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Simultaneous acquisition and writing of Analog Inputs and Frequency Measurement?


We are trying to setup a "simple" data aquisition system, recording simultaneous data from a pressure sensor that outputs a voltage and a flow sensor that outputs a pulse.


I have been attempting to modify our standard "Write to File" vi to make this happen... without much luck. I'm not sure how to combine the buffered Analog Input and the discrete Frequency measurements. Our flow sensor outputs a pulse with frequency higher than 100 Hz so the off-the-shelf frequency-to-voltage module will not work.


I'm new to Labview and know just enough to be dangerous. Any help that you can provide would be appreciated!


Labview 7.1

DAQPad 6020E





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Hey mtgregor!


It really depends on both how fast the frequency we are looking at is, as well as how synched up you need these signals to be.  Obviously, it takes some period of time for a frequency measurement to occur.  This is because the VI will count the number of edges on the counter over some period of time and use that to determine the frequency, whereas the analog input is a value at a specific point in time.


If you are looking for software synchronization in the range of milliseconds your synchronization can be accomplished just through dataflow programming, ie. by placing your frequency VI in the while loop to run parallel to the read VI.


If you are looking for a more hardware timed solution, you are going to need to count digital edges on your pulse.  There is a good example that shows this in the DAQ examples in the LabVIEW's example finder, called Count Buffered Edges.

Doug Farrell
Solutions Marketing - Automotive
National Instruments

National Instruments Automotive Solutions
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