English (GB)
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5.7.6 ClO
2
alarm value
An alarm is triggered, if the measured ClO
2
value violates an
upper or lower limit.
Fig. 17 Alarm limits
Upper limit
An alarm is triggered, if the measured ClO
2
value exceeds X mg/l
(X = upper limit + 0.5 hysteresis).
The alarm message is removed, if the measured ClO
2
value
undershoots X mg/l (X = upper limit - 0.5 hysteresis).
Lower limit
An alarm is triggered, if the measured ClO
2
value undershoots X
mg/l (X = lower limit - 0.5 hysteresis).
The alarm message is removed, if the measured ClO
2
value
exceeds X mg/l (X = lower limit + 0.5 hysteresis).
Hysteresis
The hysteresis indicates the tolerance for both alarm limits.
Alarm delay
The alarm trigger can be delayed.
5.8 Water meter
A water meter is required for dosing with proportional control and
combined control. The system can operate with water meters that
deliver a pulse signal or a current signal.
5.8.1 Water meter with pulse signal
The water meter must emit pulses with a frequency between 0.05
and 50 Hz. At least one pulse per 20 seconds must be emitted to
keep the system running.
The maximum voltage has to be 13 V.
5.8.2 Water meter with current signal
The water meter must emit a signal between 0(4) and 20 mA.
The load is 50 Ω.
5.9 ClO
2
pump type
The dosing pump for ClO
2
can be mechanical or digital.
A mechanical pump is controlled by power-on (T
on
) and power-off
(T
off
). The dosing rate depends on the following ratio:
A digital pump is controlled by a current signal 0(4)-20 mA.
5.9.1 Mechanical dosing pump
Stroke length (S
DP
)
If the dosing flow is low, reduce the stroke length at the pump. Set
the stroke length parameter to the same value at the control unit.
Consequently, the pump executes more strokes with a smaller
stroke length. The resulting dosing rate remains the same. The
ClO
2
is dispersed evenly and does not produce any clouds in the
main line.
Fig. 18 Dispersion of dosing volume at different stroke lengths
Minimum switch-on time (min. Ton)
The minimum switch-on time can be adjusted and should be kept
as short as possible.
Example: If the dosing pump executes 120 strokes per minute,
the minimum switch-on time is 0.5 seconds, which equals 1
stroke.
5.9.2 Digital dosing pump
For digital dosing pumps, the stroke length parameter has to be
set to 100 % at the control unit.
5.10 Relay polarity
The polarity of the alarm relay and warning relay can be changed
from N.O. to N.C.
N.C. means normally closed. If a power failure occurs, the relay
signals a fault. This is the fail safe setting.
TM06 0950 1214
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