Thanks very much for your help Sarah, I include here the code you asked for in your firs reply.
I tried to work out the instructions in the second post but could not make it work.
I also include the file with the output of what I'm getting with this code. I need to stamp the time of the sample taken as the first column followed by four more columns with the data read from the 4 voltage sensors, and that is what I don't know how to achieve.
Thanks again, your help is most appreciated