Hi Fernando
Most of the terms used in Data acquisition are explained on this link
http://digital.ni.com/public.nsf/allkb/DBE7AC32661BCF9B86256AC000682154
For high speed, long acquisition you should use continous acquisition. This link explains how it works
http://zone.ni.com/devzone/conceptd.nsf/webmain/F2DDCBAD754C687C86256802007B8514?OpenDocument+
You could find examples about how to do it in your c:\Archivos de Programa\National Instruments\CVI80\Samples\DAQ folder
Hope it helps
Javier Gutiérrez
NI Application Engineering