# Bode plot

1. Apr 18, 2009

### cleopatra

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. Apr 19, 2009

### MATLABdude

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):

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:

Last edited: Apr 19, 2009
3. Apr 19, 2009

### cleopatra

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..

4. Apr 19, 2009

### MATLABdude

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 $$s=\sigma+j\omega$$. If you're finding the frequency response (as you are in a Bode plot) you're only concerned with the situation where $$\sigma$$ is zero and frequency is imaginary (i.e. sinusoidal). That's why some of the previously-linked resources use $$j\omega$$ 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