Oxygen Sensor
Type A19
*** Version 2.2 ***
METROTEC
Systems for oxygen measurement
A19
METROTEC
METROTEC GmbH
Heinkelstraße 12 • D-73230 Kirchheim
Telefon 07021/95336-0 • Fax 07021/95336-13
www.metrotec.eu • info@metrotec.de
Declaration of Conformity
for
Oxygen sensor
Type A19 series
This unit is designed for industrial applications in accordance with
EN 50081-2
EN 50082-2
The shipped version of this device complies with the requirements of the EEC norms:
EMC directive: 2014/30/EU
Low voltage directive: 2014/35/EU
RoHs directive: 2011/65/EU
Additional directrives:
EN 50081-2
EN 50082-2
EN 61010-1
EN 50581
Controlled by:
Quality-Management-System DIN EN ISO 9001:2015, No. 1210027736 TMS
The user is cautioned that modifications made to the device without the approval of the
manufacturer could void the user´s authority to operate this device.
Kirchheim/Teck, 23.04.2019
Town, date Sign
Contents
1 SAFETY INSTRUCTIONS ............ 4
2 PREFACE ........................................ 5
3 INTRODUCTION ........................... 6
3.1 Measurement principle .............. 6
3.2 Sensor ........................................ 7
3.3 Converter module ...................... 8
4 ASSEMBLY ..................................... 8
4.1 Electrical .................................... 8
4.2 Mechanical ................................ 8
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5 CUSTOM DESIGNS ..................... 10
6 WIRING DIAGRAM .................... 10
7 SPECIFICATIONS ....................... 11
3
Please read through this operating manual very carefully before
installing and commissioning the unit.
Incorrect utilisation will invalidate the guarantee!
Correct functioning and the operating safety of the unit can only be
guaranteed if the ambient conditions specified in the Specifications
chapter are maintained.
Only qualified specialists are permitted to commission and operate
the unit. The owner of the unit must ensure that the installation
complies with the relevant laws and directives. These include, for
example, the EU Directives covering safety in the workplace,
national safety in the workplace regulations and the prevention of
accidents regulations, etc.
You must ensure that the power supplies concur with the details
listed on the nameplate. All of the covers needed to ensure that the
unit cannot be touched when operating must always be fitted. You
must consider the effects of the overall operation and take the
necessary precautions if the unit will be linked up with other
equipment and/or devices before you switch on.
Parts and surfaces will occasionally become and remain hot during
the installation or de-installation. Suitable precautions must be taken
in order to prevent injuries or damage to the unit from occurring.
If the unit shows signs of having been damaged and you are of the
opinion that that safe operation is no longer possible then you must
not run the unit. We recommend that periodical inspections are
carried out at our factory or by our customer service department at
least once a year.
Future disposal must always comply with the legal regulations.
1 Safety instructions
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The oxygen sensor and its accessories are subjected to
thorough quality control in accordance with DIN ISO
9001 in the course of their manufacture and testing.
They must only be installed and used in compliance with
all applicable local and special regulations, particularly
the VDE and DVGW standards that apply in Germany.
The measurement accuracy and effective function of the
measurement device will need to be checked at intervals
whose frequency will depend on the application
concerned. Such a check must be effected in the course of
a calibration and examination check on the equipment
being first put into operation.
2 Preface
With the aid of an oxygen sensor , the measurement unit serves to measure the
oxygen partial pressure in gaseous atmospheres. Such sensors work at high
temperatures and so it is necessary for measures to be taken to ensure that no
flammable gas mixtures contact the sensor or the unit. In the event of the sensor
ceramic suffering breakage the measurement gas could escape or air could enter the
measurement gas side of the unit and so suitable measures have to be taken to
avoid such an event leading to environmental pollution or damage being done to
equipment.
In the event of incorrect parameters being set or the occurance of leakage,
corrosion, condensation, etc., damage could be done to the equipment and
incorrect measurement results be indicated and so it is essential that all parts
of equipment be regularly serviced.
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EMF
R T
F
P
P
4
1
2
ln( )
R
=
8.31J/mol K
T
=
Temperature in Kelvin
F
=
96493 As/mol
P1
=
Oxygen partial pressure on the reference side with
0.20946 bar
P2
=
Oxygen partial pressure on the measurement gas
side
EMF
=
Electromotive force in Volts
3 Introduction
3.1 Measurement principle
Oxygen measurement units are designed to process signals transmitted from an
oxygen sensor constructed of stabilized zirconium oxide. Zirconium oxide, a ceramic
material that is also spoken of as a solid-state electrolyte, acts as an excellent
oxygen-ion conductor when at a high temperature.
Within certain temperature limits, that depend on the doping of the material
concerned, such ion conductors are able to fill empty spaces in their crystal lattice
with oxygen ions. The oxygen ions occur against an electrically conductive surface
that is generally of platinum.
The concentration of oxygen in a measurement gas is thus decisive for the extent of
oxygen activity, and thus for the number of oxygen ions.
An oxygen sensor consists essentially of a solid-state electrolyte with a contact
surface on both sides.
One side of the electrolyte is in contact with a reference gas such as air, and the
other with the gas whose oxygen content is to be measured. The mechanical
construction of the sensor prevents contact between the two gases so that there is
no risk of their being intermixed.
Depending on the application concerned, heated or unheated sensors are used.
Unheated sensors are generally used in furnaces while heated sensors are used for
applications where the gas to be measured is at a temperature of less than around
600 degrees Celsius (the measurement principle necessitates the sensor being
maintained at a temperature of not less than 500 - 650 degrees Celsius).
Heated sensors are maintained at a set temperature by an electronic temperature
regulator that forms part of the electronic control unit. The temperature of both
heated and unheated sensors as measured by the electronic control is an important
parameter for inclusion in the calculation of the oxygen content (oxygen partial
pressure) in accordance with the following equation:
whereby:
6
Figure 1: Sensor A19-N
3.2 Sensor
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The sensor is built into a stainless steel body, which has an aluminium housing with
plug connection serving as the connection head.
In principle the sensor can be mounted in any position. However, we recommend
assemblies with the connection head positioned at the top. The connection head has
a multi-pin plug, to which the connecting cable leading to the converter module is
attached.
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3.3 Converter module
The sensor requires a series U or Z supply unit in order to function.
Please refer to the unit's operating instructions for additional information.
4 Assembly
4.1 Electrical
Figure 2: Sensor head with connecting plug
The electrical assembly is quite simple as the result of pre-assembled cables. The
sensor is connected with the converter module.
The output signal of the converter module is connected with visualization and other
types of modules for further signal processing.
The power supply is located in the converter module.
4.2 Mechanical
The sensor can be screwed into the reaction space. It must be ensured, however,
that the temperature at the screw-in thread does not exceed 150 degrees Celsius. It
is possible that the screw-in thread will have to be cooled.
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Figure 3: Sensor A19-N with screw-in thread M27 x 2 mm
In some situations it is beneficial to guide the sample gas out of the sample gas
chamber. In such cases the sensor is built into a measuring chamber.
Figure 4: Sensor A19-P with a measuring chamber
The measuring chamber is connected with the system by means of a connection
fitting. In some applications the sample gases need to cross through masonry or
isolation materials. In such cases we recommend a sampling pipe made of metal or
ceramics. This kind of pipe ensures that the sample gas is being drawn at the desired
location and additionally that it is not modified by false air etc. on its way to the
sensor.
In cases when there is the possibility of condensate formation, this pipe must ascend
towards the sensor, and the gas outlet pipe must descend away from the sensor.
The other sensor port is connected with the point at which the sensor exhaust gases
come in. The pressure at this point must be lower than the pressure at the gas inlet
so that the gases will flow through the sensor on their way from the gas inlet to the
gas outlet.
There are several options to force gas flow:
1. Making use of the overpressure at the sample gas side.
2. Making use of the differential pressure in the system. In this case the differential
pressure must have developed between gas inlet and gas outlet.
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Sensor A19-N, A19-S, A19-P
Pin 1
Sensor -
Pin 2
Sensor +
Pin 3
Heating
Pin 4
Heating
3. A gas pump pushes or sucks the sample gases through the sensor.
With all methods described, the flow through the sensor must be kept at around 50
litres per hour.
Installing a gas flow meter and a needle valve in the gas pipes may be helpful and
necessary. For example, some applications require gas flow control with a gas flow
meter equipped with limit contacts.
5 Custom designs
The sensor A19-S has been designed for special applications. It comes without the
stainless steel safety guard at the connection head and has no screw-in thread.
Instead it is equipped with 2 opposing threaded holes M4 with which the sensor can
be mounted from within the sample gas chamber.
Figure 5: Sensor A19-S Figure 6: Mounting holes for sensor A19-S
6 Wiring diagram
10
Sensor A19-N
Measuring range
100 % up to 10 exp. -35 bar O2
Ambient temperature
Max. sample gas temperature
-10 to 80 degrees Celsius
200 degrees Celsius
Measuring accuracy
plus/minus 1 mV of the sensor's EMF
Sensor heating-up time
ca. 5 minutes
Measuring speed
ca. 2 seconds
Weight
ca. 1 kg
Connection head dimensions
Diameter ca. 70 mm, Height 75 mm incl. plug
Mounting depth
30mm incl. thread, Diameter 20 mm
Screw-in thread
M27 x 2 mm
Sensor A19-S
Measuring range
100 % up to 10 exp. -35 bar O2
Ambient temperature
Max. sample gas temperature
-10 to 80 degrees Celsius
200 degrees Celsius
Measuring accuracy
plus/minus 1 mV of the sensor's EMF
Sensor heating-up time
ca. 5 minutes
Measuring speed
ca. 2 seconds
Weight
ca. 1 kg
Connection head dimensions
Diameter ca. 70 mm, Height 75 mm incl. plug
Mounting depth
30 mm, Diameter 20 mm
Mounting
M 4, cf. section "Special designs"
7 Specifications
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Sensor A19-P
Measuring range
100 % up to 10 exp. -35 bar O2
Ambient temperature
Max. sample gas temperature
-10 to 80 degrees Celsius
200 degrees Celsius
Measuring accuracy
plus/minus 1 mV of the sensor's EMF
Sensor heating-up time
ca. 5 minutes
Measuring speed
ca. 2 seconds
Weight
ca. 1 kg
Connection head dimensions
Diameter ca. 70 mm, Height 75 mm incl. plug
Mounting depth
30 mm, Diameter 20 mm
Mounting
at the side with 2 screws M5
Measuring gas inlet
G ⅜ inch
Measuring gas outlet
G ¼ inch
Measuring gas flow
50 to 80 l/h
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