Shifted spectrogram

[Peter_Janiga]

Hello all!

I created vi for supraharmonic analysys but in freqency scale in spectrogram is the result shifted. I chcecked it by removing the specific aprox. 80kHz signal and it remove yellow points in spectrogram at 25kHz. 

Any idea why is the freqency scale in spectrogram wrong?

Thank you. 

[altenbach · Accepted solution]

Your STFT express VI has a coercion dot at the signal input because you have it configured as "real" and your frequency is manually entered as 200kHz in the express configuration, while the waveform is actually 1E6Hz.

Why not set the signal input to "waveform" instead?

[altenbach · Accepted solution]

You also need to wire a reference (right-click terminal...create...reference) to the signal indicator so it can correctly set the offsets and multipliers of the axes.

Without that reference, the axes are not correct, of course.

(Makes little sense that the reference input connector is not set as "required". It should be!)

[Peter_Janiga]

Thank you. I set the signal input to "waveform" in STFT spectrogram and also add the reference. Now it is all correct.