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FIG. 7.40.16 The total loop time delay (t1) is the sum of all dead times and time delays (lags) in the loop.

FIG. 7.40.16 The total loop time delay (t1) is the sum of all dead times and time delays (lags) in the loop.

tions of the titration curve. Increases in amplitude are difficult to detect once the oscillation moves outside the steep slope region of the titration curve.

The peak error for continuous pH control is proportional to the ratio of dead time to time constant multiplied by the open-loop error (the error with the loop in manual), if the dead time is less than the time constant. If Td exceeds t1 , the peak error is proportional to the full open-loop error. The integrated error is proportional to this peak error multiplied by the dead time. It is critical to mark these errors along the abscissa of the titration curve and translate them to the ordinate (pH axis). Peak errors will be much larger than expected for excursions along the steep slope of the curve.

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