Thnaks Steve,Andy,Raghu,Kai
I want to make it clear that I have already design an instrument in which I am calcualting power factor from zero crossing detector(ZCD) and measuring time between V an I ZCD. The voltage and current RMS value are measured by using precision rectifier and converting V and I sine wave in to DC and then measuring this DC by AD. I am unsing 12 bit AD MAX187 for this application. Then in software I am calculating all electrical parameter. The work in most of the cases. But at the places where there is lot of electrical noise (distortion) it give incorrect results, perticular in phase angle measurement. Some time there is Thyristor control load which distort current waveform and ZCD fails. Also in such cases there is lot of inaccuracy in voltage and current RMS value. That why I want to avoid ZCD. I want extract all parameter from numerial methode like digital filters so that it can work of any type of load and wave shape.

suyash
Note thanks raghu for offering the code