Overwrite error in AI buffer read when there is no scan backlog

[cbrooker]

Whilst running continuous analogue input acquisition, the -10846 overwrite error occurs in the AI buffer read vi. The scan backlog never goes above 5 and the error dosen't occur at any specific time during acquistion. (sometimes after minutes, sometimes over half an hour after starting the program).

The program originally worked correctley under Windows NT, but we are now trying to run it using the LabVIEW Real Time operating system, using a PXI-8170 embedded controller, NI-4472 Analogue acquisition card and 6527 digital I/O.

When first running it under Real time O/S, the number of scans to read had to be increased from 5 to 20 to stop buffer overwrite (the scan backlog did actually increase then).


The scan rate is set to 200, and buffer size 2000.

Any ideas what could be causing this problem?

[Chad_H]

First see KnowledgeBase Entry 1XPH5BV7.

What processor speed was the Windows NT machine? What is the processor speed of the PXI-8170 (700 or 850 MHz). How many channels are you aquiring? Which version of LabVIEW Real-Time are you using? Which version of NI-DAQ are you using? Are you using an example program or one of your own programs? What priority are you running the VI at? (Time critical priority is recommended for DAQ VIs - remember to provide sleep time to allow lower priority operations, such as the user interface thread, to run).

If you feel this behavior may be a bug, please contact National Instruments technical support.


Regards,
Chad H.
Applications Engineering
National Instruments
http://www.ni.com/ask