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4.5 Installing electrodes
4.5.1 Free Chlorine electrode OCS140
General Information
Free chlorine is defined as the sum of Hypochlorous acid (HOCL), hypochlorite ions
(OCl
̄ ) and Cl
2
, and the proportion of the different free chlorine species is pH and
temperature dependent.
The hypochlorous acid (HOCl) contained in the medium diffuses through the sensor
membrane and is reduced to chloride ions (Cl-) on the gold cathode. On the silver
anode, silver is oxidised to silver chloride. The electron release of the gold cathode
and electron acceptance on the silver anode result in a current flow which is
proportional to the HOCL concentration in the medium under constant conditions.
Since the concentration of hypochlorous acid in the medium depends on the pH
value, pH has to be measured in order to perform an accurate compensation and
present a free chlorine value.
Preparation of the free chlorine sensor for start up
NOTE:
The free chlorine sensor is shipped wet, filled with electrolyte from the factory and
does not requires electrolyte refilling before using.
NOTE:
The free chlorine cable will arrive connected to the electrodes card. For more
information about wiring the free chlorine cable look at figure 4.
1. Verify that the chlorine sensor is full with electrolyte and the membrane is not
damaged. Additional information about membrane replacement or electrolyte
refilling exist in chapter 6.4 (Chlorine electrode maintenance).
2. Install the sensor into it's position in the acrylic flow cell and HAND-tighten.
3. Route the wires (if not wired) through an open hole in the gasket and connect
to the electrodes card (figure 3). Connect wire K to CL-K terminal, wire A to
CL-A terminal and the unmarked wire (ground) to the ground terminal.
Safety hint:
Some electrolyte contains diluted acids. Please read the warnings on the electrolyte
bottle.
Safety hint:
Do not Swallow the electrolyte. Avoid contact of the electrolyte with skin and eyes.
Otherwise, wash with a lot of water. in case of eye inflammation, contact a doctor.
NOTE:
It is recommended to read the complete instruction manual provided with the sensor.