fore records the free chlorine as almost
100 % HOCI. To ensure that the concen‐
tration value measured by the ampero‐
metric chlorine measuring system corre‐
sponds to this free chlorine value, the pH
influence on the chlorine value measured
by the sensor can be compensated by the
controller. The controller can either per‐
form this pH compensation automatically,
via an integrated pH-measurement, or
manually based on a fixed pH value. We
recommend the automatic version. In
doing so, it is imperative that you also
measure the sample water temperature,
which has a significant influence on the
pH measurement. If this influence has not
been compensated, the pH value would
be measured incorrectly and the chlorine
value would therefore also be incorrectly
compensated.
No calibration is possible at high pH
values without pH compensation, because
the difference between the measurement
using the chlorine sensor and the compa‐
rative DPD 1 reference method is too
great.
The operational pH calibration range is:
pH 4.00 ... 8.50, Temperature: 5 ... 45 °C
Calibration of the chlorine
sensor with activated pH compensa‐
tion
It is imperative that you always cali‐
brate the pH sensor first before the
chlorine sensor. The chlorine sensor
always needs to be calibrated any fur‐
ther time the pH sensor has to be cali‐
brated. Otherwise the chlorine meas‐
urement will be incorrect.
Sensor type:
First select the sensor type. The sensor
type is given on the sensor nameplate.
This sensor selection is necessary and
activates the sensor-specific data in the
controller.
Measuring range of the sensors
Select the measuring range. The meas‐
uring range is given on the sensor name‐
plate. An incorrect measuring range leads
to an incorrect measurement.
Temperature
The temperature measurement is used
only for information and recording pur‐
poses, but not for temperature compensa‐
tion. Temperature compensation is per‐
formed in the sensor. If the measured
variable
[Chlorine dioxide]
and the
[CDP]
type of sensor have been selected, then a
separate temperature measurement is
needed for temperature compensation.
Setting measured variables
57
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