SST OXY-Flex User manual

© 2012 SST Sensing Ltd 1 of 12 www.sstsensing.com
DS0073 Rev 10
FEATURES
 High accuracy linear output
 Configurable outputs:
4-20mA and 0-10VDC or RS232 comms
interface
 Selectable output measurement ranges:
Standard ranges of 0-25% O2 and
0-100% O2or fully adjustable via RS232 when
configured in 0-100% O2mode
 Externally triggered automatic or manual
calibration
 Can be calibrated in normal air (20.7% O2) or in
any other known O2 concentration
 Cycling 3.3VDC logic output allows direct
monitoring of the O2 sensor pump cycle for
diagnostic purposes
 Selectable output filtering allows adaptive, fast
and dynamic or slow and stable output
SPECIFICATIONS
Maximum ratings
Supply voltage 24VDC ± 10%
Current consumption 500mA max
@ 24VDC
4-20mA Load 100 to 600Ω
Temperature limits (electronics enclosure)
Storage -10 to 85C
Operating -10 to 85C
Temperature limits
(permissible gas temperature at sensor tip)
Operating (Standard Temp) -100 to 250C
(High Temp) -100 to 400C
Gas flow rate 0 to 10 m/s
Weight <450g
Incidental permissible acceleration 30g
Repetitive permissible acceleration 5g
Sealing Rating IP65
OXY-Flex-0-H
APPLICATIONS
 Combustion control including oil, gas and
biomass boiler applications
 Composting
 Laboratory & building air quality monitoring
including confined space personnel safety
 Industrial process control i.e. gas mixing for
welding and steel making
 Oxygen generation systems
 Medical
 Scientific including respiratory studies of a
community or an organism, plants and
animals
 Food and beverage packaging
 Applications where low oxygen is key
including fermentation, rust and corrosion
prevention, inerting and purging
OXY-Flex Oxygen Analyser

© 2012 SST Sensing Ltd 2 of 12 www.sstsensing.com
DS0073 Rev 10
DESCRIPTION
The OXY-FLEX-X Series Standard Temperature
Oxygen Analyser is designed to determine the oxygen
concentration in air or inert gas mixtures with temperatures
of -100 to +250°C max.
The OXY-FLEX-X-H Series High Temperature Oxygen
Analyser is designed to determine the oxygen
concentration in air or inert gas mixtures with temperatures
of -100 to +400°C max.
These products are particularly suitable for measuring
oxygen in areas that are not easily accessible, or in
closed systems, such as ventilation pipes, flues and
containers.
The OXY-FLEX Series can be user configured to output
measuring ranges of 0-25% O2 and 0-100% O2 . The entire
measurement range is linear in both cases. Factory default
is 0-25% O2. When configured for 0-100% O2 the user can
also customise the analogue output ranges to suit their
application.
The outputs can be configured to either
4-20mA and 0-10VDC or RS232 interface. Prior to
shipping all OXY-FLEX’s are preconfigured with a
measuring range of 0.1% to 25% Vol. O2with linear
4-20mA and 0-10VDC outputs.
All settings can be changed by the customer should their
measurement or interface requirements change by simply
altering the position of jumper links on the PCB.
The actual oxygen sensor is mounted in the tip of the
stainless steel probe and is protected by a stainless-steel
sintered cap which acts as both a large particulate filter
and also as a flame trap. The IP65 waterproof die-cast
aluminium housing accommodates the electronics and is
mechanically connected to the sensor probe.
The OXY-FLEX outputs the measured values
simultaneously via 2 output channels (4-20mA and
0-10VDC or RS232 Rx and Tx) both channels are
referenced to the system GND.
A digital 3.3VDC logic output cycles at the same
frequency as the electrochemical pumping action of the
oxygen sensing cell during normal operation, thus
providing a real time sensor health check, if the output
ceases to cycle the sensor has entered a start-up or error
state. This provides fault proof operation. The digital
output is also used during the calibration process to
indicate the interface status.
A green on-board LED mirrors the CYCLE output and can
be used to visually determine the sensor status or during
the calibration process. A red LED indicates the unit has
power applied.
SST’s range of oxygen sensors do not directly measure
the oxygen concentration but instead measure the partial
pressure of oxygen within the measurement gas. In order
to output an oxygen concentration (%) the OXY-FLEX
must be calibrated, or more specifically, re-referenced in a
known gas concentration, typically normal air.
Calibration, or re-referencing, is achieved by connecting
the calibration input to GND and monitoring the status of
the digital cycle output or by visually monitoring the
on-board green LED. During the calibration process the
output will either automatically calibrate to a fixed
reference or can be manually calibrated to any output by
way of a PCB mounted potentiometer. The fixed
reference is factory set to 20.7% O2for calibration in
normal air though this value may be altered via the RS232
interface for calibration with a reference gas of any known
oxygen concentration. Calibration is stored on power loss.
Again the auto or manual calibrate function is user
configurable. Regular calibration removes the effects of
application and atmospheric pressure changes and also
eliminates any sensor drift that may occur during the first
few hundred hours of operation.
For more detailed information on the operation of
SST Sensing Oxygen Sensors please refer to the
following application note via our website:
AN0043 Operation Principle and Construction of
Zirconium Dioxide Oxygen Sensor.
OXY-Flex Oxygen Analyser

© 2012 SST Sensing Ltd 3 of 12 www.sstsensing.com
DS0073 Rev 10
PERFORMANCE CHARACTERISTICS
Characteristics Min. Typ. Max. Unit
Output inactive start up delay (heater warm up) 60 s
Initial warm up time (till stable output) 5 10 min
Measuring ranges
25% Configuration
100% Configuration
0.1 (1)
0.1 (1)
25
100
% O2
Accuracy After Calibration (2) (3) 1 % O2
Repeatability After Calibration (2) 0.5 % O2
0-10 VDC Output Resolution 0.01 V
4-20mA Output Resolution 0.01 mA
RS232 Output Resolution 0.01 % O2
Reaction time (adaptive output filtering in normal air) 1 s
Notes:
(1) Prolonged operation below 0.1% O2can damage the sensing element.
(2) Assuming barometric pressure remains constant.
(3) As the O2 sensor measures the partial pressure of oxygen (PPO2) within the measurement gas deviations in the
Barometric Pressure (BP) from that present during calibration will cause readout errors proportional to the
change. For example if the sensor was reading 21% O2at 1013.25mbar and the BP increased by 1% the sensor
readout would also increase by 1% to 21.21% O2.
OXY-Flex Oxygen Analyser

© 2012 SST Sensing Ltd 4 of 12 www.sstsensing.com
DS0073 Rev 10
OUTLINE DRAWING AND MOUNTING INFORMATION
Mounting holes accessible on
removal of housing lid
PCB LAYOUT (REMOVE HOUSING LID TO VIEW)
OXY-Flex Oxygen Analyser

© 2012 SST Sensing Ltd 5 of 12 www.sstsensing.com
DS0073 Rev 10
ELECTRICAL CONNECTIONS
Housing Connector: Amphenol Ecomate C016 30C006 100 12
Mating Connector: Binder 99-4218-00-07
(Mating Connector supplied with each product)
Output pins 5 and 6 are both referenced to the supply GND (pin 2). Due to high current flow in the supply GND, when
monitoring the 0-10VDC output (pin 6) it is recommended that a separate GND wire for the measurement system is taken
from PIN 2. This removes errors due to voltage drops in the power supply connections.
SYSYEM BLOCK DIAGRAM
PIN Description
1 24VDC ± 10%
2 GND
3Calibrate
4 Cycle
5 4-20mA/RS232 Tx
6 0-10VDC/RS232 Rx
CENTRE Housing/Probe Earth
OXY-Flex Oxygen Analyser

© 2012 SST Sensing Ltd 6 of 12 www.sstsensing.com
DS0073 Rev 10
OXY-Flex Oxygen Analyser
RS232 COMMUNICATION SETTINGS
When connecting the OXY-FLEX via the RS232 connections ensure Tx goes to Rx of the PC and Rx goes to Tx of the
PC.
The OXY-Flex communicates via standard COM port settings that are default on most PCs and many other RS232
compatible devices. If however communication problems are occurring use the settings below to configure the PC or
device COM Port.

© 2012 SST Sensing Ltd 7 of 12 www.sstsensing.com
DS0073 Rev 10
CONFIGURATION
The OXY-FLEX may be reconfigured at any time by
adjusting the position of the header pin jumper links on the
interface PCB.
WARNING: Prior to re-configuration the OXY-FLEX MUST
be powered down. The jumper links MUST also be
repositioned correctly and in the correct orientation.
Failure to adhere to the above could result in product
damage. Products damaged due to incorrect
configurations will not be covered under warranty.
 Power down the OXY-FLEX
 Remove the lid using a Philips screwdriver
 Adjust the position of the jumper links to the desired
configuration. The diagrams below and on Page 4
show the correct positioning for each user
configurable option. Thin nosed pliers should be
used to remove and replace the Jumper Links.
Ensure the Jumper Links are correctly seated before
reapplying the power
NOTE: Each Jumper Link must be placed in one of the two
positions. When selecting the output, you must choose
either 4-20mA and 0-10VDC or RS232 Tx and Rx. Ensure
the Jumper Links are always inserted horizontally between
2 adjacent pins.
RS232 OPERATION
With the OXY-FLEX RS232 outputs connected to a PC or
any other RS232 compatible device the user has the
ability to access two modes of operation, continuous data
streaming and the menu screens. Recommended
programs for communicating via PC serial RS232 are
Hyperterminal (windows default), Teraterminal and PuTTY.
A freeware PuTTY link can be found below;
http://the.earth.li/~sgtatham/putty/latest/x86/putty.exe
Continuous Data Streaming
On power up, after the initial 60s heater delay, the OXY-
FLEX will automatically begin outputting the measured O2
concentration and sensor Td as both an averaged and raw
value. The averaged values give a stable output with the
amount of averaging user variable whilst the raw un-
averaged values allow the user to detect sudden oxygen
changes. The averaged value is the measurement output
on both the 4-20mA and 0-10VDC outputs. The sensor Td
value is the measure of the partial pressure of oxygen in
the measurement gas. The O2concentration (%) is the Td
value scaled by the stored calibration value.
To stop or restart the data streaming ‘s’ (lower or upper
case) should be sent to the unit. Data streaming
automatically ceases during calibration.
Menu Screens
If the OXY-FLEX receives an enter character from the
connected PC or device it automatically enters the menu
password screen and stops outputting O2% and Td
values. After the correct password is entered followed by
the enter character, the menu screens are accessed. The
menu screens are primarily for diagnostics and information
although there are user configurable options that may be
changed. These are the automatic O2calibration %, the
amount of output filtering (averaging) and the analogue
output ranges. All three processes are further described
on Page 8. The menu access password may also be
changed by the user.
Changing the Menu Access Password
The password is factory set to ‘default’. This however may
be changed to a user specific password.
 Connect the OXY-FLEX via the RS232 interface to
the PC.
 Press Enter then enter your current security
password. Press Enter to access the menu screen.
 In the Configuration menu (menu 2) enter ‘3’ to
access the password menu screen.
 Enter the new password then press Enter to save.
 The new password is now stored in memory and is
retained on power loss.
Pressing ESC returns the screen to the previous menu.
OXY-Flex Oxygen Analyser

© 2012 SST Sensing Ltd 8 of 12 www.sstsensing.com
DS0073 Rev 10
RS232 USER CONFIGURABLE OPTIONS
Changing the Automatic Calibration Value
The system is factory set to automatically calibrate to
20.7% O2to allow simple calibration in normal air. The
auto calibration value is factory set to 20.7% to take into
account average humidity in the atmosphere. If a
calibration with a gas of a different known O2
concentration is required the factory set value may be
changed via the RS232 interface.
 Connect the OXY-FLEX via the RS232 interface to
the PC. See CONFIGURATION on Page 7.
 Press Enter then enter your security password.
Press Enter to access the menu screen.
 In the Configuration menu (menu 2) enter the auto
calibration value screen (option 1 - Enter
Auto Calib).
 The number entered should be the oxygen
concentration (%) of the calibration gas to 2 decimal
places. Press Enter to save.
 The new Automatic Calibration value is now stored
in memory. This value is retained on power loss.
If calibration is required with a different gas of known O2
concentration and access to the RS232 menus with a PC
is not available in order to change the calibration
percentage, a manual calibration must be performed.
Variable Output Filtering (Td Averaging)
The OXY-FLEX is factory default to use adaptive output
filtering to give an optimum balance between output
stability and response to oxygen changes. However this
balance may be altered by the customer to suit the needs
of the application.
 Connect the OXY-FLEX via the RS232 interface to
the PC. See CONFIGURATION on Page 7.
 Press Enter then enter your security password.
Press Enter to access the menu screen.
 In the Configuration menu (menu 2) enter the Td
average screen (option 2 - Enter Td Averaging).
 The number entered should be between 0 and 200.
0 for adaptive filtering (recommended), 1 for very
fast and dynamic output response but relatively
unstable to 200 for an extremely stable output but
very slow response to oxygen changes.
 Press Enter to save.
 The new averaging value is now stored in memory.
This value is retained on power loss.
Adjusting the Minimum and Maximum Ranges of the
Analogue Outputs (4-20mA and 0-10VDC)
The OXY-FLEX is factory default to output a range of
0-25% O2via its two analogue outputs. This range can be
expanded to 0-100% O2as described on Page 7. When
the unit is reconfigured to output 0-100% O2the user also
has the option to fully customise the output ranges via
RS232. This is extremely useful in applications where the
O2variation is within a narrow band as it allows the
analogue outputs to be tailored to this limited range.
 Ensure the OXY-Flex is configured for 0-100% and
RS232 operation, See CONFIGURATION on Page
7.
 Connect the OXY-FLEX via the RS232 interface to
the PC.
 Press Enter then enter your security password.
Press Enter to access the menu screen.
 In the Configuration menu (menu 2) enter the
maximum range screen (option 3 - Enter O2 Max
Range).
 The number entered should be between 1.00 and
100.00 to represent the maximum output range. The
number must also be greater than the saved
minimum range.
 Press Enter to save the ESC to return to the
configuration menu.
 Enter the minimum range screen (option 4 - Enter
O2 Min Range).
 The number entered should be between 0.00 and
99.00 to represent the minimum output range. The
number must also be less than the saved maximum
range.
 Press enter to save.
 The new ranges are now stored in memory and are
retained on power loss.
An example of changing the min and max output ranges
would be in an normal air atmosphere where the O2range
is between 20-21%. The user could set the minimum
output range to 19% and the maximum output range to
22% and the outputs would vary linearly in between. The
min and max ranges lock out the outputs at the set limits
so 19% O2or lower would set the analogue outputs to
0VDC/4mA and 22% O2or higher would set the analogue
outputs to 10VDC/20mA.
The min and max range adjustment does not apply to the
RS232 output and is overruled if the unit is reconfigured
for 0-25% operation.
OXY-Flex Oxygen Analyser

© 2012 SST Sensing Ltd 9 of 12 www.sstsensing.com
DS0073 Rev 10
CALIBRATION PROCEDURES
Automatic Calibration
 Ensure the OXY-FLEX is configured for automatic
calibration. See CONFIGURATION on Page 7.
 Place the sensor probe in the calibration gas,
typically normal air.
 Allow the output to stabilise for at least 5 mins. 10
mins if powering from cold.
 Apply GND to the CALIBRATE input (PIN 3) for a
minimum 12s. During the 12s the CYCLE output
(PIN 4) and the green LED will go high/on, blink
rapidly, go high/on, go low/off then return to cycling
normally to indicate normal operation has resumed.
At this point remove GND from PIN 3.
 The output will now track to the correct value for the
calibration gas.
 Calibration is complete. Calibration values are
retained on power loss.
Manual Calibration
 Ensure the OXY-FLEX is configured for manual
calibration. See CONFIGURATION on Page 7.
 Place the sensor probe in the calibration gas,
typically normal air.
 Allow the output to stabilise for at least 5 mins. 10
mins if powering from cold.
 Apply GND to the CALIBRATE input (PIN 3) for a
minimum 5s or until the CYCLE output and green
LED blink at a steady 1Hz. Remove GND from PIN
3. Manual Calibration is now initialised.
 Adjust the MANUAL CAL POT until the output
equals the correct value of the calibration gas
concentration.
 Re-apply GND to PIN 3 for a minimum 5s. During
the 5s the CYCLE output/LED will blink rapidly, go
high/on, go low/off then return to cycling normally to
indicate normal operation has resumed. At this point
remove GND from PIN 3.
 The output will now track to the correct value for the
calibration gas.
 Calibration is complete. Calibration values are
retained on power loss.
SEE PAGE 4 FOR THE LOCATION OF THE SENSOR/
POWER LEDs AND THE MANUAL CAL POT.
ERROR CONDITIONS
If the oxygen sensor is damaged the OXY-Flex will
highlight this by blinking the CYCLE output (pin 4) and
green LED in a 3 short blinks 1 long blink pattern or
continuously OFF. An error code is also displayed on the
RS232 output and the analogue outputs will go to 4mA
and 0V.
OXY-Flex Oxygen Analyser

© 2012 SST Sensing Ltd 10 of 12
DS0073 Rev 10
OXY-Flex Oxygen Analyser
SENSOR OPERATING TIPS
To get the best performance from the OXY-Flex analyser it is important that the oxygen probe is installed and
maintained in the correct manner. The following two pages outline some useful sensor operating tips and a list of gases
and materials that must be avoided to ensure a long sensor life.
Operating the Sensor in Aggressive Humid Environments:
When operating the sensor in warm, humid environments it is important the sensor remains at a higher temperature
than it’s surroundings, especially if there are corrosive components in the measurement gas. During operation this is not
a problem due the 700°C generated by the heater, but this means when the sensor or application is being powered
down the sensor heater must be the last thing to be turned off after the temperature of the surroundings have suitably
cooled. Ideally the sensor should be left powered at all times in very humid environments.
Failure to adhere to the above will result in condensation forming on the heater and sensing cell as these will be the first
components to cool due to their connections to the outside world. When the sensor is re-powered the condensation will
evaporate, leaving behind corrosive salts which very quickly destroy the heater and cell as illustrated below. Note how
the sensor’s external metalwork looks completely normal.
Protecting from Water Droplets:
In environments where falling water droplets are likely the sensor should be protected from water falling directly onto the
very hot sensor cap as this can cause massive temperature shocks to the cell and heater. Popular methods include a
hood over the sensor cap or for the sensor to be mounted in a larger diameter cylinder.
At a very minimum the sensor cap should be angled downwards in the application as this will deflect any falling moisture
and prevent the sensor cap from filling with water.
Using the Sensor With Silicones:
SST Sensing’s oxygen sensors, like all other Zirconium Dioxide sensors, are damaged by the presence of silicone in the
measurement gas. Vapours (organic silicone compounds) of RTV rubbers and sealants are the main culprits and are
widely used in many applications. These materials which are often applied as a liquid or gel still outgas silicone vapours
into the surrounding atmosphere even after they have cured. When these vapours reach the sensor the organic part of
the compound will be burned at hot sensor parts, leaving behind a very fine divided Silicon Dioxide (SiO2). This SiO2
completely blocks the pores and active parts of the electrodes.
If silicone cannot be avoided in the application we advise using high quality, high temperature cured materials which do
not outgas when subsequently heated. SST can provide guidance if there is concern about use of silicone within the
application.
When installing the sensor do not use any lubricants or grease which may contain silicone.
In addition to silicones other gases which may interfere will the sensor are listed overleaf.

© 2012 SST Sensing Ltd 11 of 12
DS0073 Rev 10
OXY-Flex Oxygen Analyser
SENSOR OPERATING TIPS continued
Cross sensitivity with other gases:
Gases or chemicals that will have an influence on the life of the sensor or on the measuring results are:
1. Combustible Gases
Small amounts of combustible gases will be burned at the hot Pt-electrode surfaces or Al2O3filters of the sensor.
In general combustion will be stoichiometric as long as enough oxygen is available, the sensor will measure the
residual oxygen pressure which leads to a measurement error. The sensor is not recommended for use in
applications where there are large amounts of combustible gases present and an accurate O2measurement is
required.
Investigated gases were:
 H2(Hydrogen) up to 2%; stoichiometric combustion
 CO (Carbon Monoxide) up to 2%; stoichiometric combustion
 CH4(Methane) up to 2.5%; stoichiometric combustion
 NH3(Ammonia) up to 1500 ppm; stoichiometric combustion
2. Heavy Metals
Vapours of metals like Zn (Zinc), Cd (Cadmium), Pb (Lead), Bi (Bismuth) will have an effect on the catalytic
properties of the Pt–electrodes. Exposure to these metal vapours must be avoided.
3. Halogen and Sulphur Compounds
Small amounts (< 100ppm) of Halogens and/or Sulphur compounds have no effect on the performance of the
oxygen sensor. Higher amounts of these gases will in time cause readout problems or, especially in condensing
atmospheres, corrosion of sensor parts. These gases often outgas from plastic housings and tubes when hot.
Investigated gases were:
 Halogens, F2(Flourine), Cl2(Chlorine)
 HCL (Hydrogen Chloride), HF (Hydrogen Fluoride)
 SO2(Sulphur Dioxide)
 H2S (Hydrogen Sulphide)
 Freons
 CS2(Carbon Disulfide)
4. Reducing Atmospheres
Long time exposure to reducing atmospheres may in time impair the catalytic effect of the Pt-electrodes and has
to be avoided. Reducing atmospheres are defined as an atmosphere with very little free oxygen and where
combustible gases are present. In this type of atmosphere oxygen is consumed as the combustible gases are
burned.
5. Others
 Dust. Fine dust (Carbon parts/soot) might cause clogging of the porous stainless steel filter and might
have an effect on the response of the sensor to oxygen changes.
 Heavy shocks or vibrations may alter sensor properties resulting in the need for a recalibration.

© 2012 SST Sensing Ltd 12 of 12
DS0073 Rev 10
ORDERING INFORMATION
Part number Output Type Probe Length Measuring Range Gas Temperature
OXY-FLEX-0 4 to 20mA and 0 to 10V or
RS232 220mm 0.1 to 25% Vol. O2 or 0.1 to 100% Vol. O2-100 to 250C
OXY-FLEX-1 4 to 20mA and 0 to 10V or
RS232 400mm 0.1 to 25% Vol. O2 or 0.1 to 100% Vol. O2-100 to 250C
OXY-FLEX-0-H 4 to 20mA and 0 to 10V or
RS232 220mm 0.1 to 25% Vol. O2 or 0.1 to 100% Vol. O2-100 to 400C
OXY-FLEX-1-H 4 to 20mA and 0 to 10V or
RS232 400mm 0.1 to 25% Vol. O2 or 0.1 to 100% Vol. O2-100 to 400C
WARNING
The sensor tip becomes very HOT during
operation and may cause injury if touched.
Personal Injury
DO NOT USE these products as safety or
Emergency Stop devices or in any other application
where failure of the product could result in
personal injury.
Failure to comply with these instructions could
result in death or serious injury.
CAUTION
Do not exceed maximum ratings and ensure sensor is
operated in accordance with all requirements of AN0043
Failure to comply with these instructions may result
in product damage.
It is the customer’s responsibility to ensure that this
product is suitable for use in their application. For
technical assistance or advice, please email us:
[email protected]m
NOTE: All variants can have their Output Type and Measuring Range reconfigured at any time using the
CONFIGURATION guide on Page 7.
OXY-Flex Oxygen Analyser
General Note: SST Sensing Ltd reserves the right to make changes in product specifications without notice or liability.
All information is subject to SST’s own data and considered accurate at time of going to print.