8
4 Operating range
(1) Only NH
4
+
ions (ammonium) are present
(2) The ratio of NH
4
+
ions (ammonium) and
NH
3
(ammonia) is 1:1
(3) Only NH
3
(ammonia) is present
Note:
The presence of ammonia in the process medium is
heavily dependent on its pH value (see above
diagram).
In the acidic range, there will be a predominance of
ammonium (NH
4
+
) ions that are
not
detected by the
sensor!
At approx. 9.3 pH, the concentration ratio of ammonia
(NH
3
) and ammonium (NH
4
+
) is about 1:1.
It is only in the heavily alkaline range that ammonia is
predominant.