47
Setpoint
Hysteresis
pH
time
Relay on
Relay off
Relay on
Relay off
Relay on
The analog output will have the value:
analog output [mA] = 4 + 16 * dosing time/Period [mA]
Note: If the measured pH is lower (or higher for acid dosing) than setpoint minus (plus) delta,
the dosing will be continuous until the pH period elapsed.
To modify the dosing setpoint, enter the “pH Menu” - “Dosing Control pH” edit the “Setpoint”
line. The value must be between pH 2.00 and 12.00. To modify the Delta, edit the “Delta”
line. The available values are 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 2.0. To
modify the dosing time edit the “Period” line.
The allowed values are between 3 and 120 seconds. The period is related only to the dosing
process. The pH measurement take place with a higher rate.
The speed of the analyzer could be modified by changing the regulator period. A new decision
regarding the pH dosing is taken only after one period elapsed.
The Setpoint and Delta could be quickly consulted on one pH measuring panel.
ON/OFF dosing
If this mode is selected the “Period” and “Delta” has no effect. The algorithm will use only “Setpoint”
and “Hysteresis”.
For alkaline dosing, the relay will stay on until the pH increases to the setpoint plus hysteresis value,
then the relay stays off until the pH decreases to a value equal to setpoint.
For acid dosing, the relay will stay on until the pH decreases to the setpoint minus hysteresis value,
then the relay stays off until the pH increases to a value equal to setpoint.
To set the hysteresis edit the “pH Menu” - “Dosing Control pH” - “Hysteresis” line. The hysteresis
value must be between pH 0.05 and 2.00.
The equation for determining the time for relay on is:
dosing time = (set value - measured value)*Period/Delta
pH SETTINGS (PCA320, PCA330, PCA340)
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