Installation - Hach Chlorine Sensor User Manual

LED color Condition Description
Green On (steady) The processor is working correctly.
Off or On The voltage is too low which has caused a
(flashing) malfunction of the processor.
Orange Off The sensor is working correctly.
On (steady) The internal signal from the working electrode
has the wrong polarity.
If the LED is on for longer than 30 minutes, do
sensor maintenance.
On (flashing) The level of chlorine concentration is too high.
Reduce the chlorine concentration.
Theory of operation
This sensor is a potentiostatic three-electrode instrument, with a
specially placed counter electrode. The measuring (working) electrode is
membrane covered and is in the electrolyte together with the reference
electrode. This electrode area contains a special electrolyte and is
separated from the measured sample by the membrane.
The sensor uses an amperometric method to measure chlorine
concentration in water. Chlorine species in the measured sample pass
through the membrane and react with the working electrode. This
reaction produces an electrical current proportional to the chlorine
concentration. The electrical signal is amplified by the sensor electronics
and is transmitted to the instrument in voltage format (mV). The third
electrode (auxiliary or counter electrode) is put in the measured sample
and is used to maintain a constant working potential on the working
electrode. The working potential is controlled by the reference electrode.
This configuration increases measurement stability.
The highly-buffered electrolyte inside the membrane cap supplies
internal compensation for pH fluctuations in the measured sample. The
buffer helps to immediately change hypochlorite ions permeating the
membrane into hypochlorous acid molecules. The electrolyte makes the
measurement almost independent of the pH of the measured sample.
The chlorine readings are independent from the temperature of the
measured water due to internal temperature compensation.
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Product components
Refer to Figure 2 to make sure that all components have been received.
If any of these items are missing or damaged, contact the manufacturer
or a sales representative immediately.
Figure 2 Sensor components
1 Chlorine sensor
2 Special abrasive paper
3 Split ring O-ring

Installation

C A U T I O N
Multiple hazards. Only qualified personnel must conduct the tasks
described in this section of the document.
4 Split ring
5 Electrolyte