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[DPRG] Current Monitoring, boring and with PWM

Subject: [DPRG] Current Monitoring, boring and with PWM
From: DeltaGraph at aol.com DeltaGraph at aol.com
Date: Wed Feb 9 18:03:50 CST 2005

Ed, I did a current sensing project using a shunt resistor 0.005 ohm and a TI 
op-amp designed for such a purpose that required one external resistor for 
scaling purposes.
If you are interested. I will hunt for the part number.

Doing micro-voltage measurements on multiple devices where there may be 
potential differences in "grounds" or "ground plane" spooks me a bit. 

Maybe read up on "high side" vs "low side" current sensing.


Of course shielding is helpful too. One thing I learned is to allow one end 
of shield to float (not be connected) to keep current flow out of shield. 
(Maybe everyone knows this).

I know this stuff is mostly applications of Ohms law (well and some EM stuff 
too - should have taken that class), I guess I have been tricked a few times 
to make me fearful, but not enough to be an expert. 

I did also buy a hall-effect current sensing device from digi-key sometime 
back.
I think current flow of 0 to 10 amps generates 0 to 5v output. About the size 
of a walnut.
I think price was $15 or $25. I should pull that puppy out to see how 
hogasious (sp?) the motors are on the big toy tank that Bill Cole bought -- and I 
bought too.

Ron



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