> Since I'm not an EE, nor do I even pretend to be, a few questions do
> spring to mind (boing!). Is the torroid that they are talking about used
> to "focus" or "enhance" the already present magnetic field, thereby
> making it easier to sense using the hall effect sensor? And why does
> there need to be wire wrapped around the torroid?

The torroid provides a "low resistance" path form the magnetic flux, thereby
concentrating it into a known geometry.  You now have a circular magnetic
field proportional to the current in the wire under test.  Changes in this
magnetic field can be sensed by any loop of wire inclosing the magnetic
flux.  This effect is often weak for our purposes, so many loops of wire
(the coil) are used to increase the strength of this signal.


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