Operation manual Oxygen sensor
Operation manual
Oxygen sensor
Using oxygen sensors made by SENSORE, oxygen can be measured in gaseous media within a concentration range
from 10 ppm O2 up to 96 % O2 depending on the sensor type. The sensor is thus characterized by the following essential
characteristics:






High accuracy
For many types a more or less linear characteristic
Small temperature dependence of the sensor signal
Low interference with other gases
Long service life
In many cases “Single point calibration“ necessary only once
Technical data see in the appendix (specification).
Definition of types
Example SO-B0-250-A100C
Customized type completion
Measuring range of the sensor (see spreadsheet measuring
ranges in the appendix)
Housing type (see spreadsheet housing types in the
appendix)
Sign for oxygen sensors
Sensor's function
If a voltage is applied to the sensor then this sensor operates as a current source, whose output current is dependent on
the oxygen concentration of the measuring gas. For this the current is at a certain oxygen concentration dependent on
the measuring range selected and on the sensor's production tolerances. Due to these production tolerances each sensor
must be calibrated individually! The required, type-dependent sensor voltages and output current ranges are listed in the
Sensor type table in the appendix.
For all sensor types and for all calibration gas concentrations the following formula is valid:
 [O ] 
I s ([O2 ])  k  ln 1  2 
 100 
I s ([O2 ])
Sensor current in the measuring medium
[O2 ]
k
Oxygen concentration in the measuring medium in %
Sensor-specific constant
To determine the sensor-specific constant the sensor must be put in a gaseous medium with a known oxygen
concentration (calibration). With the sensor current measured in this gas and the following formula the k constant can be
calculated
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
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Operation manual
Oxygen sensor
k
 I k ([O2 ])
 [O2,k ] 

ln 1 
100 

k
I k [O2 ]
Sensor-specific constant
[O2,k ]
Given oxygen concentration (calibration gas concentration) in %
Sensor current at a given oxygen concentration
For sensor types SO-xx-250 and SO-xx-960 which can be calibrated in air, the sensor current follows as a function of
the oxygen concentration the equation:
I s ([O2 ]) 
 I s (20.9%)  [O2 ] 
 ln 1 

0.2345
 100 
I s [O2 ]
I s (20.9%)
Sensor current at a given concentration
[O2 ]
Oxygen concentration in %
Sensor current measured in air [20.9 %]
For small oxygen concentrations the formula can be simplified mathematically and a linear connection results:
I1 ([O2 ])  k  [O2 ]
in which k can be determined under the same conditions as described above:
k
I ([O2 ])
[O2 ]
k
I k [O2 ]
[O2,k ]
I k ([O2 ])
[O2,k ]
Sensor current in the measuring medium
Oxygen concentration in the measuring medium in %
Sensor-specific constant
Sensor current at a given oxygen concentration
Given oxygen concentration (calibration gas concentration) in %
The sensor output current can be measured either by using a commercial ammeter or it can be converted into an easily
measurable voltage with the help of an operational amplifier circuit. The appendix contains a circuit suggestion for this.
Sensor heater operating modes
In order to operate the sensor it is necessary to heat it. This is carried out using the sensor heater integrated in the
sensor. There are two different modes.
Constant heater voltage
If the ambient temperature fluctuations are small (a few degrees °C), then the heating can be operated by means of a
constant voltage with current limitation. The necessary heater voltage depends on the sensor housing and is listed with
recommended heater current limitation in the appendix. In this heater operation mode the output signal changes by
0.034 % / °C ambient temperature.
The appendix also contains a circuit suggestion for this.
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
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Operation manual
Oxygen sensor
Constant heater resistance
However, if higher variations in temperature (e.g. exhaust gas measurement) or also higher gas flow rates occur, then
the sensor temperature must be kept constant to increase the measuring accuracy.
To keep the sensor temperature constant a rheostatic control is used, which always adjusts the sensor heater's resistance
and thus the sensor temperature to the same value independent from the ambient temperature. This desired value of the
rheostat is calculated as follows starting from the cold resistance of the sensor heater:
Rw,soll  f  R( 25C )
Rw, soll
Resistance of the sensor heating in operation
R( 25C )
Resistance of the sensor heating at 25 °C
f
Temperature factor 2.8; in some applications also 2.65
SENSORE offers an electronic circuit (EDAB-M1V2-L) by which the sensor can be operated in the simplest way (see
description in the appendix).
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
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Operation manual
Oxygen sensor
Pin connection for different sensor types
TO39 (Type SO-A0-xxx), TO8 (Type SO-Bx-xxx)
1
2
3
4
H+ (HS+)
H- (HS-)
Sen+
Sen-
(Pin-side view)
Sensors with connecting cable for 4-wire operation (SO-Bz-xxx-AxxxC, SO-Dz-xxx-AxxxC)
Sensors with connecting leads (teflon isolation with
temperature stability up to 250 °C):
Cable colour
Pin Connection
Violet 1
Violet 2
White 1
White 2
Red
Black
H+
HS+
HHS
Sen+
Sen-
Connected to
pin No.
1
2
Schematic drawing of sensor connection cable with
plug, view from backside of the plug
3
4
Basic circuit of the sensor
There are additional leads named sense drawn in the
basic circuit shown beside. With this leads the exact
heater voltage at the sensor pins can be adjusted. This
four wire measuring system is recommended for heater
operation with constant voltage. In case of operation
with constant heater resistance mode it is absolutely
necessary to use this for wire measurement system.
Ih<=Ih max
Is = f(O 2 )
+
Sensor
+
Uh
-
Sense
1
3
2
4
+
Us
-
Warning
Permanent damage to the sensor can occur due to the following circumstances:




Sensor is in the unheated state in exhaust gas which contains H2S or SOx
Contact with water or condensed humidity
Contact with gases which contains halogens like F, Cl, Br
Contact with organic vapors
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
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Operation manual
Oxygen sensor
Appendix: Operating parameters
Sensor heater / Constant heater voltage operation mode
Sensor type
SO-A0-xxx
SO-B0-xxx (except 001)
SO-B0-001-xxxxx
SO-B1-xxx-xxxxx
SO-D0-xxx- xxxxx
SO-D1-xxx- xxxxx
SO-D2-xxx- xxxxx
SO-E1-xxx
SO-E2-xxx- xxxxx
Heater voltage (*)
4.0 volt  0.05 volt
3.6 volt  0.05 volt
3.8 volt  0,05 volt
3.7 volt  0,05 volt
4.1 volt  0.05 volt
4.1 volt  0.05 volt
3.8 volt  0.05 volt
3.6 volt  0.05 volt
3.6 volt  0.05 volt
Housing
TO39
TO8
TO8
TO8 with mounting flange
Screw mountable housing
Screw mountable housing
Aluminium Screw mountable housing
TO8 with hose connection
TO8
Suggested current limitation
0.5 ampere
0.5 ampere
0.5 ampere
0.5 ampere
0.5 ampere
0.5 ampere
0.5 ampere
0.5 ampere
0.5 ampere
(*) In case of deviate heater voltage the voltage is listed separately
Sensor heater / Constant heater resistance operation mode
Resistance of sensor heating at 25°C:
Sensor type
SO-xx-xxx
Housing
All types
R(25°C) = 3.25   0.20 
Heater resistance during operation
R operation = R (25°C)*2.8
Suggested heating limitation
0,5 ampere or soft start (PWM)
Temperature dependence of the sensor signal
0.034 % measuring signal / °C ambient temperature in stagnant air(*)
(*) A temperature difference of 200 °C (e.g. exhausted gas measuring) means a raise of the sensor signal of 6.8%.
Pressure dependence of the sensor signal
in the range of 150 mbar – 800 mbar
in the range of 800 mbar – 5.0 bar
2.0 % of measuring signal / 100 mbar
0.5 % of measuring signal / 1 bar
Drift of sensor current
Neglectable
Max. potential difference between heater ground and sensor ground
 3 Volt
Marking of the sensor
Example
412 3412 D
Code for measuring range (see spreadsheet measuring
ranges in the appendix)
Date of production (week / code for the year)
Production order number
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
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Operation manual
Oxygen sensor
Packaging
SO-A0-xxx, SO-B0-xxx
All other types
Plastic case
Single or bounded to 10 pieces
Mounting
SO-A0-xxx, SO-B0-xxx
All other types
suitable to solder into a PCB; distance to PCB at least 3 mm
Mountable in any housing
Cross sensitivities
Gas
Max. concentration of the checked gas
CO2
CO2
CO
CO
NO2
SO2
CH4
H2S
H2O (humidity)
SO-xx-960 excluded
40 %
40 %
1000 ppm
1000 ppm
1000 ppm
1000 ppm
1000 ppm
400 ppm
90% abs
Cross sensitivity
[% O2 / %Gas]
-0.027
-0.01
-0.73
-0.83
1.06
-0.24
-1.77
 0.0
 0.0
at oxygen concentration
20 % O2
5 % O2
20 % O2
5 % O2
5 % O2
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
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Operation manual
Oxygen sensor
Appendix: Change of oxygen content due to humidity
Dalton's law (law of partial pressures)
The total pressure
individual gases.
exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures
Mole fraction of gas i in %
Partial pressure of gas i
Height-dependent barometric pressure (sea level Vienna ~ 160 m 
of
~ 990 mbar)
Dry air contains roughly (by volume) 78.084% nitrogen, 20.942% oxygen, 0.934% argon, and small amounts of other
gases. Water vapour which is present by an average of 0.4 vol.% (range: 0 – 4 vol.%), is not included in the above
composition, because this amount depends on several environmental conditions. When air is humid, the water vapour
associated partial pressure displaces the surrounding air, resulting in a reduction of the relative oxygen content. This
water vapour pressure is directly proportional to the temperature-dependent saturated vapour pressure.
Water vapour pressure [mbar]
Relative humidity in %
Temperature-dependent saturated vapour pressure [mbar]
Oxygen content of humid in Vol.%
Height independent oxygen content of dry air = 20.942 Vol.%
Humidity effect in air
21,0%
Relative O2 Concentration
20,9%
20,8%
20,7%
20,6%
T = 10°C
20,5%
T = 20°C
20,4%
T = 30°C
20,3%
20,2%
pbar = 990 mbar
20,1%
20,0%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Relative Humidity
Attention:
The above-mentioned reduction of oxygen content due to moisture is measurable with all Sensore O 2 sensors except for
the SO-xx-960 types. Because of a higher sensor voltage (1.6 V) they are able to split water vapour (H2O). This
additional oxygen causes a positive cross-sensitivity, which leads to an increase of the sensor signal.
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
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Operation manual
Oxygen sensor
Appendix: Sensor characteristics for different sensor types
350,0
250,0
SO-XX-020
SO-XX-001
300,0
Manufactoring scatter
Manufactoring scatter
200,0
250,0
150,0
Is [uA]
Is [uA]
200,0
150,0
100,0
100,0
50,0
50,0
0,0
0,00
0,04
0,0
0,00
0,08
0,20
0,40
0,60
0,80
1,00
O2 [%]
1,20
1,40
1,60
1,80
2,00
O2 [%]
450,0
250,0
SO-K-DXX-XX-960
SO-XX-250
400,0
200,0
350,0
Manufactoring scatter
300,0
150,0
Manufactoring scatter
Is [uA]
Is [uA]
250,0
200,0
100,0
150,0
100,0
50,0
50,0
0,0
0,00
0,0
0,00
5,00
10,00
15,00
20,00
10,00
20,00
30,00
40,00
50,00
60,00
70,00
80,00
90,00
100,00
25,00
O2 [%]
O2 [%]
Different sensor characteristics
ATTENTION: In each case only one characteristic applies per sensor!
Sensor electronics versions from SENSORE
SENSORE offers three electronic versions for easy control of the sensor:



CSB: Electronic sensor board for oxygen sensors.
EDAB-M1: Electronic board with temperature control and linearization of the characteristic sensor curve.
GSB: Compact version of EDAB-N1: temperature control and linearization of the characteristic sensor curve.
The CSB (Compact sensor board) provides a plugged/soldered sensor with a fixed heater voltage, is compatible to all
SENSORE O2 sensors of the type SO-xx-xxx and has a current or a voltage output.
EDAB-M1 contains the temperature control specified in the description and in addition to the signal conversion
mentioned also a linearization of the sensor characteristic so that a complicated conversion of the output signal to the
measured oxygen concentration is not applicable. The GSB is compared to EDAB-M1 more compact, has a current
output and can be reprogrammed according to customer requirements.
A more detailed description of the functions is contained in the respective data sheets.
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
SO001e-7 / 23.04.2015
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Operation manual
Oxygen sensor
Appendix: Simple circuit suggestion
The information contained in this document is believed to be accurate and reliable but is presented without guarantee.
SENSORE Electronic GmbH
www.sensore-electronic.com
Aufeldgasse 37-39, A 3400 Klosterneuburg
info@sensore-electronic.com
Tel. +43 2243 450 0, Fax +43 2243 450 315
SO001e-7 / 23.04.2015
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