from your experiences what is the easiest wy to calculate the rms current@60hz? Could I just meausre the current at the peak of the cycle and divide by 1.41 and get an accurate number? Or should I have to measure it at multiple points and do a little more math? The only reason I imagine the first wouldn't work is error due to the power factor, could I perhaps figure out the phase angle differance and get a really accurate number? But I guess the second method would be the same ?
AC measurements are not DC measurements.
One difficulty with this method is that unless you are assuming the load will be a pure resistance and can therefore use simple ohms law derived calculations, it's much more difficult then it may seem. In reality you must consider the load impedance which may very well find that current and voltage are not in phase (and either leading or lagging current flow) and therefore one has to deal with the fact that there is an 'apparent' current and a power factor correction need for accurate general purpose AC power consumption measurements. One only has to observer once the AC current draw waveform from a typical PC switching power supply to see the complexity one may need to deal with. I will not try and provide a 'solution' for your use but rather suggest you fully define the measurement application you are aiming for and to then determine if simple ohms law calculations are going to work to met that application requirement. A robust AC power measurement system requires either pretty complex external component/module help or pretty sophisticated DSP type signal analysis looking of both the voltage and current wave forms.
Lefty
