Re: OT: volt and current (ALSA sound recording frustration)

[Andrew Reid <reidac@bellatlantic.net>]

On Friday 28 November 2008 14:10, lee wrote:
> On Fri, Nov 28, 2008 at 06:59:06PM +0000, Tzafrir Cohen wrote:
> > A voltmeter has two connectors and shows the potential differences
> > between them.
> >
> > This is unlike an Ampermeter that shows the current flowing through it.
>
> If you have a multimeter that can measure voltage or current, both
> modes are basically the same. The difference is only in where most of
> the current flows.
>
> Is it even possible to measure a mere potential?

  You mean, in principle?  Of course.

  Put your two wires of unknown potential difference at 
opposite ends of an evacuated tube.  Arrange the geometry
so that the electric field between them is linear in space.
You can do this by hooking them up to big plates and putting
the plates close enough together, making basically a 
vacuum capacitor.

  Then, shoot charged particles into the space between
the electrodes.  From the way they deflect, and their
charge-to-mass ratio, you can deduce the electric field 
strength, and from that, the potential difference between 
the electrodes giving rise to the field.

  Alternate method:  Place a piezoelectric crystal of
known characteristics in the gap, and measure the 
change in shape.  From this, you can deduce the degree
of polarization, and thus the externally-applied field,
and from that, again, the voltage difference between
the electrodes.

 				-- A.
-- 
Andrew Reid / reidac@bellatlantic.net