wtw ConOx User manual

ba75383e04 04/2009
ConOx
Operating manual
Combined Conductivity and Dissolved Oxygen Sensor

ConOx
ba75383e04 04/2009
26
Copyright ©Weilheim 2009, WTW GmbH
Reprinting - even as excerpts - is only allowed with the explicit written
authorization of WTW GmbH, Weilheim.
Printed in Germany.

ConOx Contents
27
Contents
ba75383e04 04/2009
1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
1.1 Structure and function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
1.2 Instrument identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2 Safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.1 Scopes of delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
3.2 Getting the sensor ready for measuring . . . . . . . . . . . . . . . . . . 32
4 Measuring / Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.1 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.2 Measuring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
4.3 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5 Maintenance, cleaning, replacement . . . . . . . . . . . . . . . . . . 35
5.1 General maintenance instructions . . . . . . . . . . . . . . . . . . . . . . 35
5.2 Outside cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.3 DO module: Changing the electrolyte solution and
membrane cap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.4 DO module: Cleaning the electrodes . . . . . . . . . . . . . . . . . . . . 38
5.5 Checking the DO module for freedom from zero-current . . . . . 40
5.6 Aging of the conductivity measuring cell . . . . . . . . . . . . . . . . . . 40
5.7 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
6 What to do if... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
6.1 Error symptoms of DO measurement . . . . . . . . . . . . . . . . . . . . 42
6.2 Error symptoms of conductivity measurement . . . . . . . . . . . . . 42
7 Technical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
7.1 Conductivity basic module . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
7.2 Dissolved oxygen (DO) module . . . . . . . . . . . . . . . . . . . . . . . . 44
8 Wear parts and accessories . . . . . . . . . . . . . . . . . . . . . . . . . 47

Overview ConOx
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1Overview
1.1 Structure and function
The ConOx is a modular sensor for conductivity, dissolved oxygen (DO) and
temperature. It consists of two basic components:
zConductivity basic module, according to the quadripole measuring princi-
ple, with integrated temperature sensor
zRemovable dissolved oxygen module, according to the galvanic measur-
ing principle
Structure of the
ConOx
1Voltage electrode (inside, 2x)
2Current electrode (ring, 2x)
3Temperature sensor in a graphite enclosure
4Shaft
5Connection head
6WP 90 membrane cap (filled with electrolyte solution)
7Gold working electrode (cathode)
8Insulator
9Lead counter electrode (anode)
10 Screw thread base with ventilation area
11 Cap nut
12 Plug connection
13 Closing cap for conductivity basic module
14 Closing cap for DO module
41, 2 3 5
78961110 12
13
14
Conductivity basic module
Dissolved oxygen (DO) module

ConOx Overview
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The conductivity basic module can be used as an independent conductivity
measuring cell. For this purpose, unscrew the DO module and close the open
plug connection with a closing cap.
The DO module is connected to the conductivity basic module via a water-
tight, three-pole plug connection. The conductivity basic module measures
the temperature, which is required for the determination of the DO content.
For this reason the DO module only works in conjunction with the conductivity
basic module.
Recommended
fields of
application
zOn site measurements in rivers, lakes and wastewater
zfishfarming
zGround water measurements
zApplications in water laboratories
1.2 Instrument identification
A series number is printed on both ConOx modules. Keep these numbers
ready if you have questions to ask the WTW service department.
The series numbers contain the following information:
Conductivity basic
module The number is printed on the shaft.
Dissolved oxygen
(DO) module The number is printed on the cap nut.
1Manufacturing year 20... (example: 2003)
2Calendar week of manufacturing (CW 36)
3Sequential batch number (0013)
03360013
12 3
1Manufacturing year 20... (example: 2003)
2Calendar week of manufacturing (CW 42)
3Sensor type (type A)
4Sequential batch number (007)
0342A007
1234

Safety ConOx
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2 Safety
This operating manual contains special instructions that must be followed
during the operation of the sensor.
Always keep this operating manual in the vicinity of the sensor.
Special user
qualifications The membrane cap of the DO module is filled with a small amount of an alkaline electrolyte solution. All maintenance work that requires dealing with
the electrolyte solution must only be carried out by persons who know how to
deal with chemicals safely.
General safety
instructions The individual chapters of this operating manual use safety labels like the one below to indicate danger:
CAUTION
indicates instructions that must be followed precisely in order to avoid
slight injuries or damage to the instrument or the environment.
3 Commissioning
3.1 Scopes of delivery
3.1.1 Scope of delivery of the ConOx
zConOx combination conductivity and DO sensor,
DO module filled with electrolyte solution and ready to use
z1 closing cap for conductivity basic module
z1 closing cap for DO module
z3 exchange membrane caps, WP 90
zCalibration and storage vessel, OxiCal®-CX
zPolishing strip, SF 300
zElectrolyte solution, ELY/G
zCleaning solution, RL/G
zOperating manual for ConOx
Note
The membrane cap that is mounted on the DO sensor for delivery serves
mainly as a transport protection. Depending on the duration of the transport
and storage period, it may have a shortened operational lifetime. If the mea-
suring system cannot be calibrated (error message on the instrument),
please proceed according to section section 5.3 DO MODULE: CHANGING THE
ELECTROLYTE SOLUTION AND MEMBRANE CAP.

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3.1.2 Scope of delivery of the conductivity basic module
zConductivity basic module
z1 closing cap, mounted on the conductivity basic module
zOperating manual for ConOx
3.1.3 Scope of delivery of the DO module
zDO module, filled with electrolyte solution and operable
z1 closing cap, mounted on the DO module
z1 exchange membrane cap, WP 90
zPolishing strip, SF 300
zElectrolyte solution, ELY/G
zCleaning solution, RL/G
zOperating manual for ConOx
Note
The membrane cap that is mounted on the DO sensor for delivery serves
mainly as a transport protection. Depending on the duration of the transport
and storage period, it may have a shortened operational lifetime. If the mea-
suring system cannot be calibrated (error message on the instrument),
please proceed according to section section 5.3 DO MODULE: CHANGING THE
ELECTROLYTE SOLUTION AND MEMBRANE CAP.

Commissioning ConOx
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3.2 Getting the sensor ready for measuring
3.2.1 Measurements with the conductivity basic module
Make sure that the plug connection is tightly closed by the closing cap. When
mounted, the closing cap (1) must be screwed on up to the stop.
Before screwing on the closing cap, check the following points:
zThe sealing (2) must be clean and evenly positioned in the groove.
zThe plug connection and the inside of the closing cap must be clean.
3.2.2 Measurements with the combination sensor
Make sure that the DO module and conductivity basic module are screwed
together tightly. When mounted, the cap nut of the DO module has to be
screwed on up to the stop.
Before screwing on the DO module, check the following points:
zThe sealing (3) must be clean and evenly positioned in the groove.
zThe plug connection must be dry on both sides.
Screwing on the
DO module Position the DO module (1) on the conductivity basic module and carefully and with slight pressure turn it until the guiding nib on the DO module locks
in place in the corresponding groove on the conductivity basic module.
Subsequently tighten the cap nut (2) up to the stop. The thread only snatches
if the DO module was correctly positioned.
12
21 3

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Unscrewing the
DO module Unscrew the cap nut and remove the DO module from the conductivity basic module.
CAUTION
Inappropriate handling can lead to the release of electrolyte solution.
When unscrewing the DO module only turn the cap nut (not the
membrane cap!).
3.2.3 Preparing the measuring operation
Connect the sensor to the measuring instrument. The sensor is immediately
ready to measure. It is not necessary to polarize the DO module.
4 Measuring / Operation
4.1 Calibration
To calibrate for DO measurements, use the OxiCal®-CX calibration and
storage vessel. If the A 325/K or A 325/S armoring is used, you have to
remove the protective hood and fixing nut of the armoring first.
When determining the cell constant, observe the respective minimum
immersion depth with the closing cap or D. O. module screwed on (important:
the temperature sensor must be submersed). The minimum immersion
depths are given in chapter 7 TECHNICAL DATA.
Note
Please read the course of the calibration in the operating manual of the mea-
suring instrument.
4.2 Measuring
Please always observe the required minimum immersion depth and the
minimum approach flow that is important for DO measurements (see
chapter 7 TECHNICAL DATA).
Minimum
approach flow for
DO measurements
The minimum flow can be provided in different ways, e. g.:
zThe flow of the water to be measured is sufficient (aeration tank, water
pipe, stream)
zSlowly pull the sensor through the water by hand (lake, container), or
zUse a flow aid, e. g. a magnetic stirrer with stirring device or a battery stir-
rer (see chapter 8 WEAR PARTS AND ACCESSORIES)
Note
When using the BR 325 battery stirrer, please make sure that the protective
pipe already has the groove in the area of the conductivity basic module (from
the year of manufacture, 2004).

Measuring / Operation ConOx
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4.3 Storage
Always store the sensor with the DO module in the calibration and storage
vessel at a temperature of 0 ... +50 °C (32 ... 122 °F). Make sure that the
sponge in the calibration and storage vessel is always moist.
Calibration and
storage vessel,
OxiCal®-CX
Moisten the sponge:
zRemove the cap (1).
zTake out the sponge (2), wet it, then slightly squeeze it out.
zReinsert the sponge and close the calibration and storage vessel with the
cap.
12

ConOx Maintenance, cleaning, replacement
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5 Maintenance, cleaning, replacement
5.1 General maintenance instructions
For your safety Note the following safety instructions when handling electrolyte and cleaning
solutions:
CAUTION
The ELY/G electrolyte solution and RL-G cleaning solution irritate the
eyes and skin. Note the following points when dealing with these
solutions:
zDuring working activities, always wear suitable protective gloves
and protective goggles/face shield.
zIf it comes into contact with the skin, rinse thoroughly with water and
immediately change contaminated clothing.
zIf it comes into contact with the eyes, rinse thoroughly with water
and consult a doctor.
zNote the safety datasheets.
CAUTION
Before all maintenance activities, disconnect the sensor from the
instrument.
Note
Information on how to order wear parts and maintenance means can be
found in chapter 8 WEAR PARTS AND ACCESSORIES.
Maintenance
activities on the
DO module
For better handling, leave the DO module screwed on the conductivity basic
module. Thus, you can better immerse the sensor head in the electrolyte or
cleaning solution and the plug connection remains protected against
damage.
5.2 Outside cleaning
Cleaning agents
After cleaning, thoroughly rinse with deionized water and recalibrate if
necessary.
Contamination Cleaning procedure
Lime sediments Immerse in acetic acid for 1 minute (volume
share = 20 %)
Fat/oil Clean with warm water that contains
washing-up liquid

Maintenance, cleaning, replacement ConOx
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5.3 DO module: Changing the electrolyte solution and
membrane cap
CAUTION
Before starting to work with the sensor, please note the GENERAL
MAINTENANCE INSTRUCTIONS on page 35.
General
information WTW delivers the DO module ready to use (see section 3). The electrolyte solution and the membrane cap must only be replaced if:
za calibration error occurs and the membrane is heavily contaminated
zthe membrane is damaged
zthe electrolyte solution is exhausted.
Changing the electrolyte solution and membrane cap
Unscrew the membrane cap.
Caution: Electrolyte solution!
For disposal of the membrane
cap and electrolyte solution,
see section 5.7.
Rinse the sensor head with
deionized water.
Carefully rub and dry the
counter electrode with a lint-
free paper towel.
Immerse the sensor head in-
cluding the counter electrode
in RL/G cleaning solution.
Allow to react for 1 to 3 min-
utes.
Thoroughly rinse the sensor
head with deionized water.
Water the counter electrode in
deionized water for at least
10 minutes.
RL/G
H O
2

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Carefully shake off the drops
of water.
Fill a new membrane cap with
ELY/G electrolyte solution.
Remove any air bubbles by
carefully tapping the mem-
brane cap. Additionally, you
can prevent air bubbles by
throwing the first filling away
and refilling the membrane
cap.
Thoroughly rinse the sensor
head with electrolyte solution.
Hold the sensor inclined and
screw on the membrane cap
fingertight using a paper tow-
el. Excess electrolyte solution
is forced out of the ventilation
area.
Check the filling:
Inspect the face surface. No
air bubbles may be present
within the dashed circle. Air
bubbles outside this area do
not interfere.
Note
For measurements under high pressure the filling must be com-
pletely free of air bubbles.
Readiness to measure The DO module is ready for operation after approx. 30 to 50 min-
utes. Subsequently calibrate the sensor for DO measurements.
Note
If you want to measure very low DO concentrations (< 0.5 % satu-
ration), we recommend to let the sensor rest overnight and then
calibrate it.
ELY/G
ELY/G
Ventilation area
points upwards
4 mm

Maintenance, cleaning, replacement ConOx
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5.4 DO module: Cleaning the electrodes
CAUTION
Before starting to work with the sensor, please note the GENERAL
MAINTENANCE INSTRUCTIONS on page 35.
General
information Cleaning is only required in cases of slopes too small or too large (sensor cannot be calibrated) that cannot be resolved by changing the membrane cap
and electrolyte solution.
Cleaning the electrodes
Unscrew the membrane cap.
Caution: Electrolyte solution!
For disposal of the membrane
cap and electrolyte solution,
see section 5.7.
Rinse the sensor head with
deionized water.
Using the rough side of the
wet SF 300 polishing strip,
polish off any contamination
from the gold working elec-
trode using light pressure.
Caution: Do not use any con-
ventional sandpaper or glass-
fiber brushes.
Rinse the sensor head with
deionized water.
Wipe the counter electrode
with a lint-free paper towel
and carefully remove any
loose white deposits.
Immerse the sensor head in-
cluding the counter electrode
in RL/G cleaning solution.
Allow to react for 1 to 3 min-
utes.
SF 300
RL/G

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Thoroughly rinse the sensor
head with deionized water.
Water the counter electrode in
deionized water for at least
10 minutes.
Carefully shake off the drops
of water.
Fill a new membrane cap with
ELY/G electrolyte solution.
Remove any air bubbles by
carefully tapping the mem-
brane cap. Additionally, you
can prevent air bubbles by
throwing the first filling away
and refilling the membrane
cap.
Rinse the sensor head with
electrolyte solution.
Hold the sensor inclined and
screw on the membrane cap
fingertight using a paper tow-
el. Excess electrolyte solution
is forced out of the ventilation
area.
Check the filling:
Inspect the face surface. No
air bubbles may be present
within the dashed circle. Air
bubbles outside this area do
not interfere.
H O
2
ELY/G
ELY/G
Ventilation area
points upwards
4 mm

Maintenance, cleaning, replacement ConOx
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5.5 Checking the DO module for freedom from zero-current
The DO module is free from zero-current. Checking the module for freedom
from zero-current is only necessary in the case of malfunctions that cannot
be remedied by exchanging the electrolyte solution and membrane cap or by
cleaning the electrodes.
There are two possibilities to check the DO module for freedom from zero-
current:
zMeasurement in a nitrogen atmosphere (recommended method)
zMeasurement in a sodium sulfite solution according to DIN EN 25814/
ISO 5814.
CAUTION
If you check the sensor according to DIN EN 25814/ISO 5814, do not
leave the sensor in the sodium sulfite solution for more than 2 minutes.
Danger of sensor poisoning!
Test criterion The DO module is OK if the measuring instrument displays < 1 % DO
saturation after 2 minutes.
5.6 Aging of the conductivity measuring cell
Normally, the conductivity measuring cell does not age. Special measuring
media (e.g. strong acids and lyes, organic solvents) or too high temperatures
shorten the operational lifetime considerably or damage the measuring cell.
The warranty does not cover cases where such conditions cause failure or
mechanical damage.
Note
For measurements under high pressure the filling must be completely free of
air bubbles.
Readiness to
measure After approx. 30 to 50 minutes, the sensor is ready for operation. Subse- quently calibrate the sensor.
Note
If you want to measure very low DO concentrations (< 0.5 % saturation), we
recommend to let the sensor rest overnight and then calibrate it.

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5.7 Disposal
CAUTION
The ELY/G electrolyte solution irritates eyes and skin. When dealing
with the ELY/G electrolyte solution, observe the following points:
zDuring working activities, always wear suitable protective gloves
and protective goggles/face shield.
zIf it comes into contact with the skin, rinse thoroughly with water and
immediately change contaminated clothing.
zIf it comes into contact with the eyes, rinse thoroughly with water
and consult a doctor.
zFollow the safety datasheet.
Conductivity basic
module, DO
module and
membrane cap
For disposal, unscrew the membrane cap from the DO module. Then rinse
the entire sensor and the membrane cap with water.
We recommend to dispose of the conductivity basic module and the DO
module without membrane cap as electronic waste. The membrane cap may
be disposed of with the household refuse.
Electrolyte
solution Disposal according to the safety data sheet.

What to do if... ConOx
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6 What to do if...
6.1 Error symptoms of DO measurement
6.2 Error symptoms of conductivity measurement
Error symptom Cause Remedy
The sensor is in the air
and the display shows
0.0 mg/l or 0 % O2
– No connection between
measuring instrument and sensor
– Cable defective
– No electrolyte in the membrane
cap
– Check connection between
measuring instrument and sensor
– Replace and refill the membrane
cap (see section 5.3)
The sensor cannot be
calibrated
– Contaminated membrane cap
– Electrolyte depleted
– Replace and refill the membrane
cap (see section 5.3)
Subsequently, wait for 30 to
50 min and recalibrate.
The sensor still cannot
be calibrated after
changing the electrolyte
and membrane cap
– Contaminated electrodes or
sensor toxification
– membrane cap not screwed on
tight enough
– Clean the electrodes (see
section 5.4)
– Screw membrane cap tighter
Incorrect temperature
display
– The temperature sensor of the
conductivity basic module was not
immersed deep enough in the
measuring solution
– Temperature sensor defective
– Observe the minimum immersion
depth
– Return the sensor
Mechanical damage to
the sensor
– Return the sensor
Error symptom Cause Remedy
No temperature or con-
ductivity display
– No connection between
measuring instrument and sensor
– Cable defective
– Check connection between
measuring instrument and sensor
Measurement delivers
implausible conductivity
values
– Incorrect cell constant adjusted at
the measuring instrument
– Measuring range exceeded
– Contamination in the area of the
electrodes
– Electrodes damaged
– Check / correct the cell constant
– Observe the application range
– Clean the sensor (see
section 5.2).
– Return the sensor
Incorrect temperature
display
– The temperature sensor was not
immersed deep enough in the
measuring solution
– Temperature sensor defective
– Observe the minimum immersion
depth
– Return the sensor

ConOx Technical data
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7 Technical data
7.1 Conductivity basic module
General features Measuring principle Four-electrode measurement
Cell constant 0.475 cm-1 ±1.5 %
Temperature sensor Integrated NTC 30 (30 k:at 25 °C / 77 °F)
Dimensions
(in mm)
Weight approx. 135 g (without DO module, with 1.5 m cable)
Materials Shaft Epoxy
– Connection head POM
– Closing cap PVC
Plug connection for
DO module
PEEK
Conductivity electrodes Graphite
Thermistor enclosure Graphite
Connection cable Lengths 1.5 / 3 / 6 / 10 / 15 / 20 m
Diameter 6 mm
Smallest allowed
bend radius
Fixed installation: 50 mm
Flexible use: 80 mm
Plug type Socket, 8 pins
Connector for DO
module Plug type 3-pole, watertight plug connection with cap nut, reverse polarity protected, contacts
gold-plated
120
145
187.5
15.3 21.7 17.5

Technical data ConOx
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7.2 Dissolved oxygen (DO) module
Pressure
resistance Sensor with closed plug connection
IP 68 (3 x 105Pa or 3 bar)
Cable plug IP 67 (when plugged in)
The ConOx meets the requirements according to article 3(3) of the
97/23/EC directive ("Pressure equipment directive").
Measurement
conditions Conductivity measuring range
1 PS/cm ... 2 S/cm
Temperature range 0 ... 50 °C (32 ... 122 °F)
Max. allowed overpressure 3 x 105Pa (3 bar)
Depth of immersion min. 6 cm (with closing cap)
min. 8 cm (with DO module)
max. 20 m (depending on the cable length)
Operating position any
Approach flow not required
Storage
conditions Recommended storing method
in the OxiCal®-CX calibration and storage
vessel (moistened) or dry (without DO mod-
ule)
Storage temperature 0 ... 50 °C (32 ... 122 °F)
Characteristic data
on delivery Temperature responding behavior
t99 (99 % of the final value display after)
<20s
Precision of the temperature
sensor
±0.3K
General features Measuring principle Membrane covered galvanic sensor
Temperature compensa-
tion
IMT compensation
(calculated by the measuring instrument)
Dimensions
(in mm)
Weight approx. 20 g (filled with electrolyte)
44
15.3