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When using DAQ assistant to read frequency

When using DAQ assistant to read frequency and Task timing is set to:

N Samples, Clock settings to read 26,

Frequency setup to rising edge,

1 counter with 10 kHz to 1 kHz range.

 

I get back a single number.

Can I assume this is an average reading of 25 samples with the first sample unused?

 

What is the base clock used?

Is the “26” 26 cycles of the frequency to be measured?

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Hello,

If you choose to acquire N samples from the DAQ Assistant then it will acquire all of these samples and return them to LabVIEW as an array.  However, when you use the DAQ Assistant it outputs the data in the dynamic data type first.  This data type makes it easy to graph and run the data through other express VIs.  If you were to create a Numeric Indicator from this data type it would just display the last element from the dynamic data array.  To display this data properly in a numeric format convert the dynamic data to an array of doubles by using the Convert From Dynamic Data function in LabVIEW.  Then you can select to convert it to a 1D array of scalars and when you create an indicator off of the output of this function all of the data should be displayed.

The timebase that is used for lower frequency measurements is the onboard clock, which is internally connected to the Source.  Then you connect your signal to be measured to the Gate of the counter.  Since the frequency of the onboard clock is known it can be used to calculate the frequency of an unknown source based on when the counter is on and off (determined by the Gate). 

Have a good day,

Brian P.
Applications Engineer
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