Hanna Instruments HI 9910 - Manual (Page 26)

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PROPORTIONAL CONTROL PROPORTIONAL CONTROL PROPORTIONAL CONTROL PROPORTIONAL CONTROL PROPORTIONAL CONTROL
In order to optimize the controlling process and reduce the amount of
chemicals used, it is recommended to use a proportional dosage
appropriate for the system.
All models allow for a proportional band (0 to 2.0 pH or 0 to 200 mV
delta) as well as a time cycle (from 0 to 90 seconds) to be set. The
proportional dosage is obtained by personalizing a current pulse
whose height equals the pH or ORP proportional delta and the
length corresponds to the selected time cycle.
The controller will enter proportional dosage
proportional dosage proportional dosage proportional dosage proportional dosage at setpoint plus setpoint plus setpoint plus setpoint plus setpoint plus
or minus the preselected or minus the preselected or minus the preselected or minus the preselected or minus the preselected delta. It will then keep the dosing
relay activated for a period proportional to the difference between the
measurement and the setpoint over the cycle.
OXID
RED
SECONDS
0 90
45
0
pH
2.0
0.5
1
1.5
PROPORTIONAL SETTINGS
DOSING DIRECTION
Select the direction of dosing through the "OXID"/”RED” switch (see 8
- Functional Diagram). For reducing dosage (i.e. lowering the mV
value) leave the selector on "RED". Likewise, for oxidizing solutions (to
increase the mV) select the “OXID” position.
e.g. Dosing reducing substances
Setpoint = mV 650
Measured value = mV 700
switch to the "RED" position (see 8 - Functional Diagram).
e.g. Dosing oxidizing substances
Setpoint = mV 650
Measured value = mV 500
To adjust the sample stream to the setpoint, you need to
dose oxidants, therefore select "OXID".
OXID
RED