Operators Handbook DCU3 – System
6., Main function „Control Loops“
BAEDCU3 - Rev. 4.6 - 0504
6 - 11
6.8
pH - Control Function Operating as PID - Controller
The pH - control function of the DCU system usually works in PID - behavior. The pH - control function
triggers the corrective agent pumps (or dosing valves) in split-range mode via two pulsewidth-
modulated outputs. This allows a simultaneous control of both the acid and base pump (or valves).
As a special feature the acid and base control signals remain „off“ as long as the deviation
of the actual value lies within the parametrized dead band. This feature prevents unneces-
sary dosage of acid or base.
6.8.1 Operating
Display
For a description of the tags, the physical units or entries, the displayed value or function
and of the required inputs see the table in section
6.3,
Controller Operation in General.
6.8.2 Operating
Information
For entering controller parameters in the parametrization menu see the section „Controller
Parametrization in General“ further above.
6.8.3 Special
Notes
The dead band is the percent span of the measuring range; it is symmetrical to the setpoint.
– Example: measuring range: 2 - 12 pH, span: 10 pH, DEADB: 0,1 pH, SETP: 7,0 pH
In this example the controller output is inactive in the range of 6.9 pH to 7.1 pH
When a gas mixing system is connected, the CO
2
valve is controlled via the negative output
signal of the pH controller (0 ... (-100) %)
If you select one of the operation modes „auto“, „profile“ or „manual“, the dosing counters
ACID and BASE will automatically be switched over to the „tlize“-mode.
Summary of Contents for DCU 3
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Page 4: ...Operators Handbook DCU3 System Introduction BAEDCU3 Rev 4 6 0504...
Page 8: ...Operators Handbook DCU3 System Contents BAEDCU3 Rev 4 6 0504...
Page 10: ...Operators Handbook DCU3 System 1 Design and Function BAEDCU3 Rev 4 6 0504 1 2...
Page 74: ...Operators Handbook DCU3 System 6 Main function Control Loops BAEDCU3 Rev 4 6 0504 6 40...
Page 80: ...Operators Handbook DCU3 System 7 Main function Batch Control BAEDCU3 Rev 4 6 0504 7 6...
Page 88: ...Operators Handbook DCU3 System 8 Main Function Recipes BAEDCU3 Rev 4 6 0504 8 8...
Page 106: ...Operators Handbook DCU3 System 9 Main function Maintenance BAEDCU3 Rev 4 6 0504 9 18...
Page 110: ...Operators Handbook DCU3 System 10 Main Function Documentation BAEDCU3 Rev 4 6 0504 10 4...
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