Maximum Analog Input Transfer Rate From PCMCIA Card to the PDA Buffer Primary Software: LabVIEW Modules>>PDA ModulePrimary Software Version: 7.1 Primary Software Fixed Version: N/A Secondary Software: N/A Hardware: Multifunction DAQ (MIO)>>E Series>>DAQCard-6062E, Multifunction DAQ (MIO)>>E Series
Problem: What Is the Maximum Analog Input Rate for DAQmx Base on LabVIEW PDA? Solution: The maximum rate obtainable for analog input is approximately 200 kS/s. Note that the data acquisition rate of your PCMCIA card may be well above this. For example, the NI-DAQCard 6062E and NI-DAQCard AI-16E-4 (6041E) both have a maximum sampling rate of 500 kS/s. However, this is the rate of data transfer from your analog input to the onboard FIFO on your PCMCIA card. This data is then transferred from the FIFO to PDA memory using interrupts. Care must be taken in this situation not to overrun the FIFO with new data before the old data can be read off the FIFO and into the PDA buffer. The 200 kS/s rate is for finite acquisitions and the maximum rate for a continuous acquisition is much lower due to the overhead of doing multiple reads and memory allocation. In order to obtain the fastest analog input acquisitions for your PDA (200kS/s), use the Raw I16 1D version of the polymorphic DAQmxBase Read.vi. The Raw I16 1D version does the least amount of memory allocation, and no floating point calculations. If greater data transfer rates are required, you should consider using a PCI or PXI form factor. Data transfer through a PCI bus (used with PCs and PXI systems) uses DMA (Direct Memory Access) which has an effective transfer rate of approximately 30MS/s and is much faster than using interrupts. Related Links: Drivers and Updates: Current Version of NI-DAQmx Base NI-DAQmx Base 2.1 Readme Measurement Encyclopedia: DMA definition Measurement Encyclopedia: Interrupt definition NI Developer Zone: Data Acquisition Fundamentals Products & Services: LabVIEW PDA Module Attachments:
Report Date: 11/05/2004 Last Updated: 05/06/2008 Document ID: 3F4D52OY |
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