KROHNE OPTISENS CL 1100 EN - Manual (Page 40)

7
TECHNICAL DATA
40
OPTISENS CL 1100
www.krohne.com 01/2012 - 4001834501 - MA OPTISENS CL 1100 R01 en
Free chlorine (chlorine dissolved in water) changes its chemical composition depending on the
pH value of the water. The pH value has consequences for the disinfection strength: with
increasing pH the disinfection strength decreases.
• below pH3: Chlorine gas Cl
2
• between pH3 and pH8: Hypochlorus acid HOCl
• above pH8: Hypochlorite ClO
In order to obtain a reliable free chlorine measurement you should either control or compensate
the pH value of the measuring medium. Because the pH measurement is temperature
dependent, it also makes sense to measure the temperature. For further information on
installing a pH sensor with temperature measurement, refer to the pH sensor manual.
Figure 7-2: Composition of free chlorine depending on pH value
.book Page 40 Wednesday, February 1, 2012 11:58 AM