Re: [volt-nuts] Bohnenberger electrometer

In the lexicon of physical devices is an item called an electret. Commercially these are used in capacitive microphones. The common ones consist of polymer sheet that has been annealed in a voltage gradient. An accidental example is the swarf from methyl methacrylate (Perspex, Plexiglass) which

Re: [volt-nuts] Bohnenberger electrometer

A method in use 40+ odd years ago for measuring atmospheric electric fields was to use a slotted rotating disk rather than the rotating cylinder. A matching stationary or counter rotating disk IIRC was used either in front or behind the rotating slotted disk the the sensing disk was behind

Re: [volt-nuts] Bohnenberger electrometer

Yes Hendrik, same principle as the butterfly disk style, but mine use cylinders - the field exposure is radial instead of axial.  Ed ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to

Re: [volt-nuts] Bohnenberger electrometer

Something like this ? https://de.wikipedia.org/wiki/Elektrofeldmeter (German wikipedia as the english entry is less than stellar. They are called field mill.) Best regards Hendrik On 16.03.2018 19:53, ed breya wrote: There is another kind of static electric field meter that was commonly

Re: [volt-nuts] Bohnenberger electrometer

I once made the alu-foil type but also one with a jfet. The gate as "antenna" I have many meters but no static field elctrometer. (and no coulomb meter, never seen one in real life too) I like exotic meters. I  repaired (and modded) a 3 axis fluxgate meter a while back. The owner uses it to

Re: [volt-nuts] Bohnenberger electrometer

On 6 March 2018 at 09:40, Dr. David Kirkby wrote: > Sorry this is not precision voltage measurement, but it is not unrelated. > > As a radio club project, we are building a simple electroscope, with no > active components. The gold leave variety would work, but

Re: [volt-nuts] Bohnenberger electrometer DANGER

Here's a simplistic view that may be sufficient. Some energy (in the form of charge redistribution, which includes current flow) has to come from the capacitor, and some from the input signal, to do the work needed to push the leaf against gravity. When the input signal is removed, some of the

Re: [volt-nuts] Bohnenberger electrometer DANGER

On 8 March 2018 at 07:19, Andre wrote: > Hi, re. capacitors it might be worth mentioning that the normal equation > assumes charge and discharge through a constant current. > What 'normal equation' do you mean? > Don't forget that the equation includes a non linear term so

Re: [volt-nuts] Bohnenberger electrometer DANGER

On 7 March 2018 at 06:29, Andre wrote: > Please be VERY VERY careful. To be honest its far safer to use CCFL > drivers and rectify them with camera diodes in series and the absolute > minimum capacitance for the job, shunted with a high value resistor. > The problem with 2.2 nF

Re: [volt-nuts] Bohnenberger electrometer DANGER

b*t*h! -A From: volt-nuts <volt-nuts-boun...@febo.com> on behalf of ed breya <e...@telight.com> Sent: 07 March 2018 00:11 To: volt-nuts@febo.com Subject: Re: [volt-nuts] Bohnenberger electrometer I looked at that link that Brooke put up about

Re: [volt-nuts] Bohnenberger electrometer

I looked at that link that Brooke put up about Bohnenberger's Electroscope. I don't know what your specific arrangement needs to be, but it appears you need a plus and a minus HV wrt ground in the most general form. If so, then this would mean having to split the voltage of a single cap, or

Re: [volt-nuts] Bohnenberger electrometer

Oops - forgot to mention a detail about microwave oven caps. Sometimes they have built-in bleeder resistors, which would of course spoil this kind of application.  Ed ___ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to

Re: [volt-nuts] Bohnenberger electrometer

For static bias, look up "electret" for ideas on some other possible options. I would recommend against your option 2 capacitor - that's a dangerous amount of energy to store in something that may be fooled around with experimentally. Also, even though it's a lot of C, being electrolytic,

Re: [volt-nuts] Bohnenberger electrometer

Hi Dave: Here's a free on line book "Magnetism and Electricity", 1877 https://books.google.com/books?id=y45PYAAJ=PA169#v=onepage=false Chapter 6 Electroscopes and Electrometers starts on book page 74 (pdf pg 81) but . . Chapter 11 Voltaic, Dynamical or Current Electricity is where paragraph