Hach-Lange NO3D sc Nitrate Sensor - Manual (Page 9)

9
General Information
2.3 Theory of operation
The NO3D sc sensor utilizes ion-selective electrode technology to
measure nitrate ions (NO
3
- ) in a waste water sample. Well-known
interferences of temperature and chloride are compensated by
using appropriate built-in sensors. The reference electrode is a
differential pH technology and does not have direct contact with the
process and therefore, it is particularly stable against drift.
Ion-selective electrodes have a special membrane to which only a
specific type of ion can adhere. As a result an ion-specific potential
forms on the membrane surface. To be able to measure a potential
difference, a reference electrode is required, which is not affected
by the sample to be measured.
CARTRICAL TM technology reduces cross-sensitivities by not only
calibrating each electrode individually but also calibrating all
3 electrodes to each other.