michael_x : My initial idea was to use a rheostat and what you say does sound similar to that. Might as well give it a shot will I can get specs for the indicators.Meanwhile, I found this. http://www.allaboutcircuits.com/vol_3/chpt_8/7.htmlAny Comments about this tranconductance circuit ? Really appreciate the help!
It does not matter what resistance value Rload is, or how much wire resistance is present in that large loop, so long as the op-amp has a high enough power supply voltage to output the voltage necessary to get 20 mA flowing through Rload.
Any Comments about this