Add control to change samp. freq. and fft lines in express vi

[Ronman]

The express vi for Spectrum Analysis is excellent, but I can't figure out how to add functionality to my vi to change the sampling rate and the number of samples with front panel controls.

[Ankita]

Hi Ronman,

For any express VI, you can right-click the express VI and select "open front panel". LabVIEW would then prompt you if you really want to convert the express VI to a standard VI. If you click on the "convert" button your express VI would change to a standard VI and you can then view the block diagram of the VI. You can make any changes in the block diagram.

Do remember that once you convert the block diagram of an express VI, you cannot go back to the express VI mode.

Hope it helps.
Ankita

[Ronman]

I made a copy of my vi and did as you suggested. I still don't see any parameters to change the sampling rate or number of sampled points. I went down three levels deep.

[Dennis_Knutson]

Are you talking about Spectral Measurements Express VI? If you are, the sample rate and number of samples are all part of the signals input. The Express VI operates on the entire signal passed to it. Sample Rate and number of samples are not part of the Express VI properties so you won't find anything when you convert to a VI. You could use Extract Portion of Signal to get a subset. Sample rate is normally changed at the source of your signal but you could also modify the signal post acquisition. I haven't used express VIs and signals that much but I know you can convert a signal to a waveform data type. A waveform has a dt that can be modified with the Build Waveform function. You could also use the Get Waveform Components to extract the Y array and use Array Subset to change the number of samples.