ABB AW400 Series, Instruction Manual

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6.1.5 Chlorine / Chlorine Dioxide / Ozone
The calibration procedure is necessary to standardise the sensor sensitivity. The calibration procedure allows
to set both the slope and the offset of the curve giving the chlorine/chlorine dioxide/ozone concentration as a
function of the µA from the cell (sensitivity).
The ABB Monitor allows an easy two point calibration and the two points can be freely chosen, provided they
are distant enough and inside the selected measuring range. In this way the
instrument is given all the
parameters it needs to fix the calibration curve. The calibration procedures involve both the transmitter and
the sensor.
The following description indicates step by step the calibration procedure:
If the sensor is a new one leave it working for 24 hours so that the electrodes can gain the correct sensitivity.
Press the MENU key to enter the Instrument Calibration submenu and enter the CALIBRATION menu and
then the channel of the ORP probe. The following display will appear:
X X . X X C l 2 3 . 5 ° C
P 1 : Y Y . Y
P1 (YY.Y) indicates the first point in calibration (the lower one), XX.XX is a chlorine/chlorine dioxide/ozone
concentration reading. This reading, however is not a REAL value, but it's based upon calibration parameters
previously stored. XX.XX serves as an indication of the stability of the measure. 0.000 is a default ppm value
and can be freely changed. YY.Y is a value set at the last calibration and can be freely modified. Press
ENTER and insert the correct value.
Open the sample flow to the cell, with a chlorine concentration zero or near zero. Let the system stabilise and
then take a sample from the drain tube. Perform laboratory analysis of the chlorine species being measured
(free or total) or of the chlorine dioxide concentration. Correct the 0.000 if needed according to the lab
analysis. Confirm with the ENTER key.
If the following message appears:
-Bad Input!-
It means the buffer solution is bad since the mV generated are too close. This message can be ignored by
pressing the END key.
If ENTER is pressed new calibration data (e.g. µA corresponding to the displayed ppm value) are overwritten
to previously stored values in not volatile memory
Pass on to the second point (P2) of calibration pressing the button MENU.
Allow a sample flow to the cell with a chlorine/chlorine dioxide concentration as near as possible to the chosen
full-scale, let it stabilise for some minutes (it depends upon the plant configuration) and then take a sample
from the drain tubing.
Analyse the solution for free or total chlorine or for chlorine dioxide, (depending upon the kind of measure the
Monitor is operating).
Correct the displayed ppm value in YY.Y according to the lab analysis as previously explained. If you want to
save these values (storing the values of µA corresponding to the measured chlorine concentration) push
ENTER. If you don't want to save above mentioned calibration parameters push END. So forth, previously
stored parameters aren't destroyed and they remain still valid for the computation (if the range setting has not
been changed).
To start the measure press the END key and the display will show the measured value.