What is Free / Combined Chlorine Analyzer?
Free/combined chlorine analyzer is a system that used for monitoring free chlorine, combined chlorine, total chlorine, chlorine dioxide and dissolved ozone. It consists of two main parts:
- The meter / regulator
- The chlorine sensor
In some application it is necessary to measure before and after the process in order to obtain the difference of the two measuring. The analyzer allows a differential measuring, by using two transmitters featuring the same measuring scale.
Chlorine Analyzer Working Principle
Chlorine analyzer measures the oxidizing substances in water with two types of sensors:
- Two or three electrodes immersed in an electrolyte separated from the sample by a membrane selective to the substance to be measured.
- Three electrode amperometric cell, commonly called “potentiostatic sensor”
In the two electrodes cell, a suitable polarization voltage is applied to the two electrodes (anode and cathode) through which the electric current flows is proportional to the concentration of the oxidizers present in the solution.
In the three electrodes cell, a suitable bias voltage is applied to the two electrodes (working and counter electrode) in contact with the sample, through which the electric current flows is proportional to the concentration of the oxidizers present in the solution. A reference electrode is used to compensate the internal electrical resistance and the oxidation-reduction potential that occur on the measuring.
An oxidation-reduction reaction take place at each electrode surface when a voltage is applied which causes a current to flow. Chlorine in the solution will diffuse through the membrane to the working electrode surface as shown below. Chlorine is converted to chloride and current is generated directly proportional to the concentration of chloride in the sample.