Bühler technologies BA 5000 User manual

Gas Analysis
Installation and Operation Instructions
Original instructions
Gas analyzer for measurement of IR-absorbing gases and oxygen
BA 5000
BE555000
11/2019
Bühler Technologies GmbH, Harkortstr. 29, D-40880 Ratingen
Tel. [phone] / 49 89-0, Fax: [phone] / 49 89-20
E-Mail: [email protected]
Internet: www.buehler-technologies.com

Bühler Technologies GmbH, Harkortstr. 29, D-40880 Ratingen
Tel. [phone] / 49 89-0, Fax: [phone] / 49 89-20
Internet: www.buehler-technologies.com
E-Mail: [email protected]
Read this instruction carefully prior to installation and/or use. Pay at-
tention particularly to all advises and safety instructions to prevent in-
juries. Bühler Technologies can not be held responsible for misusing
the product or unreliable function due to unauthorised modifications.
All rights reserved. Bühler Technologies GmbH 2019
Document information
Document No..........................................................BE555000
Version...........................................................................11/2019
Part No.........................................................................9031067

BA 5000
Contents
1 Introduction..................................................................................................................................................................................................................... 3
1.1 Intended Use......................................................................................................................................................................................................... 3
1.2 Product versions .................................................................................................................................................................................................. 3
1.3 General information ..........................................................................................................................................................................................4
2 Safety instructions......................................................................................................................................................................................................... 5
2.1 Important notices................................................................................................................................................................................................ 5
2.2 General hazard warnings .................................................................................................................................................................................6
2.3 Analyzers in biogas plants................................................................................................................................................................................ 7
2.4 Analyzers in hazardous areas.......................................................................................................................................................................... 7
3 Transport and storage ..................................................................................................................................................................................................8
4 Installation and connection........................................................................................................................................................................................9
4.1 Description............................................................................................................................................................................................................9
4.1.1 Area of application.............................................................................................................................................................................. 9
4.1.2 Design .....................................................................................................................................................................................................11
4.1.3 Function ................................................................................................................................................................................................ 13
4.1.4 Technical specifications....................................................................................................................................................................19
4.1.5 Wiring diagrams................................................................................................................................................................................ 28
4.1.6 Dimensional drawings..................................................................................................................................................................... 38
4.1.7 Communication.................................................................................................................................................................................40
4.2 Installation ......................................................................................................................................................................................................... 44
4.3 Connecting ......................................................................................................................................................................................................... 46
4.3.1 Safety instructions ............................................................................................................................................................................46
4.3.2 Gas connections and internal gas path ......................................................................................................................................48
4.3.3 Electrical connection......................................................................................................................................................................... 50
5 Operation and control ................................................................................................................................................................................................ 52
5.1 Commissioning.................................................................................................................................................................................................. 52
5.1.1 General information..........................................................................................................................................................................52
5.1.2 Saftey instructions .............................................................................................................................................................................52
5.1.3 Preparation for commissioning .................................................................................................................................................... 54
5.1.4 Commissioning ...................................................................................................................................................................................55
5.1.5 System setup with several analyzers in parallel .......................................................................................................................57
5.2 Operation.............................................................................................................................................................................................................59
5.2.1 General information......................................................................................................................................................................... 59
5.2.2 User prompting.................................................................................................................................................................................. 59
5.2.3 Display and control panel ...............................................................................................................................................................60
5.2.4 Operating modes............................................................................................................................................................................... 63
5.3 Functions .............................................................................................................................................................................................................70
5.3.1 Diagnostics .......................................................................................................................................................................................... 70
5.3.2 Calibration............................................................................................................................................................................................81
5.3.3 Parameter ............................................................................................................................................................................................ 93
5.3.4 Configuration .....................................................................................................................................................................................98
5.3.5 Automatically executed functions of the H2S sensors...........................................................................................................113
5.4 Application note ...............................................................................................................................................................................................117
5.4.1 H2S sensor with 'small' measuring range..................................................................................................................................117
6 Maintenance and repair ...........................................................................................................................................................................................119
6.1 Safety instructions...........................................................................................................................................................................................119
6.1.1 General safety instructions ........................................................................................................................................................... 119
6.1.2 Safety information for analyzers used in hazardous areas................................................................................................ 120
6.2 Cleaning the device.........................................................................................................................................................................................120
6.3 Maintenance of the gas path.......................................................................................................................................................................120
6.4 Replacing spare parts......................................................................................................................................................................................121
6.5 Replacing fuses .................................................................................................................................................................................................121
6.6 Replacing the fine safety filter .....................................................................................................................................................................121
6.7 Maintenance work on the bench-top unit............................................................................................................................................... 122
6.7.1 Emptying the condensation trap.................................................................................................................................................122
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6.7.2 Replacing the coarse filter .............................................................................................................................................................122
6.8 Replacement of the UV module .................................................................................................................................................................. 122
6.9 Replacing the electrochemical oxygen sensor........................................................................................................................................ 124
6.10 Replacing the hydrogen sulfide sensor..................................................................................................................................................... 124
6.11 Replacing the paramagnetic oxygen sensor...........................................................................................................................................126
7 Service and repair........................................................................................................................................................................................................127
7.1 Error and system messages.......................................................................................................................................................................... 127
7.1.1 Maintenance requests ....................................................................................................................................................................127
7.1.2 Faults....................................................................................................................................................................................................128
7.2 Spare parts/accessories.................................................................................................................................................................................130
7.2.1 Gas path ...............................................................................................................................................................................................131
7.2.2 Electronics...........................................................................................................................................................................................134
7.2.3 Pump....................................................................................................................................................................................................136
7.2.4 IR analyzer units................................................................................................................................................................................ 137
8 Disposal.........................................................................................................................................................................................................................166
8.1 Taking out of operation and disposal .......................................................................................................................................................166
8.1.1 Repair or changing of location .................................................................................................................................................... 166
8.1.2 Scrapping the analyzer .................................................................................................................................................................. 166
9 Attached documents .................................................................................................................................................................................................168
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1 Introduction
1.1 Intended Use
Proper use within the context of this manual, means that the product may be used only for the applications described in the
catalog or the technical description, and only in combination with the equipment, components and devices of other manufac-
turers recommended or permitted by us. The product described in this manual has been developed manufactured, tested and
documented in compliance with relevant safety standards. When the handling rules described for the configuration, installa-
tion, proper operation and maintenance, as well at the safety guidelines are adhered to, therefore, there is normally no risk to
the health of persons or in respect to damage to property. This device was designed to ensure safe isolation of the primary and
secondary circuits. Low voltages that are connected must therefore also be generated with safe isolation.
WARNING
Dangerous contact voltage
After removing the housing or protection against direct contact or after opening the sys-
tem cabinet, certain parts of this device/system will be exposed that can carry hazardous
voltage. Therefore, only appropriately qualified persons are permitted to perform work
within this device. These persons must be thoroughly familiar with all sources of danger
and service activities in accordance with these operating instructions.
NOTICE
Observe the environmental conditions for the rack unit and bench-top unit
Ensure compliance with the environmental conditions listed in the technical specifica-
tions
• During operation
• In the event of maintenance
NOTICE
Environmental conditions for bench-top unit in accordance with IEC 61010-1-2010
According to IEC 61010-1-2010, the bench-top unit may only be used indoors.
1.2 Product versions
The BA 5000 gas analyzer is suitable for a wide variety of measurements and is therefore available in different versions. The
data on the label, among others, indicates which device version you have.
1. Data matrix code
2. CE conformity symbol
3. Name and address of manufacturer
4. Designation of origin
5. Measuring range(s)
6. Serial number
7. Order No. (MLFB number) of the device
8. Device name
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1.3 General information
This device left the factory in a safe and proper condition and has been tested. In order to maintain this condition and to ensure
safe operation, it should only be used in the manner described by the manufacturer. Furthermore, proper transportation, stor-
age, installation, operation and maintenance of the device are vital for ensuring correct and safe operation.
This manual contains the information required for the intended use of the described product.
It is addressed to technically qualified personnel who are specially trained or who have the relevant knowledge of automation
technology (measuring and control systems).
Knowledge and technically correct implementation of the safety notes and warnings contained in this manual are required for
safe installation and commissioning, as well as for safety during the operation and maintenance of the described product. Only
qualified personnel have the required professional knowledge for correctly interpreting the generally valid safety notes and
warnings in this manual in each specific case and to act accordingly.
This manual is an inherent part of the scope of delivery, despite the fact that it can be ordered separately for logistic reasons.
Due to the variety of technical details, it is not possible to consider every single detail for all versions of the described product
and for every conceivable case in the set-up, operation, maintenance and use in systems. For further information, or in the case
of problems which are not covered in enough detail in this document, please request the required information from your local
or responsible regional office.
NOTICE
In particular, before using the device for new research and development applications, we
recommend that you first contact us to discuss the application in question.
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2 Safety instructions
2.1 Important notices
Operation of the device is only valid if:
– the product is used under the conditions described in the installation- and operation instruction, the intended application
according to the type plate and the intended use. In case of unauthorized modifications done by the user Bühler Technolo-
gies GmbH can not be held responsible for any damage,
– when complying with the specifications and markings on the nameplates.
– the performance limits given in the datasheets and in the installation- and operation instruction are obeyed,
– monitoring devices and safety devices are installed properly,
– service and repair is carried out by Bühler Technologies GmbH,
– only original spare parts are used.
This manual is part of the equipment. The manufacturer keeps the right to modify specifications without advanced notice. Keep
this manual for later use.
Signal words for warnings
DANGER
Signal word for an imminent danger with high risk, resulting in severe injuries or death if not avoided.
WARNING
Signal word for a hazardous situation with medium risk, possibly resulting in severe injuries or death if not
avoided.
CAUTION
Signal word for a hazardous situation with low risk, resulting in damaged to the device or the property or
minor or medium injuries if not avoided.
NOTICE
Signal word for important information to the product.
Warning signs
These instructions use the following warning signs:
Warns of a general hazard Unplug from mains
Voltage warning Wear respiratory equipment
Warns not to inhale toxic gasses Wear a safety mask
Warns of corrosive liquids Wear gloves
General information
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2.2 General hazard warnings
The equipment must be installed by a professional familiar with the safety requirements and risks.
Be sure to observe the safety regulations and generally applicable rules of technology relevant for the installation site. Prevent
malfunctions and avoid personal injuries and property damage.
The operator of the system must ensure:
– Safety notices and operating instructions are available and observed,
– The respective national accident prevention regulations are observed,
– The permissible data and operational conditions are maintained,
– Safety guards are used and mandatory maintenance is performed,
– Legal regulations are observed during disposal,
– compliance with national installation regulations.
DANGER Toxic, corrosive gases
The measuring gas led through the equipment can be hazardous when breathing or
touching it.
a) Check tightness of the measuring system before putting it into operation.
b) Take care that harmful gases are exhausted to a save place.
c) Before maintenance turn off the gas supply and make sure that it cannot be turned
on unintentionally.
d) Protect yourself during maintenance against toxic / corrosive gases. Use suitable pro-
tective equipment.
DANGER Electrical voltage
Electrocution hazard.
a) Disconnect the device from power supply.
b) Make sure that the equipment cannot be reconnected to mains unintentionally.
c) The device must be opened by trained staff only.
d) Regard correct mains voltage.
DANGER Danger to life from oxygen deficiency
Oxygen is vital to humans. The breathable air should contain over 17 Vol.% oxygen. Signi-
ficantly lower concentrations will sooner or later result in death from suffocation.
System users and operators must ensure personal protection measures are taken in ac-
cordance with legal requirements if the oxygen concentration is too low.
CAUTION Damage to the unit
The sensor on the oxygen measurement system contains zirconium dioxide and plat-
inum and contaminants/catalyst poisons will destroy it (see chapter contaminants).
These therefore must not be present in the gas mixture being measured!
WARNING Improper use
A device in the standard version must never be used in hazardous areas. Explosive gas
mixtures (e.g. flammable gases together with air or oxygen in a potentially explosive ra-
tio) must not be measured with this analyzer.
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2.3 Analyzers in biogas plants
DANGER Danger of poisoning
This device is designed to measure hydrogen sulfide and dihydrogen sulfide, H2S)!
Hydrogen sulfide is highly toxic even in small concentrations! The odor threshold for hy-
drogen sulfide is very low at 0.02 vpm (20 vpb), but higher concentrations result in
numbing of the olfactory receptors in the nose so that the odor is no longer perceived.
Persons exposed to this gas in concentrations up to 100 vpm for several hours exhibit
symptoms of poisoning such as fatigue, headaches, lack of appetite, lack of concentra-
tion, irritation of the mucous membranes of eyes and respiratory tract, and throat irrita-
tions.
Inhalation of H2S concentrations of 500 vpm longer than 30 minutes can cause fatal
poisoning. Concentrations above 1 000 vpm cause death within a few minutes, concen-
trations above 5 000 vpm cause death within a few seconds!
When using this device in plant where there may be high concentrations of H2S and you
therefore need to take following continual precautions to prevent the effects of poison-
ing:
• Connect the gas outlet of the analyzer to a gas exhaust unit so that no gas can escape
into the environment!
• Before you begin maintenance on the analyzer, make sure that the H2S concentration
in the analyzer is close to 0 vpm. Before beginning work, always flush the gas path of the
analyzer and the gas sampler with ambient air or nitrogen for a duration of about 10
minutes .
• Check for leaks in the analyzer at regular intervals!
DANGER Danger of explosion
This device is used in biogas plants, among other places. When it is used in biogas plants,
you should expect that the sample gas will contain methane, which forms explosive mix-
tures with oxygen or air in certain concentrations. These conditions are possible with
certain operating states of the plant.
2.4 Analyzers in hazardous areas
WARNING Unsuitable device for the hazardous area
Danger of explosion
Only use equipment that is approved for use in the intended hazardous area and la-
belled accordingly.
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3 Transport and storage
Transport
The unit is sensitive to shock and vibration. Therefore, where possible, transport in the original packaging or large, sturdy pack-
aging at a minimum consisting of 3 layer carton, plastic or aluminium sheet. Line the inside of the packaging with padding at
least 10 cm thick on all sides.
The unit should be marked fragile for shipping.
Storage
During extended periods of non-use, protect the analyzer against moisture and heat.
Store the unit in a dry, ventilated, dust-free room. Cover the unit with suitable packaging to protect it from liquids and dirt
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4 Installation and connection
4.1 Description
4.1.1 Area of application
Overview
Up to 4 gas components can be measured continuously and simultaneously with the BA 5000 gas analyzer. The device can be
equipped with the following sensors:
– IR detector for IR-active gases
– UV photometer for UV-active gases
– H2S sensor (electrochemical)
– O2 sensor (electrochemical)
– O2 sensor (paramagnetic)
Fig.1: Figure 1: Front view of BA 5000 for measurement of CO, NO, and O2 (example of rack unit)
Areas of application
– Optimization of small firing systems
– Monitoring of exhaust gas concentration from firing systems with all types of fuel (oil, gas and coal) as well as operational
measurements with thermal incineration plants
– Room air monitoring
– Monitoring of air in fruit stores, greenhouses, fermenting cellars and warehouses Monitoring of process control functions
– Monitoring of ship emissions
– Atmosphere monitoring during heat treatment of steel
Areas of application with hydrogen sulfide sensor:
– Biogas plants
– Monitoring of fermenters for generating biogas (input and pure sides)
– Monitoring of gas-driven motors (power generation)
– Monitoring of feeding of biogas into the commercial gas network
– Sewage plants
– Drinking water treatment
Areas of application with paramagnetic oxygen sensor
– Flue gas analysis
– Inerting plants
– Room air monitoring
– Medical engineering
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Further applications:
– Environmental protection
– Chemical plants
– Cement industry
Special versions
– The BA5000 with 2 IR components without pump is also available with two separate gas paths. This allows the measurement
of two measuring points as used e.g. for the NOx measurement before and after the NOx converter.
– Only IR components are available for 19" rack units with piped gas paths.
– H2S sensors and O2 sensors are available for bench-top units.
– The BA5000 gas analyzer can be used in emission measuring systems and for process and safety monitoring.
– For measurement of CO, NO, SO2 and O2 according to 13th BlmSchV and TA Luft, TÜV- approved versions of the BA 5000 are
available.
– The analyzers of the BA2355, BA2357 and BA2358 series are suitability-tested in accordance with EN15267 (emission measure-
ments).
– Version with faster response time: There is no connection between the two condensation traps, so that the complete sample
gas flow passes through the detector (only 1/3 of the flow in the normal version of the analyzers), i.e. the response time is 2/3
faster. The functions of all other components remain unchanged.
– Version with IR detector with chopper compartment purging: This version consumes approx. 100 ml/min of purging gas; you
must set an inlet pressure of 300kPa (3bar).
– Version with specially cleaned gas path: This version is intended for applications requiring 'Cleaned for O2 service'.
– Version with UV photometer for small SO2 measuring ranges and NO2 measurements.
Benefits
– AUTOCAL can be carried out with ambient air (dependent on the measured component) and is therefore highly cost effective
because calibration gases and accessories are not required
– High selectivity thanks to multi-layer IR detectors, low cross-sensitivity to water vapor
– Sample chambers can be cleaned (dependent on the version), resulting in cost savings through reuse following contamina-
tion
– Menu-assisted operation in plain text, thus high operational safety
– Service information and logbook, cost savings through preventive maintenance and help for service and maintenance per-
sonnel
– Increased safety through coded operator levels, thus protection against unauthorized access or clumsy working
– Open interface architecture (ELAN (RS485), PROFIBUS-DP/PA), thus simplified process integration
– Communication software. SIMATIC PDM and SIPROM GA.
– Remote operation and control (via SIPROM GA and PROFIBUS
Special benefits when used in biogas plants
– Continuous measurement of all 4 important components, including H2S
– Long service life of the H2S sensor even at increased concentrations; no diluting or backflushing necessary
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4.1.2 Design
1
2345
7
6
Fig.2: Design of the BA 5000 as 19” rack unit
1. Available as bench-top or rack unit.
2. 80-digit display panel (4 lines with 20 characters each).
3. Dust-tight and washable membrane keyboard.
4. Flowmeter for monitoring the sample gas flow.
5. Gas and electrical connections at the rear.
6. O2 sensor (option) can be removed from the front after taking off the cover.
7. Control and function keys for operation.
The BA 5000 is also available as a bench-top unit. This version differs from the rack unit shown here as follows:
– Closed housing without mounting frame.
– 2 handles on the sides.
– 4 rubber feet for setting up.
– The bench-top unit is not available with Ex approval.
Enclosure
– Bench-top unit or
– 19" rack unit with 4 HU for installation in
– Hinged frame
– Cabinets
– Flow indicator for sample gas on front plate (not with piped gas paths).
– Integrated sample gas pump with bench-top unit, available as option for rack unit (not with piped gas paths).
– Gas connections for sample gas inlet and outlet as well as zero gas possible with pipe diameter 6 mm or ¼".
– Gas and electrical connections at the rear.
Display and operator panel
– Operation based on NAMUR recommendation.
– Simple, fast parameterization and commissioning of analyzer.
– Large backlit LCD for measured values.
– Menu-prompted input functions for parameterization, configuration, test functions, calibration.
– Washable membrane keyboard. User help in plain text.
– User software available in 6 languages.
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Fig.3: Operator panel of the BA 5000
1. One line per component for measured value, dimension and ID.
2. LED-backlit display; contrast adjustable using menu.
3. Freely-selectable dimension (ppm, vpm, mg/m3, %).
4. Two columns are reserved for status displays.
5. ENTER key for calling the main menu or saving the input values.
6. ↑↓→ keys for menu control and for incrementing/decrementing numerical values.
7. Scrolling back in menu or cancellation of an input.
8. Switching on and off of internal pump, pumping capacity adjustable using menu.
9. Key for starting AUTOCAL.
10. Immediate return to measuring mode
NOTICE Energy saving
The display brightness is reduced after approx. 30 minutes without an operation. This
serves for energy saving and has no influence on the other properties of the device.
The display becomes bright again when you continue with operation.
Inputs and outputs
– Three binary inputs for switching the sample gas pump on and off, triggering of AUTOCAL, and synchronization of several
devices.
– Eight freely-configurable relay outputs for faults, maintenance requests, maintenance switches, limits, measuring range
identifications, and external solenoid valves.
– Analog outputs for each component electrically isolated from analyzer ground.
– Optional: 8 additional relay outputs.
– Optional: 8 additional binary inputs.
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Communication
ELAN (RS485) present in basic unit.
Options:
– RS485/USB converter
– RS485/RS232 converter
– RS485/Ethernet converter
– Incorporation in networks via PROFIBUS DP/PA interface (via option board)
– SIPROM GA software as servicing and maintenance tool
4.1.3 Function
Several independent measuring principles which work selectively may be present in the BA 5000. These are described below.
Infrared measurement
Sample gas
outlet
Sample gas
inlet
Fig.4: Operating principle of infrared measurement
1. Capillary
2. Second detector layer
3. Microflow sensor
4. Analyzer chamber
5. Chopper wheel
6. Synchronous motor
7. IR source
8. Reflector
9. Window
10. Slide
11. First detector layer
12. Third detector layer
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This measuring principle is based on the molecule-specific absorption of bands of infrared radiation, which in turn is based on
the single-beam procedure.
A radiation source (7) operating at 600 °C (1111 °F) emits infrared radiation, which is then modulated by a chopper (5) at 8 1/3 Hz.
The infrared radiation passes through the analyzer chamber (4), into which sample gas is flowing, and its intensity is weakened
as a function of the concentration of the measured component.
The receiver chamber (detector) - set up as a two- or three-layer detector - is filled with the component to be measured. The first
detector layer (11) primarily absorbs energy from the central sections of the sample gas IR bands. Energy from the peripheral sec-
tions of the bands is absorbed by the second (2) and third (12) detector layers. The microflow sensor generates a pneumatic con-
nection between the upper layer and the lower layers. Negative feedback from the upper and lower layers leads to an overall
narrowing of the spectral sensitivity band. The volume of the third layer and, therefore, the absorption of the bands, can be var-
ied using a slide (10), thereby increasing the selectivity of each individual measurement.
The rotating chopper (5) generates a pulsating flow in the receiver chamber that the microflow sensor (3) converts into an elec-
trical signal. The microflow sensor consists of two nickel-plated grids heated to approximately 120 °C (248 °F), which, along with
two supplementary resistors, form a Wheatstone bridge. The pulsating flow together with the dense arrangement of the nickel
grids causes a change in resistance. This leads to an offset in the bridge which is proportional to the concentration of sample
gas.
NOTICE
Contamination of the analyzer chambers
The sample gases must be fed into the analyzers free of dust. Condensation should also
be prevented in the analyzer chambers Therefore, the use of gas modified for the meas-
uring task is necessary in most application cases.
Furthermore, the ambient air of the sensor must not have large concentrations of the
components to be measured.
Ultraviolet measurement
1. SO2 LED
2. NO2 LED
3. Beam splitter
4. Measuring channel photodiode
5. Reference channel photodiode
6. Sample chamber
This measuring principle is also based on the molecule-specific absorption of bands of ultraviolet radiation using a double-
beam photometer.
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The light source is a solid-state diode (LED) based on AlGaN or InGaN semiconductors (1). To improve the signal evaluation, the
light source is operated as a pulsed light source.
The ultraviolet radiation is collimated and first passes through a beam splitter (2), which generates two identically sized ray
bundles (measuring and reference radiation). The measuring ray bundle passes through the sample chamber (3), into which
sample gas is flowing, and is attenuated as a function of the concentration of the measured component. This attenuation is
evaluated according to the Lambert-Beer absorption law.
The measuring radiation is recorded by a photodiode (4) downstream of the sample chamber into which sample gas is flowing
(measuring signal). Likewise, the reference radiation is recorded by a second photodiode (5, reference signal). The ratio of meas-
uring signal and reference signal is used to calculate the concentration of the gas component.
The beam splitter also enables the coupling of a second light source for measuring a second gas component. In this way, the ab-
sorption of sulfur dioxide (SO2) and nitrogen dioxide (NO2) is measured in alternating cycles and converted into continuous con-
centration values in sensor-level electronics. Additional sample gas applications are possible through a suitable selection of
LEDs.
For stabilization of the measurement procedure, the measurement of the two gas concentrations using the reference signal is
supplemented by a thermostatic control of the overall optical setup.
NOTICE
Falsification of measuring results
The signal strength of the measuring channel and reference channel must be recorded
with zero gas (ambient air) before the measurements. This zero gas measurement can be
repeated in the specified cycle to compensate for measurement drift (AUTOCAL func-
tion).
To ensure compliance with the technical specifications, a cycle time of ≤ 24 hours must
be activated for the AUTOCAL. The technical specifications are based on a sample gas
pressure of 1013 hPa absolute, sample gas flow of 1.2 l/min and an ambient temperature
of 25 °C (77 °F).
The sample gases must be fed to the analyzer module in dust-free and aerosol-free con-
dition because any particles present in the sample gas will scatter the UV radiation, res-
ulting in increased concentration values. Therefore, the use of gas modified for the
measuring task is necessary in most application cases.
Due to the open design of the photometer, the ambient air of the analyzer should be
largely free of the gas component to be measured.
Also to be avoided are pressure differences between the ambient air and the sample gas
in the analyzer chamber, for example, due to direct discharge of the sample gas to the
atmosphere.
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Electrochemical oxygen measurement
Sample gas
Fig.5: Operating principle of the electrochemical O2 sensor
1. Gold cathode
2. Electrolyte (acetic acid)
3. Thermistor and load resistor for temperature compensation
4. Signal output
5. Lead anode
6. Oxygen diffusion membrane made of FEP
This oxygen sensor operates according to the principle of a fuel cell. The oxygen is converted at the boundary layer between the
cathode and electrolyte. An electron emission current flows between the lead anode and cathode and via a resistor, where a
measured voltage is present. This measured voltage is proportional to the concentration of oxygen in the sample gas.
The acidic electrolyte used is less influenced by interference influences (particularly CO2, CO, H2, and CH4) than other sensor
types.
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Paramagnetic oxygen measurement
Gas inlet
Gas outlet
Fig.6: Operating principle of the paramagnetic O2 sensor
In contrast to other gases, oxygen is highly paramagnetic. This property is used as the basis for this method of measurement.
Two permanent magnets generate an inhomogeneous magnetic field in the measuring cell. If oxygen molecules flow into the
measuring cell (1), they are drawn into the magnetic field. This results in the two diamagnetic hollow spheres (2) being displaced
out of the magnetic field. This rotary motion is recorded optically, and serves as the input variable for control of a compensation
flow. This generates a torque opposite to the rotary motion around the two hollow spheres by means of a wire loop (3). The com-
pensation current is proportional to the concentration of oxygen.
The calibration point is calibrated using the AUTOCAL function by connecting oxygen (analogous to calibration of the electro-
chemical O2 sensor). In order to comply with the technical data, the zero point of the paramagnetic measuring cell must be calib-
rated with nitrogen weekly in the case of all measuring ranges <5% or every two months in the case of all larger measuring
ranges.
Electrochemical hydrogen sulfide measurement
Fig.7: Operating principle of H2S sensor
1. Gas membrane
2. Working electrode
3. Reference electrode
4. Counter electrode
5. Terminal posts
6. Electrolyte (H2SO4)
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BA 5000
The hydrogen sulfide (H2S) enters the sensor through the diffusion barrier (gas membrane (1)) and is oxidized on the working
electrode (2). The reduction of oxygen in air takes place on the counter electrode (4) as a counter reaction. The transfer of elec-
trons can be tapped at the terminal posts (5) as a current that is directly proportional to the gas concentration.
The zero point is automatically recalibrated by the AUTOCAL function when connecting e.g. nitrogen or air.
Automatic calibration of the IR and UV components with air (AUTOCAL)
Clean
Polluted
Concentration
Fig.8: Calibration
The BA 5000 can be calibrated using, for example, ambient air. During this process (can be set between 1 and 24 hours, 0 = no
AUTOCAL), the analyzer chamber is purged with air by way of an internal or external 3-way valve. The detector then generates
the largest signal U0 (no pre-absorption in the analyzer chamber). This signal is used as the reference signal for zero point calib-
ration. The signal U0 also serves as the initial value for calculating the full-scale value.
As the concentration of the measured component increases, so too does absorption in the analyzer chamber. As a result of this
preabsorption, the detectable radiation energy in the detector decreases, and thus also the signal voltage. For the single-beam
procedure of the BA 5000, the mathematical relationship between the concentration of the measured component and the
measured voltage can be approximately expressed as the following exponential function:
U = U0 ⋅ e-kc with the following parameters:
– c: Concentration
– k: Device-specific constant
– U0: Basic signal with zero gas (sample gas without measured component)
– U: Detector signal
Changes in the radiation power, contamination of the analyzer chamber, or aging of the detector components have the same ef-
fect on both U0 and U, and result in the following:
U’ = U’0 ⋅ e-kc
Apart from being dependent on concentration c, the measured voltage thus changes continuously as the IR source ages, or with
persistent contamination.
Each AUTOCAL thus tracks the total characteristic according to the currently valid value, thereby also compensating temperat-
ure and pressure influences.
The influences of contamination and aging, as mentioned above, will have a negligible influence on the measurement as long
as U’ remains within a certain tolerance range monitored by the unit. The tolerance range between two or more AUTOCAL pro-
cedures can be individually parameterized on the BA 5000 and a warning output in the event of deviations. A fault message is
output when the value falls below the original factory setting of U0 < 50% U. In most cases, this is due to the analyzer chamber
being contaminated.
18 Bühler Technologies GmbH BE555000 ◦ 11/2019