Read reply #1 again. Your task is simplified if time period is constant.
To do this, I have implemented a loop while () that reads the measurement and I have used the delay function (12.5) (where 12.5 ms is 1/80) at the beginning of each cycle to simulate sampling times. Is it correct my way of work?
Please post your code.
You don't want to be using delay() for timing. The 12.5 ms readings can be triggered from either a software or hardware timer.