Function
Oxymax H COS21D
18
Hauser
Reference value for practically complete polarization of a sensor that was in storage for an
extended period beforehand:
• COS21D-A/C: 2 hours
• COS21D-B: 12 hours
After this time, measurements close to the determination limit make sense.
The polarization time needed is shorter for sensors which were in operation shortly beforehand.
5.2.2
Membrane cap
The oxygen dissolved in the medium is conveyed to the membrane by the incoming flow. The
membrane is only permeable for dissolved gases. Other substances dissolved in the liquid phase
e.g. ionic substances, will not penetrate through the membrane. Therefore, medium
conductivity has no impact on the measuring signal.
The sensor is supplied with a standard membrane cap which can be used for all common
applications.
The membrane cap is pretensioned at the factory and can be installed directly.
There are also special membrane cap kits as an option (--> Accessories):
• FDA-Kit: membrane materials are in conformity with FDA
• SIP/CIP-Kit: membrane material is specially designed for the high demands of frequent
SIP/CIP processes
!
Note!
The electrolytes in the membrane caps are specific to the sensor versions and must
not
be mixed
together!
5.2.3
Amperometric principle
The oxygen molecules diffused through the membrane are reduced to hydroxide ions (OH-) at
the cathode. Silver is oxidized to silver ions (Ag+) at the anode (this forms a silver halogenide
layer).
A current flows due to the electron donation at the cathode and the electron acceptance at the
anode. Under constant conditions, this flow is proportional to the oxygen content of the
medium.
This current is converted in the transmitter and indicated on the display as an oxygen
concentration in mg/l, as a saturation index in % SAT or as an oxygen partial pressure in hPa.
5.2.4
Memosens technology
The sensor is connected to the cable connection (CYK10) without contact. The power and data
are transferred inductively
Once connected to the transmitter, the data saved in the sensor are read digitally. You can call
up these data using the corresponding DIAG menu.
Data that digital sensors save include the following:
• Manufacturer data
– Serial number
– Order code
