Hanna Instruments PCA 310 - Manual (Page 38)

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The output will be proportional with chlorine if the read value
is between those limits.
Example: if the 0.0 to 20.0 mA recorder output has been selected, the
operator can select 0.0 mA to correspond to a concentration
of 3.00 mg/L (Min. Rec. setting) and 20.0 mA to correspond
to a concentration of 4.50 mg/L (Max. Rec. setting).
The full scale span of the recorder would then be 1.5 mg/L,
yielding a magnified view of the 3.00 to 4.50 mg/L concentration
range on the recorder.
The analog output limits can be quickly consulted in one of
the chlorine measuring panels.
CHLORINE DOSING
The PCA 310-330
analyzers contain a
simple proportional
d o s i n g a l g o r i t h m .
Proportional dosing
establishes and maintains
a controlled and consis-
tent concentration level.
The analyzer has a relay for chlorine dosing and also the 4-20 mA
outputs could be configured as dosing outputs.
The equation for determining the time for relay on is:
dosing time = (set value - measured value)*Period/Delta
The analog output will have the value:
analog output [mA] = 4 + 16 * dosing time/Period [mA]
Note: If the measured concentration is lower than setpoint minus delta,
the dosing will be continuous until the next measurement is
taken (one period).
Example: For setpoint 3.00 mg/L, delta=0.5, sample rate 5 minutes and
measured value 2.80 mg/L, the proportional dosing will be active
for the initial 2 minutes and will stop for the remaining 3 minutes.
In fact: Time = (3-2.8)*5/0.5 = 2 minutes
Analog output = 4 + 16*2/5 = 10.4 mA
To modify the dosing
setpoint, enter the
“Chlorine Menu” -
“Dosing control Cl”
and edit the “Setpoint”
line. The value must
be between 0.10 and
4.90 mg/L.
Setpoint
delta
Cl
mg/L
time
Proportional dosing
Relay on
Relay off
Setpoint :2.50 mg/L
Delta
:0.1 mg/L
Low Point:0.01 mg/L
Low Point:Inactive
Max. ON :060 min