multirecord acqusition of different sizes ni pxi6561

[Timothy 123]

Hi,

Can I do multirecord acqusition with each record being different sizes (meaning different number of samples on each record) on the pxi 6561, and how would I do this. I really would like to start and stop each record based on a data active event and an external trigger, respectively.

Thank you,

-Tim

[Ryan_M]

Tim,

In a multi record acquisition, each record will be of the same size.  If you simply need to qualify data using an external event, I would recommend using the Acquisition Pause Trigger.  If you have a Data Active signal that is synchronous to your data then you can use this as the pause trigger.  Data will only be stored into memory when the pause trigger is asserted (High or Low configurable).

[Timothy 123]

Hi,

I would like to pause the acquisition when the external trigger is issued. The problem with this approach is that the external trigger may be issued before the number of samples to acquire is reached. Will the acqusition pause even when the number of samples to acquire is not reached.

Thank you,

-Tim

[Ryan_M]

Tim,

Yes, and in fact, it will only pause while the number of points to acquire has not been reached.  Once the total number of samples have been acquired, in a non streaming application (ie not using a reference trigger), the acquisition stops and no longer pays attention to the pause signal.  Since the session is no longer interested in acquiring data, it is no longer necessary to pause the data either.