What is the gain of the system?
The gain of the system with no disturbance can be evaluated by looking at the change in the measured variable divided by the change in the manipulated variable. As shown on the graph the concentration increases from 0.5 - 0.6 giving a change of 0.1. The inlet concentrate flow increases from 1.0 -1.5 giving a change of 0.5.
Hence the gain of the process is 0.2 (time units/volumetric units).
Will the controller gain be positive or negative?
From the graph it can be seen that as the concentrate flowrate increases, the concentration in the tank increases and so the controller gain will be positive.
How quick is the response?
This question is another way of asking what is the time constant of the process. This is found to be 0.667 time units.
Is there a time delay?
The time delay is 0.5 time units.
What controller parameters does this give (ZN open-loop method)?
Now if we put together all the above information and enter it into the Zeiglar Nichols equations for open loop response tuning we find that the
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