am not so sure that MEMS would really help here. Mems tend to use electrostatic drive and this can give some direct coupling. There is also a possible insulation problem if all in in a single piece of silicon.I don't see a large advantage from small size on the mechanical side, if the resonator part is made right. Going higher in the frequency and smaller in size also has disadvantages. So the classical cm size capacitor has it's advantages.Modern MEMS parts tend to be quite small and high in resonance frequency.

author: NWerner
author_rank: Contributor
timestamp: August 21, 2020, 05:21:27 pm
content: Often MEMS accelerometers are encapsulated in vacuum to minimize damping while in resonance. SiO2 as an insulator is pretty good but could prove a weakness when compared to ptfe or sapphire especially with those tiny dimensions??

author: branadic
author_rank: Super Contributor
timestamp: August 23, 2020, 07:59:10 am
content: Where do you see zepto amps?1 pA (pico) = 1e-12 A1 fA (femto) = 1e-15 A1 aA (atto) = 1e-18 A1 zA (zepto) = 1e-21 A1 yA (yocto) = 1e-24 ASo you look at 100 aA resolution, not 100 zA.-branadic-

author: branadic
author_rank: Super Contributor
timestamp: August 23, 2020, 09:19:38 am
content: Ups, my fault.-branadic-

author: Kleinstein
author_rank: Super Contributor
timestamp: August 23, 2020, 03:34:56 pm
content: With the capacitor charge method there has to be a integrator reset from time to time. This could cause trouble of some kind. Some cosmic ray or radioactive decay could also cause spikes in the current. With just 2 spikes it is a little hard to tell.The method of getting the derivative of the integrator voltage would be sensitive to some DNL errors of the ADC.It looks a little like the readings are averaged over quite some time. So the fast side (e.f. be low some 10 or maybe even 100 seconds) of the Allan variance may just reflect the averaging. It does not make much sense to measure below aA in 0.1 second. Errors in the form of 2 large spikes is not that suitable for using the Allan variance.

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 23, 2020, 03:40:34 pm
content: Quote from: Kleinstein on August 23, 2020, 03:34:56 pmAfter integrator this instrument have differentiator and ADC after it. So, ADC DNL is not big trouble. But differentiator must have good linearity.

author: TimFox
author_rank: Super Contributor
timestamp: August 23, 2020, 05:04:15 pm
content: The isolated spikes: could they be decay alphas from materials or impurities (e.g. boron)?

author: Kleinstein
author_rank: Super Contributor
timestamp: August 23, 2020, 06:47:20 pm
content: Are those step like smaller jumps (e.g. 0.8 hours in the 1st log) the errors from the auto zero ?I would expect the Auto zero and also the integrator reset to use mechanical contacts of some kind. There is a chance to have some contact problems, especially if not used much for a long time. Even with mechanical switches there could be some kind of charge injection when opening the switch. Details one when and where the contact opens can make a difference and thus cause some instability.Impurities / radioactive decay could be an issue, but why boron ? It is usually heavy isotopes that show alpha decay, like impurities in the solder or maybe radon gas.

author: TimFox
author_rank: Super Contributor
timestamp: August 23, 2020, 07:17:43 pm
content: Boron 8, 9, and 12 have alpha-decay products. This usually happens due to incident neutrons, since the isotopes have very short half-lives.

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 23, 2020, 10:59:12 pm
content: Since at the moment the restoration work on my NK4-1 calibrator (which can performance verification of V7-45) has been completed and a long process of preliminary testing for stability of operation (general, not metrological) has begun. I now have time to work on the restoration of my B7-45. Analysis of the power supplies revealed small dead capacitors as expected. But the fact that large capacitors are completely alive after 31 years was became bit of a surprise for me. The small capacitors in the power regulators were replaced with the new Epсos long life capacitors.So, about spikes, I think this integrator reset process and charge injection from relays work.

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 26, 2020, 07:44:16 am
content: In my BVI DRK-6 turned out to be dead. I made an attempt to restore it. Seems to work.The coils were in a cliff. It turned out to be restored, since the break was near the contacts, and not inside the coils.Also one BELVAR employee confirmed that coil breakage in DRK-6 is a frequent problem.Some tests in the BVI recovery process. (10fA current test and zero offset test)In first photo on the top of БЭМ(electrometric unit - part of the BVI, contained commutator, DRK-6 and first stage of the AC amplifier) installed NK4-1 differentiator D1.On second photo zero offset current with capped input.

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 28, 2020, 11:22:17 am
content: First test for extra low current measurement capabilities after DRK-6 repair.Zero current check and 20 aA current feed from NK4-1 calibrator (using differentiator №3).First photo - zero current. (NK4-1 in "reset" state)Second photo - 20aA current feed from NK4-1 (NK4-1 in "run" state)Third photo - NK4-1 differentiator on the top of the V7-45 external integrating unit..

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 28, 2020, 09:09:44 pm
content: 10aA and 15aA tests.

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 29, 2020, 01:09:14 pm
content: Mini teardown review of the electrometric unit. Sorry, speaking on Russian language. This is my 2nd unit.The unit before has semi-disassembled, this is part of the preparation for restoration.

author: MadTux
author_rank: Frequent Contributor
timestamp: August 29, 2020, 01:48:30 pm
content: As far as I understand, the thing in the middle is the vibrating reed electrometer stage?Round things on the outside are the relays to switch resistors for transimpedance amplifier for current measurement or capacitors for charge measurement?Can the vibrating reed electrometer piece disassembled any further? Is it mechanical or MEMS type?

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 29, 2020, 02:02:03 pm
content: Quote from: MadTux on August 29, 2020, 01:48:30 pmSo, thing in the middle is resonance vibrating capacitor, acts as input modulator.Quote from: MadTux on August 29, 2020, 01:48:30 pmYes this is 5 relays, relays switch the input, one 100MOhm resistor, that using in 1E-7 and 1E-8 ranges. Amplifier in this ranges working as classical TIA.On lower ranges in feedback using capacitors. Amplifier in ranges 1E-9....1E-15 works as current integrator.Quote from: MadTux on August 29, 2020, 01:48:30 pmThe resonance vibrating capacitors is mechanical type with magnetic field drive. (used 4 coils). This capacitor (DRK-6) was designed in 1978 year. At that time, MEMS was not yet in use.In future I'm disassemble the resonance vibrating capacitor. I'l try to restore it.

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 29, 2020, 02:46:01 pm
content: Micro teardown of the DRK-6. Sorry for my bad English.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 29, 2020, 03:58:03 pm
content: The construction of the vibrating capacitor looks really nice and simple. It should also be rather robust. I would expect the 2 drive coils to be directly connected in series (parallel would work too, but thicker wire and series should be easier). Similar the sense part would likely also just give 1 signal.What is actually broken ?The obvious "defect" could be from alignment of the input plate, so that plates may touch or get too close. After mounting it would likely need some adjustment of the alignment.The resonance frequency of individual units may be slightly different. It may need some adjustment in the driver to the individual vibrating capacitor unit. With the sense coils chances are one could get away without adjustment of the frequency, but one may still need an amplitude adjustment.

author: bsw_m
author_rank: Frequent Contributor
timestamp: August 29, 2020, 05:07:34 pm
content: So, coils really connected in series.About broken:Bent output capacitor plates and stationary dynamic capacitor plate...

author: notfaded1
author_rank: Frequent Contributor
timestamp: September 01, 2020, 07:26:24 pm
content: I didn't have any trouble understanding your english btw.Bill

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 03, 2020, 06:57:00 am
content: Test for 15 attoamps current generation and measurement. And stability.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 03, 2020, 06:17:04 pm
content: I forgot. In the review of the electrometric unit, I talked about the first stage of the AC amplifier, but I did not show the amplifier itself. Here he is.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 04, 2020, 12:18:34 pm
content: I found a document on generating and measuring attoampere currents in English. I used to post it somewhere, but in Russian.That it

author: notfaded1
author_rank: Frequent Contributor
timestamp: September 04, 2020, 03:21:22 pm
content: One electron, two electron, three electron... four!

author: doktor pyta
author_rank: Frequent Contributor
timestamp: September 05, 2020, 08:46:06 am
content: Have You heard of 'В2-39 нановольтметр' ?It looks like it comes from the same series / manufacturer.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 05, 2020, 09:14:16 am
content: Quote from: doktor pyta on September 05, 2020, 08:46:06 amYes! V2-39 Nanovoltmeter from MNIPI. Have predecessor - V2-38 nanovoltmeter.This nanovoltmeters have noise floor less or equal to 1nV, and have sensitivity 1nV(V2-38) or 0.1nV(V2-39)but according to reviews, B2-38 is less noisy.

author: lukier
author_rank: Unknown
timestamp: September 06, 2020, 10:05:46 am
content: Quote from: bsw_m on September 05, 2020, 09:14:16 amQuick teardown? Maybe separate thread on this V-28?

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 06, 2020, 10:15:30 am
content: Quote from: lukier on September 06, 2020, 10:05:46 amI cannot find this nanovoltmeter yet, it is very rare (V2-39). After I find and purchase this nanovoltmeter, I will definitely start a new topic.

author: lukier
author_rank: Unknown
timestamp: September 06, 2020, 12:38:37 pm
content: Quote from: bsw_m on September 06, 2020, 10:15:30 amSure, but I was thinking about the V2-38 one you have.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 06, 2020, 01:22:29 pm
content: Quote from: lukier on September 06, 2020, 12:38:37 pmSorry, but I have none

author: lukier
author_rank: Unknown
timestamp: September 06, 2020, 02:37:12 pm
content: Ah sorry, I misunderstood your post.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 08, 2020, 11:03:40 pm
content: 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.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 09, 2020, 08:39:49 pm
content: 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.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 10, 2020, 11:02:46 am
content: 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.

author: Vgkid
author_rank: Super Contributor
timestamp: September 12, 2020, 12:03:46 am
content: That rust is not good.

author: TiN
author_rank: Super Contributor
timestamp: September 12, 2020, 03:03:28 am
content: Little rusty, makes project 10 times more fun to repair

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 12, 2020, 03:07:17 pm
content: 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.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 12, 2020, 05:31:40 pm
content: 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.

author: doktor pyta
author_rank: Frequent Contributor
timestamp: September 12, 2020, 07:09:05 pm
content: 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: September 13, 2020, 06:27:53 am
content: 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).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?

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 13, 2020, 06:25:03 pm
content: Quote from: RoGeorge on September 13, 2020, 06:27:53 amIf you can read in Russian. There is patent for that electrometric unit.

author: RoGeorge
author_rank: Super Contributor
timestamp: September 13, 2020, 07:58:44 pm
content: 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?

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 13, 2020, 08:30:54 pm
content: 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.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 16, 2020, 01:11:03 pm
content: Commutator in this instrument have very clean and nice construction!

author: exe
author_rank: Unknown
timestamp: September 17, 2020, 06:58:55 pm
content: Quote from: shodan@micron on September 17, 2020, 02:58:02 pmWhat's the price approximately?

author: Vgkid
author_rank: Super Contributor
timestamp: September 18, 2020, 05:29:45 am
content: Thanks for those, looking forward to the restoration.

author: doktor pyta
author_rank: Frequent Contributor
timestamp: September 18, 2020, 03:08:59 pm
content: 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?

author: Kleinstein
author_rank: Super Contributor
timestamp: September 18, 2020, 04:21:52 pm
content: 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.

author: TimFox
author_rank: Super Contributor
timestamp: September 19, 2020, 02:07:47 pm
content: Is this parasitic current due to chemical reactions, or piezo-electric effects in the stressed Al2O3crystalline sapphire?

author: Kleinstein
author_rank: Super Contributor
timestamp: September 19, 2020, 03:41:26 pm
content: 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.

author: TimFox
author_rank: Super Contributor
timestamp: September 19, 2020, 04:16:04 pm
content: Bulk crystalline sapphire is not piezoelectric, but the broken symmetry at the surface can have piezoelectric effects.

author: exe
author_rank: Unknown
timestamp: September 21, 2020, 10:45:34 am
content: Looks simple. I wonder how difficult it would be to reproduce this device. I guess, the devil is in details, such as calibration.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 21, 2020, 04:34:25 pm
content: Quote from: exe on September 21, 2020, 10:45:34 amThere is not much calibration to go on with the resonator - essential one gain factor related to the amplitude. If used just as a zeroing detector one may not even need that factor to be accurate or even very stable. The setup however seem to have the vibrating part at ground - so the amplitude may matter.One of the tricky parts is getting the amplitude stable and large enough. Very likely the mechanical resonator is setting the frequency. So no forced external drive but more like feedback from the sense part to the drive part and an extra loop to regulate the amplitude. Regulating the amplitude with a high Q resonator can be tricky, as the system reacts slow (seconds) and the driving signal is not just about amplitude but also the phase. It may be still doable in the analog domain, but it can be tricky, especially with the magnetic drive, that is nonlinear with more force when closer to the magnets. So without regulation the amplitude has a good chance to be unstable.I personally would consider a piezoelectric drive (or at least detection) instead of the magnetic. For the amplitude, I would expect that one may get quite some strain at some points, so a careful mechanical design and a quite hard material may be needed to avoid fatigue. If possible to machine I would consider to have the reeds thinner at the top to have less moving mass and higher frequency.If one calculates the accelerations seen at the tips of the reeds, one gets quite impressive numbers.The magnet cores taken apart look interesting with a local magnetic return - so the main carrier part could be non magnetic stainless. I was wondering how they kept the direct magnetic coupling low.

author: TimFox
author_rank: Super Contributor
timestamp: September 21, 2020, 07:18:49 pm
content: How much amplitude of the vibrating plate is required? It may be difficult to obtain with a piezo element.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 22, 2020, 09:14:12 am
content: To get a good conversion factor the capacitance should change significantly. So the plate distance should change significant by something like a factor of 2. So I would expect some 0.5-1 mm amplitude at the tip as a target.A good mechanical alignment could reduce the required amplitude - the plates should be quite well in parallel.The mechanical resonators have a high quality factor (could be at some 100-1000 - in extremes also more) so the amplitude can get quite large compared to the static displacement. So it only needs a static displacement in the 1-10 µm range. Piezos can produce quite some force - however mounting them can be tricky and glue / solder would add damping.I have seen / used at the university lab a piezo driven vibrating optical chopper that got some 5 mm amplitude, though with a much lower frequency and maybe 3 times the length.

author: MadTux
author_rank: Frequent Contributor
timestamp: September 22, 2020, 09:25:14 am
content: Quote from: Kleinstein on September 22, 2020, 09:14:12 amA thin, long piezoelectric element and vacuum inside the vibrating reed capacitor should do the trick. Air resistance of vibrating reed likely degrades Q a lot, especially at high frequency/large amplitude.Without air, it's only the mechanical power dissipation of piezo element, that degrades Q.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 22, 2020, 10:07:16 am
content: The air gives some damping, but one can still get a reasonable high Q. In vacuum I got a Q of slightly over 1 million with a silicon resonator - that is competing with quartz crystals. With metals one usually gets a Q factor more like around 1000-10000 with low damping material. It can be around 100 with high damping materials like cast iron or magnesium. There is also some intrinsic loss in the materials. The usual PZT piezos would likely be glues / soldered to the main metal part - a little like the cheap beepers. For a first test one could do some experiments with such an element and an attached reed for extension.

author: TimFox
author_rank: Super Contributor
timestamp: September 22, 2020, 12:41:22 pm
content: To get larger motion, PZ elements are used as "bi-morphs", where opposite polarity voltage is applied to parallel strips so that one expands while the other contracts (like a bimetal strip in a thermostat), exchanging increased deflection for reduced force. An interesting problem would be shielding the sensitive node of this circuit from the PZ drive voltage.

author: Kleinstein
author_rank: Super Contributor
timestamp: September 22, 2020, 01:05:42 pm
content: 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.

author: MadTux
author_rank: Frequent Contributor
timestamp: September 27, 2020, 12:26:22 pm
content: 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.

author: bsw_m
author_rank: Frequent Contributor
timestamp: September 27, 2020, 12:34:14 pm
content: Quote from: MadTux on September 27, 2020, 12:26:22 pmReliable contact for ultra-low currents.

author: MK
author_rank: Regular Contributor
timestamp: October 01, 2020, 05:30:00 pm
content: Quote from: shodan@micron on September 29, 2020, 12:13:50 pmI hope your lab is well ventilated, dont want you needing a white stick.

author: doktor pyta
author_rank: Frequent Contributor
timestamp: October 01, 2020, 07:17:35 pm
content: "За здоровье"

author: exe
author_rank: Unknown
timestamp: October 03, 2020, 08:36:45 am
content: Looks better to me. Lighter background better matches the front panel.

author: Vgkid
author_rank: Super Contributor
timestamp: October 03, 2020, 08:50:33 am
content: Agreed on the display looking better.

author: Echo88
author_rank: Frequent Contributor
timestamp: October 03, 2020, 11:02:29 pm
content: Sexy

author: chekhov
author_rank: Regular Contributor
timestamp: October 04, 2020, 11:10:24 am
content: 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.

author: Vgkid
author_rank: Super Contributor
timestamp: October 13, 2020, 11:24:54 am
content: Looking forward to seeing if there is any affect, nice job so far.

author: bsw_m
author_rank: Frequent Contributor
timestamp: October 14, 2020, 11:41:41 am
content: For those who can read in Russian. Interesting article.

author: bsw_m
author_rank: Frequent Contributor
timestamp: October 17, 2020, 10:02:56 pm
content: 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.

author: tchicago
author_rank: Regular Contributor
timestamp: October 31, 2020, 05:48:29 am
content: Quote from: shodan@micron on August 22, 2020, 05:49:41 amWhere 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

author: tchicago
author_rank: Regular Contributor
timestamp: October 31, 2020, 06:31:54 am
content: Quote from: shodan@micron on October 31, 2020, 05:51:33 amThanks! Language will not be a problem. The shipping might be...

author: drghl
author_rank: Newbie
timestamp: November 16, 2020, 11:40:01 am
content: 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?

author: drghl
author_rank: Newbie
timestamp: November 16, 2020, 03:26:08 pm
content: 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)?

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 16, 2020, 04:36:53 pm
content: Hello!Quote from: drghl on November 16, 2020, 03:26:08 pmAll good. But "ДК" is Dynamic Capacitor. where I read this document in English and seeing "DC" I think about direct current.Quote from: drghl on November 16, 2020, 11:40:01 amIf 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.

author: drghl
author_rank: Newbie
timestamp: November 16, 2020, 04:49:16 pm
content: All good. But "ДК" is Dynamic Capacitor. where I read this document in English and seeing "DC" I think about direct current.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?

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 16, 2020, 04:54:31 pm
content: Quote from: drghl on November 16, 2020, 04:49:16 pmUnfortunately, datasheet for DRK-6 is not available in any form.Some little info present in internet and patents for previous DRK-2....DRK-5.

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 16, 2020, 06:14:32 pm
content: Quote from: drghl on November 16, 2020, 11:40:01 amI 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/

author: TimFox
author_rank: Super Contributor
timestamp: November 16, 2020, 06:49:04 pm
content: 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.

author: drghl
author_rank: Newbie
timestamp: November 16, 2020, 08:59:27 pm
content: Quote from: TimFox on November 16, 2020, 06:49:04 pmIn this old PHILBRICK article they call it "vibrating capacitor" too. Nowhere a chopper. thanks for clarification.

author: TimFox
author_rank: Super Contributor
timestamp: November 16, 2020, 10:17:52 pm
content: 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

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 16, 2020, 10:40:04 pm
content: 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.

author: drghl
author_rank: Newbie
timestamp: November 17, 2020, 08:49:06 am
content: Quote from: TimFox on November 16, 2020, 10:17:52 pmThe 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.pdfSome people in the Netherlands later worked on a successorhttps://www.researchgate.net/publication/288839878_ACCURATE_VIBRATING_REED_ELECTROMETERObviously there have also been ideas to make the vibrating capacitor in MEMS Technologyhttps://core.ac.uk/download/pdf/143890037.pdfAmong 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.

author: drghl
author_rank: Newbie
timestamp: November 17, 2020, 03:14:47 pm
content: Quote from: shodan@micron on November 16, 2020, 05:05:22 pmI 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.

author: bsw_m
author_rank: Frequent Contributor
timestamp: November 17, 2020, 07:50:19 pm
content: Quote from: drghl on November 17, 2020, 03:14:47 pmSo, 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-13AThis device is digital, but build on logic, and don't have GPIB.

author: drghl
author_rank: Newbie
timestamp: November 17, 2020, 09:01:51 pm
content: Quote from: shodan@micron on November 17, 2020, 05:05:03 pmRussian 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.

author: bsw_m
author_rank: Frequent Contributor
timestamp: June 06, 2021, 02:15:29 pm
content: 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 myNK4-1.As a result, checking with theNK4-1lower 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 displayFor 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)

author: bsw_m
author_rank: Frequent Contributor
timestamp: October 03, 2021, 03:59:53 pm
content: A small modification of the external measuring block was made. The Zener diode was replaced with a more stable one in the offset compensation circuit DRK-6. Modification result:

author: Kleinstein
author_rank: Super Contributor
timestamp: October 03, 2021, 04:47:54 pm
content: That is a huge difference for a relatively small change.I don't think the very short time (well less than instrument time constant) part is really relevant. The "stability" is more the instrument rol off and not real.

author: justanothername
author_rank: Regular Contributor
timestamp: October 03, 2021, 08:06:12 pm
content: Quote from: TimFox on November 16, 2020, 10:17:52 pmAttached is an advertisement of a TR-84 from Takeda Riken.Today I've read the article from Shodan about the V7-45:https://ampnuts-com.translate.goog/v7-45/?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=de&_x_tr_pto=nui... really impressive.

author: serg-el
author_rank: Regular Contributor
timestamp: October 05, 2021, 10:19:59 pm
content: More complete description of the electrometer

author: serg-el
author_rank: Regular Contributor
timestamp: October 06, 2021, 12:35:55 pm
content: The 1991 catalog also contains a description of the TR8411, and its accessories and theory of operation.https://cloud.mail.ru/public/cHj8/KqkYY6W9gA high resolution ,1000 MB !!!https://cloud.mail.ru/public/gWqE/sUf6LTmqt

author: Vtile
author_rank: Super Contributor
timestamp: October 12, 2021, 07:08:20 pm
content: Correct me if I'm wrong, but isn't all separation actions creating a charge injection or at least charge fluctuation. As the charge field reforms again from mono to binary structure? Edit. As Interfacial phenomena in boundary double layer.Quote from: Kleinstein on August 23, 2020, 06:47:20 pm

author: Vtile
author_rank: Super Contributor
timestamp: October 13, 2021, 06:24:54 pm
content: I must say that that DRK-6 flux capacitor is fascinating piece of engineering.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 13, 2021, 06:30:31 pm
content: Quote from: Vtile on October 12, 2021, 07:08:20 pmThe is some charge fluctuation apon switching. One would have at least the so capped reset noise of sqrt(kTC). With the integrator the switching is not not done very often, especially at low current. With metallic parts there should be not much additional fluctuations.