how to measure line to line voltage in pic micro

[raman00084]

i want to measure line to line voltage that is 440v ac across r and y , y and b , b and r using resistive voltage divider method. i am scalling the voltage to 1.2v max. the problem is if any phase fails the voltage is not becoming to 0 in reduces to half how to solve this using resistive methord

 

[FvM]

I guess you mean disconnect a phase (open circuit) when you say "phase failure"? In this case, two phase-to-phase measurements drop to half the regular voltage. But in a real power supply network, the remaining voltage depends on the connected other load. Even in the open circuit case (no other load connected) you can get different results depending on the voltage divider circuit.

So please specify the measurement circuit and the load completely.