09-21-2009 05:45 PM
09-22-2009 01:17 PM
It sounds like a ground reference is missing from the signal. So that the card slowly sees it turn into 0 V as the signal bleeds off. If you ground reference is however (through bias resistors or something like that) than the signal should more quickly bleed out the voltage. Check out the field wiring diagram linked below for more information.
http://zone.ni.com/devzone/cda/tut/p/id/3344