How to know the sampling rate for NI6624?

[Y. D. Cheng]

Dears,

 

I am trying to measure a transient signal that is a time-vary counter train.  The target frequency is increased from 0 Hz to 50 Hz when the measurement time rises to 1 s from 0 s.  The NI 6624 card and the LabVIEW DAQmx have been adopted.  In the block diagram, the terminal of measurement method “Low Frequency with 1 Counter” is set in “DAQmx Create Channel (CI-Frequency).vi”, and the “Finite Samples” mode is chosen in “DAQmx Timing (Implicit).vi”.  Then the transient signal points (increasing-frequency points) will be got successfully within 1 s.  Now I have a question: how do I estimate the time step “dt” between these data points?  Knowing the default sampling rate of the card seems a better way to help me to define the "dt", and calculates the time stamp at each data point.  If the foregoing concept is true, how the internal sampling rate in NI6624 obtains?  Beside, for the transient counter signal, any way to get the time stamp of data points is also welcome.

Thanks for anyone comment,

Adan

[Ryan_V[DE]]

Adan,

When selecting "Implicit" as the DAQmx Timing type, you are indicating that a data point will be taken for every measurement the counter performs. When you create a task of type "Low Frequency with 1 Counter," the counter simply uses the card's internal timebase to measure the period between edges of your signal. It then takes this period measurement and converts it to a frequency. Therefore, the spacing between the samples you read out is simply the inverse of the subsequent frequency measurement sample.

Hope this helps,

[Y. D. Cheng]

Dear Ryan,

  I will be serious in this direction.  Thank you for your suggestions. 

Adan