ZIROX SGM7.2.4 User manual

ZIROX Sensoren & Elektronik GmbH
Am Koppelberg 21, 17489 Greifswald, Germany [phone], Fax: -29 E-mail: [email protected]
ZIROX - Oxygen Measuring Systems
SGM7.2.4
SGM7.2.6
Oxygen Measuring Device
For
Reflow Soldering Systems

2

3
SGM7.2.4
SGM7.2.6
Manual
Oxygen Measuring Device
For
Reflow Soldering Systems
Range: 2 · 105... 10 vol-ppm Power supply: 100…240 V, 47…63 Hz
Operating hour counter
Indication of maintenance interval for filter change
(depends on pump mode)

Oxygen Monitor SGM7.2.4/7.2.6 Content
4
Table of contents
1 General information .................................................................................... 6
1.1 Introduction........................................................................................ 6
1.2 Copyright........................................................................................... 6
1.3 Commonly used symbols................................................................... 7
2 Application field .......................................................................................... 8
3 Safety regulations ....................................................................................... 9
4 Functional description .............................................................................. 10
4.1 Measuring principle ......................................................................... 10
4.2 General recommendation ................................................................ 11
4.2.1 Gas flow rate........................................................................ 11
4.2.2 Accuracy of the measurement.............................................. 12
4.2.3 Special features (operating hours counter and maintenance
interval) ........................................................................................... 12
5 Technical data ........................................................................................... 13
5.1 Characteristics................................................................................. 13
5.2 Mechanical data .............................................................................. 13
5.3 Electrical engineering/electronics .................................................... 13
5.3.1 General data ........................................................................ 13
5.4 Interface data .................................................................................. 14
5.4.1 Pump control........................................................................ 15
6 Composition of the oxygen monitor SGM7.2.4 ....................................... 16
6.1 General composition........................................................................ 16
6.1.1 General overview ................................................................. 16
6.1.2 Construction principle of the solid electrolyte sensor ............ 17
6.1.3 Electronic data processing ................................................... 18
6.2 Usage and connection elements...................................................... 19
6.2.1 Current supply...................................................................... 19
6.2.2 Front .................................................................................... 19
6.2.3 Rear ..................................................................................... 20
7 Installation and initiation .......................................................................... 21
7.1 Installation conditions ...................................................................... 21
7.2 Set-up of operating state ................................................................. 21
8 Operation and parametrization................................................................. 23
8.1 Operation......................................................................................... 23
8.1.1 Switch-on and measurement indication................................ 23
8.1.2 Gas flow adjustment............................................................. 23
8.1.3 Data monitoring.................................................................... 23
8.1.4 Indication of the end of maintenance interval for carbon filter23
8.1.5 Status and error messages .................................................. 24
8.2 Parametrization ............................................................................... 25

Oxygen Monitor SGM7.2.4/7.2.6 Content
5
8.2.1 Adjustable parameters ......................................................... 25
8.2.2 Programming menus............................................................ 26
8.3 Calibration ....................................................................................... 29
8.3.1 Zero calibration .................................................................... 29
8.3.2 Span gas calibration............................................................. 29
8.3.3 Calibration status ................................................................. 30
8.4 Fault clearance................................................................................ 30
9 Maintenance, overhaul and storage......................................................... 31
9.1 General instructions......................................................................... 31
9.2 Replacement of the equipment fuse ................................................ 31
10 Appendix.................................................................................................... 32
10.1 Activated carbon filter: description and application notes.............. 32
10.1.1 Filter construction............................................................... 32
10.1.2 Application and operation of the filter ................................. 32
10.1.3 Replacement of activated carbon ....................................... 33
10.1.4 Technical data.................................................................... 34
10.2 EU Declaration of conformity ........................................................ 35
10.3 Warranty conditions...................................................................... 36
11 Your own notes and remarks ................................................................... 37

Oxygen Monitor SGM7.2.4/7.2.6 1 General information
6
1 General information
1.1 Introduction
This operation manual describes the composition, mode of operation and
use of the oxygen monitor SGM7.2.4 of ZIROX Sensoren und Elektronik
GmbH.
If not particularly marked, the specifications are valid for the SGM7.2.6 as
well.
Address of manufacturer:
ZIROX Sensoren & Elektronik GmbH
Am Koppelberg 21
17489 Greifswald
Germany
Phone: [phone]
Fax: [phone]
E-mail: [e-mail]
www.zirox.de
The manufacturer guarantees that this manual was written in accordance
with the functional and technical features of the delivered SGM7.2.4.
This manual is not subject to the amendment service. If the manufacturer
modifies the SGM7.2.4 with the aim of making technical improvements, the
user is responsible for inserting the additional or updated pages supplied.
Proper operation of the SGM7.2.4 can only be ensured if the contents of this
manual are known. Therefore, all chapters of this manual must be read
carefully prior to operating the SGM7.2.4.
The values on the device display in this manual are examples or preset
parameters of the manufacturer. The user must set process-specific
parameters.
Pages, charts and figures are numbered consecutively.
1.2 Copyright
This operation manual is copyright protected.
It must not be partially or completely reproduced, copied, or distributed,
without prior written permission of the manufacturer. The use for competitive
advantages or the distribution to third parties are not authorized either.
All rights reserved.

Oxygen Monitor SGM7.2.4/7.2.6 1 General information
7
1.3 Commonly used symbols
Symbol for imminent danger:
This symbol refers to imminent danger to persons’ life and health.
In case of disregard, fatal injuries may result.
Symbol for indirect danger:
This symbol indicates indirect danger.
The degree of the damage depends on the circumstances and the
actions of the persons involved.
In case of disregard, destruction or damage of the SGM, its single
components or other material assets as well as minor injuries may
result.
Symbol for proper handling:
This symbol appears where the manual refers to the adherence to
rules, instructions and proper operation.
In case of disregard, damage or destruction of the SGM or its single
components may result.
NOTE
danger
attention

Oxygen Monitor SGM7.2.4/7.2.6 2 Application field
8
2 Application field
The protective gas monitor SGM7.2.4 serves the continuous measuring of
the oxygen concentration in industrial, laboratory and protective gases as
well as in the process of mixing and producing 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 compounds is possible.
Designate
use
The main application fields of the oxygen monitor are:
• processes for mixing and producing of forming gases
• production processes of welding and soldering, especially gas-
shielded arc welding in steel and container production as well as plant
construction
• production processes of electronic components under buffer gas.
The introduction of explosive gas compounds, high concentrations of
halogens or sulphuric gases (e.g. SO2) into the SGM7.2.4 is not permitted.
The contact of the SGM7.2.4 with siliconic or phosphoric compounds is not
permitted either.
The SGM7.2.4
Functions
• measures and indicates the oxygen concentration in a measuring gas
continuously;
• indicates any deviations of the oxygen concentration in the measuring
gas from an adjustable set 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 provided in "Technical data" must be
strictly observed.
Any other use is treated as non-authorized use.

Oxygen Monitor SGM7.2.4/7.2.6 3 Safety regulations
9
3 Safety regulations
The following regulations for industrial safety provide basic information about
potential danger during the operation of the buffer gas monitor SGM7.2.4.
Therefore, they must be observed and strictly followed by the responsible
staff.
• A failure-free and functional operating of the SGM can only be
guaranteed with knowledge of this manual. Therefore, all chapters of
this manual must be read carefully before the installation and initiation
of the SGM.
• The SGM is to be used for the functional operation only (see chapter
2).
• The SGM is to be installed, operated, and serviced by trained staff only.
• The SGM is to be connected to an isolated ground socket (Schuko-
socket) with the supplied cable.
Explosive gas compounds, halogens in high concentration, and sulphuric
gases (e.g. SO2) are not permitted to be measured by this SGM7.2.4.
Due to the high operation temperature of the sensor, the SGM produces a
lot of heat.
Make sure the device does not overheat because of covering.
A vertical installation may cause heat accumulation and
damage to the device.
Switch off and disconnect the device from the power supply before opening
the housing cover of the SGM.
Special safety instructions for potential danger during certain working
processes are given in relevant text passages.

Oxygen Monitor SGM7.2.4/7.2.6 4 Functional description
10
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
considerable, temperature-independent oxygen concentration.
The NERNST equation is used as a basis for determining the oxygen
concentration in gases with the oxygen monitor SGM7.2.4.
NERNST
equation
U
RT
F
p
p
O air
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 measuring gas in Pa.
The sensor of the SGM7.2.4 is based on the conductivity of oxide ions in a special
ceramic substance (zirconium dioxide) with stabilizing additions. The conductivity
of these oxide ions increases exponentially with the temperature and reaches a
sufficiently high temperature above 600°C.
The gas to be measured passes through the ceramic oxide ion conductor, which
is a gas-tight tube. The ceramic tube is situated axially symmetrically in a thermally
well-insulated heater. The electrodes of the galvanic sensor are made from
platinum. The electrode on the outside of the tube, surrounded by dry air, is used
as a reference electrode with a constant, known electrode potential. (composition
see chapter 6.1.2)

Oxygen Monitor SGM7.2.4/7.2.6 4 Functional description
11
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 applies:
Equation
for oxygen
concentr.
ϕ
O2=20.64 · e (-46,42 · ) (II)
ϕ
O2 – oxygen concentration in the measuring 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%
4.2 General recommendation
The oxygen may be in free or bound form inside the measuring gas1. (see
chapter 10.1)
Thereby, the following dependencies are valid:
– for free oxygen
– for bound oxygen
The equation (II) for calculating the oxygen concentration is valid for
measuring gases with free oxygen as well as for reducing gas compounds in
which oxygen only exists in bound form (e.g. in H2/H2O- or CO/CO2-
compounds).
4.2.1 Gas flow rate
The constant flow rate of the measuring gas is ensured by an internal pump.
It can be chosen between HIGH (35 l/h, maintenance interval runs 3 times
faster than in the LOW mode) and LOW (8 l/h).
1Different conditions of oxygen in the measuring gas must be distinguished:
Free oxygen: Oxygen molecules in the gas are independent without a bond to other gas components
(inert gases such as N2or Ar).
Bound oxygen: Free oxygen molecules do not exist in the gas, only in bound form e.g. as water
vapor. Higher temperatures cause a dissociation and oxygen molecules are available. Since the
dissociation degree increases with the temperature, the measurement result depends on the
temperature.
Possibly, free oxygen can react with potential burnable gases at the hot platinum electrode. The result
can be a reducing gas.
U
T
U T~
U
T
~1

Oxygen Monitor SGM7.2.4/7.2.6 4 Functional description
12
4.2.2 Accuracy of the measurement
The manufacturer guarantees a measuring error of less than 5 % (relative
error) only with measurements of oxygen concentrations within a range of 2
· 105 ... 10 ppm. For measurements of oxygen concentrations of 10 ... 10-3
ppm, the relative error is less than 5 % if the gas inlet tube has no leaks or
permeability.
For measurements of oxygen concentrations less than 10 ppm, the following
aspects must be taken into account during evaluation:
• composition of the measuring gas (e.g. presence of burning gases)
• specific characteristics of the production process (e.g.
material used)
• temperature of the measuring gas.
To reduce the measuring error in low oxygen concentrations, the following
conditions must be provided:
• The measuring gas must be extracted where a formation of layers can
be avoided.
• The tube from the measuring point to the SGM7.2.4 must be as short
as possible in order to avoid a change in the chemical balance in the
tube.
• All gas inlet and outlet tubes must be free of leaks.
• If the measuring gas contains reducing components (e.g. alcohol), the
concentration of free oxygen cannot be determined correctly as
chemical reactions occur at the electrode. In such cases, the
measuring gas should be filtered by an activated carbon filter before
entering the SGM7.2.4 (see chapter 10.1).
4.2.3 Special features (operating hours counter and maintenance interval)
Open the menu 'OPERATING HOURS' by pressing any key.
TOTAL TIME: 1234 h
CHANGE CARBON
FILTER IN: 0 h
MAINT.INTERVAL: 600 h
RESET
USER CODE
RETURN
First, enter the password, then set the time of the preset maintenance interval
to the next filter change (choose line 'RESET' and press 'Enter').
In pump mode HIGH the maintenance interval runs 3 times faster than
in mode LOW!
NOTE

Oxygen Monitor SGM7.2.4/7.2.6 5 Technical data
13
5 Technical data
5.1 Characteristics
Description............................................. Protective gas monitor SGM7.2.4
Application............................................. Measuring of the oxygen concentration
in inert gases
Measuring range.................................... 10 vol-ppm…20.6 vol% O2
Accuracy at normal pressure ................. Relative measuring error < 5 %
Measuring gas flow rate......................... 8 resp. 35 l/h (low, high)
Max. permitted pressure of the gas........ 20 mbar over pressure
Max. permitted temp. of the gas............. 80 °C
∆p over measuring cell........................... Approx. 1 kPa (100 mm WS) at 10 l/h
Working conditions ................................ 10…45 °C, rH < 80 % at 20 °C
Storage conditions................................. -20…60 °C, rH < 95 % at 20 °C
Degree of protection .............................. IP40
5.2 Mechanical data
Dimensions............................................ 135 x 100 x 240 mm
Weight ................................................... 3 kg
Gas input ............................................... Plug connection 6 mm
Gas output............................................. Tube nipple 4 mm
5.3 Electrical engineering/electronics
5.3.1 General data
Current supply
Voltage....................................... 100…240 V AC, 47…63 Hz
Current consumption .................. 35 VA
Heater measuring cell................. 24 V DC, approx. 10 W
(controlled internally)
Keypad and display
Keypad .................................................. 3 keys
Text display ........................................... LCD dot-matrix

Oxygen Monitor SGM7.2.4/7.2.6 5 Technical Data
14
5.4 Interface data
Serial interface RS-232
Transfer rate.................................. max. 19200 Baud, adjustable
Stop bits ........................................ 1
Data bits ........................................ 8
Parity............................................. none
Handshake .................................... without
Pin-configuration connector SUB-D 9-pol. F:
Chart 1: Serial interface protocol (CR = Carriage Return)
Command Response Description
M2CR M2x.xxExxCR Oxygen concentration in ppm
A1CR A1xxxCR Cell voltage in mV
A2CR A2xxxCR Measuring cell temperature in °C
Chart 2: Error indication
Error code Description
0 ERROR0 Transmission error
1 ERROR1 Warm-up
2 ERROR2 Cell temperature too low
3 ERROR3 Thermocouple defective
4 ERROR4 Operation hour meter run out!
Change filter or carbon, then reset! (see manual)
5
6 ERROR6 System error
Analog output
SGM7.2.4: Voltage output, 0/2 - 10V, potential-free, range adjustable
SGM7.2.6: Current output, 0/4 – 20 mA, potential-free, range adjustable
Chart 3: Limit value relay
Charge Resistive charge (cosϕ
ϕϕ
ϕ= 1)
Max. switching voltage 125 V AC, 60 V DC
Max. switching current 1A
Max. switching power 62.5 VA, 30 W
Min. permissible charge 1 mA at 5 V DC
MD
TXD
RXD

Oxygen Monitor SGM7.2.4/7.2.6 5 Technical Data
15
5.4.1 Pump control
A powerful pump is integrated in the SGM7.2.4, which can be controlled via
interface RS232:
Chart 4: pump control via RS232
Command from
PC
Reply of SGM7.2.4 Remark
P0CR P0CR pump off
P1CR P1CR pump low
P2CR P2CR pump high
pCR
pXCR
scan pump state
X=0 pump off
X=1 pump low
X=2 pump high
Control input for pump relay: 24 V DC (internal inverse-polarity protection
and free-wheeling diode)
Chart 5: Pin config. for 7-pol. socket and connection cable with plug
(1.5 m long)
Pin Description Cable color
1 limit relay NC contact blue
2 limit relay NO contact brown
3 limit relay central contact green
4 pump control white
5 pump control grey
6 output + pink
7 output - yellow

Oxygen Monitor SGM7.2.4/7.2.6 6 Composition
16
6 Composition of the oxygen monitor SGM7.2.4
6.1 General composition
6.1.1 General overview
The SGM7.2.4 is a portable device. The general composition is shown in Fig. 1.
Fig. 1: General composition of the SGM7.2.4
The measuring gas gets into the sensor by means of little overpressure at
the inlet or the optional pump ingests the measuring gas. In the first case,
the optional pressure reducer or needle valve at the gas inlet can be used to
control the gas flow. If the pump is installed, the gas flow is controlled by a
flow control of the pump.

Oxygen Monitor SGM7.2.4/7.2.6 6 Composition
17
6.1.2 Construction principle of the solid electrolyte sensor
1 2 567 3 4
Measurig Gas
Fig. 2: Composition of the solid electrolyte sensor
The measuring cell (sensor) consists of a tube made of zirconium
dioxide (2/1) with two platinum electrodes. The measuring electrode
is inside the tube (2/3). The reference electrode (2/4) is located on
the outside of the tube and has a constant electrode potential. The
electrodes and the ceramic tube form a galvanic solid electrolyte
measuring cell.
Measuring cell
(sensor)
In order to gain a higher oxide ion conductivity of the zirconium
dioxide tube, the sensor is heated to 750°C. This also avoids
interfering reactions with combustible components of the measuring
gas at the electrode caused by chemical unbalances. A thermocouple
(2/5) inside the measuring cell determines the actual electrode
temperature. A regulator ensures a constant temperature.
Sensor heater
The heated measuring cell produces thermal energy. Therefore, the
SGM7.2.4 must not be covered.
1 Ceramic tube
2 Ceramic cover of reference
electrode
3 Measuring electrode
4 Reference electrode
5 Thermocouple
6 Connecting wire of
reference electrode
7 Connecting wire of
measuring electrode

Oxygen Monitor SGM7.2.4/7.2.6 6 Composition
18
6.1.3 Electronic data processing
The following block diagram illustrates the data processing.
Fig. 3: Block diagram of the SGM7.2.4
Sensor
Amplifier for
Cell Voltage
Heater
Control Microcontroller
Sensor Surveillance
Pow er
Supply
1.0 A
0.8 A
Amplifier for
Thermocouple
Display
Keyboard
DC-Output
Relay Outputs
RS-232
110
-
230 V/50
-
60 Hz
Analog out

Oxygen Monitor SGM7.2.4/7.2.6 6 Composition
19
6.2 Usage and connection elements
6.2.1 Current supply
The SGM7.2.4 is firmly connected to the current supply by a connecting
cable.
6.2.2 Front
The indicators and control elements are located on the front of the
SGM7.2.4. Depending on the size, the measuring values are displayed
either in vol% or in vol-ppm.
A green or orange light serves as operating indication depending on the
chosen limit value and actual measuring value. A red light points out
certain operating or warning conditions (see chap. 8.1.4).
A keypad is located on the right side of the front panel. It serves the
programming of the device.
Fig. 4: Front of the SGM7.2.4

Oxygen Monitor SGM7.2.4/7.2.6 6 Composition
20
6.2.3 Rear
The gas inlet and outlet, the analog output and limit value relay
(connection for pump control relay included), the RS232-Interface, the
pump switch and the power switch are located on the rear panel.
The gas inlet is connected with the carbon filter. The inlet of the filter is
located on the front side.
The line cord is permanently fixed with the device. It cannot be
connected.
Fig. 5: Rear of the SGM7.2.4