My investigations have revealed that the
B-field ( magnetic field ) around a wire is
approximately B =3D ( N I =B5 )/L .
N =3D number of turns which in this case is one.
I =3D current which for my purposes is a
minimum of one amp.
=B5 =3D permeability which is ~ [10
minus 6] for copper or aluminium.
I am guessing that L is .005 for a
wire one cm in diameter.

Using those values I get a B field of
[2 x ten minus 4 ] Tesla or 2 Gauss.

If I did the calculations correctly, it seems
that an Allegro A1323 linear hall effect sensor
( HES ) (1) should work.  This part has an output of
2.5 mv / G.  I am planning to measure a range
of 1 amp to 200 amps.  Should I make the
HES part of a magnetic ring around the
wire ? The ring would consist of two "C" sections
married to each other sandwiching the HES.
Would steel be a suitable material
given I am measuring DC to 120 Hz ?  Does the
steel have to be laminated ?  Or would a ferrite
ring be necessary ?

After single point calibration , I would like to
see an accuracy of .1% .

(1) ( costs $2 to $.60 depending on quantity. )

Gus
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