Continuous, gap-free acquisition and processing with PCI-5142 and Labview

[Alex Hegyi]

I am trying to continuously acquire data from a PCI-5142 in Labview 7.0.  I have NI-SCOPE software installed, and right now, the best I can do is to acquire the data in chunks and then stitch the chunks together.  However, this results in a short (approx. 10ms) amount of data loss between chunks.  Since I am trying to do a cross-correlation of a function with my data, across chunks, I need the chunks to be contiguous.  Additionally, I need to do this processing in real time so I cannot just stream to disk. What are my options?

[psisterhen]

Be sure that you are not stopping and re-starting the acquisition in between reads.  Also, be sure you are not reading from a new record each time.  There will be some time between separate acquisitions or separate records.

The best way to acquire continuously is to configure a single record, set the Reference Trigger to Software, and never send a Software Trigger.  Set the Fetch Relative To attibute to Read Position.  That way, every time you read data, it will start at the first unread data point.  So you shouldn't see any gaps in the data (the chunks will be contiguous).

Please refer to two examples included in the NI-Scope driver:
  - niScope EX Fetch Forever
  - niScope EX Fetch In Chunks