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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