Random values from a VI meant to measure periodic time

[PatrickClancy]

Hi,

I have set up a DAQ to a photogate. I have set up labview to measure the periodic time of a pendulum using the photogate, but I am getting random values for the period when the photogate is blocked. It is my first time using labview this way so any help would be much appreciated. I have attached the VI I am working with below.

[GerdW]

Hi Patrick,

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@PatrickClancy wrote:

I have set up a DAQ to a photogate. I have set up labview to measure the periodic time of a pendulum using the photogate, but I am getting random values for the period when the photogate is blocked.

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Why do you use the DAQAssistent?

Have you had a look at those example VIs coming with LabVIEW and DAQmx? Have you tried to execute the example VIs explaining how to use DAQmx counters?

Have you tried to measure the same using the testpanels in MAX? Does it work correctly ("as expected") in MAX?

We cannot test your VI as we don't have your DAQ device nor your UUT - you need to test on your own!

Btw. why are both frontpanel and blockdiagram set to full screen? This is really annoying - especially for such a small VI!

[altenbach]

Sorry, since I don't have drivers installed, I cannot see how your assistant is configured. can you give details?

All you read is dynamic data of unknown datatype and size that you then display as a single scalar, in a loop that does not have any timing and spins as fast as your code allows.

What does the value of the "scalar" represent? If this is a counter value (guessing from the file name), you probably want to process it for a more reasonable display. Why is it orange?

I recommend not to use a switch as stop button. Seems confusing.