Sorry,
but I have to tell you, that your 6143 does not support analog triggers.
http://digital.ni.com/public.nsf/websearch/074CF0F18BB49F9D862570260078DCE0?OpenDocument
You could use other hardware or think of solution that gives you a digital edge when your analog signal crosses a specific threshold.
I attached an example how it could be done in principal with analog trigger.
When your analog acquisition is started you could use the analog start trigger (Pulse that is given, when measurement starts) to trigger the camera. For this route the AI start trigger to a PFI as an output.
Best regards
Dermot
D. Ackermann
Applications Engineer
National Instruments Germany