Peter,
<...> and logging it on a SD card. the problem is, after some time it stop logging, and i can press reset on my Uno and it´s starts again.
The performance of SD recording is vastly affected by the SD card characteristics. In the data logging that I designed for my friend's Europa, I decided to off-load the entire process to a dedicated uC... A $2 decision that solved potential headaches.
http://forum.arduino.cc/index.php?topic=154864.msg1160998#msg1160998
Ray