BWT Bewazon VULW 45 - Page 24

EN
24
Ozone device: PID controller
During operation with the PID controller, the ozone device delivers an
ozone output that the corresponding measurement signal guides to-
ward(andmaintainsascloseaspossibleto)thedenedsetpoint.The
measurement signal is an external 4 to 20 mA signal that is supplied
via the analogue input module.
Signal source unit: Physical unit of the signal, e.g. the ozone concen-
tration measured in “mg/l”
Min. signal: 4 mA =: Measurement signal that corresponds to the 4 mA
signalling current, e.g. 0.0 mg/l
Max. signal: 20 mA =: Measurement signal that corresponds to the
20 mA signalling current, e.g. 2.0 mg/l
Controller setpoint: Default setpoint for the ozone dosage, e.g. 0.25 mg/l
TimeconstantTiandproportionalamplicationVp:Controllerconstants
that are based on the properties of the control section, e.g. the time
taken for the water to reach the metering point. The time (in seconds) it
takesthewatertoowfromtheozoneinjectortothemeteringpointcan
be used as the starting value for Ti. Approximately half of that time can
be used as a starting value for Vp. The polarity of the control response
canbepredenedbythepolarityoftheproportionalamplicationVp.
Set integrator level: A starting value for controller operation can be en-
tered here. This value corresponds to the ozone level based on which
the plant is controlled. This value can be changed manually, even when
the PID controller is operating.
Example: The time taken for the water to reach the metering point from
the injector is three minutes. The setting for the controller constants
should therefore be based on the values Ti = 180 sec., Vp = 90. These
values should then be optimised, which can also be done during ope-
ration with the PID controller.
Note: Automatic level switching is preceded by a hysteresis corres-
ponding to 0.5 steps, so that the unit does not switch back and forth
constantly when the measurement signal leads to an ozone output
around the limits for switching between two ozone levels.
Analogue output
With this option, the unit sends an analogue 4 to 20 mA output signal
based on the ozone level currently set. Thus, this signal can be used
externally for ozone capacity dependent control tasks or for monitoring.
To operate the device with the analogue output, the signal for “analogue
output” must be activated on the “Ozone device:extended settings”
screen.
Preset: The customer preset corresponds to the conventional mixing
operation, regardless of the ozone output, i.e.
airowo󰀨=>mixingo󰀨=>outputsignal=4mA
airowon=>mixingon=>outputsignal=20mA