Selecting sample clock frequency for NI 4472

HelIo:
I have been using NI 4472 DSA on a PCI slot for reading accelerations. I was reading the NI 4472 User Manual and under "Selecting your sample clock frequency", it specify two increments (95.37 uS/s for Fs<51.2 kS/s and 190.7 uS/s for Fs>51.2 kS/s). Can you explain what these increments mean? I understand the sampling frequency, but what does this time increment mean?
Also, it says "If you do not specify a rate at a multiple of the increment, NI-DAQ will automatically choose the next higher step for you". Dose that mean I cannot specify any random value for Fs? Dose it have to be a certain multiplication. Please explain this for a novice to Labview/DAQ.
Thanks a lot in advance.

Hello MiamiVipul,
Those statements in the User Manual mean that the PCI-4472 only has a finite set of sample rates that it can produce. The allowable sample rates are given by 51.2 kS/s - k * 95.37 uS/s or 51.2 kS/s + k * 190.7 uS/s, where k is an integer. As you can see, the step size is quite small, so you still have a lot of flexibility.
As an example, if you specify a sample rate of exactly 51.2 kS/s, that would be fine. However, if you try to set the sample rate to something between 51,200 S/s and 51,199.990463 S/s (51.2 kS/s - 95.37 uS/s), the driver will automatically coerce that sample rate to next highest allowable rate, or 51.2 kS/s. In order to find out the exact value that the driver is using, you can read the from the DAQmx Timing Property "Sample Clock:Rate" as shown below:
I hope this helps!
Best regards,
Message Edited by Jarrod B. on 01-04-2007 09:03 AM
Attachments:
ReadSampleRate.JPG ‏6 KB

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Solved!
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Hi Bob,
I can confirm that the ai/SampleClock will only be active while the AI task is running. As far as the other questions go:
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Best Regards,
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Message Edited by John P on 12-01-2009 07:52 PM
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Attachments:
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Hello All,
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Hi Clayton,
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