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Finding peaks in a time domain signal - LMS Test.lab

Experimenter
Experimenter

Good morning,

 

I have a time domain signal and would like to extract the peak values (crest and valleys). Can I do it in the Test.lab itself ( time data selection/processing ) or do I need to extract the data and do it outside (MATLAB) ? Also can anyone explain how to extract the time domain data outside the Test.lab ( so that I can use MATLAB for post processing ) ?

 

Thank You


Rak

7 REPLIES

Re: Finding peaks in a time domain signal - LMS Test.lab

Siemens Genius Siemens Genius
Siemens Genius

Hi Rak,

I would use time data processing to process the data.  Here I have an example:

Since I have almost 56 seconds of recording, so I set the measurement mode to Tracked, durations to 60 seconds greater than total lenght of measurement, with increments of 0.5 seconds.

frame_2.jpg

 

In the FS Acquisition tap I set the frequency resolution to one hertz, which makes the frame size to be one second.  Since my increment is 0.5 second, I have 50% overlap of data(digital signal processing).

 

frame_3.jpg

Re: Finding peaks in a time domain signal - LMS Test.lab

Siemens Genius Siemens Genius
Siemens Genius

to continue from previous post....

 

go to Section Settings->Frame Statistics->select Maximum & Minimum, under channel group select Vibration, now you can click calculate to generate data.

 

Here's what the result looks like:

frame_1.png

 

I have the Maximum, Minimum and the original time trace in blue display in the same front/back display. Please see image above for display setting parameters.

 

Hong

 

Re: Finding peaks in a time domain signal - LMS Test.lab

Experimenter
Experimenter

Thank you Hong for the solution.This is exactly what I wanted. I have one more question. Attached is the snapshot of the data( red- time domain signal , purple-minimum values/valleys). Is there any quick way to calculate the mean value of the valleys ( purple curve) for a certain period? Say I want to know the average of the valleys from 90-150 seconds.

Re: Finding peaks in a time domain signal - LMS Test.lab

Siemens Legend Siemens Legend
Siemens Legend

Hello,

 

In any display you can right click and add a double X cursor.  You can then right click on the double X cursor, go to calculations and turn on the Average.  That will provide the average value betweent the two cursors.  By using three double X cursors you can get the mean value of those three values.  You can also right click on the cursor legend and select "copy values" if you with to copy these values to Excel or some other software.

 

Kevin Grenier

Re: Finding peaks in a time domain signal - LMS Test.lab

Siemens Genius Siemens Genius
Siemens Genius

there are two way to do that:

1st method you can utilize the double cursor feature inside Test.Lab, in your current display right click anywhere in the display

frame_4.jpg

 

You want to insert a double X cursor.  Once you have the double X cursor in the display, you can move the cursors to where the location you want the calculation done.  Usually if I want to modified any setting on the cursors, I right click on the 2nd cursor(on my example which is at time 37.33 seconds) I choose  Snap to data value because I want the cursor right on my curve(no interpolating); then go to Calculations->select Average, now I should see cursor legend displaying the cursor location and the average(mean) value.  If you don't the cursor legend displaying, you'll need right click in the display again go to->cursor legend->Auto.

 

2nd method is go back time data processing workbook->Section settings->Frame Statistics->select mean, in this case, you do not have the flexibility to calculated selected segment only; it calculate the mean of total length of measurement.

 

Thanks for the feedback!  I'm glad it's working for you.

 

Hong

 

 

Re: Finding peaks in a time domain signal - LMS Test.lab

Experimenter
Experimenter

Thanks Kevin...

Re: Finding peaks in a time domain signal - LMS Test.lab

Experimenter
Experimenter
Thanks again Hong...