Take a look at Zetex ZXCT1009 and ZXCT1010 (from Mouser), which may serve your 
needs.  You can put two on them back-to-back to measure bi-directional 
current.

Cheers,
-Neil.



On Tuesday 14 November 2006 05:08, Bob Axtell wrote:
> Marcel Duchamp wrote:
> > Bob Axtell wrote:
> >> Part number is ACS750SCA050 .
> >>
> >> With 5V in, provides a nom 2.5V output with no current
> >> flowing. The chart indicates high accuracy in either direction
> >> out to 50A. Insertion R is 130uOhm. Looks like all I have to
> >> do is to acquire the 2.5V level when powering up (assuming
> >> no current flow).
> >>
> >> The specs are so good I am skeptical. Anybody?
> >>
> >> --Bob
> >
> > Check the specs over the temp range you would be encountering, Bob.
> >
> > I've been looking at the Allegro current sensors but the temperature
> > range spec I've been seeing approaches +/-11% error band.  If that's not
> > a problem for your application, then they have a lot going for them, low
> > sense resistance being number one.
> >
> > One possibility would be to try to temp-compensate them, although it
> > looks like they already have so you might be facing residual errors
> > which are usually 2nd or 3rd order.
> >
> > If you investigate further let us know.
>
> Take a look at the specs NOW. It would beat +/-11% I am sure. I believe
> they are compensating well
> with temperature.
>
> The application is not very precise; the client only wants to detect a
> FLOW of current, so that anything
> over 1 A would be acceptable. And since there can be reverse current
> direction, the old method of
> measuring across a precise resistor won't work either (because it goes
> below ground, requiring a mirror).
>
> I think this is a good choice for only $6 USD. Use a simple PIC10F222 or
> a PIC12F675 to make the
> measurement.
>
> --Bob
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