phase and null automatic detector

[elec1363]

phase and null detector

hi.
i want to make a circuit that can detect phase and null.i dont mean by hand i mean if we connected to electricity can detect phase and null.
can any body help me?

 

[lemouta]

You can use a one-phase PLL to detect the phase of the input voltage or current.

The control algorithm of the PLL can be easily implemented in a DSP or even in a PIC.