# Bode plot analysis for control engineering

Discussion in 'General Electronics Chat' started by BigMan, Nov 11, 2014.

1. ### BigMan Thread Starter New Member

Oct 20, 2014
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Hello, the last 2 rows of the table in these attached photos are not clear for me. thank you.

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2. ### BigMan Thread Starter New Member

Oct 20, 2014
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Hello, I repeat the question again, kindly refer to this pdf file pages 6 & 7. How LM calculated on the last row of the tables on pages 6 & 7? thank you

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3. ### umphrey Member

Dec 1, 2012
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Just the last row? The slope of the graph is -20 db/dec. The first column was calculated to be 40 db. 1 decade corresponds to moving the decimal place by 1 so 0.1 rad/s + 1 decade = 1.0 rad/s, etc. Since you know the slope of the line is -20 db/dec you can calculate where it will be at the next point. So log(4/.1) = 1.6 decades, 1.6 decades * -20 db/dec is -32, 40 - 32 = 8 db. Repeat for the next columns in the table except the slope is different and the initial frequency is different.

4. ### MrAl Distinguished Member

Jun 17, 2014
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Hello,

Sorry i didnt get to this until now...

Referring to your first post image controleng.png, they most likely want you to use the formula under "Eg" with the slopes given. This leads to the new LM points. So take the slopes as 'given' and just calculate the new LM points using the slopes and the previous LM point.

For the phase table it works the same way.

Oct 20, 2014
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thanks all