how to control two 6110e daq cards to acquire 8 signals simultaneously

[sunny 711]

I use two 6110e daq cards to acquire 8 signals simultaneously,but when I use a amplitude 5v ac signal connected to different two channels to test my software ,I find that I get different result from different channels.the error is about several hundreds mv.why? how to solve it.

[PdB]

My bet is that the two boards are not physically connected by the RTSI bus (on top of your boards).
If ADC sampling doesn't occur at the same time, signals will never be in sync.