ENDRESS+HAUSER  CCS240-N

Sensors for chlorine dioxide

Amperometric, membrane-covered sensors for installation in the CCA250 assembly

Chlorine dioxide is used for disinfection of water. Its dosing must be carefully controlled to suit the application. Too low a concentration makes the degree of disinfection questionable.

Too high a concentration can result in corrosion effects, impairment of taste or skin irritation.

The CCS240 and CCS241 sensors are applied for measurement of chlorine dioxide in the following fields:

• Drinking water treatment
• Pool water treatment
• Industrial water treatment

• Measurement in the CCA250 flow assembly is almost independent of flow rate in the range above 30 l/h
• No zero point calibration necessary. This means complicated installation of an active carbon filter, as in open chlorine dioxide sensors, is not necessary.
• Measured values are not affected by conductivity fluctuation of the medium.
• The CCS240 sensor is ready for measurement after a polarisation time of approx. 10 ... 30 minutes. The CCS241 sensor requires 45 ... 90 min.
• Easy membrane replacement thanks to ready-made membrane head
• Recalibration intervals approx. 1 ... 4 months under constant operating conditions

The CCS240 and CCS241 sensors are used for measurement of chlorine dioxide. The membrane-covered CCS240 / CCS241 sensors consist of a cathode serving as the working electrode and an anode acting as the counter electrode. These electrodes are immersed in an electrolyte. Electrodes and electrolyte are separated from the medium by a membrane. The membrane prevents the loss of electrolyte and the penetration of contaminants.

To calibrate the measuring system, determine the content of chlorine dioxide using the DPD method. You need a photometer with the pertaining reagents. The determined value is the calibration value for the transmitter.

The concentration of chlorine dioxide is determined according to the amperometric measuring principle. The chlorine dioxide (ClO 2 ) 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 oxidized 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 chlorine dioxide concentration in the medium. This process takes place within a wide pH and temperature range.

A complete measuring system comprises at least:

• Chlorine dioxide sensor
• Liquisys M CCM223/253 transmitter
• Special measuring cable
• Flow assembly
• Reference measuring instrument for determination of chlorine dioxide according to the DPD method