Operating Instructions Edition 10/2004 LDS 6. In-situ Laser Gas Analyzer. gas g analysisy

Transcription

1 Operating Instructions Edition 10/2004 LDS 6 In-situ Laser Gas Analyzer gas g analysisy

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3 s LDS 6 In-situ Laser Gas Analyzer Operating Instructions A5E Release 10/2004

4 The reproduction, transmission or use of this document or its contents is not permitted without express written authority. Offenders will be liable for damages. All rights created by the granting of patents or registration of a design are reserved. Technical data subject to change without notice. ULTRAMAT, OXYMAT, CALOMAT, SIPAN are SIEMENS registered trademarks. All other product or system names are (registered) trademarks of their respective owners and must be treated accordingly. According to the German law on units in measuring technology, data in inches only apply to devices for export. Weitergabe sowie Vervielfältigung dieser Unterlage, Verwertung und Mitteilung ihres Inhaltes nicht gestattet, soweit nicht ausdrücklich zugestanden. Zuwiderhandlungen verpflichten zu Schadenersatz. Alle Rechte vorbehalten, insbesondere für den Fall der Patenterteilung oder GM-Eintragung. Technische Änderungen vorbehalten. ULTRAMAT, OXYMAT, CALOMAT, SIPAN sind Marken der SIEMENS AG. Die übrigen Bezeichnungen in diesem Handbuch können Marken sein, deren Benutzung durch Dritte für deren Zwecke die Rechte der Inhaber verletzen können. Die Angaben in Zoll (inch) gelten gemäß dem Gesetz über Einheiten im Meßwesen" nur für den Export. Toute communication ou reproduction de ce document, toute exploitation ou communication de son contenu sont interdites, sauf autorisation expresse. Tout manquement à cette règle est illicite et expose son auteur au versement de dommages et intérêts. Tours nos droits sont réservés pour le cas de la délivrance d'un brevet ou celui de l'enregistrement d'un modèle d'utilité. Modifications techniques sont réservées. La divulgación y reproducción de este documento asi como el aprovechamiento de su contenido, no están autorizados, a no ser que se obtenga el consentimiento expreso, para ello. Los infractores quedan obligados a la indemnización por daños y perjucios. Se reservan todos los derechos, en particular para el caso de concesion de Patente o de Modelo de Utilidad. Salvo modificaciones ténicas. La trasmissione a terzi e la riproduzione di questa documentazione, cosiccome lo sfruttamento del suo contenuto non è permesso, se non autorizzato per iscritto. Le infrazioni comporteranno una richiesta di danni. Tutti i diritti sono riservati, in particolare nel caso di brevetti. Modifiche tecniche possibili. ULTRAMAT, OXYMAT, CALOMAT, SIPAN sont des marques déposées de SIEMENS AG. D'autres dénominations utilisées dans ce document peuvent également être des marques déposées dont l'utilisation par des tiers à leurs propres fins peut enfreindre les droits des propriétaires desdites marques. ULTRAMAT, OXYMAT, CALOMAT, SIPAN son marcas registradas de SIEMENS AG. Las otras designaciones que figuran en este documento puenden ser marcas cuya utilización por terceros para sus propios fines puede violar los derechos de los proprietarios de dichas marcas. Conforma a la "Ley sobre las unidades de medida", las dimensiones en pulgadas sólo son válidas para la exportación. ULTRAMAT, OXYMAT, CALOMAT, SIPAN sono marchi registrati di SIEMENS AG. Le denominazioni di altri prodotti menzionati in questa documentazione possono essere marchi il cui uso da parte di terzi può violare i diritti di proprietà. Conformemente alla "Legge sulle unità di misura" i dati in pollici valgono soltanto per l'esportazione. SIEMENS AG Automation and Drives Process Instrumentation D Karlsruhe Siemens Aktiengesellschaft Siemens AG 2004 Subject to changes without prior notice Order no. A5E Printed in Germany AG 1004 De 0,1 84 PU

5 CONTENT User Information Customer Information General Information Notes in Using this Manual Danger Information Approved Use Qualified Personnel Warranty Information Supply and Delivery Standards and Regulations Installation Guidelines Safety Information Installation Requirements General Information Electric Connections Power Supply Connection Connection of the Hybrid Cable Connection of Signal Cables Pin Assignment of LDS The Sensor CD General Mounting of Specific Flanges Installing and Aligning CD Mechanical Installation Dimensional Drawings Operation General Input sequence Summary of Input Functions Analyzer Status Calibration Measuring Range Parameters Configuration Alarms Alarm Response Maintenance Request Alarm Faults Alarm Transmission Alarm Limit Alarm Function Control Alarm Maintenance and Service The Central Unit i

6 5.1.1 Cleaning Instructions Cross Duct Sensor Cleaning the Wedge Windows Alignment of the Sensors Calibration Check Reconfiguration of Temperature Compensation Manual to external External to manual Reconfiguration of Pressure Compensation Manual to external External to manual Reconfiguration of the Path Length Technical Description Introduction Overview The Central Unit The Hybrid Cable The Sensor CD The Ex Sensor CD 3002Ex Protecting the Optical Surface Measurement Principle Mode of Operation Single Line Spectroscopy The Second Harmonic Spans Technical Specification Spare Parts List Spare Parts Ordering Instructions Spare Parts List Return Deliveries Addresses for Spare Parts and Returned Deliveries Returned Deliveries Form ii

7 User Information User Information Customer Information Please read this Instruction Manual before you start to work with the Siemens LDS 6 and its cross duct sensor CD 6. The manual contains important information and data. Its observance will guarantee the correct functioning of the analyzer system;alarm significantly help you to use the equipment leading to reliable results as well as save you from servicing costs. 1.2 General Information The product described in this manual has left the factory in perfect and tested conditions. In order to retain this state and to achieve correct and safe operation of the product, it must only be used as described by the manufacturer. In addition, the correct and safe operation of this product depends on its proper transport, storage and installation as well as careful operation and maintenance. This manual contains the information required for the approved use of LDS 6. It has been prepared for technically qualified personnel who have been specially trained or who possess appropriate knowledge in the field of instrumentation and control, referred to further as automation technology. Knowledge of the safety information and warnings given in this manual and their technically correct implementation are prerequisites for danger-free installation and commissioning and for safety during operation and maintenance of the described product. Only qualified persons have the required specific knowledge to correctly interpret the general safety information and warnings given in this manual and thus apply them to the particular application. This manual is delivered together with the analyzer, even if due to logistic reasons a separate ordering is also possible. For obvious reasons this manual cannot cover all possible details or applications related to the different versions of the product. Should you require further information, or should particular problems which are not deeply handled within this manual arise, help can be requested through your local Siemens office or representative. 1

8 User Information NOTE When considering use of the analyzer for new research and development applications, we recommend that you discuss your application with our specialist department. 1.3 Notes in Using this Manual This manual describes the applications of the equipment and how you can start it up, operate it and service it. Warning and information texts are of particular importance. These are highlighted from the rest of the text and specially identified by appropriate icons providing valuable tips on how to avoid improper handling. 1.4 Danger Information Enclosed you will find all the necessary information regarding safety and warnings to prevent danger to the life and health of users and/or maintenance personnel as well as to avoid damage to property. This information is specially identified by icons accompanying the explanation text. The terms used in this manual and the information on the product itself, have the following meaning: WARNING Warning means that death or severe personal injury and/or substantial damage to property may occur if the appropriate safety precautions are not observed. CAUTION Caution means that slight personal injury or damage to property can occur if the appropriate safety precautions are not observed. NOTE Note relates to important information on the handling of the product or the respective part of the manual to which particular attention should be paid. 2

9 User Information 1.5 Approved Use Approved use in the terminology of this manual means that this product may only be used for the applications described in the Catalogue and in the Technical Description and only in conjunction with other devices and components which have been recommended or approved of by Siemens. The product described in this manual has been developed, manufactured, tested and documented taking into account the appropriate safety standards. No risk therefore exists in the normal case with respect to damage to property or health of persons if the handling guidelines and safety information described for configuring, assembly, approved use and maintenance are observed. This device has been designed in such a way that safe isolation is guaranteed between the primary and secondary circuits. Connected low voltages must also be generated using safe isolation. WARNING After removing the product housing or guard, or after opening the system cabinet, certain parts incorporated in the device/systems may carry dangerous voltages. Therefore it is important that only suitable qualified personnel work on it. These persons must be entirely acquainted with all the sources of danger as well as all the maintenance measures described within this Manual. 1.6 Qualified Personnel Severe personal injury and/or extensive damage to property may occur following unqualified work on the device/system or the failure to observe the warnings described in the manual or on the device/system cabinet. Therefore only suitably qualified personnel may work on it. Persons considered as qualified in regards to the safety information given in this manual and/or on the product itself are those that: are either configuring engineers familiar with the safety concepts of automation technology; or have been trained as operators in the use of automation technology equipment and are acquainted with the contents of this manual which refer to operation; or have been appropriately trained as commissioning and/or maintenance personnel for such automation technology equipment or are authorized to energize, ground and tag circuits and devices/systems in accordance to established safety practices. 3

10 User Information 1.7 Warranty Information We wish to specifically draw your attention to the fact that the design of the product is exclusively and completely described in the sales contract. The contents of this product documentation are not part of a previous or existing agreement, commitment or statutory right and do not change these. All commitments on behalf of Siemens are given in the respective sales contract that also contains the complete and solely applicable warranty conditions. These conditions are neither extended nor limited by the contents of this Instruction Manual. 1.8 Supply and Delivery The respective scope for delivery according to the valid contract is listed on the shipping documents. Upon opening, please observe the corresponding information on the packaging material. Check that the delivery is complete and undamaged. In particular, compare the order numbers on the labels (if present) with the ordering data. Please retain the packaging material if possible so that you can reuse it if it is necessary to return the device. 1.9 Standards and Regulations The harmonized European standards have been applied as far as possible to the specification and production of this device. If no harmonized European standards have been applied, the standards and regulations for the Federal Republic of Germany apply (see also Technical Description on page 57). The standards and regulations for each country must be observed when using the product outside its range of application. 4

11 Installation Guidelines Installation Guidelines Safety Information Electrical Safety WARNING It is essential that you observe the given information and warnings! Certain parts in the gas analyzer LDS 6 carry dangerous voltages. The housing must be closed and grounded before switching on the analyzer. Death, personal injury and/or damage to persons and/or property may result if this is not observed. The cross duct sensor CD 6 meets all regulations specified in the present EU regulations (LVD regulation 73/23/EEC and EMC regulation 89/366/EEC) as well as those of the American and Canadian markets (UL- and CSA regulations). The device has to be used in an industrial environment. Laser Safety All lasers used by LDS 6 are of class 1. The emitted laser light is in most cases invisible (near infrared) and the intensity is low enough so that the unprotected eye is not damaged. However, if you look directly into the beam with focusing optics (like binoculars) there is a risk of eye damage. LDS 6 has warning labels at appropriate positions according to SSI FS 1980:2 chapter 5. Heat Safety Some metal parts and piping placed near the sensors are at elevated temperatures. The reason is high temperature purging - either from steam or from air. These parts are either isolated or equipped with protective metal sheets. Pressure Safety In some applications the process can be over pressurized. Normally this is not a situation where the measurements will be adequate. Still, from a security aspect, the sensor is tested at 6000 hpa. This pressure value should not be exceeded in operational conditions. Explosion Protection - Ex II 1G D T135 C EEx ia IIC T4 The LDS 6, with a central unit and sensor interconnected with optical fibers, is in its nature very explosion safe. Only a limited, low energy part of the electronics is located at the measurement site. The distance between the central unit and the sensors can be several hundred meters. The LDS 6 system is available in an Ex version and is then delivered with an approval for use in hazardous environments in which explosive gases are in use. The ATEX 5

12 Installation Guidelines certificate is a system certificate and is only valid if LDS 6 is installed according to the instructions given in the certificate. Approval The concept of the Ex approval is that the central unit is unchanged from a standard unit and that a special Ex sensor pair (CD 3002Ex) is used in the hazardous zone. In addition to this an explosion protection barrier is added before entry into the hazardous zone. An absolute condition for the approval is that the equipment is set up according to the Siemens Laser Analytics drawing, ADM The protection is as follows: Cross Duct Sensor - {Ex} II 1G D T135 EEx ia IIC T4. Central (Barrier) Unit - {Ex} II (1)G D T135 [EEx ia] IIC T4. Equipment Group: Group II - Surface. Equipment Category: Category 1G D - Zone 0. Flammable material can be present continuously, frequently or for long periods, in gas and dust. Type of protection: EEx ia. The equipment present in the hazardous area is intrinsically safe. Explosion group: IIC. This corresponds to a gas group containing Acetylene and Hydrogen. Temperature class: T4. The maximum surface temperature on the equipment is 135 C and the ignition temperature of the gas or vapor is between 135 C and 200 C. The sensor housing protection is IP 65 and the ambient temperature must be between -30 C and +60 C. Liability Following commissioning, the total responsibility is with the owner. 2.2 Installation Requirements General Information Mounting Conditions The central unit LDS 6, should be placed on a location which is dust-free and as free as possible from vibrations. The distance between the central unit and the measurement point, i.e. the sensor, may not exceed meters. During operation the permissible surrounding air temperature is 5 C to 45 C, with a relative humidity of maximum 85% non-con- 6

13 Installation Guidelines densing, around the central unit. Also ensure that the unit is not exposed to direct solar radiation. If these conditions can t be fulfilled the LDS 6 must be installed in a cabinet with controlled environment. NOTE As condensing is normally a problem when moving the device from outside to inside a building it is recommended that the device should be adapted to room climate for a couple of hours before starting it. The back of the unit must be accessible. There should be at least 10 cm of free space behind the LDS 6 to accommodate the signal and hybrid cables. To meet the safety requirements for air convection and cooling there must be a free space of at least 5 cm above and at least 3 cm below LDS 6. Preparations Before the sensor can be installed at the measurement point, flanges have to be welded into the measuring site. The flanges must be DN65/PN6 or ANSI 4 /150 lbf with an inner diameter of minimum 55 mm and maximum 70 mm. The flanges must protrude at least 150 mm from the wall and 0-30 mm into the furnace or funnel. Flange tubes should never be longer than the purge tube (which has a standard length of 360 mm). If longer flange tubes are needed for any reason special purge tubes (longer) have to be used. The flanges should be aligned before mounting the sensors. (See Alignment of the Sensors on page 48, for closer instructions on this process). Sensors Do not install the sensors without access to purging air or steam (see Protecting the Optical Surface on page 60). Mount and align the two sensor units, transmitter and receiver, using some kind of alignment tool. (The supplied alignment kit is recommended). Make sure to have sufficient space around the sensors, to ensure easy service. Hybrid Cables The hybrid cables should be installed so that they are protected from mechanical wear such as sharp edges or moving parts. Always keep the protective tube and the inside protective cap covering the single mode fiber (E2000 connector) so it is protected from dust. The operating temperature for the cables is -40 to +80 C and the installation temperature is -20 to +80 C. The bending radius of the cables may never be smaller than 100 mm. 7

14 Installation Guidelines NOTE Throughout the entire installation, keep the fiber ends protected by the protective tubes; observe that these should only be removed by authorized personnel. There are three kinds of cables used for the LDS 6 depending on the application: Hybrid cables for all types of systems except oxygen. These are installed between the LDS 6 and the transmitter sensor. Hybrid cables for oxygen systems only, also installed between the LDS 6 and the transmitter sensor. Loop cables, same for all systems, are installed between the transmitter sensor and the receiver sensor. 2.3 Electric Connections WARNING The respective country-specific standards for the installation of power systems with rated voltages below 1000 V must be followed. Failure to observe these regulations may result in death, personal injury and/or damage to property Power Supply Connection General Check that the local voltage agrees with that specified on the label on the analyzer. The cable must be tested according to IEC or IEC and must be suitable for 70 C. The power cable must be routed separately from the hybrid cables. Detachable Cord The analyzer is supplied with an appliance plug which may only be connected to the power supply by qualified personnel (see Qualified Personnel on page 3). The cross-section of the conductors must be at least 1 mm 2. The phase conductor must be connected to the identified position (L). Only detachable power supply cords tested by an accepted third party Lab accredited for the region where the unit is to be used is allowed. This cord must be suitable for the rated current and limited in length. This flexible cord must also be 8

15 Installation Guidelines suitable for an ambient temperature of 70 C and is not allowed to be mounted in building installations. As the kind of appliance inlet is only suitable for 70 C ambient temperature the power cord must be kept away with suitable means from surfaces of more than 70 C at max. rated operation conditions. It is not allowed to install a switch within the power supply cord. Building Installation A circuit-breaker shall be part of the building installation. It must be provided in the immediate vicinity of the analyzer (see rating plate for loading capacity). It must also be labeled to correlate with the instrument Connection of the Hybrid Cable The hybrid cable is connected at the back of the central unit, where its two optical cables and one power wire are attached, as shown in the picture LDS 6 cable connections on page 9. WARNING Keep the fiber end protected, by the protective tube, until it is time for connection. Only authorized personnel are entitled to remove the protective tube and proceed with the connecting operation Figure 2.1 LDS 6 cable connections 9

16 Installation Guidelines 1. Hybrid cable holder. 2. E2000 Single Mode fiber connector, angle polished. 3. SMA Multi Mode fiber connector. 4. Power connection. 24 V/60 ma. 5. Signal output connections (see Pin assignments for I/O connectors on page 13). 6. Network connection. Ethernet TBase-10 (RJ-45) Connection of Signal Cables CAUTION The signal voltages must be electrically isolated extra-low voltages (SELV). The max. voltage potential accessible to persons is 33 V eff or 46,7 V peak or 70 V dc. If several SELV voltages are available, then it is possible that the sum of these potentials is higher than that allowed to get in contact with the human body. WARNING The signal cables must only be connected to devices which guarantee safe isolation from their power supply. If signals (i.e. analog output 4-20 ma) are to be routed into a potentially explosive atmosphere of zone 1, they must be intrinsically safe. Supplementary retrofitting of the analyzer with energy-limiting modules is necessary. The Ex identification of these modules must be clearly visible on the housing: The signal cables in the rack mount analyzer are connected to the DSUB plugs at the rear. RC elements must be connected according to the figure Spark suppression on page 11 as a measure to suppress the generation of sparks across the relay contacts (i.e. limit relays). Note that the RC element results in a drop-out delay for an inductive component (i.e. solenoid valve). The RC element should therefore be dimensioned according to the following rule-of-thumb: R [Ω] 0.2 x R L [Ω] C [µf] I L [A] Additionally, make sure that you only use a non-polarized capacitor C. 10

17 Installation Guidelines NOTE When using direct current, it is possible to fit a spark suppression diode instead of the RC element. The cables to the relay outputs and binary inputs as well as the analog inputs and outputs must be screened. They must be connected to the corresponding trapezoidal DSUB plug according to the diagram Pin assignments for I/O connectors on page 13. The conductor cross-section should be 0.5 mm 2. It is recommended to use cables of type JE-LiYCY... BD. The cable length of the analog outputs depends on the load. Connector SUB-D 25F GND GND (-) Power supply unit (+) 24 V' max. R C I L R L R [Ω] 0,2 x R L [Ω]?? C [µf] I L [A] Figure 2.2 Spark suppression The above figure shows an example of measure to suppress sparks on a relay contact (rack mount analyzer). Since the DSUB connector and the spacings on board and on connector are only suitable for detachable voltages (signal) and as the power is located outside this powers supply, circuit must be SELV and the power must be limited according to EN (Table 13 or 14) when an over current protective device is used. The reference ground of the analog inputs is the housing potential. The analog outputs are floating, also with respect to one another. 11

18 Installation Guidelines The interface cable must be screened and connected to housing potential. The cable screen must be connected with a large-area contact to the screen of the DSUB plug. The conductor cross-section should be at least 0.5 mm 2. The interface cable must not be longer than 500 meters. In the case of two or three channel analyzers with analyzer sections connected in parallel, the signal cables of each channel are independent. Only the power plug is common to all channels Pin Assignment of LDS 6 The signal connection is carried out by using two DSUB connectors for each channel one 15 pins and one 25 pins. 12

19 Installation Guidelines Connector SUB-D 15F GND GND GND GND GND Analog output 2-P Analog output 2-N Analog output 1-P Analog output 1-N NC GND Analog input 2-P Analog input 2-N Analog input 1-P Analog input 1-N Binary input 6-P Binary input 5-P Binary inputs 5 to 6-N GND Analog outputs: floating (also to one another), R L 750 Ω Pressure correction Pressure correction Temperature correction Temperature correction Floating via opto isolator "0" = 0 V (0 to 4.5 V) "1" = 24 V (13 to 33 V) Component 2 (if present) Component 1 Non-floating analog inputs Connector SUB-D 25F GND GND GND Binary input 4-P Binary input 3-P Binary input 2-P Binary input 1-P Binary inputs 1 to 4-N Relay 6 Relay 5 Relay 4 Relay 3 Relay 2 Relay 1 GND Floating via opto isolator "0" = 0 V (0 to 4.5 V) "1" = 24 V (13 to 33 V) The relay is de-energized in the shown contact position Contact loading max. 24 V/1 A, AC/DC Figure 2.3 Pin assignments for I/O connectors 2.4 The Sensor CD General The cross duct sensor, CD 6 is designed for in situ measurements. It consists of a transmitter and receiver creating a single path measurement situation. The beam diameter is expanded to about 25 mm in order to improve performance in high dust load (>1 g/m 3 ) applications. 13

20 Installation Guidelines The transmitter includes a lens and a connection for the optical fiber located in the focal plane of the lens. The receiver contains a lens, a detector with preamplifier, driver electronics for the optical return signal, and a 24 VDC to ±15 VDC DC/DC-converter. The laser light is coupled from the optical fiber in the transmitter to the transmitter lens and passes through the measurement volume. The lens in the receiver focuses the incoming laser light on the detector where it is converted to an electrical signal. This signal is amplified and converted to an optical signal and returned to the central unit LDS Mounting of Specific Flanges There are three standard flanges available to mount the sensors for LDS 6: 1. DN65/PN6: The mounting of the sensor requires a DIN-flange (not delivered by Siemens Laser Analytics) with the dimension DN65/PN6. 2. ANSI 4 /150lbf: The mounting of the sensor requires an ANSI flange (not delivered by Siemens Laser Analytics) with the dimension ANSI 4 /150lbf. 3. Motor wedge: The mounting of the sensor requires a specially designed flange and a special motor wedge (both delivered by Siemens Laser Analytics) Installing and Aligning CD 6 The installation of CD 6 is very straightforward and can be performed by the customer. Mechanical Installation The transmitter and the receiver of CD 6 require a process flange as described in the above section. These have to be welded and aligned at the site before commissioning of LDS 6. Additionally, depending on application, one or two of the following might be needed: a supply of instrument air with hpa pressure regulation; 200 C hpa steam; electrical power for 370 W 1 phase electrical motor. The instrument air is the most common way of keeping the wedge windows clean and should be connected using 6 mm (outer diameter) semi-rigid tubing. 14

21 Installation Guidelines Figure 2.4 Sensor CD Figure 2.5 Sensor CD 6 - dismantled 1. Alignment screws. 2. Purge tube. 3. Purge flange. 4. Wedge tube. 5. Lock rings (2 pc.). 6. Lens tube. 7. Sensor housing. 8. Needle valve with fittings. 9. Cable feed through - the transmitter has two (for hybrid cable and loop cable) and the receiver has one (for loop cable). 10. Ground mount. 15

22 Installation Guidelines NOTE The process flanges must be mounted parallel to each other and the maximum error angle is ±2 deg relative to the symmetrical axis of the two flanges (transmitter and receiver). It is also important that the sensor flanges are oriented in such a way that the spring loaded bolts are located in the lower section of the flange - see Sensor CD 6 on page 15. At installation of CD 6, the fiber end and the photo-detector have to be aligned to the optical axis of the sensor pair. Note that each sensor has an optical axis of its own which is its axis of symmetry. Normally the process flanges are mounted with an angle error. CD 6 is, however, equipped with a flange pair with a spherical interface. This is used when the sensor pair is aligned to each other, see Alignment of the Sensors on page 48. In this way an angle error of up to ±2 on each side can be adjusted for. Connections Four test points are available on the sensor card. The power and signal levels can be examined here using an oscilloscope or a multi-meter. Upon installation, the signal levels should be adjusted to be between 2 and 4 volts peak. This is done with the potentiometer on the detector card. After the signal level adjustment, the analyzer lockin-phase has to be adjusted as well. The potentiometer is factory-adjusted to minimum gain. NOTE Only trained installation personnel are allowed to adjust the gain level and lockin-phase for the application. The powering of the receiver electronics is performed with a twisted pair copper cable delivering 24 VDC. This voltage feeds a DC/DC converter mounted on the sensor card which is able to give ±15 VDC and to handle 18 to 36 VDC on its input. This means that the system can handle large variations on the sensor voltage and thus will be very resistant to disturbances. 2.5 Dimensional Drawings The central unit will fit in a standard 19 rack. The dimensions of it and the sensor CD 6 are shown in the following figures. Be sure to allow at least 50 cm (20 ) behind the sensor for accessibility. 16

23 Installation Guidelines s LDS Figure 2.6 Dimensional drawings of the central unit LDS 6 17

24 Installation Guidelines 200 Ø163 Top view Customer flange Customer flange 370 (770, 1170) Customer tube Purging tube 400 (800, 1200) (770, 1170) Customer tube Purging tube 400 (800, 1200) Ø 44.5 Ø 44.5 Figure 2.7 Dimensional drawings of the sensors CD 3002Ex and CD 6 18

25 Operation Operation General Once the installation of the sensors at the measurement points is done and the connection via hybrid cables to the LDS 6 is established, the system is ready to be used. The functions in the LDS 6 are controlled through a keypad on the front of the panel. A 5 LCD screen is used to present the measurement values as well as the instrument s graphical interface LIM STO CTRL TR CODE 3 mg/nm NH 3 Ch1 %vol H 2 O Ch1 3 mg/nm NH 3 Ch2 %vol H 2 O Ch LIM STO CTRL TR CODE /- CLEAR ENTER ESC INFO MEAS Figure 3.1 The keypad and the screen on LDS 6 1. Status line (can be parameterized using function 53). If a fault occurs during operation, the message Maintenance request or Fault appears in the status line depending on the importance of the fault. This message is displayed alternately with the status messages. 2. Status display: LIM means: limit (alarm) signaling is idle and LIM means: limit (alarm) has been triggered. 3. Measured value. 19

26 Operation 4. Unit display. 5. Measured component display. 6. Function keys with adaptive meaning (soft keys). Points 1 to 6 apply to channel 1. The elements are repeated in an analogous manner in the bottom half of the display for a twochannel analyzer (as shown). Table Op.1 Switches/Keys CLEAR ENTER ESC INFO MEAS Soft key Meaning Deletes a commenced number input. Every digit input (except fast selection of a function) must be confirmed by using this key. Return by one step in the input structure. Modifications are imported. Help information. Return from any position in the input structure to service mode (possibly with request whether to import the entered data). Pressing the MEAS key again results in locking of the analyzer; i.e. changing to service mode again is only possible following input of the code. Possible adaptive meanings: Selection of item in menu tree Selection of function Switch function ON/OFF Component selection Editing of Inputs The values in the menus shown in this chapter should be understood as examples. An active input field is represented with brackets ([10]) as limiter. The cursor is positioned as a flashing line underneath the number to be entered (e.g. [23.45]). The input is terminated by pressing the ENTER key, and the value is stored. If several input fields are present in a menu, the cursor is automatically positioned to the next input field. NOTE Each input value must be confirmed with ENTER before you leave the menu. The CLEAR key can be used to delete an input. The cursor then returns to the first position of the input field. 20

27 Operation Graphic Styling Elements Switching function (ON status). Switching function (OFF status, also status display in the status line). Entry into a subsequent menu. Triggering of a function. Measuring mode: analyzer is coded. Service mode: signals are activated according to functions 71 and 77. NOTE To avoid static charges, the keyboard must only be used for servicing and input purposes. 3.2 Input sequence The figure Input sequence interacting with LDS 6 on page 22 shows the input sequence of LDS 6. The circled numbers marking certain steps in the input sequence can also be found in the text following the figure. 21

28 Operation 8 6 Modifications are imported 7 Service mode LIM STO CTRL TR CODE mg/nm NH ch1 %vol H O ch1 mg/nm NH ch2 %vol H O ch2 1 LIM STO CTRL TR CODE 9 Measuring mode Start from measuring mode To Meas. Screen Accept Modifications? 4 Yes No Only following modifications 5 Main Menu Analyzer Status Calibration Measuring Range Parameters 2 Code Configuration Input of password 3 Relay "Function control" (CTRL, function 71) Function Menu Store for analog output (function 77) Function Hard keys Soft keys Coding of analyzer Figure 3.2 Input sequence interacting with LDS 6 22

29 Operation Entry into Main Menu for a 1- or 2-Channel System Entry into Main Menu for a 3-Channel System LIM STO CTRL TR CODE mg/nm Ch %vol LIM STO CTRL TR CODE mg/nm %vol Ch2 LIM STO CTRL TR CODE 5.28 mg/nm %vol Ch3 Whilst in Measuring Mode, the component is shown on the right, with an arrow ( ). A soft key (1) is assigned to this specific component and it is called by pressing it. The appearance of the screen menu varies depending on the number of channels and the number of measured components. For a 3-channel system the soft keys of the measuring screen are assigned to channels instead of measured components. If the channel has two components it is necessary to pass a second channel-specific measuring screen before entering the component-specific main menu. Each channel can be operated independently. Channel mg/nm %vol 3 NH 3 H O 2 LIM STO CTRL TR CODE Main Menu Main Menu Analyzer Status Calibration Measuring Range Parameters Configuration Ch1 NH3 The main menu consists of the five items shown in the adjacent screen. Entering a Submenu Following the selection of a submenu, you will be asked to enter a password for service mode 2 (exception: submenu Analyzer status which requires no password and is thus freely-accessible). Analyzer status No code Calibration Access level 2 Measuring ranges Access level 1 Parameters Access level 1 Configuration Access level 2 The passwords for levels 1 and 2 are factory-set to the values 111 and 222 respectively. 23

30 Operation Return to Measuring Screen To Meas. Screen Ch1 NH3 Accept Modifications? Yes No When pressing the MEAS key you return immediately to the measuring screen from any position in the menu structure 3. A commenced input is aborted. The adjacent question is displayed before the return is carried out. The modifications are imported into the working area of the parameter memory by pressing Yes or rejected by pressing No. The ESC key leads back step-by-step to measuring screen 5. Modifications are imported without questioning 6. Coding of Analyzer After returning to measuring screen using ESC or MEAS, the symbol CODE in the status line shows that the analyzer is still in service mode 7. The analyzer can be coded again ( CODE) by pressing the MEAS key once more 8, thus entering Measuring Mode 9. Simultaneously with the symbol CODE the symbol CTRL (Function control) appears in the status line, showing that the analyzer is not in measuring mode. External signaling via a relay contact is then possible if a corresponding relay has been configured with CTRL under function 71. Fast Selection of Functions A Power user input has been incorporated to allow immediate switching from the measuring display to the desired function display if frequent inputs are necessary. It is then possible to directly access the desired function by bypassing the menu levels. The Power user input can only be started from the Measuring Screen and comprises the following input steps: Enter number of desired function in measuring screen using the digit keys; Press the soft key next to the desired component; If you do not have the required privileges to change the desired function you will be requested to enter the password. For a channel with two components on a three-channel instrument you must first press the soft key next to the desired channel and thereafter (in the next window) press the soft key next to the desired component. 3.3 Summary of Input Functions The analyzer functions can be divided into the following three categories: 24

31 Operation Analyzer-specific functions act on all channels and components of the analyzer, independently from the analyzer component through which the function was called. Channel-specific functions act on all components of the corresponding channel, independently from the analyzer component through which the function was called. Component-specific functions act on a single component, and can only be called through this. The following table summarizes the functions of the analyzer. Table Op.2 Main menu item (section) Function number Function designation 1 * 2 * 3 * Analyzer Status Analyzer Configuration Diagnostics Values Logbook Display Measuring Range x x x x x Calibration (code 2) Zero Calibration Span Calibration x x Measuring Range (code 1) 41 Define Range x Parameters (code 1) Response Time Limits Transmission Status Messages Select Display Digits LCD Contrast Date/Time Setup Logbook x x x x x x x x 25

32 Operation Main menu item (section) Function number Function designation 1 * 2 * 3 * Configuration (code 2) Analog Output Relay Outputs Binary Inputs Communication Reset Save/Load Data Store Analog Output Codes Input Levels Select Language Analyzer Test Pressure Correction Temperature Correction Water Correction Path Length Unit Dry Gas On/Off Error On/Off x x x x x x x x x x x x x x x x x 1 * Analyzer-specific functions. 2 * Channel-specific functions. 3 * Component-specific functions. Analyzer Status 2 Diagnostics Values 3 Logbook 4 Display Meas. Range Ch1 NH3 1 Analyzer Configuration Some of the existing functions on other Siemens instruments are not present in LDS 6, thus some function numbers may be missing in the table above Analyzer Status This display appears when pressing the first soft key ( Analyzer Status ), following the selection of the diagnostics functions in the main menu. The status functions are freely-accessible. You will not be asked to enter a password. 26

33 Operation 1 Analyzer Configuration 1 Analyzer Config. Ch1 NH3 Ordering-No. 7MBXXXXXXXXXXXXXXXXX Serial No OS Version CE Software CE Drv.Software Analyzer uc Drv.Software Continue Important manufacturing data of the analyzer are shown on the analyzer configuration screen. Ordering No: Information on ordering data of analyzer. Serial No: Consecutive number of analyzer. OS Version: Version number of the Windows CE operative system running in the analyzer. CE Software: Version number of the LDS 6-specific software. Analyzer uc Drv.Software: Version number of the software running on the main micro controller. Channel uc Drv.Software: Version number of the software running on the measurement channel micro controller. Opto uc Drv.Software: Version number of the software running on the opto module micro controller. Chan. FPGA Firmware: Version number of the firmware running on the measurement channel FPGA. Opto. FPGA Firmware: Version number of the firmware running on the laser controller FPGA. Ref. FPGA Firmware: Version number of the firmware running on the reference channel FPGA. 2 Diagnostics Values 2 Diagnostics Val. Ch1 NH3 Current Transmission Units Relative Transmission % Temperature C Pressure 1013 mbar Measuring Path m 3 Logbook 3 Logbook Ch1 NH3 S :43 + Optomodule Fault S :37 + Optomodule Fault W :55 - Signal quality W :54 + Signal quality Page 1...Continue The most important internal values are listed under function 2. They may be of interest for assessing faults or for adjustment operations. All faults which lead to a maintenance request (W) or fault message (S) are listed in the logbook (for a more detailed description of error handling see the chapter Alarms on page 41). Limit alarms (LIM), transmission alarms (TR), and function check (CTRL) are also recorded. However, these do not trigger a maintenance request or fault message. The logbook contains a maximum of ten pages, each of which can accommodate four messages. It operates according to the principle of a circulating buffer, i.e. the oldest message is over- 27

34 Operation written when all ten pages are full (40 messages). Fault messages are not deleted if they have not been acknowledged. The logbook entries can be deleted or blocked (function 60), or also switched off individually (function 87). NOTE If a fault occurs when the error message is switched off by function 87, there is no reaction at the interface. This applies to the analog as well as to the relay outputs. 4 Display Measuring Ranges 4 Disp. Meas.Range Ch1 NH3 Start End value mg/nm 3 The measuring range is listed using function 4. However, it cannot be modified in this menu Calibration The LDS 6 is calibrated when delivered and does not normally require on site recalibration; however, if this should be necessary the procedure should only be carried out by skilled and trained personnel. Please consult Siemens Laser Analytics if recalibration is needed. 20 Zero Calibration 20 Zero Calib. Ch1 NH3 Zero Calibration Active Calibrate When zero calibration is triggered the current measurement value is stored. This value will thereafter always be subtracted from the measurement signal. Act. Val mg/nm 3 28

35 Operation 21 Span Calibration 21 Span Calib. Ch1 NH3 Setpoint mg/nm Act. Val mg/nm 3 3 This display lists the set point and the current value. The calibration is triggered by pressing the third soft key. The current value is then set to coincide with the set point. Calibrate 41 Define Range 41 Define Range Ch1 NH3 Start Value End Value mg/nm Measuring Range It is possible to define a measuring range whose start-of-scale value is assigned to the bottom value (4 ma) and whose fullscale value is assigned to the top value (20 ma) of the analog output. Parameters 50 Response Time 51 Limits 52 Transmission Ch1 NH Parameters This display, with the selection of the parameter functions 50 to 53 appears following the selection of the parameter functions in the main menu by pressing the fourth soft key ( Parameters ). You can branch to the parameter functions 54 to 60 by pressing the fifth soft key (...Continue). 53 Status Messages...Continue 50 Response Time 50 Response Time Ch1 NH3 [5.000] Seconds This function can be used to set various time constants to reduce the noise superimposed on the measured value. Actual Measured Value: mg/nm 3 29

36 Operation 51 Limits 51 Limits Ch1 NH3 Upper Limit[30.00] mg/nm 3 The limit alarm is triggered when the value of a component exceeds the permissible range set in this screen. The alarm can be turned off here. Lower Limit 0.00 Limit Alarm On/Off mg/nm 3 The limit alarm is displayed on the status line if this has been set up by function 53. The alarm is also signaled by a relay if this has been set up by function 71. The triggering of the transmission alarm is registered in the logbook (function 3). 52 Transmission 52 Transmission Ch1 NH3 Alarm Level[5 ] % Nominal Current Set Nominal Value Units Units Relative % Transm. Alarm On/Off 53 Status Messages 53 Status Messages Ch1 NH3 Display Stored Value [STO] Display Limits [LIM] Display Func. Control [CTRL] Display Transm. Limits [TR] The transmission alarm is triggered when the transmission is outside a permissible range. The lower alarm level of the transmission for a channel is set as a percentage of the nominal transmission value, where the nominal value is registered as the fourth soft key is pressed. The upper alarm level is set to a fixed value and cannot be changed by the user. The transmission alarm is displayed on the status line if this has been set up by function 53. The alarm is also signaled by a relay if this has been set up by function 71. The triggering of the transmission alarm is registered in the logbook (function 3). This function can be used to display - within the status line - up to four different status which can be assumed by the analyzer. Table Op.3 Function Status STO: Stored Value Analog output connected to memory (see also function 77). LIM: Limit Upward or downward violation of limit (see also function 51). CTRL: Function Control TR: Transmission Start-up mode - Service mode. Upward or downward violation of transmission limit (see also function 52). The type of status Code is always present in the status line. 30

37 Operation 55 Select Digits 55 Select Digits Ch1 NH3 Supress Negative Values Digits After Automatic Decimal Point This function allows you to suppress the output of negative values on the measuring screen. It is also possible to select the number of decimal digits. The number of digits, including the decimal point, is always five when setting the function to automatic. 56 LCD Contrast 56 LCD Contrast Ch1 NH3 Brighter Darker Basic Setting Test 58 Date/Time 58 Date/Time Ch1 NH3 New Date(dd-mm-yy;24h/day) [ ] New Time: 14:44 Set Clock Actual Date Actual Time :44 You can adjust the display contrast using this function. If the contrast is wrongly adjusted you can re-establish the factory settings by pressing the third soft key ( Basic setting ). It is additionally possible to carry out an LCD test by pressing the fourth soft key ( Test ). Various test displays are then shown in succession. The test can be stopped by pressing ESC. If the LCD contrast is extremely maladjusted, and if the analyzer is in measuring mode, you can re-establish the basic setting by pressing the following key sequence: 8888 ENTER The analyzer has a system clock which is not protected against power failure (not a real-time clock). The clock is set at :00 when the analyzer is started. This function allows you to exactly set the date and time. This is particularly important to be able to assign a specific point in time to faults stored in the logbook. It can be of advantage when troubleshooting. An editing field appears when you call the function in which you can enter day, month and year as New date. Hours (24-hour system) and minutes are entered as New time. The set data are imported when you press the third soft key ( Set Clock ). The data then appear as an active display at the bottom of the screen. NOTE The date and time must be reset in case of a power failure. 31

38 Operation 60 Setup Logbook 60 Setup Logbook Ch1 NH3 Clear logbook You can use this function to delete or lock logbook entries (see also function 3). Lock logbook Configuration All functions of this block are only accessible via the password for level 2. Input Menu Configuration 70 Analog Output 71 Relay Outputs 72 Binary Inputs 73 Communication Ch1 NH3 Following selection of the configuration functions in the main menu by pressing the fifth soft key (...Continue ), you can branch to the further configuration functions....continue 70 Analog Outputs 70 Analog Output Ch1 NH3 71 Relay Outputs 4-20mA (NAMUR) Suppress negative measurement values 71 Relay Outputs Ch1 NH3 R1 Fault R2 Control R3 Maint.Req R4 Limit...Continue If the NAMUR mode is chosen in this screen, the lower and upper limits of the analog outputs are 3.8 and 21.5 ma respectively, according to the NAMUR standard. Otherwise the limits are 2 and 21 ma. If the function Suppress negative measurement values is activated, negative measured values are set to to 4 ma at the analog output. If negative measured values have an unfavorable effect on further processing, activate this function. The correct measured value is still output in the display. The basic version contains six freely configurable relays per channel that can be used for signaling (maximum 24 V/1 A). Each relay can be assigned one of the functions listed in Table Op.4. The relay is normally energized and becomes de-energized upon an alarm. Refer to the terminal assignment diagram in Section Electric Connections on page 8 for the assignments of the individual relays when de-energized. Up to four relays can be configured in one menu. By pressing the fifth (last) soft key (...Continue ) you can switch to further menus - and thus to further relays. 32

39 Operation NOTE Every change to the configuration of the relay outputs should always be stored in the user data memory using function 75. If this is not done, there is a risk that a previous (undesired) configuration is called when selecting Load user data. Table Op.4 Relay Assignments Function Vacant Fault Maintenance Request Function Control (CTRL) Transmission Limit Alarm (TR) Remarks Relay is permanently de-energized. signaling for faults specified in Operation chapter. signaling for Maintenance Requests specified in Operation chapter. signaling when analyzer is in start-up mode or in service mode (coded). Upward or downward violation of transmission limit (see also function 52). Limit Alarm (LIM) Upward or downward violation of limit (see also function 51). Stored Value (STO) Relay may be de-energized simultaneously with fault, transmission alarm or function control depending on the configuration of function Binary Inputs 72 Binary Inputs Ch1 NH3 B1 Ext. Fault Temp. B2 Ext. Fault Prs. B3 Ext. Fault Purging B4 Ext. Maint.Req. Temp....Continue You can freely configure the six floating binary inputs [ 0 = 0 V ( V); 1 = 24 V ( V)] available in the basic version. You can assign one of the control functions listed in Table Op. 5 to each input. The binary input should normally be energized. De-energizing the binary input will result in signaling of a fault. Refer to Section Electric Connections on page 8 for the assignments of the individual inputs. Up to four relays can be configured in one menu. Switching to further menus - and thus to further relays - is always carried out by pressing the fifth (last) soft key (...Continue ). NOTE Every change to the configuration of the binary inputs should always be stored in the user data memory using function 75. If this is not done, there is a risk that a previous (undesired) configuration is called when selecting Load user data. 33

40 Operation Table Op.5 Binary Input Assignments Function Vacant External Fault General External Fault Temperature External Fault Pressure External Fault Purging External Maintenance Request General Remarks Relay is permanently de-energized. Binary input should be de-energized upon fault signal from unspecified equipment. Binary input should be de-energized upon fault signal from temperature transducer. Binary input should be de-energized upon fault signal from pressure transducer. Binary input should be de-energized upon fault signal from purging equipment. Binary input should be de-energized upon fault maintenance request from unspecified equipment. Binary input should be de-energized upon maintenance request signal from temperature transducer. External Maintenance Request Pressure External Maintenance Request Purging Binary input should be de-energized upon maintenance request signal from pressure transducer. Binary input should be de-energized upon maintenance request signal from purging equipment. 73 Communication 73 Communication Ch1 NH3 IP Address Type Static IP Address : : Subnet Mask : : Gateway : : Port Number :5100: The communication screen should only be accessed by service personnel. It is therefore provided with a higher access level (3). 74 Reset 74 Reset Ch1 NH3 This function is used to carry out a cold restart of the analyzer, i.e. in case of a fault in program execution. Trigger Reset You must wait for the start-up time to elapse, before trying to use the display. The analyzer will automatically start to measure and will be ready for use after 1 to 3 minutes. 34

41 Operation 75 Save/Load Data 75 Save/Load Data Ch1 NH3 Save User Data Load User Data Load Factory Settings Erase EEProm Section You can use this function to save or load user-specific data in the user data memory on the EEPROM. Saving of data should always be carried out after a successful starting-up of the system. All individual settings are then saved and can be recalled if necessary (load user data). This is significant if repairs or maintenance are to be carried out on an analyzer or if new parameter settings are to be tried. 75 Save/Load Data Ch1 NH3 Erase Work Section The working area data and the user data on the EEPROM can be erased by this function. The factory data can never be erased. Erase User Section Main Memory RAM Parameter Memory EEPROM Factory Data Fct. 75 Current Operations User Data Fct. 75 After every change Working Area The above figure provides a summary of the interactions between RAM and EEPROM. The basic status of the analyzer (factory settings) can be reestablished using the function Load Factory Settings (function 75). 35

42 Operation 77 Store Analog Output 77 Store Ch1 NH3 Store Fault Store Function Control You can use this function to define the response of the analog output with certain alarms. The response for fault (S), transmission alarm (TR) or for start-up and function control (CTRL), can be defined independently. Store Transmission The analog output can be set to show; either 77 Store Fault Ch1 NH3 Analog Output To: 3/1 ma - the last measured value; or - 3/1 ma. (3 ma if the NAMUR mode is choosen for the analog output in screen 70, and 1 ma otherwise) The function can also be turned off. When an alarm occurs and the analog output is set to the last measured value or 3/1 ma, the display of the concentration value in the measuring screen will be suppressed. 79 Codes Input Levels 79 Codes Ch1 NH3 Code 1 [111] You can use this function to replace the factory-set codes ( 111 for level 1 and 222 for level 2) with your own. The value 000 disables the code and unrestricted access is granted to the corresponding access level. Code Analyzer Test The analyzer test comprises: 80 Analyzer Test Ch1 NH3 Keyboard Test Relay And Binary Test Analog Test Keyboard test Relay and binary test Analog test Analyzer-specific Channel-specific Channel-specific Keyboard Test The keyboard test can be used to check various keys on the input panel. The five soft keys at the right margin can make the associated point disappear or appear. If the digit keys and the sign key are pressed, the corresponding digit is stored in the editing field in the bottom line of the display. A message will be displayed in plain text as you press the INFO key; the MEAS and ESC keys retain their return functions. 36

43 Operation Relay and Binary Test NOTE First remove data plugs. 81 Select Language 81 Select Language Ch1 NH3 English The first display shows 6 of the relay and binary channels. Individual relays can be activated using the relay test. This is carried out by using the input field. A 1 makes the relay pull up, a 0 makes it return to the de-energized state. Digits other than 0 and 1 are not accepted by the input field. After leaving function 80, the relays reassume their former status, prior to selection of the relay and binary test. The column Binary shows the current status of the binary inputs in this display. Analog Test The analog test can be used to parameter the analog output with a constant current of 0-24 ma for test purposes. The analog input permanently shows the input currents in ma. You can use this function to switch the analyzer to a different dialogue language. Deutch 82 Pressure Correction You can use this function to select: 82 Pressure Corr. Ch1 NH3 Mode: Internal Measuring Range: [700.0] mbar Limits: mbar Manual Value: 1013 mbar Ana.Inp.2: 4-20mA(NAMUR) Pressure correction using an internal pressure sensor in the central unit; Pressure correction using an external pressure sensor via analog input 2; Pressure correction using a manual pressure value (example as shown on left). The selected measuring range corresponds to the analog input signal range 4-20 ma. No other ranges or input signals can be used. If the pressure sensor is configured according to the NAMUR standard, the NAMUR mode should be selected for the analog input signal. Only input signals within the range?? -?? ma are then accepted. If the NAMUR mode is not selected, input signals within the range?? -?? ma are accepted. 37

44 Operation The limits should normally mark the interval in which pressure compensation is possible. If the pressure signal exceeds the specified limits this will be reported as a fault on the instrument. The parameters for the pressure correction in the corresponding factory function are component-specific. Selection of the pressure mode in function 82 is channel-specific. It is possible to switch off the pressure correction. 83 Temperature Correction You can use this function to select 83 Temp. Corr. Ch1 NH3 Mode: Manual Measuring Range: [0.00 ] C Limits: C Manual Value: C Ana.Inp.1: 4-20mA(NAMUR) Temperature correction using an external temperature sensor via analog input 1 (example as shown on left); Temperature correction using a manual temperature value; Temperature correction using the internally calculated process temperature. This is only possible if the LDS 6 is set up to measure the temperature at the measuring point. The parameters for the temperature correction in the corresponding factory function are component-specific. Selection of the temperature mode in function 83 is channel-specific. The selected measuring range corresponds to the analog input signal range 4-20 ma. No other ranges or input signals can be used. If the pressure sensor is configured according to the NAMUR standard, the NAMUR mode should be selected for the analog input signal. Only input signals within the range ma are then accepted. If the NAMUR mode is not selected, input signals within the range 2-21 ma are accepted. The limits should normally mark the interval in which temperature compensation is possible. If the temperature signal exceeds the specified limits this will be reported as a fault on the instrument. It is possible to switch off the temperature correction. 84 Water Correction 84 Water Corr. Ch1 NH3 Water Correction Active Manual Value: 23.0 %vol In this screen it is possible to activate or deactivate the water correction function. Water correction is necessary for some applications to correct for influences of water vapor on other gases. The function should be turned off at calibration to dry gas. If water is not calculated by the instrument itself, a water concentration value should be manually entered here. 38

45 Operation 85 Path Length 85 Path Length Ch1 NH3 [1.000] m The length of the measuring path for the specific channel should be set in this screen. 86 Unit 86 Unit Ch1 NH3 3 mg/nm EU The unit for a specific component can be set in this screen. Possible units for concentrations are: ppm, %vol, mg/nm 3 EU (metric standard) or mg/nm 3 US (American standard). Possible units for temperature are: C, F or K. 87 Dry Gas On/Off 87 Dry Gas On/Off Ch1 NH3 Dry Gas It is possible to display the dry value of the concentration, i.e. the calculated concentration when the volume of water vapor has been subtracted from the total volume of gas. This function can be activated in the adjacent display. 88 Error On/Off 88 Error On/Off S1 Optomodule Fault Ch1 NH3 signaling of maintenance requests and faults (xxx see Tables 6.3 and 6.4) can be switched off individually using this function so that neither an entry in the logbook, nor a status signal or external signaling take place. S2 Laser Current Fault S3 Signal Quality Fault S4 Compensation Temp. Limit...Continue Error messages which do not apply to this channel are identified by the absence of text following the error number. 39

46 Operation 40

47 Alarms Alarms Alarm Response LDS 6 is able to recognize and alarm for irregularities in its functions. There are five types of alarms that can be triggered depending on the nature of the error: Maintenance request alarm Faults alarm Transmission alarm Limit alarm Function control alarm Status Row When the alarms limit (LIM), transmission limit (TR) or function control (CTRL) occur, their corresponding square symbol in the status row will be lit (if this has been set up in function 53). If a Maintenance request or a Fault is triggered the text Maintenance request or Fault will appear on the status line. This message is output alternately with the status messages. STO and CODE may also appear in the status line, but these are not signaling for alarms (see Operation on page 19). Logbook 3 Logbook Ch1 NH3 S :43 + Optomodule Fault S :37 + Optomodule Fault W :55 - Signal quality W :54 + Signal quality...continue Page 1 At the same time that an alarm is activated (marked with a + sign) and inactivated (marked with a - sign) a new message will appears in the logbook (function 3). The message will also show the time when it was recorded in the logbook together with a short text describing the alarm. Faults are considered to be more severe than other alarms and are therefore treated somewhat different in the logbook. When a fault message first appears in the logbook it is marked with a filled circle to the right. To inactivate the fault alarm the fault message must be acknowledged by pressing the soft key next to it. This also removes the circle. The text in the status line as well as the response by functions 71 and 77 will not change until the fault message has been acknowledged. If the cause that triggered the fault alarm has not been corrected, a new message will appear directly as soon as the first fault message is acknowledged. Every time a new message occurs, the report stored in the logbook is shifted by one memory location. A total of 40 locations are available, and the oldest of the 40 reports is deleted when a new one occurs. A power failure will delete all reports. 41

48 Alarms Function 60 can be used to switch off the logbook and also to delete the messages stored in it. The output of messages can be particularly inconvenient during test runs. They can therefore be switched off using function 87. It is not recommended to use this facility during normal operation. Relays If the relay output of the analyzer has been configured accordingly (see also 71 Relay Outputs on page 32), it is possible to output a signal when an alarm occurs. Stored Value The response of the analog output can be set to the last measured value or to 3 ma when an alarm occurs (function 77). This response signal is only possible for Fault alarm, Transmission alarm and Function control alarm. 4.2 Maintenance Request Alarm A Maintenance request alarm is set when a modification of the analyzer is needed. The measuring ability of the analyzer may not be affected during the time this alarm is active. However, to guarantee reliable measurement in the future, it may be necessary to carry out corrective measures. The following table shows the different alarm messages signaling for maintenance request that can appear in the logbook. These can be individually deactivated using function 87. No. Error Message Possible Causes Action W1 Opto module Laser damage. Leaking reference cell. Reference cell displacement. Electronics damage. W2 Laser current Decreasing laser current due to aging of laser. Contact service. Contact service. W3 External maintenance request Maintenance request from outside. Check external equipment. W4 Set clock LDS 6 has been switched off. Set date and time. 42

49 Alarms No. Error Message Possible Causes Action W5 Ambient Analyzer Ambient temperature or pressure are beyond limits specified in technical data. W6 Ambient Channel Ambient temperature is outside limits specified in technical data. Make sure that the ambient temperature ranges between 5 C - 45 C and the ambient pressure corresponds to a place below 2000 m above the sea level. Make sure that the ambient temperature ranges between 5 C - 45 C. W7 Analog Out Error in calibration of analog output. Re-calibration is necessary. Contact service. W8 Error Handler Analyzer Internal error log is full. Contact service. W9 Error Handler Channel Internal error log is full. Contact service. W10 Data Flow Analyzer Electronics failure in internal communication. Contact service. W11 Data Flow Channel Electronics failure in internal communication. Contact service. 4.3 Faults Alarm Any faults in the hardware that makes the analyzer unable to carry out measurements, result in a fault alarm. The measured value flashes, and then it is always necessary to take corrective measures. The faults listed in the following table lead to a fault alarm message in the logbook. These can be individually deactivated by using function 87. No. Error Message Possible Causes Action S1 Opto module Laser damage. Leaking reference cell. Reference cell displacement. Electronics damage. S2 Laser Current Decreasing laser current due to ageing of laser. S3 Signal Quality Signal amplitude too high due to high component concentration. Contact service. Contact service. Contact service. 43

50 Alarms No. Error Message Possible Causes Action Signal amplitude too low when measuring temperature. Contact service. S4 Compensation Temperature Limit External temperature signal is outside the limits. Check signal. Make sure that the temperature is within the limits specified by function 83. S5 Compensation Pressure Limit External pressure signal is outside the limits. Check signal. Make sure that the pressure is within the limits specified by function 82. S6 External Fault External signaling. Check external equipment. S7 Supply Voltage Channel Internal power failure. Contact service. S8 Supply Voltage Analyzer Internal power failure. Contact service. S9 Serial EEProm Internal EEProm failure. Contact service. S11 FPGA Channel Electronics failure in data acquisition unit. S12 CAN Analyzer Electronics failure in internal communication. S13 CAN Channel Electronics failure in internal communication. Contact service. Contact service. Contact service. S14 Data Flow Analyzer Electronics failure in internal communication. Contact service. 4.4 Transmission Alarm The alarm (TR) appears either if the transmission falls below a limit defined by function 52 or if it exceeds a fixed limit. The following table shows the possible reasons that can set it: Possible Causes Dirty windows. Sensors not aligned. Purging not working. Transmission too high. Action Clean windows. Align sensors. Make sure purging is working. Clean purging tubes. Adjust the potentiometer of the detector. 44

51 Alarms 4.5 Limit Alarm The limit alarm (LIM) appears if the signal exceeds the limits set by function Function Control Alarm The function control (CTRL) is activated when the analyzer performs an action during which the measurement value may be incorrect. The triggering of CTRL should normally not require an action from the user. The following table shows some possible causes to why CTRL is activated: Possible Causes Start-up procedure is active. Analyzer is de-coded. Analyzer is communicating with external service software. Analyzer is shutting down. Analyzer is saving data to EEProm or Flash memory. 45

52 Alarms 46

53 Maintenance and Service Maintenance and Service 5 During normal use, the central unit LDS 6 requires no service. The sensor with its optical surfaces will need regular maintenance. Depending on application and purging method, the interval of maintenance may vary from 1 to 12 months. 5.1 The Central Unit Cleaning Instructions Use only a dry cloth without any cleaning agents. Since the central unit contains optical surfaces great care should be taken when cleaning. Only outer surfaces may be cleaned. 5.2 Cross Duct Sensor If the transmission in a channel drops below the level set by the user, the transmission alarm will be activated. The sensor in this channel needs to be serviced by cleaning the wedge windows or realigning the optical path Cleaning the Wedge Windows Before the sensors are removed make sure that: If there is steam purging turn it off! WARNING It is very important to turn off the steam since if over-heated it is invisible and can cause severe burn damages. No hazardous or hot gases can escape from the process. Appropriate protection against hot surfaces on and around the sensor is used. 1. Release the lock ring closest to the process use an appropriate tool and pull the sensor out. 2. Clean the window on the wedge tube. If the optical lens needs cleaning the second lock ring needs to be released. Extra care should be taken since the lens is anti-reflection coated and sensitive to scratches. 3. Clean the optical surface with a soft cloth or window cleaner containing ammonia. Soap water also works fine in many cases. Start at the centre and work with circular movements towards the rim. 47

54 Maintenance and Service 4. Remove all dust particles using pressurized air or flushing water. 5. When the sensor is re-installed make sure that the guide pin fits the hole on the purging flange. Screw on the lock ring and tighten it gently with the tool. If this operation is performed properly, it will not affect the alignment of the sensor Alignment of the Sensors Mount the sensors, receiver and transmitter, with gaskets on the flanges and cross tighten the bolts. Align the sensors in the following steps: Roughly align the adjustable flange so that the two discs are parallel. Receiver side Figure 5.1 Remove the receiver sensor box Release the receiver lock ring furthest from the process use the supplied tool and remove the receiver sensor. 48

55 Maintenance and Service Receiver side Figure 5.2 Mount flash light Fasten the supplied alignment plate. It screws on easily with the help of an O-ring. The alignment plate is included in the supplied alignment kit, Order No. A5E Turn the flashlight on and mount it on the alignment plate. In dusty environments or long path-lengths use a stronger light source such as a 55 W/12 V lamp, an option supplied by Siemens Laser Analytics. Transmitter side Figure 5.3 Remove the launcher Remove the optical fiber launcher on the transmitter end. 49

56 Maintenance and Service Transmitter side Figure 5.4 Align the transmitter Mount the cross-hair and align the transmitter with the two hexagonal socket screws, by tightening and loosening them until the light dot is centered in the inner ring of the cross-hair. 50

57 Maintenance and Service Transmitter side Figure 5.5 Center the light dot The light dot should have a perfect round shape. If the light dot is oval or scattered it might be necessary to adjust the welded flanges or remove any objects that might be blocking the lightpath. Transmitter side Figure 5.6 Mount the flash light in the transmitter Move the flashlight to the transmitter and replace the cross-hair with it. 51

58 Maintenance and Service Receiver side Figure 5.7 Align the receiver Remove the alignment plate and remount the receiver sensor. Tighten the quick coupling firmly. Remove the detector card and replace it with the cross-hair. Align the receiver with the two hexagonal socket screws, by tightening and loosening them until the light-dot is centered on the cross-hair. NOTE The stability of the sensor alignment depends on the stability of the construction to which the customer s flange is mounted. If the incinerator wall or smoke duct is subject to movements due to, for instance, thermal changes CD 6 will need repeated realignment. 52

59 Maintenance and Service This can be avoided by mounting the sensor pair on an external, more stable base, like a concrete or steel support. 5.3 Calibration Check The calibration can be checked at any time by using the optional teflon coated verification cell FC3002 or FC3002H which is a heated version. Normally the LDS 6 does not have to be re-calibrated but due to local regulations the calibration may have to be checked with regular intervals. CAUTION The calibration procedure is critical and should only be performed either by Siemens Laser Analytics AB or by certified personnel at site. 5.4 Reconfiguration of Temperature Compensation Manual to external 1. Starting from Measuring Window, navigate to the component or channel for which you want to change the compensation mode. Press the soft key for Configuration. Enter the password for privilege level 2 (the password is factory-set to the value 222, but may have been replaced by a new one). Press Continue twice and then choose 83 Temperature Correction. 2. Press the first soft key to change the text manual temp. value to external temp. signal on input Set the measuring range to the temperatures that correspond to the analog input signal 4 ma and 20 ma respectively. 4. Set the limits to suitable values. If the temperature signal exceeds the limits a fault will be triggered. Note that the limits cannot be set outside a certain range. 5. Make sure that the symbol next to the text Temperature corr. active is marked (it should be a filled square). 6. Press MEAS to return to measurement screen. Press MEAS again to loose privileges. 7. Hardware connections: Connect the 4-20 ma wires to pin 3 and 11 on the 15 pin trapezoidal plug (D-SUB plug) at the rear. The conductor cross-section should be >0.5 mm 2. It is recommended to use cables of type JE-LiYCY... BD. 8. The procedure has to be repeated for other channels. It is not necessary to repeat it for more than one component per channel since it is a channel specific function. 53

60 Maintenance and Service External to manual 1. Starting from Measuring Window, navigate to the component or channel for which you want to change the compensation mode. Press the soft key for Configuration. Enter the password for privilege level 2 (the password is factory-set to the value 222, but may have been replaced by a new one). Press Continue twice and then choose 83 Temperature Correction. 2. Press the first soft key to change the text external temp. signal on input 1 to manual temp. value. 3. Set the manual value to the preferred value. 4. Make sure that the symbol next to the text Temperature corr. active is marked (it should be a filled square). 5. Press MEAS to return to measurement screen. Press MEAS again to loose privileges. 6. The procedure has to be repeated for other channels. It is not necessary to repeat it for more than one component per channel since it is a channel specific function. 5.5 Reconfiguration of Pressure Compensation Manual to external 1. Starting from Measuring Window, navigate to the component or channel for which you want to change the compensation mode. Press the soft key for Configuration. Enter the password for privilege level 2 (the password is factory-set to the value 222, but may have been replaced by a new one). Press Continue twice and then choose 82 Pressure Correction. 2. Press the first soft key to change the text manual pressure value to external pressure signal on input Set the measuring range to the pressures that correspond to the analog input signal 4 ma and 20 ma respectively. 4. Set the limits to suitable values. If the temperature signal exceeds the limits a fault will be triggered. Note that the limits cannot be set outside a certain range. 5. Make sure that the symbol next to the text Pressure corr. active is marked (it should be a filled square). 6. Press MEAS to return to measurement screen. Press MEAS again to loose privileges. 7. Hardware connections: Connect the 4-20 ma wires to pin 4 and 12 on the 15 pin trapezoidal plug (D-SUB plug) at the rear. The conductor cross-section should be >0.5 mm 2. It is recommended to use cables of type JE-LiYCY... BD. 8. The procedure has to be repeated for other channels. It is not necessary to repeat it for more than one component per channel since it is a channel specific function. 54

61 Maintenance and Service External to manual 1. Starting from Measuring Window, navigate to the component or channel for which you want to change the compensation mode. Press the soft key for Configuration. Enter the password for privilege level 2 (the password is factory-set to the value 222, but may have been replaced by a new one). Press Continue twice and then choose 82 Pressure Correction. 2. Press the first soft key to change the text external pressure signal on input 1 to manual temp. value. 3. Set the manual value to the preferred value. 4. Make sure that the symbol next to the text Pressure corr. active is marked (it should be a filled square). 5. Press MEAS to return to measurement screen. Press MEAS again to loose privileges. 6. The procedure has to be repeated for other channels. It is not necessary to repeat it for more than one component per channel since it is a channel specific function. 5.6 Reconfiguration of the Path Length 1. Starting from Measuring window, press the soft key next to the component for which you want to change the path length. Press the soft key for Configuration. Enter the password for privilege level 2 (the password is factory-set to the value 222, but may have been replaced by a new one). Press Continue twice and then choose 84 Path Length. 2. Press first soft key to edit the path length. Enter the new path length and press ENTER. 3. Press MEAS to return to measurement screen. Press MEAS again to loose privileges. 4. The procedure has to be repeated for other channels. It is not necessary to repeat the procedure for more than one component per channel since this function is a channel-specific function. 55

62 Maintenance and Service 56

63 Technical Description Technical Description Introduction The LDS 6 is a system for on-line in situ gas analysis providing continuous presentation of accurate and real-time measurements. The gas concentration is measured using line absorption spectroscopy. Cross sensitivities to other gases are eliminated in the measurements due to the frequency purity of the laser enabling selective detection of individual absorption lines. The LDS 6 consists of a sensor pair (measuring heads) and a central unit interconnected using optical fiber cables. The central unit and the sensor can be installed several kilometers apart. The light source is a diode laser with a wavelength that can be tuned within a narrow spectral range. An optical fiber guides the light from the central unit to the sensor, where it is directed into the measuring section. The laser beam passes through the gas in the measuring section and is partially absorbed there. The light attenuated in this way is detected by the receiver and is returned to the central unit. The variation in the intensity of the laser light in the vicinity of the absorption line is measured, and the concentration of the gas being measured is calculated using the second harmonic of the detected signal. The LDS 6 can measure at three locations simultaneously. Each measurement point needs a receiver board in the central unit as well as a sensor with cabling. The LDS 6 operates as an independent unit. A VAC main power supply is all that is required. The gas concentration and instrument status are indicated on the graphical display. The gas concentration is also continuously given as an analog 4-20 ma output. Several different alarms can also be obtained externally. The unit also accepts different inputs, analog and binary, such as process temperature and pressure. LDS 6 can also be operated remotely via the Ethernet port with a PC running Windows 95/98/ME or Windows NT/2000/XP. It is also possible to connect to LDS 6 via modem over the public telephone net. The external connection requires the optional software LDSComm (LDS Communication Client) to be installed on the remote computer. All aspects of LDS 6 can be controlled in this way. 57

64 Technical Description 6.2 Overview The LDS 6 consists of a central unit, hybrid cables and a sensor (CD 6 or CD 3002Ex). The hybrid cables contain optical fibers and a low voltage electrical cable (24 V), and connect the different types of sensors available to the central unit The Central Unit The central unit incorporates a control panel with display, built-in keyboard, control computer, laser, reference cell, control electronics for the laser and slots for up to three receiver channels. An on-board non-volatile memory is used to hold the software and necessary files for the operation. This simplifies the software updating which is done remotely through the Ethernet port. No moving media like hard drives are used. Figure 6.1 LDS 6 central unit Depending on the measurement situation, a response time down to 0.1 sec. is achievable. Each channel in the central unit also handles a large number of IO-units for 4-20 ma input/output, digital input/output and relay output - for further information see Pin Assignment of LDS 6 on page 12. The I/O setup is completely flexible and can be configured to the customers specification. As an example LDS 6 can present concentration and transmission values (4-20 ma) give alarms on system fault (common alarm) and transmission drop and read process temperature (4-20 ma). It is also possible to connect to the Ethernet port on LDS 6, either directly or via a LAN modem. With sufficient privileges all aspects of LDS 6 can be controlled this way. This option is preferably used before service visits to diagnose the status of LDS The Hybrid Cable The hybrid cable is constructed for very harsh environments and consists of two optical fibers, one for transmission of the laser light to the measurement volume and one for the return of the detected signal. Two electrical wires are used for powering the electronics in the sensor (24 VDC). 58

65 Technical Description Figure 6.2 Hybrid cable The Sensor CD 6 The cross duct sensor, CD 6 (a sensor for measuring through a gas channel) is designed for in situ measurements. It consists of a transmitter and a receiver creating a single path measurement situation. The beam diameter is expanded to about 25 mm in order to improve performance in high dust load (>1 g/m 3 ) applications. Figure 6.3 Sensor CD 6 (one of a pair of two) The transmitter includes a lens and a connection for the optical fiber located in the focal plane of the lens. The receiver contains a lens, a detector with preamplifier, driver electronics for the optical return signal, and a 24 VDC to ±15 VDC DC/DC-converter. The laser light is coupled from the optical fiber in the transmitter to its lens and passes through a wedge module (for protection of the lens) and then through the measurement volume. The lens in the receiver (also protected with a wedge module) focuses the incoming laser light on the detector where it is converted to an 59

66 Technical Description electrical signal. This signal is amplified and converted to an optical signal and returned to the central unit. The mounting of the sensor requires a flange with the dimensions DN65/PN6 or ANSI 4 /150 lbf The Ex Sensor CD 3002Ex The sensor is also available in an Ex-version. This has very low power electronics - intrinsically safe - and an IP65 enclosure. Figure 6.4 Ex sensor CD 3002Ex (one of a pair of two) For further information regarding the Ex option please refer to Explosion Protection - Ex II 1G D T135 C EEx ia IIC T4 on page Protecting the Optical Surface The wedge windows are in many applications exposed to very nasty environments and will get stained very quickly if no measures are taken. A number of existing methods available to keep the wedge windows in good shape are described in the following sections. Instrument Air Purging This is the standard solution to keep the wedge windows free from contamination. It requires a flange equipped with an inlet for purging gas to create an air flow in front of the wedge windows and into the process. NOTE Instrument air is rather expensive and therefore measures should be taken to minimize the consumption. Therefore a pressure regulator should be used at the instrument air connection point to facilitate adjustment of the flow if no flow regulation is applied. If very high air flows (>100 l/min.) are needed an air blower should be used. As an option a needle valve can be supplied and be used instead to give an adjustable air flow of approx l/min. (with 6000 hpa instrument air). 60

67 Technical Description Gas Flow Calculations Gas flow calculations are slightly complex because gases are compressible fluids whose density changes with pressure. In addition, when the outlet pressure is less than one half of the inlet pressure, the gas reaches sonic velocity in the valve. This is known as choked flow, because a further decrease in outlet pressure does not increase the flow. In this application we are dealing with choked flow. The following empirical equation can be used to calculate the flow under these circumstances - assuming that the process pressure (P p ) is 1023 hpa: q = C v P 1 sqrt[1/((t ) G g )] where q = the flow rate on the low pressure side [Nltr/min.] C v = the flow coefficient (0,1 for the needle valve in our standard sensor) P 1 = the inlet absolute pressure [hpa] G g = the gas specific gravity (air = 1.0) T 1 = the upstream temperature [ C]. The flow (q) of instrument air at p 1 = 6000 hpa and T 1 = 25 C through the needle valve when it is fully opened would then be a little more than 110 Nltr/min. For a more complete detail see the picture below. It shows the flow (q) as a function of the up-stream pressure (P 1 ). There are two parameters in the diagram, i.e. the process pressure (P p ) and the temperature of the purge gas which is assumed to be air (G g = 1.0). The diagram shows the flow through a system with a total C v of 0.1. The flow increases linearly with C v T 1 = 25 C q (Cv = 0.1) [Nltr/min] P p = 2026 hpa P p = 1013 hpa T 1 = 100 C 20 P p = 3039 hpa P 1 [x1013 hpa] Figure 6.5 Purge air flow rate 61

68 Technical Description Purging with Air Blower In applications with high dust load purging with air blower must be considered. The air speed when standard purging is used is too low to prevent build-up of dust in the flange tubes. Our standard air blower solution will provide up to about 1000 l/min. Steam Purging If overheated steam is available it is a candidate for purging of the wedge windows. It has some advantages like high temperature (to prevent salt condensation) and low maintenance. An additional advantage when oxygen is measured is that steam is free of oxygen and will not interfere with the measurements; consequently when water is measured this becomes a disadvantage. When oxygen is measured N 2 purging of the sensor housing might also be necessary to obtain maximum performance. The requirements on the steam are that it must be ~200 C and overheated at the sensor location. See the steam installation instruction provided by Siemens Laser Analytics AB. As an option a steam conditioning unit can be offered. We recommend its use for this kind of applications. 6.3 Measurement Principle The LDS 6 measures the gas concentration by using line absorption spectroscopy. If the absorption of a gas mixture is plotted versus the wavelength, it can be seen that absorption only takes place at certain wavelengths in the spectral region. These extremely narrow absorption peaks are referred to as absorption lines as shown in the figure below H 2 O 15% NH 3 5ppm Figure 6.6 Absorption lines 62

69 Technical Description The measured gas (here ammonia) is identified by comparing with the spectrum from a built in reference cell. To perform line absorption spectroscopy, the LDS 6 uses a diode laser as light source since its spectral width is much narrower than the width of the absorption line. Furthermore, the wavelength of the laser can be selected to be near one absorption line of the gas to be measured. By varying the current and temperature the laser wavelength is tuned to cover the required narrow spectral range which includes the absorption line. When tuning the laser light over the absorption line it is partially absorbed. From the received laser signal the area beneath the absorption line can be extracted, which is a measure of the gas concentration. The light emitted from the laser is split into five beams. The first beam passes through a reference gas and is then detected. This reference signal is used for continuous self-calibration and zero point determination of the system, taking temperature and pressure into account. The second beam is used for measuring the intensity of the laser and provides the control unit with information relating to the state of the laser. The third, fourth and/or fifth beams (depending on how many channels are in use) are conducted via the optical fiber with the E2000 connectors to the sensor heads, where it enters the measuring sections. When the laser light passes through the gas in the measuring section it is partially absorbed. The light is detected by the receiver and after signal conditioning it is converted to an optical signal and returned to the central unit using the multi mode optical fiber (with the SMA connectors). 63

70 Technical Description CPU and presentation Signal processing Central unit Laser light Electrical signals Return LED light P 0 Laser control Diode laser Optical coupler Hybrid cable Measurement path Smoke stack P T P R Reference cell Figure 6.7 Block diagram of LDS 6 The concentration of the measured gas is calculated from the absorption spectrum for the measurement channel (P T ). Any change in the measurement conditions, for example as a result of a higher dust load in the flue gas or contamination of the optical components, is compensated for automatically to guarantee the accuracy of the measurement results under a wide range of operating conditions. 6.4 Mode of Operation The operation of LDS 6 is based on the fact that light propagating through a gas mixture will be absorbed - obeying the Beer-Lambert law - at certain narrow wavelength bands. This is where the gases possess molecular transitions forming narrow absorption lines. The light source in LDS 6 is a semi-conductor laser tuned to an appropriate absorption line for the gas to be measured. The laser light is spectrally much narrower than the gas absorption line 64