At first, thank you for your fast answer pylon....My problem is the precission: When I put a refresh time It takes samples good and makes a timestamp that seems good, but when it has 30-150 samples (it depends, and its aleatory-I think), the timestamp goes 1 second after, as I describe in my first post, for example if the sample rate is 30 seconds and begins in second 00: the routine is 00 30 00 30 00 [....]30 00 31. It may be a solution for this (this is an end of studies project, for the university, and I wish to do it perfect). Thank you 