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Instruction Manual
Figure 7-32.
Split Range (A) and Deadband
Control (B) illustrations.
pH Deadband
The pH control loop utilizes a deadband around the setpoint. The setpoint deadband upper and lower limits are configurable. The system
does not allow for entries wherein the upper limit is lower than the lower limit or vice versa. See Deadband Control in Figure 7-32B.
Region A shows when the pH is higher than the lower deadband limit and lower than the upper deadband limit, the Controller Value is
set and held at 50%. This means that the base pump flow rate is set to zero and the CO
2
MFC flow rate is set to the appropriate value in
accordance with the minimum CO
2
% setpoint entered in the Media Maintenance Phase.
Region B shows when the pH loop is above the upper deadband limit. The loop is in automatic control, and the Controller Value is limited
to a maximum of 50%.
Region C shows when the pH is below both the setpoint and the lower deadband limit. The loop is in automatic control, and the
Controller Value is limited to a minimum of 50%.
NOTE:
Deadband parameters are sign sensitive. The user may set a negative upper deadband limit to adjust the value below the pH
setpoint as in Figure 7-32B(ii). This allows the CO
2
to control to setpoint without entering the deadband Region A. The base pump (Region
C) will generally always be operated with a positive deadband.