HI,
I WANT DO DEVELOP POWER METER BY USING PIC. SENS INPUTS ARE FROM CT(I),AND TRANSFORMER(V).IT IS USED TO SENS FREQUENCY AND VOLT,CURRENT.BUT HOW DO CALCULATE W,VA,PF,VAh.
PLEASE HELP ME.

 

VA is easy. simply Voltage x Current
Assuming you have a sine wave current, to calculate W you need to know the phase shift between voltage and current. If you are not having sine wave current it gets more complicated as you would need to take LOTS of samples to calculate the area of your current wave form and you still will need to know the phase shift. Don't know if your microcontroller is capable of doing so.

Once you have found VA and W you can easily determine PF.

Cheers

 

You can buy one (based on a PIC) here... I have one, and it works well.