Just a thought...
Hi Roger,
I don’t know how to separate the voltage reference grounds on PIC’s ADC channels. It would be interesting to find out if it is possible.
You could move the Zener to the “high side” (32VDC) and then measure between GND and the 25 Zener’s anode. This would subtract the 25 Volts. You would still need to “voltage divide” the ~7V, to fit the limits of the PIC ADC.
Both of these schemes cause a small error introduced by the tiny drop on the 0,1 Ohm shunt resistor.
You could reference both…. at the 0,1 Ohm shunt resistor / Battery junction.
Then, make your 10x gain amplifier-op circuit an inverter to get a positive voltage out, for the “current” channel. You would have to isolate the PIC’s power supply and have a plus/minus supply for the op-amp.
-Adam-
Ohm it's not just a good idea... it's the LAW !
Bookmarks