On Wednesday 30 January 2008, Douglas A. Tutty wrote:
quoted text
> On Thu, Jan 31, 2008 at 02:11:54AM +0100, ropers wrote:
> > On 30/01/2008, Douglas A. Tutty <dtutty@porchlight.ca> wrote:
> > > She's also sensitive to lower-freq and even DC electric fields
> > > (e.g. a battery with no external current flow) but in a different
> > > manner.
> >
> > I don't understand what you mean by "DC electric fields" in this
> > context. A battery without any current flow is just a container
> > with chemicals inside. No electricity, no magnetic field, nothing.
>
> Sure it does.  It has a static electric field since there's a voltage
> potential between the two poles.  Electricity doesn't just appear
> once you put a meter onto a battery; current yes, potential no. 
> Potential is, well, potential.  Also, no batteries are electrically
> perfect so they all contain some capacitance that can then interact
> if placed in an occilating EMF (IOW, they can act like an antenna).
>

Voltage is, by definition, potential difference. You can burry two 
plates of metal a meter apart from each other and get voltage. When you 
subject those plates to an increased electro-magnetic field, you get 
more voltage.

http://chem.ch.huji.ac.il/history/bain.html

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> It all seems strange.  Yes, I know the physics of it, but before this
> happened, it was something that you paid a lot of money to build a
> detector for, for research.  
>

Yes and no. Doing it "right" in a research environment means you'll pay 
extrodinate amounts of money for accurate and sensitive measurement 
equipment (as well as a specialized buildng to use the equipment 
without interference).

*BUT* doing it on the cheap is perfectly possible. One of the most 
fiendishly clever things I've ever seen done was by a "Bring-Up 
Engineer" (i.e. the guys who debug the initial "bring-up" of newly 
created circuit board designs) at a poor startup. A very 
mysterious "something" was causing a component to behave erratically 
when the power was on but the component tested out perfectly on all of 
the prototypes. Since there was no way we could afford proper 
equipment, the guy took a very thin copper wire, wound it around a 
pencil a few times, separated the coil a bit so it wasn't touching 
anywhere, then attached a ohm-meter. He ran it over the running board 
to figure out if the problem was due to significant interference 
causing the part to malfunction. Sure enough he found it, as well as 
the source, made a make-shift faraday cage around the source and 
everything worked.

Debugging your wife (if you pardon the analagy) is really not much 
different; the goal is simply finding and eliminating the sources of 
the interference.

-JCR