Bromine Dosing - Hanna Instruments PCA 311 Instruction Manual

Example: if the 0.0 to 1.0 V recorder output has been selected, the

BROMINE DOSING

Note:
Example: For setpoint 8.0 mg/L, delta=2.0, sample rate 10 minutes and
3 8
The output will be proportional with bromine if the read value
is between those limits.
operator can select 0.0 V to correspond to a concentration of
5.0 mg/L (Min. Rec. setting) and 1.0 V to correspond to a
concentration of 7.5 mg/L (Max. Rec. setting).
The full scale span of the recorder would then be 2.5 mg/L,
yielding a magnified view of the 5.0 to 7.5 mg/L concentra-
tion range on the recorder.
The analog output limits can be quickly consulted in one of
the iodine measuring panels.
The PCA 311-331 ana-
lyzers contain a simple
proportional dosing al-
gorithm. Proportional
dosing establishes and
maintains a controlled
and consistent concen-
tration level.
The analyzer has a relay for bromine dosing and also the
4-20 mA output could be configured as a dosing output.
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]
If the measured concentration is lower than setpoint minus
delta, the dosing will be continuous until the next measure-
ment is taken (one period).
measured value 7.5 mg/L, the proportional dosing will be active
for the initial 2 minutes and will stop for the remaining 3 minutes.
In fact: Time = (8.0-7.5)*10/2.0 = 2.5 minutes
Analog output = 4 + 16*2.5/10 = 8 mA
To modify the dosing
setpoint, enter the
"Bromine Menu" -
"Dosing control Br"
and edit the "Setpoint"
line. The value must
be between 0.1 and
9.9 mg/L.