7.2___PROPORTIONAL IN TIME
Example:
If we enter a pH set point = pH 7.20 and a safety range BND = pH 0.20, we can control the pH,
keeping it between 7.20 and 7.40 with the Ton and Tof times.
If we enter a Redox set point = 700 mV of chlorine and a safety range BND = 50 mV, we can
control the content, keeping it between 650 ppm and 700 ppm with the Ton and Tof times.
There are two permissible control modes within this range:
1) Ton and Tof having different values
Example: Ton = 10 sec Tof = 5 sec.
The metering time of the pump will always be: ON for 10 seconds and OFF for 5 seconds, within
the range that has been set.
2) Ton and Tof having the same values
Example: Ton = 10 sec Tof = 10 sec.
The metering time of the pump will be proportional in time as the Set Point is approached within
the range that has been set.
Example of proportional control:
Proportional control as described above is shown in the following diagrams. In addition, the type of
control that would be implemented if the operator were to set a hysteresis (HIS) value is shown as
a dotted line.
Set Point = pH 7.20
HIS = 0.10 pH (the control implemented is shown as a dotted line)
Ton = 10 Secs
Tof = 10 Secs
BND = pH 0.20
Set Point = 700 mV
HIS = 50 mV (the control implemented is shown as a dotted line)
Ton = 10 Secs
Tof = 10 Secs
BND = 50 mV
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