ZIROX SGM7.2 User manual

ZIROX Sensoren & Elektronik GmbH Greifswald
Am Koppelberg 21, D-17489 Greifswald ++49 3834 8309 -00, Fax: -29 e-mail: [email protected]
ZIROX®-Oxygen Measuring Systems
SGM7.2
Oxygen measuring device for inert
and reactive gases
Manual

SGM7.2
Manual
Oxygen measuring device
for the determination of oxygen concentrations
in inert and reactive gases
Range: 2 · 105... 10-20 Vol.-ppm Power supply: 100…240 V, 47…63 Hz
HB_SGM72_Rehm_eng.DOC 2

Oxygen Monitor SGM7.2 Contents
Table of contents
1General Information...................................................................................... 5
1.1 Introduction......................................................................................... 5
1.2 Copyright............................................................................................. 5
1.3 Safety symbols and terms................................................................... 6
2Application Field........................................................................................... 7
3Safety Regulations........................................................................................ 8
4Functional Description................................................................................. 9
4.1 Measuring principle............................................................................. 9
4.1.1 General recommendations.................................................... 10
4.1.2 Gas flow quantity .................................................................. 11
4.1.3 Precision of the measuring ................................................... 11
5Technical Data............................................................................................. 12
5.1 Characteristics.................................................................................. 12
5.2 Mechanical data................................................................................ 12
5.3 Electrical engineering/electronics ..................................................... 12
5.3.1 General data......................................................................... 12
5.4 Interface data.................................................................................... 13
6Construction of the Oxygen Monitor SGM7.2 .......................................... 15
6.1 Principle construction........................................................................ 15
6.1.1 General overview.................................................................. 15
6.1.2 Construction principle of the solid electrolyte sensor............ 15
6.1.3 Electronic measured-value processing.................................17
6.2 Using and connection elements........................................................ 18
6.2.1 Power supply ........................................................................ 18
6.3 Front side.......................................................................................... 18
6.3.1 Rear side............................................................................... 19
7Placement and putting into operation ......................................................20
7.1 Installation conditions........................................................................ 20
7.2 Setting up of the operating state....................................................... 20
8Operation and parameter setting .............................................................. 22
8.1 Operation.......................................................................................... 22
8.1.1 Switch on and measurement indication................................ 22
8.1.2 Gas flow adjustment ............................................................. 22
8.1.3 Measuring value monitoring.................................................. 22
8.1.4 Status and error messages................................................... 23
8.2 Parameter Setting............................................................................. 24
8.2.1 Adjustable Parameter ........................................................... 24
8.2.2 Programming menus............................................................. 25
8.3 Calibration......................................................................................... 28
8.3.1 Zero Gas Calibration............................................................. 28
HB_SGM72_Rehm_eng.DOC 3

Oxygen Monitor SGM7.2 Contents
8.3.2 Span Gas Calibration............................................................ 28
8.3.3 Calibration state.................................................................... 29
8.4 Trouble Shooting............................................................................... 29
9Maintenance, overhaul and storage.......................................................... 30
9.1 General Hints.................................................................................... 30
9.2 Replace the equipment fuse............................................................. 30
10 Anhang......................................................................................................... 31
10.1 Fundamentals of the use of potentiometric ZrO2 solid electrolyte
sensors for the optimal guidance of combustion processes ...................... 31
10.2 Mounting Hints for Swagelok®-Fittings........................................... 35
10.3 Charcoal Filter: Description and Using Hints................................. 36
10.3.1 Filter Construction............................................................... 36
10.3.2 Application and Operation of the filter................................. 36
10.3.3 Replacing............................................................................ 36
10.3.4 Technical Data.................................................................... 36
10.4 EU Declaration of Conformity ........................................................ 37
10.5 Warranty Conditions ...................................................................... 38
11 Remarks and Own Notes............................................................................ 39
HB_SGM72_Rehm_eng.DOC 4

Oxygen Monitor SGM7.2 1 General Information
1 General Information
1.1 Introduction
This operation manual describes the design, function and
operation of the oxygen monitor SGM7.2 of the ZIROX GmbH.
Address of manufacturer:
ZIROX Sensoren & Elektronik GmbH
Am Koppelberg 21
D-17489 Greifswald
Phone: ++49 38 34 8309 -00
Fax: ++49 38 34 8309 -29
e-mail: [email protected]
www.zirox.de
The manufacturer assures that this operation manual has
been written in accordance with the functional and technical
features of the delivered SGM7.2.
This operation manual is not subject to the amendment service.
If the manufacturer modifies the SGM7.2 with the aim of making
technical improvements the user is responsible to insert the
additional or updated pages supplied.
Secure and proper function of the SGM7.2 can only be
guaranteed when the contents of this manual are known.
Therefore, all chapters of this manual must be read carefully
before installation and operation of the SGM7.2.
The values shown on the device display in this manual are
samples or presettings of the manufacturer. The process
specific values must be set by the user.
1.2 Copyright
This operation manual is copyright protected.
It may not be partially or totally reproduced, copied, or
distributed, without prior written admission from the
manufacturer, neither are unauthorized use for the purposes of
competition or the handing over of the manual to third parties
permitted.
All rights reserved.
HB_SGM72_Rehm_eng.DOC 5

Oxygen Monitor SGM7.2 1 General Information
1.3 Safety symbols and terms
Symbol for direct imminent hazards
This symbol is shown with recommendations for industrial
safety if a direct danger to the life and health of persons
exists.
If these recommendations are not thoroughly observed, fatal injuries
may result.
Symbol for indirect imminent hazards
This symbol informs about situations where indirect hazards occur.
Degree and intensity of the damage depend on the triggering
actions and the behavior of the persons involved.
Disregard of these hints may result in damage to or destruction
of the entire SGM7.2 or single components, other property, as
well as minor injuries.
Symbol for proper usage
This symbol can be found where the observance of instructions,
regulations, and proper order of actions/events is important.
Not observing these hints may result in damage or
destruction of the SGM7.2 or its single components.
HB_SGM72_Rehm_eng.DOC 6

Oxygen Monitor SGM7.2 2 Application Field
2 Application Field
The protective gas monitor SGM7.2 serves for the continuous
measuring of the oxygen concentration in industrial, laboratory
and protective gases as well as during mixing, production and
processing of special forming gases in industry. The measuring
of the free oxygen concentration in inert gases and also the
measuring of bound oxygen in gas mixtures is possible.
The SGM7.2 is a modification of the SGM7 for using in soldering
applications.
As
agreed
use
The main application area of the SGM7.2 is the monitoring of technical protecting
gases.
The introduction of explosive gas mixtures, high concentrations of
halogens or sulphuric gases (e.g. SO2) into the SGM7.2 is not
permitted.
The contact of the SGM7.2 with silicon- or phosphorus containing
components is also not permitted.
The SGM7.2 Functions
• measures and indicates the oxygen concentration in a measured
gas continuously
• indicates deviations of the oxygen concentration in the measured
gas from a rated value
• monitors the course of a particular production process under buffer
gas
• checks the purity of buffer gases and determines whether the
requested protective effect of the buffer gas is reached.
The requirements and limit values given in the "Technical Data" must be strictly
observed.
Any other use is treated as non-authorized use.
HB_SGM72_Rehm_eng.DOC 7

Oxygen Monitor SGM7.2 3 Safety Regulations
3 Safety Regulations
The following regulations for industrial safety give basic
information about possible hazards during handling and
operation of the buffer gas monitor SGM7.2. Therefore, they
must be observed and strictly followed by the operation and
service staff.
• Secure and proper function of the SGM7.2 can only be
guaranteed when the contents of this manual are known.
Therefore, all chapters of this manual must be read
carefully before installation and operation of the SGM7.2.
• The SGM7.2 may only be used for applications stated as
authorized (see chapter 2).
• The SGM7.2 may only be installed, operated, and
maintained by trained staff.
• In any case, the SGM7.2 must be connected to the main
supply with a socket with earth connection by the supplied
cable.
Explosive gas mixtures, halogens in high concentration, and
gases containing sulfur (e.g. SO2) are not permitted to be
measured by this SGM7.2.
Due to the high operation temperature of the sensor, the SGM7.2
produces much heat.
It has to take care that the piece of equipment is not covered so
strongly that it will be come to overheatings.
Vertical installation is not permitted to avoid possible damages
to the device by localization of heat.
Switch off and disconnect the device from the power supply
before opening the housing cover of the SGM7.2.
Special safety recommendations for possible hazards during
special work or sequences of work are given in the relevant
text.
HB_SGM72_Rehm_eng.DOC 8

Oxygen Monitor SGM7.2 4 Functional Description
4 Functional Description
4.1 Measuring principle
In industry and laboratories the measurement of the oxygen
concentration in gases is often required. Mostly, it is measured in
gases which have a remarkable temperature independent oxygen
concentration.
The NERNST-equation is used as a basis for determining the
oxygen concentration in gases with the oxygen monitor SGM7.2. NERNST-
Equation
U
RT
F
p
pOair
O meas gas
=4
2
2
ln ,
,.
(I)
U– cell voltage in V
R– molar gas constant, R = 8,314 J/(mol · K)
T– measuring temperature in K
F– Faraday-constant, F = 9,648 · 104C/mol
pO2,air – partial pressure of the oxygen at the reference electrode
in dry air in Pa
pO2,meas.gas – partial pressure of the oxygen at the measuring electrode
in the measured gas in Pa.
The sensor of the SGM7.2 is based on the conductivity of
oxide ions in a special ceramic substance (zirconium
dioxide) with stabilising additives. The conductivity of these
oxide ions increases exponentially with the temperature and
it is sufficiently high for temperatures above 600°C.
The gas to be measured passes through the ceramic oxide
ion conductor which is a gas-tight pipe. The ceramic pipe is
situated axially symmetric in a thermally well-insulated
heater. The electrodes of the galvanic sensor are made from
platinum. The electrode on the outside of the pipe,
surrounded by dry air, is used as a reference electrode with
a constant, known electrode potential.
HB_SGM72_Rehm_eng.DOC 9

Oxygen Monitor SGM7.2 4 Functional Description
Based on the assumption that the total pressures of the
gases are almost the same at both electrodes (in this case
the volume concentrations may be used in the calculation
instead of the partial pressures) and replacing the
parameters by numbers in equation (I) the following equation
is valid:
Equation
for Oxygen
Concentrati
on
ϕ
O2=20,64 · e(-46,42 · U
T)(II)
ϕ
O2 – oxygen concentration in the measured gas in vol.-%
U– potential difference in mV
T– measuring temperature in K
20,64 – oxygen concentration in air with a relative
humidity of 50% in vol.-%.
4.1.1 General recommendations
The oxygen may be in free or bound form inside the measuring gas1.
Thereby, the following dependencies are valid:
– for free oxygen
UT~
UT
~1– for bound oxygen
The equation (II) for calculating the oxygen concentration is
valid for measured gases with free oxygen as well as for
reducing gas mixtures in which oxygen only exists in bound
form (e.g. in H2/H2O- or CO/CO2-mixtures).
In reducing gas mixtures, the oxygen partial pressure is
inversely proportional to the temperature. For converting the
measured value at the measuring temperature into other
temperatures special thermodynamic equations are required.
1It has to be distinguished between different conditions of the oxygen in the measuring gas:
Free oxygen: There are the oxygen molecules in the gas independently without every relationship
relation to the other gas components (inert gases such as N2or Ar)
Bound oxygen: There aren't any free oxygen molecules, but only in bound form e.g. as steam in
the gas. At higher temperatures a dissociation is carried out and oxygen molecules then are
availably. Since the dissociation degree increases with the temperature, the measurement result is
also dependent on the temperature.
Circumstances permitting free oxygen can react with perhaps available burning gasses at the hot
platinum electrode, a reducing gas then can be also in the result through what.
HB_SGM72_Rehm_eng.DOC 10