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Spectral Measurements VI - problem with scales


I am generating a chirp signal using MathScript node and plotting it's PSD. Then I am passing the signal to DAQ (X Series) acquiring it on an analog input and plotting its PSD again. Both times I am using the same "Spectral Mesurements" VI to calculate the PSD. I am not using any windows or averaging and both results are in dB. I am also plotting the time domain signals. As expected, the time domain signals look exactly the same, and the PSD looks the same except for the Y scale. So, I am trying to understand where the difference in the Y scale is comming from.

I am attaching the screenshot and the VI

Thanks a lot for any help.




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Message 1 of 3

I took a look at your attached VI, one suggestion I have for you is to wire the "Stimulus" to a Convert From Dynamic Data VI before wiring it to the Signals input of the Spectral Measurments 3 express VI. Just to see if data type has any effect on the PSD of the signals.


-Jake B.

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Message 2 of 3

Thank you, I will try that.

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