Endress+Hauser Oxymax COS22 Series User manual

Products Solutions Services
Operating Instructions
Oxymax COS22
Analog sensor for the measurement of dissolved oxygen
BA00446C/07/EN/04.15
71306871

Table of contents
2 Endress+Hauser
Table of contents
1 Document information .............. 3
1.1 Warnings ............................ 3
1.2 Symbols .............................. 3
2 Basic safety instructions ............ 4
2.1 Requirements for personnel ............... 4
2.2 Designated use ........................ 4
2.3 Occupational safety ..................... 4
2.4 Operational safety ...................... 5
2.5 Product safety ......................... 5
3 Device description, function ......... 6
3.1 Amperometric measuring principle .......... 6
3.2 Sensor design ......................... 6
3.3 Membrane body ....................... 6
3.4 Polarization ........................... 6
4 Incoming acceptance and product
identification ....................... 7
4.1 Incoming acceptance .................... 7
4.2 Product identification .................... 7
4.3 Scope of delivery ....................... 8
4.4 Certificates and approvals ................ 8
5 Installation ........................ 9
5.1 Installation conditions ................... 9
5.2 Mounting the sensor ................... 10
5.3 Installation examples ................... 11
5.4 Post-installation check .................. 13
6 Electrical connection .............. 14
6.1 Connecting the sensor .................. 14
6.2 Ensuring the degree of protection .......... 14
6.3 Post-connection check .................. 14
7 Calibration and adjustment ........ 16
7.1 Types of calibration .................... 16
7.2 Calibration in air ...................... 16
7.3 Calculation example for the calibration
value ............................... 17
7.4 Zero point calibration ................... 18
8 Commissioning .................... 19
8.1 Function check ....................... 19
8.2 Sensor polarization .................... 19
8.3 Sensor calibration ..................... 20
9 Troubleshooting .................. 21
10 Maintenance ...................... 22
10.1 Maintenance schedule .................. 22
10.2 Maintenance tasks ..................... 22
10.3 Clean sensor ......................... 23
10.4 Wear parts and consumables ............. 23
11 Accessories ....................... 26
11.1 Assemblies (selection) .................. 26
11.2 Measuring cable ...................... 26
11.3 Zero-point gel ........................ 26
11.4 Maintenance kit ...................... 27
12 Repair ............................ 28
12.1 Spare parts and consumables ............. 28
12.2 Return .............................. 28
12.3 Disposal ............................ 28
13 Technical data .................... 29
Index .................................. 34

Oxymax COS22 Document information
Endress+Hauser 3
1 Document information
1.1 Warnings
Structure of information Meaning
LDANGER
Causes (/consequences)
Consequences of non-compliance
(if applicable)
‣Corrective action
This symbol alerts you to a dangerous situation.
Failure to avoid the dangerous situation will result in a fatal or serious
injury.
LWARNING
Causes (/consequences)
Consequences of non-compliance
(if applicable)
‣Corrective action
This symbol alerts you to a dangerous situation.
Failure to avoid the dangerous situation can result in a fatal or serious
injury.
LCAUTION
Causes (/consequences)
Consequences of non-compliance
(if applicable)
‣Corrective action
This symbol alerts you to a dangerous situation.
Failure to avoid this situation can result in minor or more serious injuries.
NOTICE
Cause/situation
Consequences of non-compliance
(if applicable)
‣Action/note
This symbol alerts you to situations which may result in damage to
property.
1.2 Symbols
Symbol Meaning
Additional information, tips
Permitted or recommended
Not permitted or not recommended
Reference to device documentation
Reference to page
Reference to graphic
 Result of a step

Basic safety instructions Oxymax COS22
4 Endress+Hauser
2 Basic safety instructions
2.1 Requirements for personnel
• Installation, commissioning, operation and maintenance of the measuring system may
be carried out only by specially trained technical personnel.
• The technical personnel must be authorized by the plant operator to carry out the
specified activities.
• The electrical connection may be performed only by an electrical technician.
• The technical personnel must have read and understood these Operating Instructions
and must follow the instructions contained therein.
• Measuring point faults may be repaired only by authorized and specially trained
personnel.
Repairs not described in the Operating Instructions provided may only be carried out
directly by the manufacturer or by the service organization.
2.2 Designated use
The oxygen sensor is suitable for continuous measurement of dissolved oxygen in water.
The specific suitability depends on the sensor design:
• COS22-*1 (standard, measuring range 0.01 to 60 mg/l)
– Measuring, monitoring and regulating the oxygen content in fermenters
– Monitoring the oxygen content in biotechnology facilities
• COS22-*3 (trace measurement, measuring range 0.001 to 10 mg/l, preferred
operational range 0.001 to 2 mg/l), also suitable for high CO2 partial pressure
– Monitoring inertization equipment in the food industry
– Monitoring the residual oxygen content in carbonated fluids of the beverage industry
– Trace measurement in industrial applications such as inertizations
– Monitoring the residual oxygen content in boiler feedwater
– Monitoring, measuring and regulating the oxygen content in chemical processes
NOTICE
Molecular hydrogen
Hydrogen causes sensitivity in other substances and leads to false low readings or, at the
worst, total failure of the sensor.
‣Only use the COS22-*1/3 sensor in media free of hydrogen.
Use of the device for any purpose other than that described, poses a threat to the safety of
people and of the entire measuring system and is therefore not permitted.
The manufacturer is not liable for damage caused by improper or non-designated use.
2.3 Occupational safety
As the user, you are responsible for complying with the following safety conditions:
• Installation guidelines
• Local standards and regulations
• Regulations for explosion protection
Electromagnetic compatibility
• The product has been tested for electromagnetic compatibility in accordance with the
applicable European standards for industrial applications.
• The electromagnetic compatibility indicated applies only to a product that has been
connected in accordance with these Operating Instructions.

Oxymax COS22 Basic safety instructions
Endress+Hauser 5
2.4 Operational safety
1. Before commissioning the entire measuring point, verify that all connections are
correct. Ensure that electrical cables and hose connections are undamaged.
2. Do not operate damaged products, and safeguard them to ensure that they are not
operated inadvertently. Label the damaged product as defective.
3. If faults cannot be rectified:
Take the products out of operation and safeguard them to ensure that they are not
operated inadvertently.
2.5 Product safety
The product is designed to meet state-of-the-art safety requirements, has been tested, and
left the factory in a condition in which it is safe to operate. The relevant regulations and
European standards have been observed.

Device description, function Oxymax COS22
6 Endress+Hauser
3 Device description, function
3.1 Amperometric measuring principle
The oxygen molecules that diffuse through the membrane are reduced at the cathode to
hydroxide ions (OH-). At the anode, silver is oxidized to silver ions (Ag+) (this forms a
silver halide 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.
3.2 Sensor design
1 2 345
78
96
A0011868
 1 COS22
1
2
3
Plug-in head
Thrust collar
Sensor shaft
4
5
6
O-ring 8.5 x 1.5 mm
Membrane body
Shaft sleeve
7
8
9
Glass portion with anode and cathode
Process seal 10.77 x 2.62 mm
Process connection Pg 13.5
3.3 Membrane body
The oxygen dissolved in the medium is transported to the membrane by the necessary
flow. The membrane is permeable for dissolved gases only. 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 shipped with a standard membrane body, which can be used for all common
applications. The membrane is pretensioned at the factory and can be installed
immediately.
Electrolytes are version-specific and cannot be mixed in a single application!
3.4 Polarization
When the sensor is connected to the transmitter, a fixed voltage is applied between the
cathode and anode. The polarization current this creates can be identified on the
transmitter with a display that is initially high, but decreases with time. The sensor cannot
be calibrated until the display is calibrated.
Reference value for nearly complete polarization of a sensor that was previously stored for
a long time:
• COS22-*1: 2 hours
• COS22-*3: 12 hours
After this time, even measurements close to the determination limit are useful. The
necessary polarization time is reduced for sensors that were in use a short time before.

Oxymax COS22 Incoming acceptance and product identification
Endress+Hauser 7
4 Incoming acceptance and product
identification
4.1 Incoming acceptance
1. Verify that the packaging is undamaged.
 Notify your supplier of any damage to the packaging.
Keep the damaged packaging until the matter has been settled.
2. Verify that the contents are undamaged.
 Notify your supplier of any damage to the delivery contents.
Keep the damaged products until the matter has been settled.
3. Check the delivery for completeness.
 Check it against the delivery papers and your order.
4. Pack the product for storage and transportation in such a way that it is protected
against impact and moisture.
 The original packaging offers the best protection.
The permitted ambient conditions must be observed (see "Technical data").
If you have any questions, please contact your supplier or your local sales center.
4.2 Product identification
4.2.1 Nameplate
The nameplate provides you with the following information on your device:
• Manufacturer identification
• Order code
• Extended order code
• Serial number
• Safety information and warnings
Compare the data on the nameplate with your order.
4.2.2 Product identification
Product page
www.endress.com/cos22
Interpreting the order code
The order code and serial number of your product can be found in the following locations:
• On the nameplate
• In the delivery papers
Obtaining information on the product
1. Go to the product page for your product on the Internet.
2. In the navigation area on the right-hand side, select "Check your device features"
under "Device support".
 An additional window opens.
3. Enter the order code from the nameplate into the search field.
 You will receive information on each feature (selected option) of the order code.

Incoming acceptance and product identification Oxymax COS22
8 Endress+Hauser
4.3 Scope of delivery
The scope of delivery comprises:
• Oxygen sensor with watering cap (filled with tap water) for protecting the membrane
• Electrolyte, 1 bottle, 10 ml (0.34 fl.oz.)
• Tool to push out the membrane body
• Brief Operating Instructions
4.4 Certificates and approvals
4.4.1  mark
Declaration of Conformity
The product meets the requirements of the harmonized European standards. As such, it
complies with the legal specifications of the EC directives. The manufacturer confirms
successful testing of the product by affixing to it the  mark.
4.4.2 Material certificates
Manufacturer declaration of FDA compatibility
The manufacturer declares the use of FDA-listed materials.
Ask your Sales Center for the certificates.
Product FDA certificate for
COS22-****22 Membrane, O-rings, process seal
COS22Z-*2*2 Membrane, O-rings, process seal
COS22-****23 Membrane, O-rings
COS22Z-*2*3 Membrane, O-rings
Material test certificate
A test certificate 3.1 in accordance with EN10204 is supplied depending on the version (→
Product Configurator on the product page).
EHEDG
Compliance with EHEDG's criteria for hygienic design
• TÜV Rheinland, Apeldorn, Netherlands
• Certificate type: Type EL Class I

Oxymax COS22 Installation
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5 Installation
5.1 Installation conditions
5.1.1 Orientation
10° 10° Not permissible!
Not permissible!
Permissible angle of installation
A0005584-EN
 2 Permitted orientations
The sensor must be installed at an angle of inclination of 10 to 170 ° in an assembly,
bracket or appropriate process connection. Recommended angle: 45°, to prevent the
formation of air bubbles.
Inclination angles other than those mentioned are not permitted. Do not install the sensor
overhead.
Observe the instructions for installing sensors in the Operating Instructions for the
assembly used.
5.1.2 Mounting location
• Choose a mounting location that can be easily accessed at a later stage.
• Ensure that upright posts and fittings are fully secured and vibration-free.
• Select an installation location which produces a typical oxygen concentration for the
individual application.

Installation Oxymax COS22
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5.2 Mounting the sensor
5.2.1 Measuring system
A complete measuring system comprises:
• An Oxymax COS22 oxygen sensor
• A transmitter, e.g. Liquisys COM2x3
• Measuring cable COK21
• Optional: an assembly, e.g. permanent installation assembly CPA442, flow assembly
CPA240, or retractable assembly CPA875
1 2
3
4
A0024029
 3 Example of a measuring system with COS22-*1
1 Retractable assembly CPA875
2 Transmitter Liquisys COM253
3 Measuring cable COK21
4 Oxygen sensor COS22
5.2.2 Installing a measuring point
Installation in suitable assembly is required (depending on the application)
LWARNING
Electrical voltage
In the event of a fault, non-grounded metallic assemblies may be under voltage and then
are not touchable.
‣When using metallic assemblies and installation equipment, observe the national
grounding provisions.

Oxymax COS22 Installation
Endress+Hauser 11
For a complete installation of a measuring point, proceed as follows:
1. Install a retractable or a flow assembly (if used) into the process.
2. Connect the water supply to the rinse connections (if you use an assembly with
cleaning function).
3. Install and connect the oxygen sensor.
NOTICE
Installation error
Cable open circuit, loss of sensor due to cable separation, unscrewing of membrane cap
‣Do not install the sensor suspended from the cable.
‣Screw the sensor into the assembly so that the cable is not twisted.
‣When installing or uninstalling the sensor body, hold it tightly. Turn using only the
hexagonal nut on the armored coupling. Otherwise you might unscrew the membrane
cap. This will then remain in the assembly or process.
‣Avoid exerting excessive tensile force on the cable (e.g. from jerky pulling).
‣Select an installation location that is easy to access for later calibrations.
5.3 Installation examples
5.3.1 Permanent installation (CPA442)
The permanent installation assembly CPA442 enables easy adaptation of a sensor to
nearly any process connections from Ingold nozzles to Varivent or Tri-Clamp connections.
This kind of installation is very well suited for tanks and larger pipes. You will achieve a
defined immersion depth of the sensor into the medium in the simplest way.
5.3.2 Flow assembly
CPA240
The flow assembly CPA240 offers up to three installation spaces for sensors with a shaft
diameter of 12 mm (0.47"), a shaft length of 120 mm (4.7"), and a Pg 13.5 process
connection. It very well suited for use in pipelines or hose connections. To prevent

Installation Oxymax COS22
12 Endress+Hauser
measured error with trace measurements, pay particular attention to complete ventilation
of the assembly.
A0005720
 4 Flow assembly CPA240 with protective cover
1
7
6
5
3
2
4
A0005721
 5 Bypass installation
1 Main pipe
2 Medium removal
3, 6 Manually actuated or solenoid valves
4 Sampling
5 Flow assembly with installed sensor
7 Medium return
Flow assembly for water treatment and processes
The compact stainless steel assembly offers space for a 12-mm sensor with a length of
120 mm. The assembly has a low sampling volume and, with the 6-mm connections, it is
best suited for residual oxygen measurement in water treatments and boiler feedwater.
The flow comes from below.
1 2
3
4
A0014081
 6 Flow assembly
1 Built-in sensor
2 Drain
3 Wall mount (clamp D29)
4 Inflow

Oxymax COS22 Installation
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5.3.3 Retractable assembly (CPA875 or CPA450)
The assembly is designed for installation on tanks and pipes. Suitable nozzles must be
available for this.
Install the assembly at places with constant flow. The minimum pipe diameter is DN 80
(3").
5
3
41
2
3
4
2
A0005722-EN
 7 Permissible and impermissible sensor installation positions with retractable assembly
1 Ascending pipe, best position
2 Horizontal pipe, sensor top down, impermissible due to air cushion or foam bubble forming
3 Horizontal pipe, lateral installation with permissible installation angle (acc. to sensor version)
4 Down pipe, impermissible
NOTICE
Sensor not in the medium all the way, buildup, overhead installation
Results in incorrect measurements
‣Do not install the assembly at places where air cushions or foam bubbles can be
formed.
‣Avoid deposits on the sensor membrane, or remove them regularly.
‣Do not install the sensor overhead.
5.4 Post-installation check
• Are the sensor and cable undamaged?
• Is the orientation correct?
• Is the sensor installed in an assembly and is not suspended from the cable?
• Avoid the penetration of moisture by fitting the protective cap to the immersion
assembly.

Electrical connection Oxymax COS22
14 Endress+Hauser
6 Electrical connection
LWARNING
Device is live
Incorrect connection may result in injury or death.
‣The electrical connection may be performed only by an electrical technician.
‣The electrical technician must have read and understood these Operating Instructions
and must follow the instructions contained therein.
‣Prior to commencing connection work, ensure that no voltage is present on any cable.
6.1 Connecting the sensor
A multi-core COK21 measuring cable is used for the electrical connection of the sensor to
the transmitter.
PK
GN / YE
BN
YE
BU
S
12
90
91
11
Assignment Terminal
External shield
Cathode
Anode
NTC temp. sensor
Active internal shield
(NTC temp. sensor)
A0005583-EN
 8 Measuring cable COK21
The polarization voltage must be set at the transmitter as follows:
Standard measuring range: -650mV
Trace measuring range: -550mV
The voltage is applied between the working electrode (cathode) and the reference
electrode (anode).
6.2 Ensuring the degree of protection
Only the mechanical and electrical connections which are described in these instructions
and which are necessary for the required, designated use, may be carried out on the device
delivered.
‣Exercise care when carrying out the work.
Otherwise, the individual types of protection (Ingress Protection (IP), electrical safety, EMC
interference immunity) agreed for this product can no longer be guaranteed due, for
example, to covers being left off or cable (ends) which are loose or insufficiently secured.
6.3 Post-connection check
Device condition and specifications Notes
Are the outside of the sensor, assembly, junction box, cable
undamaged?
Visual inspection
Electrical connection Notes
Are the installed cables strain-relieved and not twisted?

Oxymax COS22 Electrical connection
Endress+Hauser 15
Device condition and specifications Notes
Is a sufficient length of the cable cores stripped, and is it
positioned in the terminal correctly?
Check the fit (by pulling gently)
Are all the screws terminals properly tightened? Tighten
Are all cable entries mounted, tightened and leak-tight? For lateral cable entries, make sure the
cables loop downwards to allow water to
drip off
Are all cable entries installed downwards or mounted laterally?

Calibration and adjustment Oxymax COS22
16 Endress+Hauser
7 Calibration and adjustment
Calibration is a means of adapting the transmitter to the characteristic values of the
sensor.
Calibration of the sensor is required after:
• Initial commissioning
• Changing the membrane or electrolyte
• Long pauses in operation without power supply
Within the framework of system monitoring and supervision, for example, the calibration
can also be cyclically monitored (at typical time intervals, depending on operating
experience) or renewed.
7.1 Types of calibration
You can carry out a slope or zero point calibration for the sensor.
In most applications, single-point calibration in the presence of oxygen is sufficient
(=calibration of the sensor slope). When switching from process to calibration conditions,
you have to allow a longer settling time for the sensor.
The additional calibration of the zero point improves the accuracy of the measurement
results at trace concentrations. You can calibrate the zero point using nitrogen (min.
99.995%) or oxygen-free water. Make sure that the sensor is polarized and the measured
value is settled at the zero point (at least 20-30 minutes) to prevent later incorrect
measurements at trace concentrations.
The following describes calibration of the slope in air (saturated with water vapor) as the
easiest and recommended calibration method. However, this type of calibration is possible
only if the air temperature is ≥ 0 °C (32 °F).
7.2 Calibration in air
1. Remove the sensor from the medium.
2. Clean the outside of the sensor with a damp cloth.
3. Allow approx. 20 minutes for the sensor temperature to adapt to the ambient air.
Make sure that the sensor is not exposed to any direct ambient influences (direct
sunlight, drafts) during this time.
4. When the measured value display on the transmitter is stable, carry out the
calibration according to the operating instructions for the transmitter. Pay particular
attention to the software settings for the stability criteria for calibration.
5. Where necessary:
Adjust the sensor.
6. Then insert the sensor into the medium.
Make sure you comply with the instructions for calibration in the Operating
Instructions of the transmitter.

Oxymax COS22 Calibration and adjustment
Endress+Hauser 17
7.3 Calculation example for the calibration value
As a check, you can calculate the expected calibration value (transmitter display) as shown
in the following example (salinity is 0).
1.
Determine:
• the sensor temperature (air temperature for the calibration type "air", water
temperature for the calibration type "air-saturated water")
• the altitude above sea level
• the current air pressure (= rel. air pressure to sea level) at the time of calibration. (If
undeterminable, use 1013 hPa (407 in H2O)).
2.
Define:
• the saturation value S acc. to Table 1
• the altitude factor K acc. to Table 2
Table 1
T
[˚C (˚F)]
S
[mg/l=ppm]
T
[˚C (˚F)]
S
[mg/l=ppm]
T
[˚C (˚F)]
S
[mg/l=ppm]
T
[˚C (˚F)]
S
[mg/l=ppm]
0 (32) 14.64 11 (52) 10.99 21 (70) 8.90 31 (88) 7.42
1 (34) 14.23 12 (54) 10.75 22 (72) 8.73 32 (90) 7.30
2 (36) 13.83 13 (55) 10.51 23 (73) 8.57 33 (91) 7.18
3 (37) 13.45 14 (57) 10.28 24 (75) 8.41 34 (93) 7.06
4 (39) 13.09 15 (59) 10.06 25 (77) 8.25 35 (95) 6.94
5 (41) 12.75 16 (61) 9.85 26 (79) 8.11 36 (97) 6.83
6 (43) 12.42 17 (63) 9.64 27 (81) 7.96 37 (99) 6.72
7 (45) 12.11 18 (64) 9.45 28 (82) 7.82 38 (100) 6.61
8 (46) 11.81 19 (66) 9.26 29 (84) 7.69 39 (102) 6.51
9 (48) 11.53 20 (68) 9.08 30 (86) 7.55 40 (104) 6.41
10 (50) 11.25
Table 2
Altitude
[m (ft)]
K Height
[m (ft)]
K Height
[m (ft)]
K Height
[m (ft)]
K
0 (0) 1.000 550 (1800) 0.938 1050 (3450) 0.885 1550 (5090) 0.834
50 (160) 0.994 600 (1980) 0.932 1100 (3610) 0.879 1600 (5250) 0.830
100 (330) 0.988 650 (2130) 0.927 1150 (3770) 0.874 1650 (5410) 0.825
150 (490) 0.982 700 (2300) 0.922 1200 (3940) 0.869 1700 (5580) 0.820
200 (660) 0.977 750 (2460) 0.916 1250 (4100) 0.864 1750 (5740) 0.815
250 (820) 0.971 800 (2620) 0.911 1300 (4270) 0.859 1800 (5910) 0.810
300 (980) 0.966 850 (2790) 0.905 1350 (4430) 0.854 1850 (6070) 0.805
350 (1150) 0.960 900 (2950) 0.900 1400 (4600) 0.849 1900 (6230) 0.801
400 (1320) 0.954 950 (3120) 0.895 1450 (4760) 0.844 1950 (6400) 0.796
450 (1480) 0.949 1000 (3300) 0.890 1500 (4920) 0.839 2000 (6560) 0.792
500 (1650) 0.943

Calibration and adjustment Oxymax COS22
18 Endress+Hauser
3.
Calculate the factor L:
Relative air pressure at calibration
L= -----------------------------------------------
1013 hPa
4.
Calculate the calibration value C:
C = S . K . L
Example
• Air calibration at 18 °C (64 °F), altitude 500 m (1650 ft) above sea level, current air
pressure 1009 hPa (405 in H2O)
• S = 9.45 mg/l, K = 0.943, L = 0.996
• Calibration value C = 8.88 mg/l.
You do not need factor K in the table if your measuring device returns the absolute air
pressure L abs (air pressure depending on altitude) as the measured value. The formula
for calculation is then: C = S . Labs.
7.4 Zero point calibration
The zero point is not so important when working with relatively high concentrations of
oxygen.
This situation changes, however, once oxygen sensors are used at low concentrations and
in the trace range and where they are also to be calibrated in the zero point. Zero point
calibrations are demanding as the ambient medium - usually air - already has a high
oxygen content. This oxygen must be blocked off for zero-point calibration of the sensor.
Calibration with zero-point gel can be used here:
The oxygen-depleting gel COY8 (→  26) creates an oxygen-free medium for zero point
calibration.
Prior to sensor zero point calibration, check:
• Is the sensor signal stable?
• Is the value displayed plausible?
1. If the sensor signal is stable:
Calibrate the zero point.
2. If necessary:
Adjust the sensor to the zero point.
The reference method (sample calibration in zero point) can also be used here if
appropriate collecting vessels or reference measurement are available.
If the oxygen sensor is calibrated too early, this can result in an incorrect zero point.
Rule of thumb: Operate the sensor in zero-point gel for at least 0.5 h.
If the sensor was already operated in the trace range before the zero point calibration,
the time specified above generally suffices. If the sensor was operated in air,
significantly more time must be factored in to also remove residual oxygen from any
dead volume inherent to the design. Here a value of 2 hours applies as a general rule.

Oxymax COS22 Commissioning
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8 Commissioning
8.1 Function check
Before first commissioning, check if:
• the sensor is correctly installed
• the electrical connection is correct.
If using an assembly with automatic cleaning, check that the cleaning medium (e.g. water
or air) is connected correctly.
LWARNING
Escaping process medium
Risk of injury from high pressure, high temperatures or chemical hazards
‣Before applying compressed air to an assembly with cleaning facility, make sure the
connections are correctly fitted.
‣Do not install the assembly in the process if you cannot make the correct connection
reliably.
8.2 Sensor polarization
NOTICE
Incorrect measurements due to ambient influences
‣Be absolutely certain to avoid direct sunlight on the sensor.
‣Make sure you comply with the instructions for commissioning in the Operating
Instructions of the transmitter.
The sensor has been tested at the factory for proper function and is shipped in ready-to-
operate condition.
To prepare for the calibration, carry out the following steps:
1. Pull off the sensor protection cap.
2. Expose the sensor, which should be dry on the outside, to the air atmosphere.
 The air should be saturated with water vapor. Therefore, install the sensor as
close as possible to a surface of water. However, the sensor membrane must
remain dry during calibration. Therefore, avoid direct contact with the surface of
water.
3. Connect the sensor to the transmitter.
4. Switch on the transmitter.
 When the sensor is connected to the transmitter, the polarization takes place
automatically after the power-up of the transmitter.
5. Wait for the polarization time to run out.

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20 Endress+Hauser
8.3 Sensor calibration
Calibrate the sensor (e.g. air calibration) immediately after the polarization time runs out.
The calibration intervals depend greatly on:
• The application
• The installation position of the sensor
The following method helps you determine the necessary calibration intervals:
1. Inspect the sensor one month after commissioning. Take it out of the medium and
dry it.
2. After 10 minutes, measure the oxygen saturation index in air.
 Decide depending on the result: If the measured value is not 100 ±2 %SAT, you
must calibrate the sensor. Otherwise, double the length of time to the next
inspection.
3. Proceed as per Point 1 after two, four and/or eight months. In this way, you can
determine the optimum calibration interval for your sensor.
In any case, calibrate the sensor at least once a year.