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Reservoir system

  1. Sep 7, 2017 #1
    Hello,
    Excuse my bad english.Could someone help me please to understand how does this systems works?
    the role of the system is to maintain the constant water level in the reservoir.I don't understand how the opening and closing of the valve is controlled. How the lever system works. in the description of the system they talk about a comparison made between the height h (t) in the reservoir and the reference height hr fixed by the length of the bar connecting the float to the lever system.
    Thank you and sorry for my english
     

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  2. jcsd
  3. Sep 7, 2017 #2

    DrClaude

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    What is represented at the surface of the water is probably a float. It goes up or down with the level of the water, and the vertical arm pivots. On the other side of that pivot arm is a mechanism that controls the valve, e.g., when it gets pushed down the valve reduces the flow.
     
  4. Sep 7, 2017 #3
    Further, this is a schematic of a simple mechanical feedback system.
    The different pivot arm lengths l1 & l2 provide a means of setting the "gain" of the system (l1/l2).
    • A short l1 (with long l2) will give small valve opening adjustments for large changes in tank level: low gain, slow response.
    • A long l1 (with short l2) will give large valve opening adjustments for small changes in tank level: high gain, fast response.
     
  5. Sep 8, 2017 #4
    Thank you DrClaude and tygerdawg for your answer. L1 and L2 will change depending on the position of the float in the water by mean depending of the level of the water in the reservoir? how can we fix the input command (hr) in this system.
     
    Last edited: Sep 8, 2017
  6. Sep 8, 2017 #5

    Nidum

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    Just set the float to a height where the valve gets shut off when the water level is correct . The box with the black blob is an adjustment mechanism for the height of the float .

    The ratio of L2 to L1 sets the mechanical gain and the response sensitivity of the control system .

    upload_2017-9-8_10-0-48.png
     
    Last edited: Sep 8, 2017
  7. Sep 8, 2017 #6

    CWatters

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    No. L1 and L2 would be set by the system designer...

    So the equation for qi(t) would be something like... qi(t) = (L1/L2) * (h(t) - h(r))

    Although not exactly that because there is a time delay due to the distance d.
     
  8. Sep 8, 2017 #7
    thank you Nidum and Cwatters for your help its start to be clear. Last question please why mechanic gain is L1/L2 and not L2/L1
     
  9. Sep 8, 2017 #8

    CWatters

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    Edited: It's the way levers work. If you make L1 longer the valve moves further. If you make L2 longer the valve moves less for the same change in water depth.
     
  10. Sep 11, 2017 #9
    THanks you CWatters
     
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