> 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 sensors have optimum gauss ranges and some twiddling
with the magnetic field may be needed. In some cases this means
adding a concentrator such as a block of iron, in other cases it
means stepping-down by a transformer such as a wound ferrite.
The main aim is to optimise the field strength range for the sensor

I've not used the linear UGN devices so can't comment on them
as ammeter sensors. The only uses I've ever had for them have
been as detectors and switches

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