Endress+Hauser COS51D Specifications

Technical Information

Oxymax COS51D

Digital sensor for measuring dissolved oxygen
Longterm-stable sensor for water and wastewater applications

Application

The continuous measurement of the dissolved oxygen
concentration is very important in many areas of water
management:

• Sewage treatment plants:Oxygen measurement and
regulation in the activated sludge basin for a highly efficient
biological cleaning process

• Water monitoring:
Oxygen measurement in rivers, lakes or seas as an indicator of
the water quality

• Water treatment:
Oxygen measurement for status monitoring of drinking water
for example (oxygen enrichment, corrosion protection etc.)

• Fish farming:
Oxygen measurement and regulation for optimum living and
growth conditions

Your benefits

• Sensor with digital data transmission:
– Storage of calibration data in sensor
– Insensitive to electromagnetic interferences thanks to

digital communication to the transmitter

• Maximum measurement accuracy:
– Longterm-stable measurement thanks to potentiostatic

amperometric three-electrode system
– Long maintenance intervals
– Intelligent sensor self monitoring

• Membrane covered sensor, i.e.:

air

selectivity

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– high O
– Minimum maintenance effort
– Minimum calibration effort thanks to simple calibration in

Further benefits offered by Memosens technology

• Maximum process safety through contactless inductive signal
transmission

• Data safety through digital data transmission

• Easy handling thanks to storage of sensor-specific data in the
sensor

• Predictive maintenance possible thanks to registration of
sensor load data in the sensor

TI00413C/07/EN/13.12
71153930

Oxymax COS51D

Function and system design

Measuring 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,
μg/l, ppm, ppb or Vol%, as a saturation index in % SAT or as an oxygen partial pressure in hPa.

Potentiostatic amperometric three-electrode system

Memosens technology Maximum process safety

The high-impedance, current-free reference electrode plays an important role.
The formation of a silver bromide or silver chloride coating on the anode uses up the bromide or chloride ions
dissolved in the electrolyte
In the case of conventional membrane-covered sensors working with the two-electrode system, this causes an
increase in signal drift.

This is not the case with the three-electrode system:
The change in bromide or chloride concentration is registered by the reference electrode and an internal control
circuit holds the working electrode potential constant. The advantages of this principle are significantly
increased accuracy of the signal and considerably extended calibration intervals.

The inductive and non-contacting measured value transmission of Memosens guarantees maximum process
safety and offers the following benefits:

• All problems caused by moisture are eliminated.
– The plug-in connection is free from corrosion.
– Measured value distortion from moisture is not possible.

Correct transfer of minimum measured values, e.g. with amperometric sensors.

– The plug-in system can even be connected under water.

• The transmitter is galvanically decoupled from the medium. The result: No more need to ask about
"symmetrically high-impedance" or "unsymmetrical" (for pH/ORP measurement) or an impedance
converter.

• EMC safety is guaranteed by screening measures for the digital measured value transmission.

• Application in explosion-hazardous areas is unproblematic; the integrated electronics are intrinsically safe.

Data safety through digital data transfer

The Memosens technology digitalizes the measured values in the sensor and transfers them to the transmitter
contactlessly and free from interference potential. The result:

• An automatic error message is generated if the sensor fails or the connection between sensor and transmitter
is interrupted.

• The availability of the measuring point is dramatically increased by immediate error detection.

Easy handling

Sensors with Memosens technology have integrated electronics that allow for saving calibration data and
further information such as total hours of operation and operating hours under extreme measuring conditions.
When the sensor is mounted, the calibration data are automatically transferred to the transmitter and used to
calculate the current measured value. Storing the calibration data in the sensor allows for calibration away from
the measuring point. The result:

• Sensors can be calibrated under optimum external conditions in the measuring lab. Wind and weather do
neither affect the calibration quality nor the operator.

• The measuring point availability is dramatically increased by the quick and easy replacement of precalibrated
sensors.

• The transmitter does not need to be installed close to the measuring point but can be placed in the control
room.

• Maintenance intervals can be defined based on all stored sensor load and calibration data and predictive
maintenance is possible.

• The sensor history can be documented on external data carriers and evaluation programs at any time. Thus,
the current application of the sensors can be made to depend on their previous history.

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Oxymax COS51D

Measuring system A complete measuring system comprises at least:

• the digital oxygen sensor Oxymax COS51D

• a transmitter, e.g. Liquiline CM42

• a special measuring cable, CYK10

• an assembly, e.g. immersion assembly CYA112 or retractable assembly COA451

Optional (see accessories):

• Holder system CYH112 for immersion operation

• Junction box RM (with cable extension)

• Automatic cleaning system Chemoclean with spray head

Measuring system (example)

1 Digital oxygen sensor Oxymax W COS51D
2 Retractable assembly COA451
3 Liquiline M CM42
4 Measuring cable CYK10

a0006735

Input

Measured variable Dissolved oxygen [mg/l, μg/l, ppm, ppb, % SAT or hPa]

Measuring range 0.01 to 100 mg/l

0.00 to 1000 % SAT
0 to 2000 hPa

Wiring

Electrical connection The sensor is electrically connected to the transmitter by means of the special measuring cable CYK10.

Special measuring cable CYK10

a0003350

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