English (GB)
24
Setpoint control
The setpoint control mode is particularly suitable for industrial
water applications:
• A setpoint for the target ClO
2
concentration in the main line
has to be specified.
• The control unit measures the actual ClO
2
concentration with
a measuring cell.
• The setpoint control mode compares the actual values with the
setpoint. Based on the deviation, it calculates the quantity of
ClO
2
solution required to achieve the setpoint.
• The setpoint control sends an actuating variable to the dosing
pump.
• The dosing pump doses the corresponding quantity of ClO
2
solution from the internal batch tank into the main water line.
Combined control
This control mode combines setpoint control and proportional
control. The actuating variable calculated by the setpoint control
is scaled in proportion to the current water flow in the main line.
Fig. 15 Control mode scheme
5.6.2 Actuating variable (y-out)
The actuating variable is the control signal for the ClO
2
dosing
pump (0-100 %). The actuating variable is calculated
continuously by the dosing control.
5.6.3 Added quantity (added)
The added quantity is the quantity of ClO
2
in mg/l that is added to
the water flow in the main line in proportional control mode.
5.6.4 Setpoint (setp)
The setpoint is the target ClO
2
concentration in the main line
which the system tries to achieve continuously.
The setpoint is used for setpoint control or combined control.
5.6.5 Control characteristic
The setpoint control and combined control operate with the
control characteristics P, PI or PID.
5.6.6 Proportional range (Xp)
Proportional range is a setting of the control characteristics P, PI
or PID.
5.6.7 Reset time (TN)
Reset time is a setting of the control characteristics PI or PID.
The step-response from the PI control is composed of two parts:
the actuating variable (corresponding to X
P
) and the rate at which
it increases. Reset time indicates the rate, at which the control
signal increases. The higher the value of reset time, the slower
the rate at which the control signal increases over time.
5.6.8 Derivative action time (TV)
Derivative action time is a setting of the control characteristic
PID.
5.6.9 Maximum dosing flow (Qmax)
This setting is useful, if the maximum capacity can not be limited
at the pump.
Example: The pump has a fixed dosing flow of 5 l/h at 20 mA. To
limit the pump to a maximum flow of 2.5 l/h, set Q
max
to 50 %.
5.6.10 Dosing stop input
The dosing stop input can be connected to a higher-level control
system. A signal to this input stops the ClO
2
dosing pump.
5.6.11 Dosing time monitoring
The alarm is triggered, if the actuating variable exceeds the
maximum dosing flow for the specified time, see section
5.6.9 Maximum dosing flow (
Qmax
).
5.6.12 Failure input
The failure input can be connected to a gas warning device. A
signal to this input terminates the ClO
2
production and stops the
ClO
2
dosing pump.
TM06 0640 1214
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