How to calculate the period of an input signal?

Hi,

I am carrying out an investigation where I have applied an impluse to an object. What is the best way to calcualte the duration of the impusle? I have attached a photo of the graphs I have created to give a visual representation of the data I have collected.

Any help would be much appreciated.

Max

Answer 1

[Image Analyst]

You can use thresholding and find(). Pick some Force value that you consider to be in the pulse. Assuming just one pulse:

leftIndex = find(Force > someValue, 1, 'first');
rightIndex = find(Force > someValue, 1, 'last');
pulseWidth = t(rightIndex) - t(leftIndex); % Compute delta time using time vector, t.

If there are multiple pulses, then you'll have to do a little more to get the width of each one separately. Hint: use regionprops():

props = regionprops(Force > someValue, 'PixelIdxList');

It can also get more complicated if you want to do things like get rid of short noise pulses, etc.

[Maxwell MacFarlane]

Thank you for this suggestion. I'm still struggling with what values to pick. Ideal I would like to choose the starting value however you can see before 2 seconds in the first graph there is a slight increase therefore this code picks up that point instead of the start of the impulse.

Do you have any suggestions on how to over come this when batch processing for all my data points?

[Image Analyst]

What threshold value did you use? If you need more help, attach your data in a .mat file.

In the meantime, you might try the findchangepts() function.