Creating a waterfall diagram from a single frequency domain signal?

[Matthew.cf828br]

Hi All,

I wonder if anyone can advise me of the procedure in DIAdem to create a "waterfall" diagram from a single frequency domain signal? I have a data set which I am attaching. From the analysis tab I pass this data through the FFT function to create a frequency domain signal which is shown in the first picture of the spectrum and waterfall attachment. Now what I would like to do is to create the waterfall diagram shown below it but am at a loss of the steps involved. Can anyone advise how I create the data or the steps involved in taking the frequency domain signal to plot this waterfall diagram?

Thanks a lot for your help in advance.

Regards

Matthew

[Brad_Turpin]

Hi Matthew,

You first need to convert the waveform channel loaded from the *.wav file into the Data Portal in DIAdem into 2 numeric channels, with the new one being the Time channel-- there's an ANALYSIS dialog that does this.  You then need to run what DIAdem calls a "Time Interval FFT", which will result in many individual FFTs, each calculated from a different time window of the original time series data.  You can set this parameterization in the same FFT dialog you were in to create the simple FFT over the full time series.  Then you need to arrange the resulting channels in what DIAdem calls "3D Matrix structure" in a new Group in the Data Portal.  From there you just drag the resulting Group of channels into a new VIEW or REPORT graph.

The interactive method to do this is outlined with detailed descriptions and screenshots in Exercise 5 of the DIAdem 2010 Hands-On Exercises, which you can find here:

http://zone.ni.com/devzone/cda/epd/p/id/5393

There is also an example application that you can download and run that will do all this for you automatically-- that's how I generated the pictures I'm attaching:

http://zone.ni.com/devzone/cda/tut/p/id/3549

Brad Turpin

DIAdem Product Support Engineer
National Instruments

[Matthew.cf828br]

Hi Brad,

Thanks for the reply. I managed to work out the basic fundamentals of the process yesterday. As you say the first trick is to convert the waveform channel into a numeric channel and to perform a time interval FFT. However some of what you have written is new information to me that I hadn't even thought about. I look forward very

much to following your links and see what is written there.

Thanks a lot for your help.

Regards

Matthew