KING FAHD UNIVERSITY CHEMICAL ENGINEERING COURSE NOTES (Process Control)-Lec35

KING FAHD UNIVERSITY CHEMICAL ENGINEERING COURSE NOTES (Process Control)-Lec35

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1 Chapter 13 Bode Diagrams A special graph, called the Bode diagram or Bode plot , provides a convenient display of the frequency response characteristics of a transfer function model. It consists of plots of AR and as a function of ϖ . Ordinarily, ϖ is expressed in units of radians/time. φ Bode Plot of A First-order System ( 29 1 N 2 2 1 AR andφ tan ωτ ω τ 1 - = = - + Recall: N N ω 0 and ω 1) : AR 1 and ω 0 and ω 1) : AR 1/ωτ and A τ = ϕ = 0 τ = ϕ = -90 At low frequencies ( At high frequencies ( o = ?
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2 Chapter 13 Figure 13.2 Bode diagram for a first-order process.
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3 Chapter 13 Note that the asymptotes intersect at , known as the break frequency or corner frequency . Here the value of AR N from (13-21) is: ω ω 1/ τ b = = ( 29 N 1 ARω ω 0.707 (13-30) 1 1 b = = = + Some books and software defined AR differently, in terms of decibels . The amplitude ratio in decibels AR d is defined as d AR 20 log AR (13-33) =
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4 Chapter 13 Integrating Elements The transfer function for an integrating element was given in
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This note was uploaded on 09/22/2009 for the course CHEMICAL CHE 401 taught by Professor Dr.muhammadal-arfaj during the Spring '09 term at King Fahd University of Petroleum & Minerals.

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KING FAHD UNIVERSITY CHEMICAL ENGINEERING COURSE NOTES (Process Control)-Lec35

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