Any way to add harmonic cursors to fft data?

[Ronster]

I have a vi that plots vibration data from accels.  I would like to place markers on the fft peaks that identify harmonics of the main cursor.  Anyone out there that has done this?

Thanks in advance,

Ron Brook

[Nitin_T]

Hi Ronster

I would suggest programatically adding the markers to the graph with the property node XScale.MarkerVals[]. Using the Property Node, you can place the Markers at points of you choice, in this case at the fft peaks. Hope this helps.

[Ronster]

Nitin,

Thanks for the advice.  I have a problem with the property node already that maybe you have seen.  The file is saved with the operating speed as input by the user.  On recall, that variable is read into the cursor property node for x position.  I have three overlays and three cursors on one plot.  It NEVER populates all three cursors.  Maybe two, then the third one is blank. ???

[Nitin_T]

Hi Ronster,

One way to work with multiple plots and cursors is to choose the Active Cursor and the Active Plot using Property Nodes. These can be used in a loop to select the right cursor. Once the required cursor is selected, it's positions can be changed. Let me know if I answered your question.

[Ronster]

I assumed that the way to make it work flawlessly would be to use property nodes.  I'll let you know after I get some time to implement that.  I am also working right now on performing a peak search on my fft data.  I have it working, but the peak frequencies don't match the data.  I am still in trouble shooting mode on this one as well.  My basic vi, which saves all six time waveforms and averaged spectra to the server, with another vi to recall all of it, including calculated overalls works very well.

Ron

[Nitin_T]

Hi Ronster,

Good to know that most of the code works well. Do post if there are any more difficulties after you finish implementing/troubleshooting.

[Jack_A. · Accepted solution]

Hey Ron -

This might be an interesting XControl for you to take a look at:

http://zone.ni.com/devzone/cda/epd/p/id/6404

It doesn't automatically choose the peak values, but does let you interactively move the cursors.  It also has sideband cursors as well.

-Jack

[Ronster]

Jack,

Thanks, that would work fine.  Unfortunately, I have remained at 7.1, due to the fact that I have multiple sites using my code and it all works, so I felt it best not to rock the boat.

Regards,

Ron