I need to measure and log power, and I want to do it mostly correctly. I would greatly appreciate a listing of the errors I have made in my method. I want to measure (and log) the power output of a small 3-phase generator.
200 w, 24 v, 200 rpm - 3 phase delta generator
200 w buck/boost mppt controller
-10 v to 10 v DATAQ DI-149 data logger
Three 2-ohm, 25 w. resistors
I think logging the voltage is not a problem: measure across the 75k of a 75k/91k pair. The DI-149 can internally convert to rms and log same.
The DI-149 measures the 20 v. span in increments of 0.02 v. My plan was to put a 2 ohm resistor between each of the 3 outputs of the generator and the inputs of the MPPT and log the rms voltage drop and convert to current.
I will multiply the rms voltage and calculated current to arrive at power (and then throw in I^2 R to account for the power lost in the resistor?)?
I would be satisfied with +/- 10% accuracy. Is this going to get me there?