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11
Measurement, control, dosage
(pH value, redox value, chlorine/bromine)
The following figure shows the correlation between the current
measured value and the dosing output for various configurations of the
proportional range for pH (dosage direction D-).
1
dosing output in %
2
Measured pH value
3
Configured setpoint pH 7.20
4
Proportional range 0.50 pH (pH 7.20 - 7.70)
5
Proportional range 1.00 pH (pH 7.20 - 8.20)
6
Proportional range 2.00 pH (pH 7.20 - 9.20)
7
At the end of the proportional range, dosing output reaches
100%, i.e. the dosage pump runs permanently.
INFO
Basic rules for the proportional range
The following basic rules are helpful for the proportional
range:
A larger proportional range will result in a lower
dosing output.
For example, doubling the proportional range will halve
the dosing output.
A smaller proportional range will result in a higher
dosing output.
For example, halving the proportional range will double
the dosing output.
INFO
Pool volume and dosing output
The default values indicated for the proportional range
are orientated toward the following general conditions.:
Assuming a pool volume of ca. 40m³
•
dosing output on pumps ca. 1.5 l/h
•
For pool volumes that are larger in relation to pump
dosing output, the proportional range generally
has to be reduced.
This leads to longer switch-on times on the dosage
pump, and therefore to higher dosage overall.
For smaller pool volumes in relation to pump
dosing output, the proportional range generally
has to be increased.
This leads to shorter switch-on times on the dosage
pump, and therefore to lower dosage overall.
11.4.5
Minimum dosing rate
A purely proportional control system generally has problems in actually
attaining the desired setpoint. When approaching the setpoint, the
dosing output drops even further and approaches 0%.
In order to guarantee the setpoint is reached, a minimum dosing
output is configured that is maintained until the setpoint is actually
reached.
The following figure uses the pH control system as an example to
show the progress of dosing output while accounting for the minimum
dosing rate.
1
dosing output in %
2
Measured pH value
3
Configured setpoint pH 7.20
4
Configured minimum dosing rate (5%)
5
Constant
upon approaching the setpoint
6
Theoretical progression without minimum dosing rate
User Manual PoolManager
®
INFO
Influence on the control system
In the following cases, the proportional range should be
reduced, thereby increasing the dosing output:
If the control system reacts slowly, and the setpoint
•
is not approached or is only approached slowly
In the following cases, the proportional range
•
should be increased, thereby decreasing the
dosing output:
If the control system reacts too quickly or unstably
•
dosage
of
the
minimum
INFO
Control system output when near the setpoint
The control system and dosage output when near the
setpoint, i.e. for marginal rule deviations, is determined
by the configured minimum dosing output. The
proportional range exerts no influences when near the
setpoint.
dosing
rate
30
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