KROHNE OPTISENS CL 1100 EN - Manual (Page 39)

TECHNICAL DATA
7
39
OPTISENS CL 1100
www.krohne.com 01/2012 - 4001834501 - MA OPTISENS CL 1100 R01 en
Technical data
7.1 Measuring principle
The sensor has three electrodes: a measuring electrode (gold), a counter electrode (gold), and a
reference electrode (Ag/AgCl). A precise potential is built up between the measuring and the
counter electrode. The measuring electrode starts polarizing, i.e. negative charges collect close
to the measuring electrode. After polarization the electrical current decreases to 0 mA as long
as the polarising layer is not changed.
Free chlorine molecules that hit the surface of the measuring electrode take a defined portion of
the charge with them, changing the potential of the measuring potential. The signal converter
constantly measures the potential between measuring and reference electrode and immediately
readjusts the potential as soon as it begins to change. The current needed to maintain a constant
potential is directly correlated to the free chlorine concentration in the measuring medium.
Free chlorine measurement
Figure 7-1: Free chlorine measurement
1 Reference electrode
2 Voltage measurement
3 Current needed to maintain the constant potential
4 Counter electrode
5 Measuring electrode
.book Page 39 Wednesday, February 1, 2012 11:58 AM