Michael said:
Thanks John,
I'm thinking about using a shunt resistor, with a voltage divider either
side fed into a 741 setup as a diff amp. Would that cause any problems?
If you use a shunt resistor, the full scale signal voltage
is small, to begin with, just to keep the resistor power
waste down, so adding a pair of dividers to that, to get the
signal within the common mode voltage range of the 741 is a
step backwards. I'm not saying it can't work, but it is a
hard climb.
An integrated high side sensor chip is handy for when the
shunt is in the positive supply side of the circuit. They
convert the small differential voltage to a current to
ground, that will produce a much larger, but proportional
voltage across a grounded resistor, for the current
controller to use as a process measurement.
Here is one example at random, that you can use to pull key
words from, to look for more:
http://www.maxim-ic.com/appnotes.cfm/appnote_number/746/
Isolated Hall effect current sensors are even more
convenient, since that don't involve the voltage of the
current carrying conductor, at all.
http://www.allegromicro.com/techpub2/current_sensing/bsp_v1_52.pdf