-209802 error while running RT acquisition

[Taylor.Kendall]

I am trying to get a PCIe6259 to acquire for an RT control that is running at 10kHz.  I want about 50% of the loop time to be reserved for collecting analog signals and the other time for doing calculations and sending out analog signals. If I try and do a sample clock of 1kHz or above I get the 209802 error.  I know that the 6259 should be able to acquire 16 channels in one task at more than 10kHz. I just need a bit of help getting all the settings correct for this application.  

 I know that in the LV7.1/TradDAQ there was a setting called Scan Interval that could be used to speed up the acquisition time.  The replacement for scan interval is Sample Clock Timebase Divisor  it is less clear how to use this new setting to speed up acquire times. 

Thanks

[Steve_B · Accepted solution]

Hi tsksesa,

You mention the Scan Clock in your post which corresponds to the Sample Clock in DAQmx, but you seem to be setting this properly already for your application. I believe you might be referring to the Channel Clock which has a DAQmx equivalent called the Convert Clock. This clock will dictate how quickly the hardware will multiplex between channels in order to take a reading. You can see more information about the difference between these clock in a knowledgebase link below.

The driver will choose an appropriate Convert Clock rate to ensure that the samples are acquired within each period of the Sample Clock and meet the settling time requirements for the ADC. The DAQmx Timing Property Node has an AI Convert Clock property that can be read from and written to. I included a link to a knowledgebase about the Convert Clock that will describe the formula the driver uses to choose its default convert clock.

The error you are describing is related to not being able to read back the data from the device fast enough throguh software. This issue can be system dependent, but regardless of the system you may benefit from reading multiple samples at a time through a buffered aquisition. If you are already using this type of acquisition there may be some application changes to improve the rate you are reading. A producer consumer type of architecture would be recommended in order to speed up the rate at which you are calling the DAQmx read because you can isolate the read from the processing.

Difference Between the Sample Clock (Scan Clock) and the Convert Clock (Channel Clock)
http://digital.ni.com/public.nsf/allkb/4D1435DF82EF494186256D8A006DD6D4?OpenDocument

How is the Convert (Channel) Clock Rate Determined in NI-DAQmx and Traditional NI-DAQ?
http://digital.ni.com/public.nsf/allkb/42484E84DA98053686256D32006E0494?OpenDocument