×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Fourier Series
2

Fourier Series

Fourier Series

(OP)
Hi - Can any anyone help me graph the 1st harmonic. Please see attached data.

Thanks,

RE: Fourier Series

2
Incidentally you might want to fiddle the data slightly - runout at 360 should equal runout at 0

OK, first thing to do is to interpolate the data so that you have 64 samples, not 36

Then you need to install the data analysis add-in

then you need to use the Fourier Analysis in that menu.

Then you need the magnitude, use imabs

Then you need to read up on the scale factor used in Fourier.

Eyeballing I'd expect an amplitude of somewhat less than 3 mm for the first order component, and get 2.24 mm

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Fourier Series

(OP)
Thanks! Greg

RE: Fourier Series

I think you've just calculated the centreing error, ie the DC component of the fourier series.

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Fourier Series

Sorry, I was wrong, you are working the Fourier coefficnts out the old fashioned way (nice to see). Incidentally your x axis is screwy, the first value is 11 degrees, not 0

If you've done it right you have calculated the amplitude of the sine and cosine parts of the first order, so now generate a sine wave and multiply it by a, and a cos wave and mutliply it by b, and add them up, and that should be the first order component.

You've got a - sign problem in b,

the correct formula is 0.34*cos(x)-1.83*sin(x), and it looks OK

I don't know where I got 2.24 before, that is wrong.

Cheers

Greg Locock

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Fourier Series

Thanks for taking the time to review my problem. Thank you!

TC

RE: Fourier Series

If someone is truly helpful, the traditional way to thank them is to award a star. It cost you nothing but a few seconds.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: Fourier Series

I'll do it, LOL!

RE: Fourier Series

(OP)
My apologies, I'm new to the forum and I don't know how to give someone a star.

Greg - thank you once again.

RE: Fourier Series

Just click
Thank GregLocock
for this valuable post!

RE: Fourier Series

(OP)
Thanks guys! Awarded Grag with star

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources