NIScope Finite Acquisition using PXI-5105

[somit]

I am looking to develop an application that acquires data (4-channels at 1MSPS per channel) for the NIScope PXI-5105 in continuous and finite modes. The NI example "niScope EX Fetch Forever" clearly explains how to continuously fetch low rate data.

However suppose the user, prior to acquisition, wanted to select an option between continuous and finite acquisition. For the finite case, should I simply break the loop after a certain number of points have been fetched, or is there a more elegant way of accomplishing finite acquisition?

Thanks.

[David S.]

Hi somit -

Continuous and Finite acquisition are fundamentally different programming techniques on our digitizers.  A finite acquisition acquires a set number of records, then stops.  These records are triggered with Reference triggers, and Advance and Pause triggering can be used, too.  A continuous acquisition, however, is performed by "tricking" the hardware into acquiring one record of infinite length. By configuring it for a Software Reference trigger and never actually sending the trigger, we force the device to keep acquiring pretrigger samples forever.  The limitation is that we can never use Reference or Advance triggers, nor can we group the acquisition into multiple records.

Because the two methods are so different, the best approach is to take this input from the user before configuring the session at all.  Then you can select which configuration to use--finite multirecord for triggerring, finite single-record without triggerring, or continuous--based on this input.

[somit]

Thank you for the description. FYI, my application appears to be working using a controlled while-loop for both finite and continuous acquisitions.

Is there an example VI for finite acquisition (single or multirecord) using an NIScope card (PXI-5105)?

Thanks,

 -Somit

[David S.]

Hi Somit -

Every example program except for the one you mentioned is, by definition, finite. 🙂  When you configure an acquisiton normally -- without setting up a non-existant software reference trigger -- the device will acquire the number of records specified, then stop.  Good examples to look at are niScope EX Getting Started and niScope EX Configured Acquisition.  (The latter sets up all the basic features of the device in one session.  Very nice example when building user interfaces.)