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Block Diagram Manipulation

  1. Dec 11, 2014 #1
    Screen Shot 2014-12-11 at 18.12.51.png
    Hi there,

    I am struggling to understand how moving the summation (with H3) to before G1 will cause H3 to have to be divided by G1. I tried writing down how the equations would work to make sense of it but I still can't see how it works out.

    Please can someone explain this to me?

    Thanks,
    Laura Morrison
     
    Last edited by a moderator: Dec 11, 2014
  2. jcsd
  3. Dec 11, 2014 #2

    donpacino

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    Gold Member

    If you move the summation block backwards, then the ENTIRE result of the summation block will be multiplied by G1, not just one of the terms


    you are multiplying V3 by H3, then subtracting it from V1*G1, so your expression looks like
    V1*G1-V3*H3

    notice how the V3*H3 term is completely independant of the value of G1.

    If you move the summation block before G1, then the expression will be

    (V1-V3*H3)*G1 which is also V1*G1-V3*H3*G1

    notice how the second term will change as G1 changes.

    make sense?
     
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