On Fri, 10 May 2002, Herbert Graf wrote:

>How about using a hall effect type of system? I've never tried it but I
>think it should work. TTYL

I tried and it works fine if you use bare linear Hall sensor bridges that
have a non-iron chip grid support, because if they do then you have
hysteresis problems and you will misread a lot at low current. It appears
that all inexpensive bare bridge Hall sensors made for motor and sensor
applications have a magnetisable chip grid. The remanent magnetisation of
the best is 2.5 times Earth field. WHY??!! FYI a straight wire with about
3A through it makes a field comparable to the Earth field at 1 inch
distance (very roughly) so your lower measuring limit with such a simple
arrangement and considering what I wrote above (hysteresis) will be 6 to
10A. Of course you can use a specialised Hall current probe which comes
readily for your amps range for a price.

Peter

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