Buffer size

[Simbani]

My system is composed of : Dell Dimension 4600 with 512 Mb RAM, NI PCI 6250 serie M, LabVIEW 7.1., NiDaq 7.4., ApplicationBuilder 7.1.

I am acquiring at 10000 samples per second with with a buffer size of 40000 samples and 200 samples average and the program blocks. If I reduce the size of the buffer the program runs OK. How large should the buffer siez be ?

[Belens]

Hello Simbani

Memory allocation is typically handled automatically for you if you use the DAQmx Timing.vi: 

• If the acquisition is finite (sample mode on the DAQmx Timing.vi is set to Finite Samples), NI-DAQmx allocates a buffer equal in size to the value of samples per channel.
  
  
• If the acquisition is continuous (sample mode on the DAQmx Timing.vi is set to Continuous Samples), NI-DAQmx will allocate a buffer according to the following table:

Sample Rate	Buffer Size
0 - 100 S/s	1 kS
100 - 10,000 S/s	10 kS
10,000 - 1,000,000 S/s	100 kS
> 1,000,000 S/s	1 MS

You can override these values calling  DAQmx Configure Input buffer.vi, but in general with the automatic values the system woks OK. You can find this information into NI-Daqmx help>>Key NI-DAQmx concepts>>Reading and writing data>>buffering.

Hope this helps

Belens