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Measure frequency over time of a signal?

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Hello,

 

I would like to measure the frequency of a signal over time like drawn in the attached draft. Is this with Diadem possible? I could not find a function for that. The frequency to be measured is expected in a specific range (40-80 Hz). But the signal has noise (Much higher frequency), so if only the time between zero crossing is measured, this will give no proper result (Maybe there is an option to discard higher frequencies?)

 

Thanks very much for answers!

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Message 1 of 11
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Hi Tooly,

 

The short answer is that you need to perform a time interval FFT, sometimes called a Joint Time Frequency Analysis.  You've reduced the display in your attached picture to show only one frequency for each time region.  In general there will be a spread of frequencies for each time region where each frequency will have a different amplitude.  Typically this is displayed as a 3D graph or a 2D intensity graph where the coloring indicates amplitude intensity for each frequency component.  Here's an example in DIAdem that is the easiest way to get started with this.

 

http://www.ni.com/tutorial/3549/en/

 

If you're using DIAdem 2015, I'll need to post an updated version for you.  All previous DIAdem versions will work with the example you can download from that link.

 

Brad Turpin

DIAdem Product Support Engineer

National Instruments.

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Hi Brad Turpin,

 

thank you very much for your reply! Yes, I am using DIAdem 2015. Would be great if you could upload the example which works with this version. I think the function "RPMs Channel from Tach. Channel" is what I am looking for. Of course, my signal is not a perfect pulse signal like in your example, but maybe I can filter out the noise to get a smooth curve...

 

Best regards

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Solution
Accepted by topic author Tooly

Hi Tooly,

 

I posted the beta version that works with DIAdem 2015 to our outgoing ftp site, you can get from here for the next couple of days before it is automatically removed:

 

"ftp.ni.com/outgoing/Time Frequency Order Analysis 2015 Beta.zip"

 

The RPM Calculation has filtering/smoothing options on both the Y and X axes.

 

Brad Turpin

DIAdem Product Support Engineer

National Instruments

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Hello Brad_Turpin

 

thanks very much for the upload. It works fine with the 2015 Version!

 

Best regards!

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Message 5 of 11
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Hi,

I'm using Diadem 2015.

I have to calculate the variable frequency of my signal(it's sine signal & the frequence doubles every minute. attached file). I understood we can use the function "order analysis(frequency domain)" .

I checked but I found the function but I can't use it (it's grey attached file).

Could you help me please.

regards.

 

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Message 6 of 11
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Hi,

I'm using Diadem 2015.

I have to calculate the variable frequency of my signal(it's sine signal & the frequence doubles every minute. attached file). I understood we can use the function "order analysis(frequency domain)" .

I checked but I found the function but I can't use it (it's grey attached file).

Could you help me please.

regards.

 

Download All
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Message 7 of 11
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Hi,

I'm using Diadem 2015.

I have to calculate the variable frequency of my signal(it's sine signal & the frequence doubles every minute. attached file). I understood we can use the function "order analysis(frequency domain)" .

I checked but I found the function but I can't use it (it's grey attached file).

Could you help me please.

regards.

 

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Message 8 of 11
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Hi,

 

for OrderAnalysis you need the DIAdem Professional Version

 

Greetings

Walter

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Message 9 of 11
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Hi,

It's exactly what I have, I asked to contact our NI support and I'm waiting there answers.

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Message 10 of 11
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