Hello Alann,
This is most likely because you do not have a signal connected to the Scope channel you are reading from. When performing a binary acquisition using the niScope EX Binary Acquisition VI, found in the Example Finder under
Hardware Input and Output»Modular Instruments»NI-SCOPE (High-Speed Digitizers)»General, I observed the following behavior:
Without a signal connected the 8-bit fetch would acquire a signal that rapidly oscillated between 0 and -1.

I hope this helps to clarify what is happening with your system.
When you change the fetch to 16-bits the noise is seen much better.
With the signal connected however, the signal can be seen in both the 8-bit and 16-bit fetch.

Message Edited by Dan_K on 03-13-2009 10:18 AM