In order to determine the power consumption of an unknown load circuit both its current and voltage must be determined, as well as any phase difference between them. The current measurement is made non-intrusively by using a Rogowski coil, which picks up the magnetic field created by the current through either the supply or the return wire. The coil outputs a voltage which is proportional to the rate of change of current through the wire. This voltage is integrated and sent to a PIC18 microcontroller for further processing and storage. The PIC also implements a voltmeter via the onboard A-D converter to determine the voltage dropped across the load. The current and voltage signals are analyzed to determine the phase difference, and the actual rms current, rms voltage, power factor, and average power are computed. These values are displayed in real-time on an LCD screen, and all data can be uploaded to a computer for graphical analysis
