Hanna Instruments PCA 310 - Manual (Page 43)

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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” - “Dos-
ing Control pH” edit the “Setpoint” line. The value must be
between 2.00 and 12.00 pH.
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, 1.5, 2.
To modify the dosing time edit the “Period” line. The allowed
values are between 3 and 120 seconds.
Note: The period is related only to the dosing process. The pH mea-
surement take place with a higher rate.
Note: 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 set-
point 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
0.05 and 2.00 pH.
OVERDOSING PROTECTION
To prevent overdosing a “Detector Error” is generated if the
dosing command is on for the Max. ON time and the read
value is changing less than 0.1 pH.
The acid/alkali dosing is stopped and the SYSTEM ERROR
LED starts blinking. The dosing could be resumed only by
restarting the controller.
Setpoint
Hysteresis
pH
time
Relay
on
Relay
of
f
Relay
on
Relay
of
f
Relay
on