Tom,
the input voltages will be taken off test points on a locomotive high voltage system.
the volts on the locomotive will go up to 1000VDC but I built a voltage drop circuit to make it a 5 volt max to the Arduino. (hints the *200 for volts)
the millivolt reading is taken off a high voltage shunt on the locomotive where the spec for that is 1mVdc across the shunt = 80 amps. usually maxing at 40mV off the shunt.
so essentially I'm trying to find HP from the watts by /700, in know its supposed to be 746 but the railroad world uses 700.
since I don't have access to a locomotive at home, I built two voltage reduction circuits starting with 5vdc and using pots and resistors.
A1 receiving 4vdc and A7 receiving about 50mVdc.