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Bode plot

  1. Apr 18, 2009 #1
    1. The problem statement, all variables and given/known data

    How do you draw a bode plot?
    I have a simple equation: H(S)=s+10 but no school book. Can you teach me?
     
  2. jcsd
  3. Apr 19, 2009 #2

    MATLABdude

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    How about a tutorial?
    http://www.facstaff.bucknell.edu/mastascu/elessonsHTML/Freq/Freq5.html

    When you're drawing by hand, usually only the asymptotes are required; the effects of zeros, poles, higher ordered zeros and poles, and most of the simple cases are usually tabulated in the first chapter of any controls textbook.

    EDIT: Summary for drawing asymptotic transfer functions (agrees with what I remember):
    http://en.wikipedia.org/wiki/Bode_plot#Rules_for_hand-made_Bode_plot

    EDIT: This post might've been better in the EE or Engineering homework subforum.

    EDIT: Thought I recognized the username... Since you asked a MATLAB question, you may also want to look in this thread:
    https://www.physicsforums.com/showthread.php?t=303967
     
    Last edited: Apr 19, 2009
  4. Apr 19, 2009 #3
    I don´t have any poles and no zeros either.
    So what do I do then? Or do I have one zero? = -10 ?

    But I really don´t understand those webpages because they all have jw sth..
     
  5. Apr 19, 2009 #4

    MATLABdude

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    Yes, there's one zero. I'm not sure how far along you are in your complex math or controls course, but s is the 'generic' frequency [tex]s=\sigma+j\omega[/tex]. If you're finding the frequency response (as you are in a Bode plot) you're only concerned with the situation where [tex]\sigma[/tex] is zero and frequency is imaginary (i.e. sinusoidal). That's why some of the previously-linked resources use [tex]j\omega[/tex] instead of s (even though the transfer function is given in terms of s)

    Put another way, if your transfer function is called H(s), you're finding |H(jw)| (the magnitude of the frequency response) and the phase
     
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