[Vwdiesel] Different GP monitoring cct stuff

[Smith, Michael]

Hi Dieselheads ! Clatter clatter clatter (marbles in a glass bowl)

Well, I finally got my 5 Allegro Hall-Effect current sensors (ACS750xCA-050)
in the mail here today and tried them out. (free samples btw !)
Output voltage swing is very slight.  For 2.5A of current (I used a 12v/100w
light bulb) @ ~12VDC, the output is about 3.2V....
Even w/o any current being drawn (lightbulb off)  the output is about 2.5V
According to the spec sheet, even at 10A (what a GP might draw) I am
probably only looking at a very slight increase....aprox 3.5V I think.
(they also require a Vcc of 5Vdc....I can use 16Vdc max, but the outputs are
very squirrely to say the least, even @ 12Vdc)

If I were to put one inline with each GP, I'd still be down into the mV
range of variance w/o using some kind of op-amp cct to boost the overall
output swing.

I suppose we could say, if I read *anything* over the resting output voltage
of 2.5V, then we have current flow, thus the GP *is* working.

They are rated @ 50A each, so I could stick just one in the main line, just
after the fuse and would see a 2.5V-4.0V (40A) swing if all plugs were
working, however the voltage swing is so slight you probably wouldn't notice
if only 3GP's were working.  Of course, this theory is all out the window on
the second attempt to crank,  when your battery is weak, or you're cranking,
the dome light is on....anything to change the Vcc from its
nominal(original) 12Vdc before you touch the key !

Hmmmmmmmm...maybe I'll just go back to the big honkin' blocking diodes and
LED's (Mark the Miser)....or a cheapie $10 multimeter and a 4P switch like
Hagar... Was it Val who used Hall-Effect sensors in the past? (I forget)

11 pages- Data Sheet http://www.allegromicro.com/datafile/0750-050.pdf 
Main page http://www.allegromicro.com/sf/0750/

Mike in NB, Canada