Power factor measurement

Hi all!!!!!!
I am doing my project with PIC 16f876 controller.
I need to measure the power factor of input supply. (i.e cosine of angle between voltage and current.)
can any one suggest a way to do this. I am using MPLAB with assembley code.....
Bye!!!!!!!!!!!!!!!!!

You can measure the voltage directly and use a sense circuit to measure the current. You can just take some samples (you can even undersample), and determine the relationship of the signals using code to do a phase detector.

If you use copmarators to turn your sin waves into square waves then you can use an xor gate as a phase detector. It will output a pulse that is the lenght of the phase difference. Then you can use a PIC timer to time the pulselength.

Brent