Hach-Lange WTOS P-RTC - Manual (Page 16)

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Parameterization and operation
4.1.2 Closed-loop control according to measured phosphate values
For the closed-loop control of the precipitant dosing, the
measuring point for the phosphate concentration is downstream
of the precipitant dosing point.
Program 3
Closed-loop control:
• Measured value of the phosphate concentration in the reactor
outlet
• Specified profile for the flow rate (can be deactivated)
Note: The prerequisite for this program is that the PO
4
-P measurement
signal is valid. "Valid" means that the signal is present at the relevant
input.
Program 4
Load-proportional closed-loop control:
• Measured value of the phosphate concentration in the reactor
inlet
• Flow rate measurement
Note: The prerequisite for this program is that both measurement signals
are valid. "Valid" means that the signal is present at the relevant input.
4.2 Program change
4.2.1 Automatic program change
If a measurement signal drops out, an automatic program change
occurs and the system refers to the specified profile. The
program selection can be limited manually. The change between
programs occurs with a 5 minute delay, whereby the last
manipulated value set for the dosing is retained at the output.