Hey Turbot,
Thanks for contacting National Instruments support. If you want to synchronize two channels on the same 5102 you simply add both channels to the channel list by typing 0,1. I have a attached a vi that does this.
That said if you want to synchronize both 5102 devices together, than that is a bit more complicated, but there is a shipping example that does just that. It is located C:\Program Files\National Instruments\LabVIEW 8.2\examples\instr\niScope if you have LabVIEW 8.2, but yo have an older version of LabVIEW it would located in that folder. It is also in the Example Finder, and if you go to the Start >> All Programs >> National Instruments >> NI-Scope >> Examples, and then the LabVIEW version you have. The name of this example is niScope EX 5102 Synchronization.vi
Let me know if you have further questions or cannot find the example I am describing.
Regards,
Kenn North
Principal Product Manager - Search, Digital Analytics
http://ni.com/search