Analog Output; Ph Dosing - Hanna Instruments PCA 311 Instruction Manual

ANALOG OUTPUT

pH DOSING

PROPORTIONAL DOSING
4 2
The type of analog output could be set as described in "Analog
output" chapter. The analog output span for pH could be set in
"pH Menu" - "Analog Output pH".
"Min. Rec" will set the recorder low limit and "Max. Rec" will
set the recorder high limit. The Max. Rec. value must be greater
than Min. Rec. value.
The output will be proportional with pH value if the read value
is between those limits.
The analog output limits could be quickly consulted in one of
the pH measuring panel.
The PCA 321 and PCA 331 can use ON/OFF or proportional
dosing algorithm to stabilize the pH.
The analyzer has a relay for acid or alkali dosing and also the
4-20 mA output could be configured as a dosing output.
To select the type of pH
dosing edit the "pH
Menu" - "Dosing
Control pH" - "pH
Control" line.
The available options
are Proportional and
ON/OFF .
The acid or alkali dosing is set in the "pH Menu" - "Dosing
Control pH" - "Dosing Type". When "Acid" is selected, the
analyzer will dose when the pH value is higher than the setpoint
and when "Alk" is selected, the analyzer will dose when the
pH value is lower than the setpoint.
The proportional dosing
algorithm turns on the
dosing relay proportion-
ally with the difference
between the setpoint and
measured value.
The equation for determining the time for relay on is:
dosing time = (set value - measured value)*Period/Delta
pH
Relay off
Proportional dosing
Relay on
Setpoint
time