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TGA Series Trace Gas Analyzers

1. fg Temperature MS PreAmp E Calculations Reference Sample Concentration Analog Input Temp 40 00 40 00 C Other TGA Temperatures PID control gain 0 03 Data Output Serial Numbers PID control tau 4 00 About TGA Themistor Rzero 4 95 Thermistor gain 4369 00 Themnistor offset FIGURE 7 15 Controlling the detector temperature settings Most TGAs have detector temperatures that are controlled by TE coolers The Temp parameter on the Reference and Sample tabs is the setpoint Set the detector temperatures to optimize the signal levels as discussed in Appendix D 3 Detector Temperature Some TGAs have LN cooled detectors for measuring absorption at longer wavelengths The temperature of these detectors is not measured or controlled For LN cooled detectors uncheck the Control detector temperatures box The rest of the detector parameters should be set to the defaults shown in FIGURE 7 15 The parameters for the sample detector are not shown but are the same as for the reference detector PreAmp The Settings gt Detectors gt PreAmp window and parameters are the same for both versions of the software and are shown in FIGURE 7 16 See Appendix D Optimizing Detector Parameters for details on optimizing the detector preamp parameters 7 2 3 3 Calculations TGA Series Trace Gas Analyzers rameter Settings Laser Temperature Current t Line Lock Other V Auto gain
2. sssssseeeeeeenen nene 31 6 1 1 Plumbing Connections 0 0 0 ccceecesecesecseeereeeseeeeeeeeeeeeeeeeenseensees 33 6 1 2 Data Output Connections 20 0 0 cee ceccesececeereeeseeeeeeeseeeeeeeeenteeneees 35 NMAMMd uS M M 37 6 2 TGA Software Installation sese 39 6 2 1 Installation of PC Software sssssssssseeeeee 39 6 2 2 Updating TGA Operating System sss 40 6 2 3 Configure Ethernet Connection sssssssseseeeee 42 6 2 4 Set TGA Serial Number and Identification String 45 6 2 5 R n the PC Software 4 neue eere ir eden 46 6 3 Detailed Setup Instructions ssssssssseseeeeeeeneenenee 46 EG runt 46 7 1 Routine Operatii ea a E ener 46 Telt Startup Procedure enaa aa ce Gagne negem 46 7 1 2 Routine System Checks sse 47 7 1 3 Shutdown Procedure sse 48 7 2 Software User Interface sssssssssssseeeeeeeeeeeeeneneneennn 49 7 2 1 Connect Window esee ee eed ner en 49 1 2 2 Stat s Window e eerie teens redet 51 17 2 3 Settings Window esee ee eee eren 52 4 2 3 1 LASS iss ecc de ete tete e Ore RH err dus 53 P2352 Detectors eR er eH ere etes etre tns 59 7 2 3 3 Calculations eene eee ree 61 TQ BA Oth r iiie eret eee tis 66 7 2 4 Laser Window eee reden 70 7 2 4 1 View Less View More sse 71 7 2 4 2 Tabbed Expand sse 72 7 24 3
3. the N2O CHA laser is not available for the TGA200A the ammonia laser is not available for the TGA200A The concentration of the reference gas 1s used to calculate the concentration of the sample gas therefore it must be entered into the TGA software The calculated sample concentration 1s scaled by this value If it is not correct the measured concentration will have a corresponding scale error For many trace gas flux measurement applications a measurement of the reference gas accurate to 2 is adequate A 5 Appendix A Configuring TGAs for Specific Gas Species NOTE A 3 Detectors For applications that require a more accurate concentration measurement the TGA may be calibrated using two well known calibration tanks as discussed in Appendix E Calibration For these applications the reference gas concentration provides only a preliminary estimate that is superseded by the measurements of the calibration gases This makes a highly accurate measurement of the reference gas concentration unnecessary The user must provide an appropriate regulator for the cylinder of reference gas The delivery pressure is normally set to approximately 0 psig and the flow is typically set to 10 ml min so the regulator should be chosen for good performance at low delivery pressure and flow The reference gas flow is generally set by a needle valve and monitored with a flow meter A reference gas connection assembly pn 15837 is avail
4. Status Settings Laser Find Graph Data Files FIGURE 7 4 Toolbar before top and after bottom connection 7 2 2 Status Window The TGA Status window displays the TGA laser and detector temperatures sample cell pressure and line lock status The toolbar will show one of two icons for the TGA status depending on whether or not an error is detected The lower panel of FIGURE 7 5 shows the Status icon of the TGA toolbar when an error has been detected 51 TGA Series Trace Gas Analyzers ORUA Status Settings Laser Find Graph Data Files Connection X A Settings n Find Ies E1 kd FIGURE 7 5 TGA Status with a detected error bottom Any detected errors will be highlighted in red with error messages displayed at the bottom as shown in the right panel of FIGURE 7 6 Laser Temp Smp Det Temp Smp Det Temp Ref Det Temp Ref Det Temp TGA Pressure TGA Pressure Lines Locked Lines Locked FIGURE 7 6 TGA Status window without error left and with error right and line lock manually disabled NOTE The TGA Windows is used for LN2 cooled lasers and reports the laser temperature in K The 7GA TEC software is used for TE cooled lasers and reports the laser temperature in C 7 2 3 Settings Window The Settings window is used to display and change parameters associated with the laser detectors calculations and other miscellaneous information In the Settings window the
5. The TGA200A Input Module pn 7730 is shown in FIGURE H 2 The blue label identifies this module as being updated for use with TE cooled lasers FIGURE H 2 TGA input module The TGA200A Output Module pn 7726 is shown in FIGURE H 3 The blue label identifies this module as being updated for use with TE cooled lasers eee a a U MEYN FIGURE H 3 TGA output module CAUTION Do not use unmodified input or output modules without the blue label for TE cooled lasers Do not use modified input or output modules with blue label for cryogenic lasers A mismatch between electronics and laser will damage the laser The input and output modules shipped with a TGA200 may be returned to the factory to be updated The modules will be reconfigured for TE cooled laser operation tested and identified by affixing a blue sticker NOTE If the input and output modules are upgraded to use with TE cooled lasers they may not be reconfigured for cryogenic lasers Users that may wish to go back to use a cryogenic laser at a later date should purchase new input and output modules for TE cooled laser operation The input and output modules mounted in the electronics are shown in FIGURE H 4 Appendix H Upgrading Early Generation TGAs to TE cooled Laser FIGURE H 4 Modules mounted into TGA200A electronics The TGA TEC software pn 30723 is an updated version of the TGA Windows software which has been modified for use with TE cooled las
6. H 1 3 Power Module Optionally the power supplies of a TGA200 may be upgraded to the pn 30981 TGA200A power module see Section 4 1 1 1 TGA Power Module for detail on the TGA200A power module This upgrade is not required to use the TE cooled laser but it is available in the event that the TGA200 s power supply fails This upgrade requires a special connector assembly to be mounted in the TGA200 Contact Campbell Scientific for details H 1 4 Purge Boot H 2 TGA100A The TGA200 was supplied with a purge boot between the laser dewar and the optical assembly The purge boot mounted to the front lens holder and pushed up against the laser dewar to enclose the air gap between the laser dewar and the lens The TGA200 purge boot can be pushed up against the TE cooled laser assembly in the same way as for the laser dewar If the purge boot becomes damaged it can be replaced with pn 21573 H 2 1 Basic Upgrade Upgrading a TGA100A is similar to upgrading a TGA200 It requires the same laser assembly input and output modules and software See Section 6 2 2 Upgrading TGA Operating System for details In addition to this basic upgrade a TGA100A may require the following upgrades Appendix H Upgrading Early Generation TGAs to TE cooled Laser H 2 2 Detectors If the TGA100A was supplied with LN2 cooled detectors these should be replaced with TE cooled detector assemblies Contact Campbell Scientific for availability Most TGA100As were
7. Dimensions and Part Numbers for Swagelok Inserts Tubing OD in Tubing ID in Swagelok pn CSI pn 1 4 1 8 B 405 2 15834 1 4 0 17 B 405 170 15830 1 4 3 16 B 405 3 15713 3 8 1 4 B 605 4 9845 1 2 3 8 B 815 6 17380 5 8 1 2 B 1015 8 19495 Ferrules Each Swagelok fitting comes assembled with the front and back ferrules included These ferrules are permanently swaged onto the tubing at the first assembly so spare ferrules may be needed for replacing the ends of tubing gt Back ferrule ON M w Front ferrule FIGURE G 2 Front and back Swagelok ferrules TABLE G 3 Dimensions and Part Numbers for Swagelok Ferrules Tubing OD in Swagelok pn front back CSI pn 1 set 1 8 B 203 1 B 204 1 N A 1 4 B 403 1 B 404 1 15890 3 8 B 603 1 B 604 1 15889 1 2 B 813 1 B 814 1 N A 5 8 B 1013 1 B 1014 1 N A G 3 Appendix G Using Swagelok Fittings Plugs Swagelok plugs are used to plug a fitting when its tube is disconnected It is strongly recommended to plug all fittings to keep them clean Spare plugs may be needed if they become lost or damaged FIGURE G 3 Swagelok plug TABLE G 4 Dimensions and Part Numbers for Swagelok Plugs Tubing OD in Swagelok pn CSI pn 1 8 B 200 P 26803 1 4 B 400 P 15891 3 8 B 600 P 13712 1 2 B 810 P 17381 5 8 B 1010 P N A Caps Swagelok caps are used to cap the end of tubes when they are disconnected
8. Example of using Laser Line Find function to determine laser threshold current Appendix C Optimizing Laser Parameters C 3 High Current Laser Current Laser Temperature Wavenumber temperature Wavenumber current Wavenumber combined Detector Response High current too low Equilibrates slowly The laser cools slightly at the start of the spectral scan when it is turned off by reducing its current to the zero current value as discussed in Section 4 2 5 Laser Scan Sequence If the actual spectral scan started immediately thereafter the laser temperature would rise during the entire spectral scan The rise in temperature would be more rapid at first but slow near the end of the scan as the temperature approached equilibrium The change in temperature would change the laser s emission frequency adding an undesired spectral modulation as illustrated in the far left panel of FIGURE C 6 To minimize this problem the laser current is increased above the DC current by an amount specified in the High current offset parameter The duration of this high current pulse is determined by the laser High current count parameter When these parameters are properly set the heat from the increased current compensates for the heat lost when the current is reduced stabilizing the laser temperature more quickly High current too high High current correct Overshoots onstant during ramp Positive slope Nearly
9. Modulation Current and initiate the line locking function For multiple ramp operation each of the ramps must be locked onto the proper absorption line If the expected absorption line is not found easily use the laser Find tool Section 7 2 5 Find A 5 Air Gap Purge For isotope ratio applications the air gap between the laser and lens and the short sample cell should be purged as shown in FIGURE A 1 TGA100 or TGA100A or FIGURE A 2 TGA200 or TGA200A This is not required for most trace gas applications where the ambient concentration is very low and there is very little absorption The sample cell is at low pressure making the sample absorption very narrow compared to the pressure broadened ambient absorption Thus the concentration measurement is relatively insensitive to trace gases in the ambient pressure air gap This is not the case however for CO or water isotope measurements where the ambient concentration is relatively high and can change rapidly for example if the cover of the TGA is off and a person in the vicinity exhales Because these types of applications require extremely high accuracy the air gap should be purged to prevent absorption A tank of compressed nitrogen should be connected to the purge inlet A flow of approximately 10 ml min is recommended The regulator on the user s tank may be connected to the purge using the flow meter needle valve and tubing included in the reference gas connection
10. New Values written to FLASH BMPSvr port 3000 listening Initialized TGA100A TGA200 TGA200A Pause StertExport SendFile FIGURE 6 20 Device configuration utility Terminal tab 6 2 4 Set TGA Serial Number and Identification String The TGA serial number and an identification string are stored in nonvolatile memory The serial number can be displayed and edited on the Settings tab of the Device Configuration Utility Set the serial number to match the serial number of your TGA The serial number for a TGA100 or TGA100A is found on the laser mounting plate inside the analyzer enclosure The serial number for a TGA200 or TGA200A is found next to the plumbing connections on the outside of the analyzer enclosure This setting allows the TGA Windows or TGA TEC software to verify it is connected to the proper TGA before sending parameters see Section 7 2 1 Connect Window 45 TGA Series Trace Gas Analyzers 46 The identification string is also displayed and edited on the Settings tab of the Device Configuration Utility The identification string is intended as a device nickname and to be a more user friendly way than the serial number by which to identify which TGA is connected to the PC software The identification string is displayed at the top of the toolbar when the TGA software is connected to a TGA The identification string can be any text up to 19 characters 6 2
11. TGA TOLAD OT eT oshisi eod e Re ret bere Re DER redes eds 22 TGA heated intake filter tete overhead 22 TGA filter element replacement sssssssssseeeeee 23 47 mm replacement filters essent 23 TGA100 and TGA100A optical configuration ess 24 TGA200 and TGA200A optical configuration esse 24 TGA laser scan sequence ssssssssssesseeeeneeenenen enne 26 Basic components required for TGA100 operation 30 Basic components required for TGA200 and TGA200A operation 31 TGA200A enclosure sees eene 31 TGA100 and TGA100A transport locks sees 32 TGA200 and TGA200A shipping clamps seesss 33 Feedthrough cover of TGA200A ssssssssseseseeeeeeee 33 Plumbing connections located under feedthrough cover of TCEA200 Aic ie eve e ete ebat qe e POTE e ER ca 34 SDM connections of TGA ssessssseeeeeeeeren eene 35 SDM cable connector on TGA CPU board esses 36 SDM cable tied to electronics box eee 36 DC power cable connected to TGA200A and secured on electronics boX 1 aieo n p e tH e te EI Pes 37 Routing of SDM and power cable through TGA200A feedthrough bracket nente erem ree te eid ds 38 TGA200A power module with cables installed 39 PC shortcut icons for TGA Windows left and TGA TEC right 40 S
12. The TGA100 and TGA100A have an optical assembly that includes a long sample cell a short reference cell and a short sample cell The beamsplitter of the early TGAs was located at the back of the instrument near the detectors TheTGA200 and TGA200A optical configuration has the beamsplitter at the front near the laser with similar long sample and reference cells The optical alignment hardware and shipping clamps are also different Temperature Control Early TGA100s had fans inside the enclosure to ensure all parts of the optical system in particular the sample cell and the reference cell remained at the same temperature but had no heater or temperature controller An optional accessory the TGAHEAT was introduced in 2002 TGAHEAT controlled power to a pair of heaters attached to fans which maintained the temperature of each end of the optical bench For TGA100As the TGAHEAT was included as a standard component Temperature control was improved in the TGA200 and TGA200A by controlling the temperature of the air at each end of the enclosure instead of the optical bench and including temperature control in the TGA Windows software This allows the temperature setpoint to be changed through software rather than opening the TGA enclosure to turn a potentiometer It also allows the user to monitor and record the fraction of power used for the heaters TGA100s with the TGAHEAT option and TGA100As that are running the TGA Windows or TGA T
13. by telephoning 435 227 9000 USA You are responsible for conformance with governing codes and regulations including safety regulations and the integrity and location of structures or land to which towers tripods and any attachments are attached Installation sites should be evaluated and approved by a qualified engineer If questions or concerns arise regarding installation use or maintenance of tripods towers attachments or electrical connections consult with a licensed and qualified engineer or electrician General e Prior to performing site or installation work obtain required approvals and permits Comply with all governing structure height regulations such as those of the FAA in the USA e Use only qualified personnel for installation use and maintenance of tripods and towers and any attachments to tripods and towers The use of licensed and qualified contractors is highly recommended e Read all applicable instructions carefully and understand procedures thoroughly before beginning work e Wear a hardhat and eye protection and take other appropriate safety precautions while working on or around tripods and towers e Do not climb tripods or towers at any time and prohibit climbing by other persons Take reasonable precautions to secure tripod and tower sites from trespassers e Use only manufacturer recommended parts materials and tools Utility and Electrical e You can be killed or sustain serious bodily injury if th
14. concentration should equal the reference gas concentration set to 1000 above Sample detector nonlinearity will cause the measured concentration to be underestimated If the measured concentration is too low increase the value of the sample detector linearity coefficient until the measured concentration is 1000 A typical value is 0 3 Repeat the previous step for each ramp if in multiple ramp mode Restore the plumbing to its normal configuration and set the reference gas concentration and cell length parameters back to their proper values Appendix E Calibration The predominant sources of error in the TGA s concentration measurement are the offset error caused by Fabry Perot interference and gain errors caused by errors in reference gas analysis or by different pressure or temperature in the reference and sample cells For eddy covariance or gradient flux applications the offset error cancels out and only the gain errors are significant For measurements of absolute concentrations the offset errors are also significant Therefore the appropriate calibration procedure depends on the application All applications will benefit from the basic span calibration described in the next paragraph It should be performed after the TGA has been set up as discussed in Section 6 Installation The TGA calibration may be checked by switching the sample inlet between two calibration tanks Normally one tank should have near ambient concentrat
15. that contains the laser mounted on a thermoelectric cooler equipped with a thermistor to measure its temperature The standard detectors used in the TGA are thermoelectrically TE cooled and operate at wavelengths up to 5 microns These detectors are used for most gases of interest including nitrous oxide N20 methane CH4 and carbon dioxide CO2 Some gases such as ammonia NH3 have the strongest absorption lines at longer wavelengths and require the optional long wavelength liquid nitrogen cooled detectors These detectors can operate to wavelengths beyond 10 microns The TGA200A uses only ICLs which cannot 25 TGA Series Trace Gas Analyzers 26 reach these long wavelengths Therefore the TGA200A always uses TE cooled detectors 4 2 5 Laser Scan Sequence The laser is operated using a scan sequence that includes three phases the zero phase the high current phase and the modulation phase This is illustrated in FIGURE 4 27 The modulation phase performs the actual spectral scan During this phase the laser current is increased linearly over a small range typically 0 1 to 1 0 mA The laser s emission wavenumber depends on its current Therefore the laser s emission is scanned over a small range of frequencies typically 0 03 to 0 06 cm During the zero phase the laser current is set to a value below the laser s emission threshold Zero signifies the laser emits no optical power it does not mean the
16. 192 168 5 8 Port 3000 Parameter Synchronization Receive Parameters from TGA Send Parameters to TGA TGA Connection Update Interval in ms 100 Backup Parameter Files Synchronized from TGA Load from Backup file Save to Backup File FIGURE 7 2 Connect window of TGA software interface To connect to a TGA enter the TGA s IP address To set the TGA s IP address use the Device Configuration software as described in Section 6 2 3 Configure Ethernet Connection Select Port 3000 which is always used for TGA PC communication Choose the Parameter Synchronization approach Normally this should be set to Receive Parameters from TGA This allows connecting to the TGA without disrupting its current settings The Send Parameters to TGA option can be used to restore parameters that had previously been backed up after loading the backup file If sending parameters to the TGA the software will first check to make sure the TGA serial number in the parameter file matches the serial number stored in the TGA s nonvolatile memory If the serial numbers do not match the software will not send the parameters to the TGA and the message shown in FIGURE 7 3 will be displayed If this happens verify the parameters are correct for the TGA and edit the serial number in the parameter file Section 7 2 3 4 Settings gt Other or in the TGA Section 6 2 4 Set TGA Serial Number and Identification String as
17. 5 Run the PC Software Start the TGA Windows for LN2 cooled laser or TGA TEC for TE cooled laser software which will bring up the toolbar Descriptions of the toolbar functions are given in greater detail in Section 7 2 Software User Interface 6 3 Detailed Setup Instructions Operation 7 1 When the TGA is first installed or if it is reconfigured for example with a new laser the operational parameters must be set for optimal performance Appendices A through E give detailed instructions to configure the TGA for a specific gas species performing the optical alignment optimizing the laser parameters optimizing the detector parameters and calibration If the TGA has already been configured see Section 7 1 1 Startup Procedure for routine startup instructions Routine Operation Once the TGA has been set up it should be checked periodically to verify proper operation and to perform routine maintenance Consistently recording operating parameters such as pressure and detector signals is strongly encouraged Significant changes in these values from one operational period to the next is often indicative of problems with the system Startup Procedure NOTE NOTE 1 This section describes the routine procedure for starting the TGA If the TGA is equipped with a LN cooled laser cool the laser dewar If the TGA is equipped with a TE cooled laser it will be cooled automatically 2 If the TGA is equipped with LN2 coole
18. 8 80 Laser 4 1 2 2 AC Mains Power Cord Depending on the geographic location the system is to be used detachable AC mains power cords are available from Campbell Scientific to accommodate local electrical requirements For reference the part numbers and associated geographic regions are summarized in TABLE 4 2 11 TGA Series Trace Gas Analyzers 12 TABLE 4 2 Available AC Mains Power Cords by Region Part Number Geographic Compatibility 13999 North America 18652 Continental Europe 18653 United Kingdom and Ireland 18672 Australia and New Zealand 19295 China 4 1 2 3 Power Module Mounting Brackets Various mounting brackets are available such that the TGA power module can be mounted at a location that is compatible to the measurement site and convenient for the user The mounting brackets available are summarized in TABLE 4 3 TABLE 4 3 Power Module Mounting Brackets Part Number Mounting Location 19002 Tripod Mast Mounting 18955 CMIXX Leg Mounting 19017 Tower Mounting 27390 Pole Mounting 10 25 cm 4 10 in diameter pole 18520 Pole Mounting 8 cm 3 in diameter pole 4 1 3 Common Accessories 4 1 3 1 TGA Reference Gas Connection A TGA reference gas connection pn 15837 is available for connecting a reference gas source to the TGA The assembly includes a flow meter needle valve 6 2 m 20 ft tubing and 1 4 in Swagelok fittings at either en
19. 8 Ib Power 140 W Pumping speed 1 slpm at 50 mb 60Hz Ambient temperature range for operation 10 to 40 C Ultimate vacuum lt 2 mb For detailed installation and operating instructions refer to the user manual supplied with the pump 4 1 4 5 Bypass Vacuum Pump Some TGA applications such as atmospheric profiles and chamber measurements use a sampling system to switch between multiple inlets These sampling systems require a bypass pump to maintain air flow through the non selected inlets The actual flow rate and pressure required will depend on the application Two bypass vacuum pump options are available from Campbell Scientific The DOAV502 has a capacity of 50 L min and is adequate for most low flow applications The DAAVOS L has a capacity of 100 L min and is used for higher flow applications The pumps are supplied with the tubing and fittings needed to connect to the sampling system A brief overview of each of the pumps is given in the following descriptions DOAVS502 Vacuum Pump The DOAVS502 shown in FIGURE 4 15 is a single head diaphragm pump that is often used with a trace gas analyzer system in low flow applications such as atmospheric profile or chamber measurements The DOAV502 comes with 30 m 100 ft of plastic tubing with an outer diameter of 1 27 cm 0 5 in and an inner diameter of 0 95 cm 0 375 1n FIGURE 4 15 DOAV502 vacuum pump DOAV 502 specifications Length 22 7 cm 8 9 in Width 16
20. 9 pin male serial data cable pn 20730 is included It is shown in FIGURE 4 7 The serial cable is used to connect the RS 232 port on the TGA to an RS 232 port on a user supplied PC f lt 7 ume FIGURE 4 7 Serial data cable 4 1 1 9 TGA TEC Support Software and Operating System Included is a CD pn 30723 that contains installation files for TGA TEC Support Software and current TGA firmware used to support the TGA200A or prior TGA models that have been upgraded to use a thermoelectrically cooled TE cooled laser TGA TEC is a user interface software package that allows users to connect to the analyzer set settings and monitor real time analyzer performance The TGA firmware includes the OS that must be uploaded to the analyzer s CPU board before operating a TEC laser The software 1s compatible with Windows XP operating systems or newer 10 TGA Series Trace Gas Analyzers TGA Windows Connected to sn 22205 eek ee Find Gah Dua Fhe j rl A IT Pi n Wi N A EA Xa NANI VA OTN ML y Sta WOWECXJ6O05H8 XS Hiro C Inbo 4 1 2 Optional Components 4 1 2 1 Laser Depending on the gas to be measured the TGA200A can be configured with any one of the five lasers described in TABLE 4 1 TABLE 4 1 Part Numbers for Available Gas Species Lasers Part Number Description 30478 N20 Laser 30477 CH Laser 31121 N20 and CO Laser 31119 CO and 6P C Laser 30877 CO 52C and
21. B 7 B 8 and B 9 To use the alignment tool place it against the tip tilt screws Back the screws out as needed to allow the gage to fit against the screw threads Then screw the screws in until the heads of the screws just touch the gage Back the screws out just enough to remove the tool The tip tilt mirrors will now be at their nominal positions FIGURE B 7 shows the positioning of the alignment tool for the screws for the mirror in the beamsplitter block The view is from the user s perspective FIGURE B 8 shows the same scenario but from a different perspective The figure illustrates the way that the alignment tool fits against the screws FIGURE B 9 illustrates how the alignment tool fits against the detector tip tilt screws Refer back to FIGURE B 5 and FIGURE B 6 for the positioning of the mirror tip tilt screws B 10 Appendix B Optical Alignment FIGURE B 7 Use of alignment tool for aligning mirror in TGA beamsplitter block FIGURE B 8 Use of alignment tool for aligning mirror in TGA beamsplitter block alternate angle Appendix B Optical Alignment FIGURE B 9 Use of alignment tool to position tip tilt screws for aligning detector side mirrors 7 Adjust the horizontal and vertical alignment knobs to look for the sample detector signal and then proceed to the next section If no response is observed contact Campbell Scientific for assistance B 2 3 Horizontal and Vertical Alignment Once the system is al
22. Det Signal CO2 Laser DC Current CO2 Smp Transmittance CO2 Ref Transmittance CO2 Ramp B Ramp C Isotope Ratios Miscellaneous Laser Temperature Laser Heater Pressure TGA analog input TGA Temp 1 TGA Temp 2 Duty Cycle TGA Heater 1 Duty Cycle TGA Heater 2 Detectors OO EH Cancel FIGURE 7 40 Options for graphical display of data in TGA Windows TGA TEC The steps to select data to be graphed are slightly different for TGA TEC Click on a parameter edit the options if necessary and then press Add as shown in FIGURE 7 41 Repeat these steps to add more parameters to the graph An example of the graphical output of the TGA TEC is shown in FIGURE 7 42 85 TGA Series Trace Gas Analyzers g5 Line Width 1 E Num Decimal Points 3 E Do Not Plot in Graph FIGURE 7 41 Adding parameters to a graph in TGA TEC Ia uw OS ZC vtr OFS Data Values U N20 Conc StdDev 0 0011 ppm N20 Conc 0 281 ppm il Graph Width Auto 1m23s Manual 8 58 52 8 59 02 8 59 12 8 59 22 8 59 32 8 59 42 FIGURE 7 42 Example graph showing N2O concentration and standard deviation Clicking Options will bring up a window to add remove or change the way a trace is shown or to change the axes or the other visual aspects of the graph The Add button can also be used to add traces 86 7 2 7 Data TGA Series Trace Gas Analyzers Keeping the Graph Wi
23. Ifthe laser is to be operated again in the near future it is recommended to keep the laser cold to avoid temperature cycling the laser e Ifthe TGA will not be used for an extended period allow the laser to warm up and evacuate the dewar 7 2 Software User Interface When the TGA program is started as described in Section 6 2 5 Run the PC Software the toolbar is displayed as shown in FIGURE 7 1 The functions are listed below and described in greater detail in the following sections an Graph ki Files Status Settings m vy Find Data x Laser FIGURE 7 1 TGA tool bar functions Connect Connect or disconnect from TGA set the data interval and save and load parameter files Status Display TGA status Settings Display and change parameters Laser Display reference and sample signals and modify laser parameters Find Find the absorption line s Graph Set up and display real time graphs of TGA measurements Data View TGA measurements in numerical form Files Collect TGA data to the PC hard disk 7 2 1 Connect Window The Connect window is used to connect or disconnect from the TGA set the IP address of the TGA to communicate with set the interval at which the software updates data from the TGA and to save and load parameter files The Connect window is shown in FIGURE 7 2 49 TGA Series Trace Gas Analyzers 50 Connection mx Connect To
24. Laser Temperature Col 5 C02 Conc StdDey Selection Col 6 Laser Heater Col 6 13C Conc Conc Col 7 Laser DC Current CO2 Col 7 Mean 13C Conc Detectors Col 8 Pressure Col 8 13C Conc StdDev RAE Col 9 TGA Temp 1 Col 9 180 Conc 5 Col 10 TGA Temp 2 Col 10 Mean 180 Conc Misc Col 11 TGA Status Flags Col 11 180 Conc StdDev Advanced Col 12 Del13C File Names Col 13 Mean Del13C Sai sais bao Other Col 16 Mean Del180 Event Log Col 17 Del180 StdDev Col 18 Ref Det Temp Col 19 Ref Det Cooler Col 20 Ref Det Gain Col 21 Ref Det Offset Col 22 Ref Det Signal CO2 Col 23 Ref Transmittance CO2 Col 24 Ref Det Signal 13C Col 25 Ref Transmittance 13C Col 26 Ref Det Sianal 180 z FIGURE 7 44 Controlling PC recorded data options in the TGA The Settings column in the Data Files window is used to select what is displayed on the remainder of the window Files display the names of the values set up to be collected File Lists Show the values in both the Data File and Housekeep Data File Set ASCII or Binary output Data File List just the data file Housekeep File List just the Housekeeping file The Housekeep file contains all data Selection Chose the values to be stored in the data file Conc Chose the concentrations and isotope ratios to store Detectors Chose the detector values to store Laser Chose the Laser values to store Misc Chose the miscellaneous v
25. Rate eie ti epi t ed e RORR F 1 F2 Sample R te sued te end Incem eme pet F 1 E3 Digital Filters a suos dat eo an ena ea ea tt ent F 2 Feds Synchtronicity recette en Oe CREE F 4 F 5 Sample Cell Residence Time sse F 5 Table of Contents G Using Swagelok Fittings G 1 Gil General Notes doin toii a a nte G 1 G2 Assembly sedes ota sehe aie G 1 G 3 Common Replacement Parts ssssesssssseeeeeene G 2 H Upgrading Early Generation TGAs to TE cooled Laser H 1 FL x TGA DOO bes rire ertet ee eig eee erede H 1 Hille Basic Upgrade ueteres eR RSS H 1 H12 Detectot I a H 4 H 13 Power Module tiere E EO R H 4 HAE Purge Boot onset tercie rene eerte ess H 4 H2 TGXAIO0A nitet tete temet ette eee tete ettet H 4 H 2 T Basic Upgrade tieess ost e H 4 H22 Detects nan eed Ee ie tese mete RA HERE H 5 H 2 3 Holes in Enclosure for Cryocooler Refrigerant Tubes H 5 H 2 4 Temperature Control Upgrade sese H 5 H 2 5 Power Module 2 N eee bn OE H 6 H 2 6 Puree Boot enedonisetabne aet ad H 6 H3 TGAL00 oon d etie a d tente mer e te et ire ets H 6 H 3 I Basic Upgrade s aseos v ausa eene ba ep H 6 IT 3 2 CPU Module on pen Aen o e pede H 6 H 3 3 Input and Output Modules sse H 6 H 3 4 Detectors and Detector Cables sssssssssss H 7 H 3 5 Temperature Contro
26. Status window see Section 7 2 2 Status Window Record the DC current and compare it to the expected value An abrupt change in the DC current may indicate the laser has shifted to 47 TGA Series Trace Gas Analyzers 48 another absorption line A persistent trend over time in the DC current may indicate premature aging of the laser Record the reference transmittance and compare it to previously recorded values A change in the reference transmittance may indicate a problem with the reference gas supply It can also be caused by a shift to a different absorption line or a change in the pressure or temperature in the sample cell Record the sample pressure and compare it to previously recorded values If the TGA sample pressure is actively controlled by the datalogger a change in the pressure indicates a problem with the flows and pressures in the sampling system If the pressure is not actively controlled it will be determined by the sample flow and the pump capacity In this case the pressure will decrease over time as the sample intake filter s becomes plugged If the TGA is equipped with a LN cooled laser record the laser heater voltage and compare it to previously recorded values The vacuum inside the laser dewar will gradually degrade This degradation reduces the thermal isolation between the outer wall of the laser dewar and the laser itself Over time as more heat is transferred to the laser by the degraded vacuum les
27. Temperature K FIGURE C 3 Typical concentration noise as a function of laser temperature In some cases the minimum concentration noise may be at a different laser temperature than the minimum reference transmittance If the DC current is near the laser threshold current the laser s optical power output may be reduced significantly at higher laser temperatures lower DC current This can be verified by looking at the sample detector signal as a function of laser Appendix C Optimizing Laser Parameters temperature This is shown in FIGURE C 4 for the example described in the figures above Sample Signal mV 102 5 103 103 5 104 104 5 105 105 5 Laser Temperature K FIGURE C 4 Typical sample detector signal as a function of laser temperature In this case it may be possible to compensate for the reduced laser power by reducing the detector temperatures see Appendix D 3 Detector Temperature If adjusting the detector temperatures results in low concentration noise at the laser temperature which gives the minimum reference transmittance this is the optimal laser temperature The other condition that can give a different optimum laser temperature for reference transmittance and concentration noise is that in which the position of a mode hop may also move with laser temperature If the laser has a mode hop near the absorption line the concentration noise may increase as the mode hop approaches the
28. also slightly different for an initial installation than for subsequent reassembly First time assembly plastic tubing 1 Cut the tubing to length 2 Make sure the cut is square and free of burrs 3 Some types of plastic tubing have an aluminum layer Take care not to flatten the tube as you cut it 4 Push an insert into the end of the tubing 5 Do not remove the nuts and ferrules from the fitting Simply insert the tube into the assembled fitting until it bottoms out 6 Rotate the nut finger tight 7 While holding the fitting body steady tighten the nut one and one quarter turns For 1 16 in or 1 8 in sized fittings tighten the nut three quarters turn G 1 Appendix G Using Swagelok Fittings First time assembly metal tubing Extra care is needed to avoid overtightening brass fittings when used with metal tubing These notes apply to reducers and port connectors as well as metal tubing NOTE No insert is required with metal tubing 1 Do not remove the nuts and ferrules from the fitting Simply insert the tube into the assembled fitting until it bottoms out 2 Rotate the nut finger tight 3 While holding the fitting body steady tighten the nut until it feels tight This will normally be less than one full turn Tightening a full one and one quarter turns will damage the threads on the fitting and nut Reassembly plastic or metal tubing You may disassemble and reassemble Swagelok tube fittings
29. are shown in TABLE F 2 The processing lag for a 100 ms moving average is shown for comparison in TABLE F 2 The lags are different for each ramp in two ramp A B or three ramp mode A B C The filters are designed with these different lags to correct for the fact that the three ramps are not measured at the same time Ramp B is measured 2 ms after ramp A and ramp C is measured 4 ms after ramp A The concentration measurements for all three ramps are synchronized when using the EC filter option The moving average lag is half the moving average time and is the same for all ramps The concentration measurements for multiple ramps are not synchronized when using the moving average Appendix F TGA Frequency Response TABLE F 2 Processing Lags for EC filters Ramp A Ramp B Ramp C EC filter 1 ramp 372 EC filter 2 ramp 750 748 EC filter 3 ramp 746 744 742 100 ms moving average 50 50 50 TGA measurements are triggered by the TGA s internal clock asynchronous of any SDM or analog data acquisition system The synchronicity of correlated measurements for example sonic anemometer data and TGA data in an eddy covariance system will be limited by how often the TGA updates its measurement This update time varies from 2 ms to 6 ms depending on the measurement mode one two or three ramps the digital filter and the output mode The different times are summarized in TABLE F 3 The maximum del
30. as programming to customer specifications electrical connections to Products manufactured by CSI and Product specific training is part of CSI s product warranty CSI EXPRESSLY DISCLAIMS AND EXCLUDES ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE CSI hereby disclaims to the fullest extent allowed by applicable law any and all warranties and conditions with respect to the Products whether express implied or statutory other than those expressly provided herein Assistance Products may not be returned without prior authorization The following contact information is for US and international customers residing in countries served by Campbell Scientific Inc directly Affiliate companies handle repairs for customers within their territories Please visit www campbellsci com to determine which Campbell Scientific company serves your country To obtain a Returned Materials Authorization RMA contact CAMPBELL SCIENTIFIC INC phone 435 227 9000 After an application engineer determines the nature of the problem an RMA number will be issued Please write this number clearly on the outside of the shipping container Campbell Scientific s shipping address is CAMPBELL SCIENTIFIC INC RMA 815 West 1800 North Logan Utah 84321 1784 For all returns the customer must fill out a Statement of Product Cleanliness and Decontamination form and comply with the requirements specified in it The fo
31. but other power options are available The capacity of the RB0021 L is adequate for most high flow TGA applications such as eddy covariance It ships with 2 54 cm 1 0 in ID suction hose pn 7123 length specified per the order and 2 qts of pn 8143 oil The pump is shown in FIGURE 4 13 FIGURE 4 13 RB0021 sample pump 15 TGA Series Trace Gas Analyzers RB0021 L specifications Length Width Height Weight Power Pumping speed Ambient temperature range for operation Ultimate vacuum 44 2cm 17 4 in 29 2 em 11 5 in 26 9 cm 10 6 in 19 kg 42 Ib 950 W 18 slpm at 50 mb 60Hz 10 to 40 C 2 mb For detailed installation and operating instructions refer to the user manual supplied with the pump XDD1 Sample Pump The XDD1 is a four head three stage diaphragm pump It is modified to include a bleeder filter and needle valve a 1 2 in Swagelok fitting for connection to the TGA and a 1 4 in Swagelok fitting for connection to a pressure controller shown in FIGURE 4 14 It ships with 15 2 m 50 ft ofa 1 27 cm 0 5 in OD LDPE tubing pn 25539 The pump can be used on AC mains supplies ranging from 100 to 120 Vac 50 or 60 Hz or 200 to 230 Vac 50 or 60 Hz selected by a voltage changeover switch FIGURE 4 14 XDD1 sample pump XDDI specifications Length Width Height 16 31 3 cm 123 in 14 4 cm 5 7 in 21 5 cm 8 5 in TGA Series Trace Gas Analyzers Weight 6 7 kg 14
32. cable ties evenly spaced Route the cable through the hole in the electronics mounting bracket and fasten with a cable tie Appendix I Install Temperature Control Upgrade Fasten the other thermistor probe to the sample cell midway between the laser dewar and the electronics assembly using cable ties See the final configuration in FIGURE I 3 FIGURE 1 3 Location of second thermistor probe attachment Fasten the cable to the sample cell with three cable ties evenly spaced Route the cable through the hole in the electronics mounting bracket and fasten with a cable tie Remove the RTD connectors RTD 1A RTD 1B RTD 2B RTD 2A from the temperature control module Remove the jumper wires that tie these connectors to the analog inputs Wire the thermistors into the analog inputs as described below and referring to FIGURE I 4 1 2 G no connection 3 white of thermistor 1 detector end 4 green of thermistor 1 detector end G black and shield of thermistor 1 detector end 5 white of thermistor 2 laser end 6 green of thermistor 2 laser end G black and shield of thermistor 2 laser end 7 8 G pressure sensor Left pin of EXT Red wires from both thermistors and the pressure sensor Appendix I Install Temperature Control Upgrade xi 3 TGAN ein fh RTD IA RTD 18 FIGURE l 4 Thermistor cable wiring to analog inputs 1 2 Connect the Control Cable Connect the control cable to the CSIO por
33. can be found perform the following checks e If two lasers are installed verify they are aligned to the correct laser e Verify the dewar cable is installed correctly if two or more lasers are installed verify the correct cable is being used e Verify the detector cables are correctly installed e Verify the laser is enabled in the TGA program e Recheck the laser temperature and the settings for zero DC modulation and high current If a detector response is still not observed Contact Campbell Scientific for assistance B 1 2 Horizontal and Vertical Alignment NOTE Once the system is aligned well enough to see a response in the sample detector follow these steps to optimize the horizontal and vertical alignment Adjust the horizontal alignment screw see FIGURE B 3 to maximize the sample detector signal The sample and reference signals may not reach their maxima simultaneously If so ignore the reference detector signal and adjust the alignment to maximize the sample detector signal Adjust the horizontal position past the peak in each direction far enough to make sure there is a single response peak If there is a single peak leave it at the center of the peak If there are multiple peaks leave the horizontal alignment at the center of the group of Some older systems used a relatively coarse pitch screw for the horizontal alignment at the laser end and a second horizontal adjustment screw at the detector end This scr
34. cell containing a prepared reference gas having a known concentration of the target gas The reference signal provides a template for the spectral shape of the absorption line allowing the concentration to be derived independent of the temperature or pressure of the sample gas or the spectral positions of the scan samples The reference signal also provides feedback for a digital control algorithm to maintain the center of the spectral scan at the center of the absorption line The simple optical design avoids the alignment and contamination problems associated with multiple path absorption cells The number of reflective surfaces is minimized to reduce errors caused by Fabry Perot interference TGA Series Trace Gas Analyzers CPU The TGA100 used a CPU module based on transputers These CPU modules had limited processing capability so the TGA100 required a DOS PC with another transputer on an expansion card to be connected in real time via a fiber optic cable The TGA100A used a new CPU module with sufficient processing power to make the PC unnecessary This transformed the TGA from a PC based system to a synchronous device for measurement SDM sensor Most of the TGA100s have been upgraded to this new CPU module Contact Campbell Scientific if you have questions regarding this upgrade Software There have been four generations of TGA software The TGA100 software was distributed between three microprocessors the transputer in the TGA100
35. current is zero The zero phase is used to measure the detector s dark response The reduced current of the zero phase dissipates less heat in the laser causing it to cool slightly The laser s emission frequency depends on its temperature as well as its current Therefore the temperature perturbation caused by reduced current during the zero phase introduces a perturbation in the laser s emission frequency During the high current phase the laser current is increased above the current to be applied during the modulation phase to replace the heat lost during the zero phase This stabilizes the laser temperature quickly minimizing the effect of the temperature perturbation The entire scan sequence is repeated every 2 ms Each scan is processed to give a concentration measurement every 2 ms 500 Hz measurement rate Modulation Phase High Current Phase Spectral Scan Temperature Stabilization Laser Current Zero Phase Laser Off Omitted Used in Calculation er Detector Response 2ms FIGURE 4 27 TGA laser scan sequence TGA Series Trace Gas Analyzers TGAs can be configured to measure two or three gases simultaneously by alternating the spectral scan wavelength between nearby absorption lines This technique requires that the absorption lines be very close together within about 1 em Given this it can only be used in very specific cases The multiple ramp mode is used to measure isotope ratios
36. discontinuity was caused by a mode hop this indicates the end of the temperature tuning range for the selected absorption line It is generally not necessary to actually plot the data For reference FIGURE C 1 shows a graph of a typical data set where the same absorption line is scanned with a range of temperatures Laser DC Current mA 102 5 103 103 5 104 104 5 105 105 5 LaserTemperature K FIGURE C 1 Typical laser DC current as a function of temperature Next look at the reference detector transmittance as a function of temperature The transmittance should have a minimum at the optimum laser temperature It should be higher at temperatures above and below the optimum temperature This increased transmittance results from an increased fraction of the laser s energy at undesired frequencies multimode operation Again it is usually not necessary to plot the data but FIGURE C 2 shows a typical example Appendix C Optimizing Laser Parameters Reference Transmittance 102 5 103 103 5 104 104 5 105 105 5 Laser Temperature K FIGURE C 2 Typical reference transmittance as a function of laser temperature Optionally look at the concentration noise as a function of temperature The concentration noise should generally have a minimum at the optimum laser temperature as determined by the minimum reference transmittance This is illustrated in FIGURE C 3 Concentration Noise ppb 104 Laser
37. factory and is stored in nonvolatile memory Ifthe memory storing the MAC address becomes corrupted it will be displayed as all zeros 0x000 To reenter the MAC address execute the following steps 1 Power down the TGA 43 TGA Series Trace Gas Analyzers 2 Remove the CPU module and note the serial number Convert the serial number from decimal to hexadecimal base 16 Web based converters are available FIGURE 6 19 shows an example converting serial number 1458 to it representation in hexadecimal 5B2 File Edit Viev 01 Decimal to Hexadecimal Converter wow binaryhexconverter com decimal to hex converter B Most Visited Getting Started Suggested Sites Web Slice Gallery BinaryHex Converter Decimal to Hexadecimal Converter To use this decimal to hex converter tool you have to type a decimal value like 79 into the left field below and then hit the Convert button Therefore you can convert up to 10 decimal characters to hex DEI 3 109 Decimal Value max 9 digits Hexadecimal Value 1458 582 Converter Decimal to hex conversion result in base numbers 1458 10 5B2 i6 v v Firefox automatically sends some data to Mozilla so that we can improve your experience Choose What I Share Xx FIGURE 6 19 Web based decimal to hexadecimal converter 3 Reinstall the CPU module and power up the TGA 4 Connect to the TGA with Device Configuration Utility 5 Select Termina
38. far left side provides drop down menus which allow the user to set the parameters or retrieve additional information for each of four major categories e Laser e Detectors e Calculations e Other The left panel is shown in FIGURE 7 7 with the submenu for each category expanded The submenus are explained in the following sections 52 7 2 3 1 Laser CAUTION TGA Series Trace Gas Analyzers Laser Temperature Current Line Lock Other Detectors Temperature PreAmp Calculations Concentration Analog Input Other TGA Temperatures Data Output Serial Numbers About TGA FIGURE 7 7 Expanded view of the menu in the TGA s Settings window Temperature The Settings gt Laser gt Temperature window is different for TGA Windows and TG TEC TGA Windows FIGURE 7 8 supports LN2 cooled lasers that measure temperature in K and have a heater to control their temperature above the LN tank temperature TGA TEC FIGURE 7 9 supports TEC lasers that measure temperature in C and have a TE cooler to control their temperature The laser temperature setpoint should be set and optimized for the individual laser See Appendix C 1 Laser Temperature for details on how to set the laser temperature The laser temperature may also be set from the Laser window see Section 7 2 4 Laser Window The maximum laser temperature K or C provides a safety shutdown If the laser is warmer than this the TGA will automatically turn
39. filter which is implemented as a convolution of the data with a filter function There are 5 sets of filter coefficients This allows the user to select the passband 1 2 3 4 or 5 Hz The graph below shows the FIR filter coefficients The five blue curves are for the 1 2 3 4 and 5 Hz passband EC filters The 5 Hz passband filter is the tallest narrowest one A moving average can also be thought of as an FIR filter with uniform weighting For comparison FIGURE F 1 shows the red curve as the filter coefficients for a 100 ms moving average Time sec FIGURE F 1 EC filter coefficients FIGURE F 2 shows the frequency response of the filters An ideal filter would have a flat response in the passband and drop to zero at the passband cutoff The EC filters blue curves are very flat to just beyond the passband cutoff and then roll off to near zero by about 5 Hz above the passband cutoff The graph includes the 100 ms moving average frequency response red for comparison The moving average shows no truly flat passband and it rolls off more slowly than the EC filters No units No units o r 0 001 0 0001 1e 005 4 0 A Appendix F TGA Frequency Response Hertz FIGURE F 2 EC filter frequency response linear scale FIGURE F 3 graphs the same frequency response curves as shown in FIGURE F 2 but with a logarithmic Y axis and an extended frequency range to show the attenuation beyond the pas
40. offset Detectors Temperature D IPreAmp Preamp gain 45 00 Automatically adjust detector gain offset Calculations et Concentration Reference Sample Analog Input B Other TGA Temperatures Data Output Offset 4 Serial Numbers About TGA CH4 linearity coeff 0 000 Gain 3 AI iial FIGURE 7 16 PreAmp window default settings Concentration The Settings gt Calculations gt Concentration window and parameters are the same for both versions of the software The TGA measures the gas concentration every 2 ms and applies a digital filter to these measurements before they are output The top section of the Settings gt Calculations gt Concentration window as shown in FIGURE 7 17 allows the user to select the type of digital filter either a moving average or a finite impulse response FIR filter that is optimized for eddy covariance applications If Moving average is selected enter the averaging time in ms If EC filter is selected enter 1 2 3 4 or 5 depending on the amount of filtering that is desired See Appendix F TGA Frequency Response for details 61 TGA Series Trace Gas Analyzers 62 nIm ES TGA Parameter Settings x Laser Concentration Filter Current Line Lock Moving average ms 100 Other d a Detectors y EC filter Hz 1 Temperature PreAmp Reference Gas Concentration Caladations CHA 500 00 Co
41. so the temperature must be stabilized at the start of each spectral scan Overdriving the current as discussed in Section 4 2 5 Laser Scan Sequence can help to stabilize the laser temperature more quickly but setting the zero current as high as possible minimizes the temperature perturbation The TGA Windows software has an Auto button for setting the Zero current In some cases this function gives an incorrect result The suggested procedure for setting the zero current for all lasers is given below This automatic function has been removed from the TGA TEC software Set the zero current to 0 mA Run the Laser Line Find refer to Section 7 2 5 Find starting with the DC current at 0 mA View the resulting graph to determine the laser s threshold current DC current at which the reference voltage begins to rise In the example shown in FIGURE C 5 the reference signal is near zero up to a DC current of 50 mA and rises steeply beyond 50 mA This is the laser s threshold current Set the Zero current to approximately 90 of the threshold current 45 mA in this example For multiple ramp mode set the zero current to this value for each ramp In some cases the zero current may be reduce below this value for some ramps see 0 High Current gt E o a m o gt n o c D iz D 2 D a 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 Laser Find 8 00 DC Current mA FIGURE C 5
42. sss B 1 Bihl Initial Alignment einer B 4 B 1 2 Horizontal and Vertical Alignment sess B 5 B 1 3 Focus Adjustment sse eie eer enda B 6 B 1 4 Reference Detector Coalignment sse B 7 B 2 Optical Alignment of TGA200 and TGA200A sss B 7 B 2 1 Configure the TGA PC Software B 9 B22 Initial Alignment esee eie eda B 9 B 2 3 Horizontal and Vertical Alignment sssssssss B 12 B24 Focus Adjustment tte etie tI RR TI NETUS B 13 C Optimizing Laser Parameters C 1 Colt Laser Temperatute t retro eq ae qas C 1 42 Zero Currentses see E datei eee ae OP C 5 9 igh Currents sn tdeo ete ee eee C 7 C 3 1 High Current Count sssssssssseeeeeeeeenenenee C 10 CA Omitted Data Count eee eene C 11 C 5 Modulation Current esee nennen C 11 C 6 Laser Maximum Temperature and Laser Maximum Current C 12 C 7 Laser Multimode Correction seen C 12 D Optimizing Detector Parameters D 1 D 1 Detector Gain and Offset sssssssssssssseeeeeeene D 1 D Detector Preamp Gan i aree re E D 1 Di3 Detector Temp rature uie etre i beoe eere D 1 D 4 Detector Linearity Coefficients sssssssssseeeeee D 2 E Calibration uiii tice oor ERR ERE 132 SA pep sa ducens E 1 F TGA Frequency Response F 1 F 1 Measurement
43. stored in two places in the parameter file and in the TGA s nonvolatile memory These serial numbers must match in order for the PC software to be connected to the TGA as discussed in Section 7 2 1 Connect Window The TGA serial number may be edited only when the TGA is disconnected Use extreme caution when sending parameters to the TGA to make sure the correct parameters are being sent If the wrong parameters are sent for the laser in the TGA the laser may be damaged The TGA description is intended as a device nickname and to be a more user friendly way than the serial number by which to identify which TGA 1s connected to the PC software It may be set only through the Device Configuration Utility see Section 6 2 4 Set TGA Serial Number and Identification String The identification string is displayed at the top of the toolbar when the TGA software is connected to a TGA The serial numbers for the laser dewar and detectors provide a historical record in case these components are replaced by the user TGA Series Trace Gas Analyzers The site name description allows the user to enter text to describe the physical location of the TGA This is stored in the parameter file as a historical record Laser Temperature Current Line Lock H t Other 5 Detectors i PreAmp Calculations Concentration E Other i TGA Temperatures Data Output zx serial Numbers About TGA Temperature Analog
44. supplied with TE cooled detectors and require no changes to the detectors or detector cables H 2 3 Holes in Enclosure for Cryocooler Refrigerant Tubes If the TGA100A was supplied with a cryocooler system for the laser the end of the TGA enclosure has feedthrough holes for the refrigerant tubes The feedthrough grommets may be removed and the holes plugged with pn 15542 hole plug and pn 23 nut two of each required This is not required for the TE cooled laser upgrade but it is recommended to seal the holes previously used for the cryocooler refrigerant tubes Most TGA100As shipped with an LN dewar for the laser and already have the hole plugs installed FIGURE H 5 shows the feedthrough grommets for the cryocooler refrigerant tubes and the holes plugged with the recommended hardware FIGURE H 5 Cryocooler feedthrough holes with grommets above and plugs below H 2 4 Temperature Control Upgrade TGA100As shipped with a temperature control module that provided power to fans and heaters inside the enclosure to maintain temperature at each end of the enclosure The original design worked independently from the TGA electronics and software A temperature control upgrade is available to allow the TGA temperature to be controlled through software The temperature control upgrade includes thermistor probes and a control cable It gives more a more accurate temperature measurement the convenience of software control and provides bette
45. the laser current off to protect the laser This limit should be set for the individual laser Setting the maximum laser temperature parameter above a laser s safe operation temperature greatly increases the risk of damaging the laser The parameters on the bottom part of the window should normally be set to the factory defaults as shown for each type of laser in FIGURE 7 8 and FIGURE 7 9 53 TGA Series Trace Gas Analyzers i TGA Temperatures Data Output j Serial Numbers Laser Temperature Laser temperature set point K Laser temperature measured Maximum Laser Ratings Maximum laser temperature K Laser Temperature Calculations Laser temperature slope K V Laser temperature offset K Laser Heater Calculations Laser heater update interval Laser heater control gain Laser heater control zero Hz Laser heater control pole Hz FIGURE 7 8 TGA Windows laser settings Data Output Serial Numbers Laser Temperature Laser temperature set point C Laser temperature measured Maximum Laser Ratings Maximum laser temperature C Laser Temperature Calculations Thermistor Rzero Themnistor gain Thermistor offset Laser Cooler Calculations Laser cooler update interval Laser cooler control PID gain Laser cooler control PID tau FIGURE 7 9 TGA TEC laser settings 54 CAUTION TGA Series Trace Gas Analyzers Current The Settings gt Laser gt Current window is sli
46. the relevant section below for details B 1 Optical Alignment of TGA100 and TGA100A The TGA100 and TGA100A have a simple robust optical design that makes it easy to adjust and maintain its optical alignment The optical system illustrated in FIGURE B 1 includes the laser a collimating lens in front of the laser a beamsplitter to reflect some of the laser s energy onto the reference detector and two focusing lenses mounted in front of the sample and reference detectors Reference To pump Sample amp detector JU N2 Beamsplitt NOTE defector 4 Reference gas in Dewar Sample cell EM laser iw To pump Sample in FIGURE B 1 TGA100 and TGA100A optical layout To adjust the TGA100 and TGA100A optical alignment complete the following steps 1 Loosen the transport lock screw and axial lock screw at the detector end refer to FIGURE B 2 These screws should both be loose during all periods of operation to allow the detector end to move slightly as the length of the long sample cell changes with temperature The transport lock screw and axial lock screw should be tightened only for transporting the TGA B 1 Appendix B Optical Alignment NOTE FIGURE B 2 shows the horizontal adjustment screw that was included with older units Newer units use a fine pitch horizontal adjustment screw at the laser end which makes horizontal adjustment at the detector end unnecessary Horizontal
47. the transputer in the PC and the PC itself The PC provided the user interface as well as storing data on the hard drive The TGA100A which included the new CPU module separated the TGA firmware operating system of the TGA itself from the user interface software which ran on the user s PC With this upgrade the TGA became a stand alone sensor and the PC became necessary only to check and adjust the operation of the TGA The second generation of the interface software ran only under DOS PCs The third generation of user interface software TGA Windows was developed for the TGA200 TGA Windows greatly improves the ease of use and allows the use of a modern PC running a Windows operating system This software is available as an upgrade for both the TGA100 with CPU upgrade and TGAI00A The fourth generation software TGA TEC is a minor update to the TGA Windows software that is compatible with the thermoelectrically TE cooled lasers used in the TGA200A TGA Windows and TGA TEC are not mutually compatible TGA Windows is used only with LN2 cooled lasers and TGA TEC is used only for TE cooled lasers A representative screen of the TGA Windows software is shown in FIGURE 4 1 TGA Series Trace Gas Analyzers 9 Laser Settings TGA windows Connected to sn 1110 miz View Less Ta M ified v Colors pr lt Fics DE carent EZEK DE cieni EZE CO2 Conc 180 Conc T FRE Wa 2 Manual a FIGUR
48. to access in the field It allows the convenience of replacing the entire heated filter holder in the field and then opening the filter holder to replace the filter element later If there is convenient access to the sample intakes a lower cost option is to simply replace the filter element pn 17575 FIGURE 4 22 TGA heated intake filter The filter element pn 17575 is a 7um pore size filter element used in Swagelok 1 4 in inline filter holders pn 17574 It is used as a replacement element for the heated filter pn 18058 heated filter amp orifice pn 18072 and the PD625 sample air dryer The replacement filter element is shown in FIGURE 4 23 TGA Series Trace Gas Analyzers FIGURE 4 23 TGA filter element replacement 4 1 6 3 TGA Filter Elements 47mm Qty 100 A box of 100 polypropylene filter elements 10 um pore size is available as pn 9838 and shown in FIGURE 4 24 These are used with 47 mm filter holders such as the pn 20553 TGA High Flow filter holder The filter elements may be purchased as a replacement item FIGURE 4 24 47 mm replacement filters 4 2 Theory of Operation Campbell Scientific TGAs measure trace gas concentration in an air sample with tunable diode laser absorption spectroscopy TDLAS This technique provides high sensitivity speed and selectivity The optical configuration of the TGA100 and TGAT100A is different than TGA200 and TGA200A as described in the following sections 4 2 1 Optic
49. to measure its concentration every 2 ms 500 Hz measurement rate driven by its own internal clock If it is measuring multiple species it alternates its measurement scans between them For example if it is configured to measure N2O and CHa each will be measured on alternate scans every 4 ms 250 Hz measurement rate If it is configured to measure O and PC isotope ratios in CO each of the three isotopologs will be measured every 6 ms 167 Hz measurement rate F 2 Sample Rate The TGA does not store data so its measurements must be sampled and stored by an external device The sample rate is determined by the data storage device Three options are supported e Campbell Scientific datalogger CR6 CR1000 CR3000 or CR5000 e Windows PC e Analog output requires an optional interface module Datalogger When using a datalogger the TGA is configured as an SDM sensor The TGA responds to the datalogger s data request by sending back the most current digitally filtered sample of the high rate concentration measurements Thus the sample rate is determined by the datalogger program PC When TGA data are sampled by a PC the user selects the update interval in ms on the connection window The TGA will send data to the PC at the specified interval which is based on the TGA s internal clock These data will be the most current digitally filtered sample of the high rate concentration measurements Thus the sample rate is determi
50. value This will disable line locking if the signal level drops during optical alignment adjustment for example Set the Max transmittance well above the normal measured reference transmittance A typical setting would be half way between the measured transmittance and 100 Setting the parameter this way will disable line locking if there is a problem with the reference gas such as forgetting to open the valve on the reference gas cylinder amp m Y TGA Parameter Settings e B Laser Temperature Current Maximum Pressure for line lock to be enabled Other B Detectors Temperature PreAmp Calculations Minimum Reference Detector Signal for line lock Concentration Analog Input Min signal strength 1 00 4 66 mV B Other i TGA Temperatures Data Output Serial Numbers About TGA Max pressure 100 00 54 80 mb Maximum Reference Transmittance for line lock Max transmittance 85 73 91 FIGURE 7 12 Typical Line Lock parameter settings 57 TGA Series Trace Gas Analyzers 58 Other The Settings gt Laser gt Other parameter window is the same for both versions of the software Laser Temperature t Current Number of Ramps i Line Lock i Number of ramps 15 B Detectors Temperature i oe PreAmp CH4 B Calculations Concentration Analog Input Gas name CH4 B Other Multimode power 0 00 TGA Temperatures Data Output Serial Numbers About TGA L Ram
51. with the following steps 1 Open a Laser Settings window 2 Select the Magnified display mode Appendix C Optimizing Laser Parameters Set the high current to an initial value start at zero mA when in doubt Click the padlock icon next to DC current or press T to start line lock Click the Auto button next to the Mod current to adjust the modulation current Click the padlock icon next to DC current or click on the detector graph and press I to stop line lock Click on the detector graph to enable adjustment of the DC current by using the lt and gt cursor keys alternately you may click in DC current box and use the A and V cursor keys or simply click the up and down adjuster boxes Repeatedly press the 4 cursor key to decrement the DC current in 0 1 mA steps until the center of the absorption line is at the right edge of the spectral scan Count the number of steps required Start line lock again Watch the reference detector display as the lines to come to the center of the spectral scan Stop line lock and repeatedly press the cursor key to increment the DC current in 0 1 mA steps until the center of the absorption line is at the left edge of the spectral scan Count the number of steps required Start line lock again Watch the reference detector display as the lines come to the center of the spectral scan Evaluate the results and iterate as needed using the steps below and referring to FI
52. 00 and TGA200A focus is adjusted at the factory and normally no further adjustment is needed If a system is configured for multiple lasers that have greatly different wavelengths however the focus may need to be adjusted when switching between these lasers To adjust the focus loosen the locking ring on the lens mounting tube and screw the lens mounting tube in or out to maximize the detector signals Retighten the locking ring when the optimum focus is achieved Appendix B Optical Alignment Appendix C Optimizing Laser Parameters Normally the laser parameters are adjusted only when a new laser is installed after transporting the system or warming and recooling the laser LN2 cooled laser These parameter settings optimize the performance for a specific absorption line so these steps should be performed after the correct absorption line is chosen see Appendix A 4 Finding the Absorption Line C 1 Laser Temperature NOTE If the TGA s laser were perfect it would emit at only one frequency single mode This emission frequency would depend only on the injection current and the emission frequency could be tuned over a wide range In fact the real laser s emission frequency is dependent on both its current and temperature it may emit some of its optical energy at other frequencies multimode and its emission frequency can be tuned over only a small range before it jumps to a different frequency mode hop The multi mode p
53. 0877 Carbon Dioxide 6 C and 6 50 12160160 30160160 and 120180160 A 1 3 Dewar Cables For LN cooled lasers the standard laser dewar can accommodate up to two lasers Each laser position position 1 and position 2 requires a corresponding dewar cable Position 1 and 2 cables are nearly identical but they are wired to connect the Laser Current output from the TGA electronics to different pins on the dewar s connector Inside the dewar these pins are connected to the lasers mounted in position 1 and 2 Connecting the position 1 or 2 dewar cable therefore determines which laser is active See Appendix A 1 4 Changing Lasers for additional details on selecting the laser An optional second laser mount assembly will allow up to two more lasers to be installed in the dewar The same position 1 and position 2 dewar cables are used for the lasers on the second mount If a replacement dewar cable is needed see TABLE A 3 TABLE A 3 Replacement Cables for TGA Dewars Position 1 Position 2 TGA100A 17895 17896 TGA200 21954 22001 Dewar cables for the TGA100 are no longer available However in most cases the TGA100 electronics may be upgraded to use the TGA100A cables Contact Campbell Scientific for details TE cooled lasers do not require a dewar or a separate dewar cable The appropriate cabling 1s supplied as part of the laser assembly A 1 4 Changing Lasers This section outlines the procedure to swap out the laser assem
54. 1 42 TGA Series Trace Gas Analyzers Device Configuration Utility 2 10 Beta File Backup Options Help Deke Tipe Settings Editor Send OS Terminal Logger Control Logger Program El Current Program CPU tga cr9 El El Last Compiled 01 08 13 15 26 52 ri Last Compile Results cpu tga cr9 Compiled OK TGA100A TGA200 Communication Port Baud Rate Program Send Status Click Send Program to send a new program Send Program FIGURE 6 17 Device configuration utility Logger Control tab 6 2 3 Configure Ethernet Connection There are two ways to set up the Ethernet connection between the TGA and a PC Ifa local area network LAN is available connect the TGA and your PC to the LAN This option allows a PC to connect to the TGA from any location in the world as long as both are connected to the internet If no LAN is available connect your PC directly to the TGA with an Ethernet crossover cable pn 18148 is supplied with the TGA for this purpose This option requires the PC and the TGA to be physically close but it requires no additional infrastructure Configure your PC for a peer to peer network with the TGA Consult your information technology support group as needed With either type of Ethernet connection the TGA s IP address Netmask Gateway and IP port must be set These settings are stored in the CPU module s nonvolatile memory They can be change
55. 100s had no temperature controller for the enclosure The TGAHEAT temperature controller was made available as an option for TGA100s in 2002 and was always included in the TGA100A This temperature controller is not required for the TE cooled laser but it is recommended for all TGAs to help maintain a steady temperature within the TGA enclosure To install a temperature controller in an older TGA100 contact Campbell Scientific for details A later upgrade for the TGA temperature controller allowed the temperature to be controlled through software See Appendix I Install Temperature Control Upgrade for details Appendix H Upgrading Early Generation TGAs to TE cooled Laser Appendix I Install Temperature Control Upgrade This section shows how to install the TGA temperature control upgrade so that the TGA temperature can be controlled through software This upgrade is available for TGA100As and TGA100s with the optional Temperature Controller and the CPU upgrade This upgrade requires a kit containing these parts e two thermistor probes pn 22209 e one special control cable FIGURE I 1 FIGURE I 1 Special control cable 1 1 Install Thermistor Probes Fasten one of the thermistor probes to the sample cell midway between the detector block and the electronics assembly using cable ties as illustrated in FIGURE I 2 FIGURE 1 2 Location of first thermistor probe attachment Fasten the cable to the sample cell with three
56. 2 Fraction of full power applied to the TGA 5 1 enclosure laser end arb Given in C if TGA TEC Voltage of cooler if TGA TEC 93 TGA Series Trace Gas Analyzers 94 Status Flags The TGAStatus value gives an indication of the overall status of the TGA A value of zero indicates a normal condition A nonzero value indicates one or more of the bits are set The meaning of each of the bits is given in TABLE 7 4 TABLE 7 4 Descriptions of TGAStatus Values Bit Decimal Value Description 0 1 Line Lock for ramp A is OFF 1 2 Line Lock for ramp B is OFF 2 4 Line Lock for ramp C is OFF 3 8 Sample detector signal exceeded input range 4 16 Reference detector signal exceeded input range 5 32 Sample detector temperature is outside its specified range 6 64 Reference detector temperature is outside its specified range 7 128 Laser temperature outside its specified range 8 256 Pressure is above its upper limit 7 3 2 TGA Output to PC The Ethernet connection from the TGA to the user s PC does allow data to be collected via the TGA Windows or TGA TEC software This is normally used only for testing and troubleshooting the TGA 7 3 3 TGA Analog Outputs For applications that require analog outputs instead of this SDM connection it is possible to add an analog output module that can be driven by the SDM connection Contact Campbell Scientific for details Troubleshooting and Ma
57. 3 TGA200A power module with cables installed 6 2 TGA Software Installation 6 2 1 NOTE This manual documents the TGA Windows and TGA TEC software These two software packages are very similar but they are not interchangeable TGA Windows is used with LN cooled lasers while TGA TEC is used with TE cooled lasers These two packages are very similar so most of the discussion applies to both Differences are noted as applicable The TGA software runs on the user s PC which must be running Windows XP or newer operating system The software provides the user interface to the TGA allowing the user to view the operation of the TGA and set parameters The software can also be used to collect TGA data although in most cases a Campbell Scientific datalogger is used to collect data Early DOS based versions of the TGA software are no longer supported Any TGA100A or a TGA100 with an upgraded CPU module may be upgraded to the TGA Windows or TGA TEC software Contact Campbell Scientific for details Installation of PC Software To install the software run the setup exe file on the installation disk This will install the TGA software file TGA_Windows exe or TGA TEC exe on your PC 39 TGA Series Trace Gas Analyzers 40 The default path is C Program Files Campbellsci TGA The installation will install a shortcut to this file and put it on your desktop For users with multiple TGAs and a combination of cryogenic and TE cooled l
58. 3 2 TGA Insulated Enclosure Cover sss 13 4 1 4 Other Accessories seo ue eeann ar EERE RESER 14 4 1 4 1 TGA Air Sample Intake 0 0 eeeeeeeseesteeneeeneeeeeees 14 4 1 4 2 TGA Heated Intake Filter amp Orifice sseussse 14 4 1 4 3 TGA High Flow Filter Holder ssssss 14 4 1 4 4 Sample Vacuum Pump cc ecceeceesceeeceseceteceeeeneeeneeeneeees 15 4 1 4 5 Bypass Vacuum Pump seen 17 4 1 46 Sample Air Dryers sete 18 A47 DIGASROmelet sh eerte tds 21 4 1 5 Support Software s 5 soie Sorted waked eee 22 4 16 Replacement Partsi eb d is 22 4 1 6 1 TGA Heated Intake Filter sese 22 4 1 6 2 Filter Element sess 22 4 1 6 3 TGA Filter Elements 47mm Qty 100 23 Theory of Operation eene enne 23 4 2 1 Optical System nennen 23 2 272 ESSGE o trit cod eret tere eset e E io EE 25 2 PPA E D TAE CEDE E 25 4 2 Am Detectors eee ee rette eee A reet ie ERR 25 4 2 5 Laser Scan Sequence nenea a aA ERE aa eT NSR 26 4 2 6 Concentration Calculation sssssssseseeeeeee 27 Table of Contents 5 SpecIfICcallolis n nocere ee eee botcveevshennectaceeneeee 28 5 1 Measurement Specifications essen 28 5 2 Physical Specifications 29 5 3 Power Requirements ipse erener eren 29 6 InstallatiOno iiis sicci ree audae p a cu rev R Rea nasa wees 30 6 1 Analyzer Installation
59. 5 06 L s TGA Model L ms TGA100 0 480 95 TGA100A 0 480 95 TGA200 0 420 83 TGA200A 0 200 40 The residence time is less than 100 ms in every case Therefore the recommended EC filter passband setting is 5 Hz see TABLE F 1 Appendix G Using Swagelok Fittings G 1 General Notes G 2 Assembly This appendix gives a few tips on using Swagelok tube fittings For more information consult your local Swagelok dealer or visit their web site at www swagelok com Do not use fitting components from other manufacturers they are not interchangeable with Swagelok fittings Do not attempt to use metric fittings Six mm is very close to 1 4 in but they are not interchangeable Metric fittings can be identified by the stepped shoulder on the nut and on the body hex Make sure that the tubing rests firmly on the shoulder of the tube fitting body before tightening the nut Never turn the fitting body Instead hold the fitting body and turn the nut Keep tubing and fittings clean Always use caps and plugs to keep dirt and debris out Do not overtighten fittings as it will damage the threads If a nut cannot be easily tightened by hand this indicates the threads have been damaged Replace any damaged nuts and fittings The first time a Swagelok fitting is assembled the ferrules become permanently swaged onto the tube Assembly instructions vary depending on plastic or metal tubing The assembly instructions are
60. 5 cm 6 5 in Height 25 4 cm 10 0 in Weight 8 2 kg 18 0 Ib Power 250 W 17 TGA Series Trace Gas Analyzers 18 Pumping speed 50 L min Ultimate vacuum 180 mb DAAV505 L Sample Pump The DAAVS505 shown in FIGURE 4 16 is a double head diaphragm pump used for applications that require more flow than the DOAV502 can supply The L on a product model indicates that the tubing length is specified at the time of order FIGURE 4 16 DAAV505 vacuum pump DAAV505 L specifications Length 29 8 cm 11 7 in Width 16 5 cm 6 5 in Height 25 4 cm 10 0 in Weight 11 4 kg 25 1 Ib Power 370 W Pumping speed 100 L min Ultimate vacuum 180 mb 4 1 4 6 Sample Air Dryer Accurate measurements of trace gas fluxes by eddy covariance or gradient techniques require that variation in water vapor concentration be eliminated either by drying the sample gas before it is measured or by correcting the trace gas flux Four sample air dryers are available the PD200T PD625 PDIT and the PD1T 1 5 See TABLE 4 4 to compare specifications for these dryers Webb E K Pearman G I and Leuning R 1980 Correction of flux measurements for density effects due to heat and water vapor transfer Quart J Met Soc 106 85 100 TGA Series Trace Gas Analyzers The dryers work by forcing the humidity in the sample air through the walls of the Nafion tubing where it is carried away by the purge flow The sample air flow
61. 9 Controlling the detector temperature settings sssssssss 60 PreAmp window default settings sssessseseeeee 61 Calculation concentrations settings 62 Default settings for Channel 1 in analog input screen 63 Channel 2 settings for a TGA with thermistor probe 64 Typical pressure value inputs values are specific to each TGA 65 Typical values for calculating 613C on a TGA set with multiple FAMPS i E 66 Table of Contents 7 22 7 23 7 24 7 25 7 26 7 27 7 28 7 29 7 30 7 31 7 32 7 33 7 34 7 35 7 36 7 37 7 38 7 39 7 40 7 41 7 42 7 43 7 44 7 45 7 46 A 1 A 2 B 1 B 2 B 3 B 4 B 5 B 6 B 7 B 8 B 9 C 1 C 2 C 3 C 4 C 5 C 6 C 7 C 8 C 9 F 2 F 3 TGA temperature control window for the two TGA enclosure heaters a n eite ERU P RU ERE 67 Data output setting window for SDM see 68 Setting a TGA serial number and identification string 69 About TGA window isse Pr REP nies Dar oe OE ERE det 70 The TGA TEC screen for setting laser parameters 71 View Less View More function of the Laser Settings window 72 Tabbed Expand function of the Laser Settings window 73 Laser display modes sse 74 Raw mode of laser display sesssssseseeeeee 75 Maximum V
62. CTS THE CUSTOMER ASSUMES ALL RISK FROM ANY INJURY RESULTING FROM IMPROPER INSTALLATION USE OR MAINTENANCE OF TRIPODS TOWERS OR ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS CROSSARMS ENCLOSURES ANTENNAS ETC Table of Contents PDF viewers These page numbers refer to the printed version of this document Use the PDF reader bookmarks tab for links to specific sections 1 2 3 4 Overview Introduction eet 1 Cautionary Statements 2 Initial Inspection zu oie i enc oro poison Eater ote 3 PEN 3 System Componenlts eere eter t enne entered E ias 6 4 1 1 Standard Components sse 7 4 1 1 4 TGA Power Module sese 7 4 1 1 2 TGA Accessory amp Tool Kit sss 8 4 1 1 3 TGA Test Int ke ecee aee tete rere 8 4 1 1 4 TGA Leak Check Nozzle sen 8 4 1 1 5 TGA SDM Cable nennen 9 4161 6 Plastic Tubing xe ER abo eae eects 9 4 1 1 7 CATS Ethernet Crossover Cable 9 41 1 8 Serial Data Cable erred 10 4 1 1 9 TGA TEC Support Software and Operating System 10 4 1 2 Optional Components c ceccesceeseeseeeceeceeeeeeeeeeeeeneceeenseenaes 11 ALT LaSi ERE 11 4 1 2 2 AC Mains Power Cord sse 11 4 1 2 3 Power Module Mounting Brackets sss 12 4 1 3 Common Accessories eet eee ye e eee dene 12 4 1 3 1 TGA Reference Gas Connection 12 4 1
63. Display Mode isses 73 12 44 COTS 22 oh cee Recents tette thes eter a eee 81 PED Som nu C 81 12 67 Graphen ee eR E 84 T2 Da tdnssceiisesupeeni ne dotted i n rS 87 1 2 9 E seca ettet epi era Vt er ets 88 7 3 Data Quip ut oeieo e indent ses RI O EE ORE 90 73 1 SOM QUEDUt ter tit edere tite E t M Ee HESS 90 Peds Suri q PC MH 91 1 3 1 2 Remarks hs ee ees A RER 91 732 TGA Output to PC edipi eene etis 94 7 3 3 TGA Analog Outputs oett retire ete sees 94 8 Troubleshooting and Maintenance 94 8 1 Lasers and Detectors essen 94 82 Reference C EEE ed edet e te go 95 83 Filtration and Sample Cell Cleaning esses 95 84 Sample Pumps uie dccem reci 95 Table of Contents Appendices A Configuring TGAs for Specific Gas Species A 1 A Laser Select ice ete a Pe etes A 1 A11 LN cooled lasers eeeeeeeeneeeereen ene A 1 A 1 2 TE cooled Lasers irni ninen ite ree A 1 AN3 Dewar Gables eere tee ettet A 2 ATA Changing Lasets 5 eerte arre Ee tete A 2 A2 Reference Gas ss iiie heec nr ha OPE aere ee A 4 A3 Detectors een rient n she Eco ee iin ree iae A 6 A Finding the Absorption Line A 6 ASS Ai Gap Purge scun i kn Adana ae ere an edt A 7 B Optical Alignment cccceeeceeeeeeeeeeeeeeeeeeeeneeeeeees B 1 B 1 Optical Alignment of TGA100 and TGA100A
64. E 4 1 Screen of TGA Windows software Laser The lead salt diode lasers used in the TGA100 TGA100A and TGA200 required cryogenic cooling These lasers were available at any wavelength from 3 to 10 um and could be specified to detect many different gases Most early TGAs used liquid nitrogen to cool the laser but some TGA100As used a closed cycle refrigeration system cryocooler These lasers became unavailable in 2012 when the only manufacturer discontinued production of the laser A new room temperature thermoelectrically TE cooled interband cascade laser ICL became available in 2014 This enabled the release of the TGA200A These ICLs are available as an upgrade for some of Campbell Scientific s older TGAs See Appendix H Upgrading Early Generation TGAs to TE cooled Laser for details Dewars The TGA100 was introduced with a small dewar 1 5 L that required refilling with LN once or twice per day A much larger 10 4 L dewar was introduced in 2002 with the evolution of the TGA100 The larger dewar allowed LN filling only twice per week rather than daily Along with this new larger dewar a cryocooler system was introduced as an alternative The 10 4 L dewar and the cryocooler were also used for the TGA100A The TGA200 used an even larger LN dewar 14 5 L to extend the refill interval to once per week TGA Series Trace Gas Analyzers The TE cooled laser of the TGA200A operates without a LN2 dewar Optical Configuration
65. E Older units were supplied with a horizontal adjustment screw at the detector end but newer units use a fine pitch horizontal adjustment screw at the laser end which makes horizontal adjustment at the detector end unnecessary 2 Use the horizontal adjustment screw at the laser end to align the long sample cell with the laser 3 Sight along the long sample cell to point it at the laser which can be viewed through the dewar window hanging below the laser mount CAUTION The TGA uses a Class 1M laser Do not view the laser directly with optical instruments 4 Use the vertical adjustment screw to align the long sample cell with the laser If no detector response is observed set the vertical adjustment near the center of its adjustment range Appendix B Optical Alignment Alternately adjust the horizontal and vertical alignment screws When a response is observed in the sample detector proceed to the next section If a response is not observed troubleshoot with the following steps If a detector response is not observed it may be helpful to defocus the optics intentionally This will make the laser s image on the detector larger and easier to locate Loosen the axial clamping screw at the laser end Slide the long sample cell back away from the laser about 5 mm from the center of its adjustment range and retighten the axial clamping screw Alternately adjust the horizontal and vertical adjustment screws If no detector response
66. EC software may be upgraded to control temperatures through software See Appendix I Install Temperature Control Upgrade for installation details 4 1 System Components The TGA200A consists of several components some of which must be supplied by the user Some additional accessories are required to complete a fully functioning TGA200A system and are described and illustrated in the sections that follow FIGURE 4 2 illustrates the main system components as well as additional equipment needed to operate the TGA200A The other TGA models are similar TGA Series Trace Gas Analyzers TGA200 Analyzer Datalogger e EENAA ca ene axe d Suction Hose Sample Intake Ro M B _ oe al H a T Reference Gas Sample Pump FIGURE 4 2 TGA200A system components 4 1 1 Standard Components The newest version of Campbell Scientific s trace gas analyzers the TGA200A comes with the components described in the following sections 4 1 1 1 TGA Power Module The TGA200A power module pn 30981 is a power module included with the TGA200A that provides 12 Vdc and 24 Vdc to the TGA200A It is shown in FIGURE 4 3 The 12 Vdc is used to power the electronics of the trace gas analyzer while the 24 Vdc is used to power the heaters and fans that regulate the TGA enclosure temperature A 4 6 m 15 ft power cable with keyed connectors is included with the module Corresponding keyed connectors are found inside the power module enc
67. Flat Negative slope Reduced Normal Increased Mu o Q 2 v z 2 T o Steep slope y FIGURE C 6 S Symmetrical about center Falls off at left edge Effects of temperature perturbation NEGET C 7 Appendix C Optimizing Laser Parameters 0 6 mA 0 3 mA Line lock on 0 3 mA 0 6 mA C 8 AA JA As shown in FIGURE C 6 improper high current adjustment makes the absorption line appear asymmetrical The goal of the high current adjustment procedure is to make the absorption line symmetrical about its center A more objective method to evaluate this symmetry is to adjust the DC current to move the absorption line to the left and right of the center line If the high current is adjusted properly the absorption line will move the same distance left right of center for the same change in DC current This is illustrated in FIGURE C 7 The left panel shows that with the high current too low changing the DC current by 0 6 mA moves the absorption line only halfway to the left edge of the scan but changing the DC current by 0 6 mA moves it all the way to the right edge of the scan In the center panel the absorption line moves symmetrically all the way to the left and right edge of the spectral scan for the same change in DC current High current High current High current correct too high FIGURE C 7 High current adjustment procedure To set the high current proceed
68. GA200 and TGA200A are located at the side of the enclosure Other components such as a sample air dryer valves to switch between multiple intakes calibration gases and others may also be required depending on a given user s application TGA100 Analyzer TGA100 PC Fiber Optic Cable Reference Gas Connection Suction Hose Sample Intake Reference Gas Sample Pump FIGURE 6 1 Basic components required for TGA100 operation 30 TGA Series Trace Gas Analyzers TGA200 Analyzer Datalogger o Computer Ethernet Cable SDM Cable Een i aa Suction Hose Sample Intake Bese ii 1 T We uem eR ERmEECMWMBE Reference Gas Sample Pump FIGURE 6 2 Basic components required for TGA200 and TGA200A operation 6 1 Analyzer Installation The TGA analyzer is housed in an insulated fiberglass enclosure FIGURE 6 3 equipped with a temperature controller that allows the TGA to operate in a wide variety of environmental conditions FIGURE 6 3 TGA200A enclosure The analyzer must be placed on a stable surface If placed on uneven ground wooden blocks or other supports can be used under the two pairs of rubber feet near the ends of the enclosure NOTE Early TGA100s had a third pair of rubber feet under the center of the enclosure These TGAs should be placed on blocks to lift the TGA so these center feet are not used for support Once the TGA is positioned loos
69. GURE C 7 e Ifthe high current is too low it will take more steps to move the line to the left edge than to move the line to the right edge The absorption line may become narrower as it approaches the left edge and wider as it approaches the right edge Additionally if line lock is started with the absorption line at the left or right edge the absorption line may move relatively slowly to the center If this is observed increase the high current and repeat the steps above e Ifthe high current is set correctly it will take the same change in DC current to move the absorption line to the left or right edge and this will be approximately equal to the modulation current the width of the absorption line will not change noticeably as it is moved from left edge to right edge and when line lock is started with the absorption line at the left or right edge the absorption line will jump quickly to the center e If it takes fewer steps to move the line to the left edge than to move the line to the right edge or if the absorption line becomes wider as it approaches the left edge or if starting Appendix C Optimizing Laser Parameters C 10 line lock with the absorption line at either edge causes it to overshoot the center this means the high current is too high Decrease the High current and repeat the test above Usually these criteria will give a clear indication of the correct value for the High current However sometimes other cri
70. Input TGA Identification TGA S N TGA description Serial Numbers Laser S N Dewar S N Sample detector S N Reference detector S N Site name description 1113 Lab TGA200 1476 21 8 8745 8770A CSI TGA Lab FIGURE 7 24 Setting a TGA serial number and identification string About TGA The Settings gt Other gt About TGA window is shown in FIGURE 7 25 The window gives the version of the PC software and also documents the version of the firmware if a TGA is connected 69 TGA Series Trace Gas Analyzers TGA TEC Parameter Settings G Laser Tena bE CAMPBELL SCIENTIFIC Line Lock Other Detectors mae amugu PreAmp B Calculations Concentration x TGA TEC Interface Software TGA Temperatures Version 1 0 0 37 Data Output Copyright 2014 Campbell Scientific Inc Serial Numbers TGA TEC Firmware Version TGA TEC 1 0 21 OS Date 08 08 14 11 21 12 ID string Lab TGA200 Copyright 2014 Campbell Scientific Inc http www w campbellsci com FIGURE 7 25 About TGA window 7 2 4 Laser Window The Laser window is used to display reference and sample detector signals and to modify laser parameters The value of a parameter may be adjusted by several methods e Manually entering the new value in the box with the keyboard number keys e Clicking the up or down arrow next to the box e Click in the box and use the up and down arrow keys
71. K Other Detectors ro Temperature CH4 PreAmp B Calculations s 1 DC current 400 00 Concentration Analog Input Mod current 0 60 tn Other Zero current 320 00 TGA Temperatures High current 30 00 2 Data Output Serial Numbers About TGA Maximum Laser Ratings Maximum laser current mA 600 00 FIGURE 7 10 Laser current parameter settings for TGA Windows 55 TGA Series Trace Gas Analyzers 56 F PEERS TGA Parameter Settings mm Laser Temperature Current V Laser on Line Lock p men cHa B Detectors Temperature PreAmp B Calculations Concentration Analog Input Zero current 50 00 Other TGA Temperatures Data Output Serial Numbers About TGA Maximum Laser Ratings DC current 88 15 Mod current 1 30 HE High current 0 00 Maximum laser current mA 100 00 FIGURE 7 11 Laser current parameter settings for TGA TEC Line Lock The Settings gt Laser gt Line Lock window sets limits used to temporarily disable the line lock function during an error condition The line lock function locks the absorption line to the center of the spectral scan by automatically adjusting the DC current Line locking must be active for normal operation see Section 7 2 4 Laser Window for information on making line lock active and see Section 7 2 2 Status Window for details on viewing the TGA line lock status The TGA monitors three conditions e sample cell press
72. New New New CPU upgradeable Software Transputer DOS TGA Windows TGA TEC Lead salt Lead salt Lead salt Interband Laser Cascade Cooling options LN LN or Cryocooler LN Thermoelectric Dewar capacity L 1 5 10 4 14 5 None Beamsplitter at Beamsplitter at Beamsplitter at Beamsplitter at Optical detector end detector end laser end Long laser end configuration sample and reference cells Absorption cells Long sample cell short reference cell Long sample cell short reference cell Long sample and reference cells Long sample and reference cells Temperature control Fans only TGAHEAT optional starting 2002 TGAHEAT included Software Software TGA Series Trace Gas Analyzers Before proceeding please study e Section 2 Cautionary Statements e Section 3 Initial Inspection e Section 6 Installation Operational instructions critical to preserving accurate measurements of the system are found throughout this manual Before proceeding please study this manual Several other user manuals provide additional information and should be consulted before using the TGA These include CR6 Measurement and Control Datalogger CR1000 Measurement and Control Datalogger CR3000 Micrologger CR5000 Measurement and Control System all available at www campbellsci com 2 Cautionary Statements e DANGER O All Campbell Scientific TGAs use Class 1M lasers These lasers are safe under al
73. TGA Series Trace Gas Analyzers Revision 10 14 Copyright 1992 2014 Campbell Scientific Inc IVONVIN NOILONALSNI Limited Warranty Products manufactured by CSI are warranted by CSI to be free from defects in materials and workmanship under normal use and service for twelve months from the date of shipment unless otherwise specified in the corresponding product manual Product manuals are available for review online at www campbellsci com Products not manufactured by CSI but that are resold by CSI are warranted only to the limits extended by the original manufacturer Batteries fine wire thermocouples desiccant and other consumables have no warranty CSI s obligation under this warranty is limited to repairing or replacing at CSI s option defective Products which shall be the sole and exclusive remedy under this warranty The Customer assumes all costs of removing reinstalling and shipping defective Products to CSI CSI will return such Products by surface carrier prepaid within the continental United States of America To all other locations CSI will return such Products best way CIP port of entry per Incoterms 2010 This warranty shall not apply to any Products which have been subjected to modification misuse neglect improper service accidents of nature or shipping damage This warranty is in lieu of all other warranties expressed or implied The warranty for installation services performed by CSI such
74. TGA TEC with the exception that the units for the laser temperature are different and the minimum current step size is different The Interactive mode selected at the bottom of the Laser Line Find screen maps the laser at one temperature but then allows the user to select an absorption line by first clicking on the key to select which ramp to set and then clicking on the absorption line in the graph Alternately the vertical colored band that represents the spectral scan may simply be dragged to the desired absorption line It is helpful to display the Laser Settings window beside the Laser Line Find window FIGURE 7 37 while making these adjustments If preferred the Laser Settings window as described in Section 7 2 4 Laser Window may be used to make the adjustments and view the changes interactively in the Laser Line Find window An example is shown in FIGURE 7 38 for a CO isotope laser 81 TGA Series Trace Gas Analyzers If the two windows do not agree well try repeating the laser map with a smaller step size for the DC Current iLaser Line Find Step Size X ampbellScivT 35D ataFlles mmad yyyyhhrimmap Advanced kile Options FIGURE 7 37 Laser line find window 82 TGA Series Trace Gas Analyzers 9 Laser Find 350 00 to 450 00 ma E vp sx o o1 sll Laser Find 99 70 Co2 Reference Voltage mv FIGURE 7 38 Interactive Laser Find window for a CO2 isotope laser The non interac
75. able from Campbell Scientific for this purpose see Section 4 1 3 1 TGA Reference Gas Connection for more details This assembly includes a flow meter needle valve and 6 2 m 20 ft of tubing with Swagelok fittings to connect to the TGA The outlet of the regulator must have a 1 4 in Swagelok fitting to attach this assembly A tank of reference gas 5 7 m 200 f will last approximately one year at a continuous flow of 10 ml min The most commonly measured trace gases methane nitrous oxide and CO isotopes as well as many other gases have strong absorption lines at wavelengths from 3 to 5 um and can be measured with the standard TE cooled detectors Some gases such as ammonia water isotopes or the combination of N20 and CH must be measured at longer wavelengths and require the optional LN cooled detectors The TGA100 and TGA100A were supplied with custom LN cooled detectors which required daily filling The TGA200 had optional LN cooled detectors with a much larger dewar that required filling twice weekly The TGA200A always uses TE cooled detectors because its TE cooled lasers cannot reach the longer wavelengths that require LN cooled detectors A 4 Finding the Absorption Line A 6 The spectral scan of the TGA must be locked onto a selected absorption line When the TGA is restarted it will perform an automated sequence to reestablish this line lock by waiting until the laser temperature has stabilized and th
76. aded to use the thermistor probes see Appendix I nstall Temperature Control Upgrade The settings for the Channel 2 tab are shown in FIGURE 7 19 The Channel 3 tab is similar but the Name is TGA Temp 2 63 TGA Series Trace Gas Analyzers 64 Channel 2 Channel 3 Pressure Name TGA Temp 1 5 PRT sensor TGA100A Themistor TGA200 Bie 222109 Input Manual scale offset TGA Temperatures Scale 0 00 Data Output m m Serial Numbers ur i About TGA FIGURE 7 19 Channel 2 settings for a TGA with thermistor probe Channel 4 measures sample cell pressure Each TGA pressure sensor is individually calibrated to determine appropriate values for the Zero output V and the Full range output V These are recorded in documents supplied with the TGA Typical values are shown in FIGURE 7 20 TGA Series Trace Gas Analyzers Zero output V 0 230 Full ange output V 47008 Full ange pressure mb 1013 00 Measured pressure 54 14 mb FIGURE 7 20 Typical pressure value inputs values are specific to each TGA Isotopes The sotopes parameters are the same for both versions of the software This window is hidden if the number of ramps is set to 1 An example of typical values for calculating 5 C is shown in FIGURE 7 21 65 TGA Series Trace Gas Analyzers 66 7 2 3 4 Other TGA TEC Parameter Settings Laser Temperature Current Line Lo
77. adjustment screw Tighten only when transporting Horizontal lock screw Axial lock screw FIGURE B 2 Alignment hardware of detector end of TGA100 and TGA100A 2 Loosen the horizontal and vertical clamping screws at the laser end refer to FIGURE B 3 Horizontal adjustment screw Horizontal clamping screws Appendix B Optical Alignment Vertical Axial adjustment clamping screw screw Vertical clamping screw Vertical clamping screw FIGURE B 3 Alignment hardware of laser end of TGA100 and TGA100A If the TGA is equipped with an iris in front of the focusing lens open it fully this is recommended for normal operation Start the TGA program and make sure the laser and detector parameters are set appropriately for the laser Display the reference detector signal and the sample detector signal in a graph The goal of the alignment procedure is to maximize these signals Edit the graph options to move one of the traces to the right axis Set the minimum value of each Y axis to zero and let the maximum of each Y axis scale automatically Set the reference and sample detector gains to zero This will disable automatic gain and offset adjustment which can cause confusion during the alignment process when active Set the detector temperatures as needed to avoid saturation This adjustment may need to be repeated during the alignment process if the signal level increases too much It is not important to h
78. after the zero and high current phases of the scan The Omitted count parameter specifies how many scan points to omit The parameter may have a set value from 4 to 20 counts where each count represents a 20 us interval to give a total duration of omitted data of 80 to 400 us To set this parameter look at the reference detector transmittance in Magnified mode The leftmost portion of the graph is at a different color to mark the omitted data counts meaning that those data are not used to calculate concentration This parameter is found on the Settings gt Laser gt Other window Increase the omitted data counts to move this line to the right decrease it to move it to the left The reference transmittance should be flat or rising slightly as it approaches the left edge as shown on the right in FIGURE C 8 Set the omitted data counts to avoid the use of data that drop into the ghost line as shown on the left in FIGURE C 8 When in doubt it is usually better to omit a few extra counts V Too few omit counts Y Correct omit counts o D D a O Drops at left edge Flat at FIGURE C 8 Adjustment of omitted data counts Adjusting this parameter usually makes little difference in the TGA s performance so when in doubt this parameter should simply be left at the default which is 20 counts For multiple ramp mode the omitted count parameter is common to all ramps and it should generally be set to its default C 5 Modula
79. al System TGA100 and TGA100A The TGA100 and TGA100A optical configuration is shown schematically in FIGURE 4 25 Infrared radiation from the laser is collimated and passed through a 1 5 m 4 9 ft long sample cell where it is absorbed proportional to the concentration of the target gas A beamsplitter directs most of the energy through a focusing lens and a short sample cell to the sample detector and reflects a portion of the beam through a second focusing lens and a short reference cell to the reference detector A reference gas of known concentration flows through the reference cell Reflective surfaces are minimized to reduce errors caused by Fabry Perot interference This simple optical design avoids the alignment problems associated with multiple path absorption cells 23 TGA Series Trace Gas Analyzers Reference defector H To pump i Reference gas in Dewar i ZA n E Sample cell f CN Sample a mm Laser detector I l ji UPC To pump Sample in FIGURE 4 25 TGA100 and TGA100A optical configuration TGA200 and TGA200A The TGA200 and TGA200A optical system is shown schematically in FIGURE 4 26 The laser is partially collimated by a first lens Most of the energy then passes through the beamsplitter and a collimating lens and into the sample cell The beamsplitter reflects a portion of the beam to an alignment mirror and then through a second collimating lens into the reference cell The
80. alues to store Advanced Set file names and the location for the files File Names Set parameters for the file naming the folder in which to store the files Sample Rates Set the rates at which data are collected and stored 89 TGA Series Trace Gas Analyzers Other look at the event log Event Log View or save a log of the status of the communication with the TGA An example of the messages in the log file is shown in FIGURE 7 45 B Files i File Lists Data File i Housekeep File Selection i Misc B Advanced p File Names Sample Rates Other Event Log Connected To Connected to 192 168 76 31 Lab TGA200 Time J Messaae 09 17 14 08 29 26 Parameter File C CampbellSci TGA ParameterFiles t gaConfiguration prm The 09 17 14 08 29 45 Connected to 192 168 76 31 3000 Lab TGA200 09 17 14 08 46 06 TGA starting up Waiting for laser temperature to stabilize before establishing line 09 17 14 08 48 20 TGA laser stabilized Line Lock tumed on Line found 09 17 14 09 08 46 Data Collection Toggled On Clear All J Save events to File FIGURE 7 45 Example of log file messages 7 3 Data Output The TGA may be configured to output data to the user s PC or for analog outputs but normally data are sent to a datalogger via an SDM cable 7 3 1 SDM Output 90 SDM is a Campbell Scientific communication protocol that allows synchroni
81. amp C 1 Appendix C Optimizing Laser Parameters Open the Laser Settings window to view the absorption line set the laser temperature and view the DC current reference detector transmittance and the sample detector signal Open either a Data window or graph to view the concentration noise Enable the line locking function and the automatic detector offset and gain adjustment function Record the laser operating temperature the laser DC current and the reference detector s percent transmittance at the center of the ramp displayed at the top of the reference detector transmittance The sample detector signal and the concentration noise may also be useful to note although these are not absolutely necessary 10 Record these values in a notebook 11 TABLE C 1 gives an example of the process described in steps 6 8 TABLE C 1 Example Laser Temperature Optimization Data Laser Laser DC Reference Concentration Sample Signal Temperature K Current mA Transmittance Noise ppb mV 103 7 482 6 65 9 7 30 0 103 9 477 4 66 2 8 27 6 104 1 472 1 66 4 9 24 9 104 3 466 6 67 3 10 21 9 104 5 460 8 69 1 13 18 3 104 7 454 9 72 0 20 14 4 104 9 448 7 78 2 45 10 0 105 1 442 2 90 5 350 4 9 Transmittance and noise much worse try going down 103 5 487 7 65 8 7 32 5 103 3 492 6 67 7 6 34 5 103 1 497 5 77 8 15 36 3 102 9 502 9 89 5 85 38 7 Transmittance and noise worse aga
82. ascade laser TE cooled ICL became available that is operable at ambient temperature without additional cooling Campbell Scientifics s TGA200A instrument was released shortly after the TE cooled laser became available Some of the older TGAs can be upgraded with this laser See Appendix H Upgrading Early Generation TGAs to TE cooled Laser for details All lasers used in the TGA are infrared diode lasers with wavelengths longer than 3 microns and a divergent exit beam Optical power for lead salt lasers is specified as gt 0 1 mW with typical powers up to approximately 1 mW ICL optical power is gt 1 mW typically 2 to 4 mW For both types of lasers the power varies from one laser to another Consult the vendor data sheet for the individual laser for more information The safety classification for both types of lasers is Class 1M The TGA uses a Class 1M laser Do not view the laser directly with optical instruments The TGA100 came with a small LN laser dewar 1 5 L that required refilling with LN2 once or twice per day A much larger 10 4 L LN laser dewar was introduced in the evolution of the TGA100 in 2002 This dewar required LN filling twice per week Along with this new larger dewar a cryocooler system was offered as an alternative The TGA200 used an even larger LN dewar 14 5 L which extended the refill interval to once per week The TEC ICL of the TGA200A requires no LN dewar This laser is housed in a sealed package
83. asers it is possible to have both programs installed on a PC The shortcut icons to start these two programs are distinguished by the color and the text as shown in FIGURE 6 14 Installing the software also starts a communication process that runs in the background and registers the software for later installation or updates Lm T TG uw MAC TGA TGA TEC FIGURE 6 14 PC shortcut icons for TGA Windows left and TGA TEC right 6 2 2 Updating TGA Operating System Run the installation program for example TGA_Firmware2 1 exe in the TGA Operating System folder on the installation disk This will extract the TGA OS file for example TGA_2 0bj and the TGA program tga cr9 and place them in the default directory C Campbellsci Lib OperatingSystems 1 As shown in FIGURE 6 15 connect the PCs COM port to the RS232 port on the TGA s CPU module with a serial cable pn 20730 is supplied for this purpose AlddNs HIMOA SAMO 0106 YaMog FIGURE 6 15 Serial cable connecting PC to RS232 port of TGA CPU module TGA Series Trace Gas Analyzers 2 Run the Campbell Scientific Device Configuration Utility part of LoggerNet or available for free from Campbell Scientific 3 Select device type TGA100A TGA200 and follow the directions to connect to the TGA 4 Select the Send OS tab and follow the directions FIGURE 6 16 to send the new operating system to the TGA Device Configuration Utility 2 10 Beta File Backu
84. at of the PD200T The PD625 s inlet filter tubing connections and purge flow meter range are also smaller than for the PD200T The PD625 is normally used in the two dryer configuration so it does not include the sample flow meter or sample needle valve included in the PD200T The PD625 is shown in FIGURE 4 20 gt gt FIGURE 4 20 PD625 air sample dryer 4 1 4 7 TGA Rotameter The TGA rotameter pn 19541 measures air sample flow in high flow applications such as eddy covariance It is temporarily attached to the sample inlet while adjusting the needle valves that control the sample and bypass flows In FIGURE 4 21 the front of the rotameter is shown on the left and the connectors at the back are shown on the right 21 TGA Series Trace Gas Analyzers 22 4 1 6 2 Filter Element napi nuez TAE ard b o 3 FIGURE 4 21 TGA rotameter 4 1 5 Support Software The PC support software and the TGA firmware are supplied on a CD with the shipment pn 30723 4 1 6 Replacement Parts Replacement parts for the TGA200A are described in the following sections 4 1 6 1 TGA Heated Intake Filter This heated filter pn 18058 may be used to replace the sub assembly of the TGA heated intake filter pn 18072 see Section 4 1 4 2 TGA Heated Intake Filter amp Orifice when that filter becomes plugged This spare heated intake filter shown in FIGURE 4 22 is recommended when the air sample intake is difficult
85. ave large Appendix B Optical Alignment signals during alignment When in doubt set the detector temperatures relatively high for relatively low signals 9 Ifno sample detector signal can be seen perform the initial alignment see Appendix B 2 2 Initial Alignment 10 Once a signal can be observed on the sample detector adjust the horizontal and vertical alignment Appendix B 2 3 Horizontal and Vertical Alignment 11 Adjust the focus Appendix B 1 3 Focus Adjustment 12 When the focus and the horizontal and vertical alignment have been optimized tighten the horizontal vertical and axial clamping screws NOTE Remember to leave the transport lock and axial lock screws loose 13 Make sure the reference detector is coaligned with the sample detector Appendix B 1 4 Reference Detector Coalignment B 1 1 Initial Alignment If the optical system is significantly misaligned there may be no observable detector response This initial alignment procedure will help to align the system well enough to see a response As soon as a detector response is observed the system is ready for the horizontal and vertical alignment procedure described in Appendix B 1 2 Horizontal and Vertical Alignment 1 Ifthe TGA is equipped with a horizontal adjustment screw at the detector end loosen the horizontal lock screw adjust the horizontal position to near the center of its adjustment range and retighten the horizontal lock screw NOT
86. ay represents a random lag jitter that cannot be removed by EC post processing algorithms However the jitter is small enough 2 to 6 ms to be insignificant even for EC applications TABLE F 3 Summary of TGA Update Times Sampling Mode Filter Ramps Maximum Delay ms SDM Moving Avg 1 2 or 3 2 EC 1 6 2 4 3 6 Analog Moving Avg or EC 1 6 4 3 6 PC Moving Avg or EC 1 2 or 3 2 F 5 Sample Cell Residence Time The frequency response of the TGA is ultimately determined by the time it takes for a sample to flow through the sample cell This residence time depends on the volume of the sample cell and the actual flow rate as given by the equation t v q where t residence time s v sample cell volume L q actual flow rate L s F 5 Appendix F TGA Frequency Response F 6 A typical example is using an RB0021 L sample pump see Section 4 1 4 4 Sample Vacuum Pump for eddy covariance This pump has a capacity of 18 slpm at 50 mb Assuming 3 slpm is used to purge a PD200T dryer see Section 4 1 4 6 Sample Air Dryer leaves 15 slpm for the TGA Converting standard flow to actual flow and converting units from minutes to seconds gives 50 A60 This gives a sample cell residence time for the various TGA models as shown in TABLE F 4 TABLE F 4 Sample Cell Residence Time as a Function of Sample Cell Volume and TGA Model Sample Cell Volume Residence time
87. be 1 8 tube 1 4 Swagelok 1 4 Swagelok e Purge 3 8 Swagelok 1 2 Swagelok 3 8 Swagelok 1 2 Swagelok Sample pressure drop at standard mb per 1 T 4 13 10 5 temperature and pressure min 0 5 zz o l Flow rate for 15 C dewpoint 1 min 0 C dewpoint 0 5 2 16 Sample volume internal volume af deyerbibine ml 1 4 6 7 10 80 Purge flow meter range min NA NA 0to 5 Oto 10 PDIT The PDIT dryer FIGURE 4 17 uses a 6 ft length of 0 086 in ID Nafion tubing similar to Permapure MD110 72 www permapure com It will dry 0 5 lpm to 15 C dewpoint 19 TGA Series Trace Gas Analyzers 20 FIGURE 4 17 PD1T air sample dryer The sample inlet and outlet connections are 1 18 in OD stainless steel tubes These SS tubes connect directly to the Nafion tube inside the dryer shell This design completely eliminates dead volume in the sample flow The purge connections are 1 2 in Swagelok and the dryer shell is 0 5 in OD Synflex 1300 tubing This large size minimizes pressure drop in the purge flow to allow the dryer to be purged with the output of the TGA reflux mode The dryer shell is flexible Synflex 1300 tubing to allow it to be integrated easily into the sampling system typically between a multiport sampling manifold and the TGA inlet PDIT 1 5 The PDIT 1 5 shown in FIGURE 4 18 is similar to the PDIT but is designed for lower capacity at lower cost It is designed to remove en
88. ber of ramps parameter the TGA will return zero for the ramp B and or C values See TABLE 7 3 for complete information TABLE 7 3 TGA Instruction Name Description DataList ScanMode ConcA Trace gas concentration measured in Ramp 1 1 A ppmv ConcB Trace gas concentration measured in ramp B 1 2 ppmv ConcC Trace gas concentration measured in ramp C 1 3 ppmv TGAStatus Status flags see TABLE 7 4 1 1 TGAPressure Sample cell pressure mb 2 1 LaserTemp Laser temperature K 2 1 DCCurrentA Laser DC current for ramp A mA 2 1 DCCurrentB Laser DC current for ramp B mA 2 2 DCCurrentC Laser DC current for ramp C mA 2 3 TGAAnalogl TGA Analog Channel 1 voltage V 3 1 TGATempl Mi AR inside TGA enclosure detector 3 1 end C TGATemp2 Tepe inside TGA enclosure laser 3 1 end C Voltage applied to the laser heater to LaserHeater maintain the laser at the specified 4 1 temperature V Reference detector signal at the center of the RerDer analy spectral scan for ramp A mV 1 TGA Series Trace Gas Analyzers TABLE 7 3 TGA Instruction Name Description DataList ScanMode RefDetSignalB Reference detector signal at the center of the 4 2 spectral scan for ramp B mV RefDetSignalC Reference detector signal at the center of the 4 3 spectral scan for ramp C mV Reference detector transmit
89. bly TE cooled lasers or to change which laser is active multiple LN2 cooled lasers in a dewar CAUTION DANGER NOTE WARNING WARNING WARNING Appendix A Configuring TGAs for Specific Gas Species The TGA laser can be damaged by operating at a temperature or current outside maximum limits which are unique to each laser Follow the steps carefully to avoid damaging the laser The TGA uses a Class 1M laser Do not view the laser directly with optical instruments 1 Turn the analyzer electronics off 2 Disconnect the laser cable as appropriate for the laser LN cooled laser Disconnect the laser cable from the electronics and the dewar TE cooled laser Disconnect the laser cable from the electronics the laser cable is permanently attached to the TE cooled laser assembly If switching between position 1 and position 2 lasers skip step 3 3 Ifthe dewar must be rotated to select a laser in the optional second laser mount or if the dewar or TE cooled laser assembly is to be exchanged remove the four mounting screws rotate exchange the dewar or TE cooled laser assembly and reinstall and tighten the mounting screws Do not connect the dewar cable at this time 4 Startthe TGA software on your PC Read an appropriate parameter file for the new laser To avoid damaging the laser ensure that the parameters are valid for the new laser In particular verify the laser maximum temperature and laser maxi
90. center the three clamping screws in their slots Align the reference detector to the sample detector by loosening the three screws that attach the reference detector holder to the beamsplitter block turning the alignment cams to maximize the reference signal and then retightening the mounting screws The optical alignment is now complete B 2 Optical Alignment of TGA200 and TGA200A Like its predecessors the TGA200 and TGA200A also have a simple robust optical design making it similarly easy to adjust and maintain optical alignment The optical system illustrated in FIGURE B 4 includes the laser collimating lenses in front of the laser a beamsplitter to reflect some of the laser s energy through the reference cell and three mirrors for aligning the beam through the reference cell and onto the sample and reference detectors Appendix B Optical Alignment Sample detector Detector alignment mirrors Reference alignment mirror Reference detector FIGURE B 4 TGA200 and TGA200A optical layout The TGA optical alignment does not change during normal operation but it should be checked after transport FIGURE B 5 illustrates the horizontal vertical and reference mirror tip tilt adjustment knobs shown with the laser removed for clarity Sample Horizontal Sample Vertical Reference Mirror Tip Tilt FIGURE B 5 Alignment hardware of laser end of TGA200 variants B 8 Appendix B Optical A
91. ck V Calculate isotope ratios Other Detectors Isotope Ratio Temperature PreAmp oc Del 13C standard isotope ratio 0 01117970 Concentration Analog Input Isotopes B Other TGA Temperatures Data Output Serial Numbers About TGA Isotope ratio definition 13C 12C Y FIGURE 7 21 Typical values for calculating 613C on a TGA set with multiple ramps TGA Temperatures The Settings gt Other gt TGA Temperatures window is shown in FIGURE 7 22 To enable the heaters to maintain the TGA at a steady temperature check the Control TGA temperatures box and set Control Parameters as shown in FIGURE 7 22 Set the two temperature setpoints as needed to maintain a steady temperature Usually this will be 5 to 10 C above the highest likely ambient temperature Normally the two setpoints are set to the same value However if one of the two heaters generally works harder than the other higher duty cycle adjust the setpoints to slightly different temperatures usually within one C to balance the two heaters TGA Series Trace Gas Analyzers g Laser Temperature l Current V Control TGA temperatures Line Lock Control Parameters i i Other Detectors Pulse period 0 10 Temperature PreAmp Control coefficients P 2 00 Calculations Control coefficients I 0 01 Concentration Control coefficients D 20 00 i Analog Input 3 Other TGA Temperature 1 Data Output e 23 36 Serial Numb
92. cm 83 in 211 cm 83 in 211 em 83 in 211 cm 83 in Width 47 cm 18 5 in 47 cm 18 5 in 47 cm 18 5 in 47 cm 18 5 in Height 55 cm 21 5 in 55 cm 21 5 in 55cm 21 5 in 55 cm 21 5 in Weight 74 5 kg 164 Ib 88 9 kg 195 5 Ib 78 6 kg 173 Ib 62 8 kg 138 5 Ib Sample path length 153 08 cm 60 27 in 153 08 cm 60 27 in 146 6 cm 57 72 in 146 4 cm 57 64 in Reference path length 4 52 cm 1 78 in 4 52 cm 1 78 in 146 6 cm 57 72 in 146 4 cm 57 64 in Sample cell volume 480 ml 480 ml 420 ml 200 ml Operating temperature 20 to 45 C 20 to 45 C 20 to 45 C 20 to 45 C Weight of the TGA100A and TGA200 is shown for most common configuration LN2 laser dewar and TE cooled detectors PDoes not include the weight of the power module pn 30981 which is 5 4 kg 12 0 Ib with the accompanying power cable 5 3 Power Requirements Analyzer LN2 cooled laser Analyzer TE cooled laser Heater 90 to 264 Vac 47 to 63 Hz 42 W max 24 W typical 90 to 264 Vac 47 to 63 Hz 34 W max 22 W typical 90 to 264 Vac 47 to 63 Hz 150 W max 50 W typical 29 TGA Series Trace Gas Analyzers 6 Installation The basic components required to operate a TGA are shown in FIGURE 6 1 and FIGURE 6 2 The systems are very similar with the exception of the connections The connections are located at the end of the enclosure in the TGA100 and TGA100A whereas the connections of the T
93. d The assembly is shown in FIGURE 4 8 For applications requiring a purge gas the assembly may be ordered for delivering zero gas to the purge inlet on the TGA TGA Series Trace Gas Analyzers FIGURE 4 8 TGA reference gas connection 4 1 3 2 TGA Insulated Enclosure Cover The insulated TGA enclosure cover pn 16599 is recommended when the TGA is operated in the field without additional shelter The cover has a rainproof white exterior to reflect the sun s heat and additional insulation to dampen diurnal temperature fluctuations The cover is shown installed on a TGA in FIGURE 4 9 The cover fits over the TGA attaching with integral hook and loop fasteners The 16599 cover was introduced in 2002 for use with the TGA100A These early covers had one flap over the access hole in the top of the TGA enclosure to allow easy refilling of the liquid nitrogen cooled laser dewar A second flap was added in 2008 with the introduction of the TGA200 to allow access to the optional LN2 cooled detectors Both flaps are omitted for the TGA200A FIGURE 4 9 TGA with insulated cover enclosure To install the TGA cover place the bottom uninsulated piece under the TGA The bottom is the loops portion of the hook and loop fastener strip around the periphery Orient the bottom piece so the periphery folds up with the strips on the outside Place the top insulated piece over the analyzer oriented with the flap s over the deck plate s to allow the
94. d detectors used for long wavelength operation cool the detectors with liquid nitrogen If the TGA is equipped with the standard TE cooled detectors they will be cooled automatically 3 Start the sample vacuum pump 4 Turn on the reference gas A regulator pressure of 0 psig and a flow rate of approximately 10 ml min are recommended 10 11 12 TGA Series Trace Gas Analyzers Turn on the purge gas if required high accuracy applications A flow rate of approximately 10 ml min is recommended Power up the TGA analyzer It is supplied with universal input power supplies Connect the power supplies to AC power 90 to 264 Vac 47 to 63 Hz On a user supplied PC start the TGA program and connect to the analyzer and check its status see Section 7 2 2 Status Window Verify the TGA pressure is consistent with the previous operation of the TGA The sample pump capacity the total flow at the pump and pressure control by the sampling system determine the pressure If the pressure has changed it may indicate a problem in the plumbing Verify the correct absorption line is being scanned Usually it is sufficient to simply verify the DC current reference detector transmittance concentration and concentration noise are consistent with normal operation see Section 7 1 2 Routine System Checks If any of these values have changed significantly from their normal values see Appendix A 4 Finding the Absorption Line Veri
95. d only through the Device Configuration Utility These settings are normally retained when the TGA operating system is updated but it is good practice to verify them Connect to the TGA with the Device Configuration Utility and select the Settings Editor TGA Series Trace Gas Analyzers tab to review or edit these settings The IP address subnet mask and gateway should be set as directed by your information technology support group Set the IP port for the TGA to 3000 Device Configuration Utility 2 10 Beta File Backup Options Help M Settings Editor Send OS Terminal Logger Control Device Type M Current Setting P Address Phone Modem Radio IP Address h92 168 76 31 Gateway 192 168 2 19 Netmask 255 255 240 0 IP Port soo Serial Number 1113 Y Identification string Lab TGA200 MAC Address Ox00D02C030562 TGA100A TGA200 Unknowr Wireless Sensor IP Address Communication Port l Specifies the IP address for the TGA100A TGA200 Jse IP Co Baud Rate Appl Cance Factory Defaults Read File FIGURE 6 18 Device Configuration utility Settings Editor tab NOTE The TGA requires a static IP address Some local area networks are set up to require the network administrator to know the MAC address of devices connected to the network The Settings Editor tab also displays the TGAs MAC address but does not allow it to be edited The MAC address of each TGA is set at the
96. dard deviation of the concentration sampled at 10 Hz and calculated over a relatively short time 10 s The TGA multiple scan mode can be used to measure suitable pairs of gases Typical performance for isotope ratio measurements is given in delta notation For example the 6 C for CO is given by R c E 4 VPDB where R ratio of the isotopolog concentrations measured by the TGA CO CO Ryppg the standard isotope ratio C 12C 8 C is reported in parts per thousand per mil or o ii Allan D W 1966 Statistics of atomic frequency standards Proc IEEE 54 221 231 TGA Series Trace Gas Analyzers TABLE 5 1 Typical Measurement Noise Part Number Description Chemical Formula Typical Noise Units 30478 Nitrous Oxide N20 1 5 nmol mol 30477 Methane CH 7 0 nmol mol 31121 Nitrous Oxide and N20 1 8 nmol mol Carbon Dioxide CO 0 3 umol mol 31119 Carbon Dioxide CO 0 15 umol mol and 81 C 83C 0 5 o 30877 Carbon Dioxide CO 0 5 umol mol DC and 6 O LC 2 0 o 5180 2 0 o Preliminary specifications are subject to change without notice ballan deviation with 100 ms averaging time Based on the C 60 60 isotopolog 5 2 Physical Specifications The physical specifications of all of the TGA variants are summarized in TABLE 5 2 TABLE 5 2 Physical Specifications of TGA Variants TGA100 TGA100A TGA200 TGA200A Length 211
97. ded by folding about the center line averaging the data with a reversed copy of the data This process forces the data to appear symmetrical about the center of the spectral scan the center vertical dashed line amp Laser Settings View Less Expand Folded Colors 17 00 17 00 C FIGURE 7 34 Folded mode of laser display 79 TGA Series Trace Gas Analyzers Absorbance Absorbance mode displays the absorbance of the folded data instead of the transmittance Laser Settings mx View Less Expand Absorbance v Col 17 00 17 00 C FIGURE 7 35 Absorbance mode of laser display 80 7 2 4 4 Colors 7 2 5 Find TGA Series Trace Gas Analyzers The Colors view shown in FIGURE 7 36 is used to customize the laser settings window colors The default colors for the laser can be reset from this window ETTTEMPBMERS X Background Colors Used in Calculations Discarded Color Text Back Color Normal Color Detector Saturation Text Color m i Center Line Color FIGURE 7 36 Setting options for laser window display The Find tool is used to find and identify absorption line s It tunes the laser s output wavelength by varying the laser current and or temperature and displays a graph of the reference detector signal versus current This graph also called a laser map is comparable to a transmittance spectrum The Find tool is similar for TGA Windows and
98. dth in auto mode will scale the graph to the native resolution of the display each datum is matched to one screen pixel Resizing the graph window width changes the amount of data time that will be displayed This mode is generally preferred because the data scroll more smoothly The screen width may also be set manually in which case the traces may not scroll as smoothly The graph may be zoomed by drawing a box from left to right around the portion of the graph to be displayed This will temporarily rescale the axes and freeze the display To resume scrolling with the previous axis scaling draw a box from right to left or click the Resume button in the upper right corner of the graph Alternately you may compress or expand the scales or step up down or left right by clicking one of the icons at the top of the graph Most of these functions have keyboard shortcuts Click anywhere on the graph window to select it and hover over an icon to bring up a help box that explains it function and gives the keyboard shortcut The Data tool on the TGA toolbar brings up the Watch Window This window is used to view the TGA measurements in numerical form Expand the headings to see the values FIGURE 7 43 shows the Ramp A and Detectors headings expanded This tool is similar for TGA Windows and TGA TEC except for the names and units associated with measurements and control of the laser temperature 87 TGA Series Trace Gas Analyzers Watc
99. e Dest The Dest parameter is an array where the results of the measurement can be stored The length of the input variable array depends on the values of parameters DataList and ScanMode SDMAddress The SDMaddress parameter is a constant that defines the address of the TGA with which to communicate Valid addresses are 0 through 14 The SDM address is entered as a base 10 number unlike older jumper settable SDM instruments that used base 4 91 TGA Series Trace Gas Analyzers 92 DataList The DataList parameter is a constant that specifies the data to be retrieved from the sensor If DataList 1 only concentration and status are returned If DataList 2 then sample cell pressure laser temperature and DC Current are returned in addition to concentration and status If DataList 3 then the TGA analog signal 1 and TGA temperatures are also returned If DataList 4 then all data except DutyCycle1 and DutyCycle2 are returned If DataList 5 then all data are returned ScanMode The ScanMode parameter is a constant that specifies the number of values to be retrieved for scan specific data Normally the ScanMode parameter corresponds to the TGA Number of ramps parameter that specifies how many absorption lines are being measured If ScanMode is set to a lower number than the TGA Number of ramps parameter the data for ramp B and or C will not be retrieved from the TGA If ScanMode is set to a higher number than the TGA Num
100. e individual laser s data sheet This will help to protect the laser if the laser warms up or if the laser current parameters are inadvertently set for too much current C 7 Laser Multimode Correction An ideal laser would emit at only one frequency single mode Unfortunately some multimode lasers emit some of their power at frequencies other than the desired frequency side modes This side mode power is not absorbed by the selected absorption line therefore it gives an error in the measured concentration The TGA software can correct for a laser s multimode power if it is known what percentage of the laser s power is in the undesired side modes If known this value may be entered into the Settings gt Laser gt Other window There are three different methods to estimate the multimode power depending on the type of laser and the TGA model TE cooled lasers The TE cooled lasers used in the TGA200A are manufactured with a distributed feedback DFB feature to suppress any side modes For these lasers set the Multimode power to 0 LN cooled lasers The LN cooled lasers used in earlier TGAs do not have the DFB feature to suppress side modes These lasers are specified to have not more than 10 of their output in undesired side modes For these lasers the user may determine the multimode power experimentally The experiment consists of increasing the amount of the target gas in the absorption path to absorb virtually all
101. e tripod tower or attachments you are installing constructing using or maintaining or a tool stake or anchor come in contact with overhead or underground utility lines e Maintain a distance of at least one and one half times structure height 20 feet or the distance required by applicable law whichever is greater between overhead utility lines and the structure tripod tower attachments or tools e Prior to performing site or installation work inform all utility companies and have all underground utilities marked e Comply with all electrical codes Electrical equipment and related grounding devices should be installed by a licensed and qualified electrician Elevated Work and Weather e Exercise extreme caution when performing elevated work e Use appropriate equipment and safety practices e During installation and maintenance keep tower and tripod sites clear of un trained or non essential personnel Take precautions to prevent elevated tools and objects from dropping e Do not perform any work in inclement weather including wind rain snow lightning etc Maintenance e Periodically at least yearly check for wear and damage including corrosion stress cracks frayed cables loose cable clamps cable tightness etc and take necessary corrective actions e Periodically at least yearly check electrical ground connections WHILE EVERY ATTEMPT IS MADE TO EMBODY THE HIGHEST DEGREE OF SAFETY IN ALL CAMPBELL SCIENTIFIC PRODU
102. ease the concentration noise slightly but it will improve accuracy by reducing the detector nonlinearity This is especially important for measuring Isotope ratios D 4 Detector Linearity Coefficients An ideal detector would have linear response such that any increase in the incident optical power would increase its signal proportionally In reality real detectors have nonlinear response As the incident optical power is increased the incremental response becomes gradually lower Detector nonlinearity 1s worse at lower detector temperatures and at higher flux density large detector signals Appendix D Optimizing Detector Parameters The TGA software corrects detector nonlinearity using the quadratic polynomial r r Cr where r detector response r linearity corrected response C the linearity correction coefficient The linearity correction coefficients are defined separately for the reference and sample detector and for each ramp if using multiple ramp mode These coefficients are settable in the Settings gt Detectors gt Preamp window The reference detector linearity coefficient should be set to zero based on the assumption that the reference detector is perfectly linear This is assumed because it is difficult to quantify the nonlinearity in the reference detector and because it generally gives good results Although the reference detector may not be perfectly linear it is much more linear than the sample detec
103. eda G 3 G 2 Front and back Swagelok ferrules ssssssss G 3 G3 Swagelok plug esee ee eene IR Ee ee dee G 4 G4 OSwagelok amp cap aede ert eR UN te ee G 4 H 1 TE cooled laser assembly installed in a TGA 200A H 1 H 2 TGA input module esee nennen H 2 H 3 TGA output module sssssssssseeeeeenenene nennen H 2 H 4 Modules mounted into TGA200A electronics ss H 3 H 5 Cryocooler feedthrough holes with grommets above and plugs below toes tedio temi isst ies foerit H 5 H 6 Older style TGA input module shipped with TGA1005s H 7 H 7 Older style TGA output module shipped with TGA100s H 7 H 8 Older style two piece detector holder and short cell H 8 H 9 Newer style combined detector holder short cell shown with newer style cable sse H 9 T 1 Special control cable seeneeeeens I 1 I 2 Location of first thermistor probe attachment ssss I 1 I 3 Location of second thermistor probe attachment I 2 I 4 Thermistor cable wiring to analog inputs sssseese I 3 I 5 Control cable connection seen I 3 Tables 1 1 Historical Summary of Campbell Scientific Trace Gas Analyzers 1 3 1 Parts Included with the TGA200A sse 3 4 Part Numbers for Availab
104. edure will help to align the system well enough to see a response As soon as a detector response is Appendix B Optical Alignment observed the system is ready for the horizontal and vertical alignment procedure described in Appendix B 2 3 Horizontal and Vertical Alignment 1 Make sure the clamp knobs are loose and that the optical assembly is in position 2 Use the horizontal adjustment screw at the laser end to align the sample cell with the laser 3 Use the vertical adjustment screw to align the sample cell with the laser If no detector response is observed set the vertical adjustment near the center of its adjustment range 4 Alternately adjust the horizontal and vertical alignment screws When a response is observed in the sample detector proceed to the next section 5 Ifno detector response can be found perform the following checks e If two lasers are installed FGA200 verify you are aligning to the correct laser e Verify the dewar cable is installed correctly If two or more lasers are installed TGA200 verify you are using the correct cable e Verify the detector cables are correctly installed e Verify the laser is enabled in the TGA program e Recheck the laser temperature and the zero DC modulation and high current settings 6 Ifnoresponse is observed use the alignment tool pn 25897 to put the reference tip tilt mirror and the detector mirrors at their nominal positions as shown in FIGURES
105. en lock onto the strongest absorption line within its spectral scan Normally this will be the same absorption line it was locked onto previously In some cases however the automatic startup sequence will not find any absorption line or it will lock onto the wrong line It is recommended that the user verify that the correct absorption line has been locked The laser s emission frequency can be changed manually by changing the DC current and the modulation current It may be helpful to think of the reference detector display as a viewing window looking upon a portion of the transmittance spectrum Increase the DC current to move the window to the Appendix A Configuring TGAs for Specific Gas Species right and decrease the DC current to move the window to the left It may also be helpful to temporarily increase the width of the spectral scan by increasing the modulation current See Section 7 2 4 Laser Window for details on displaying the absorption line and adjusting the laser DC current and modulation current After the absorption line is found adjust the DC current up or down to find nearby absorption lines Compare the spacing and relative depth of the observed absorption lines to the transmittance spectrum provided in the laser s user manual to verify it is the desired absorption line Adjust the DC current to position the selected absorption line near the center of the spectral scan Readjust the modulation current see Appendix C 5
106. en the shipping clamps 31 TGA Series Trace Gas Analyzers 32 NOTE TGA100 and TGA100A The TGA200 and TGA100A used nylon belts to secure the optical bench inside the enclosure Loosen these belts and then loosen the transport lock and the axial lock screws as shown in FIGURE 6 4 Horizontal adjustment screw Tighten only when transporting Horizontal lock screw Axial lock screw AURI eme ULL FIGURE 6 4 TGA100 and TGA100A transport locks TGA200 and TGA200A The TGA200 and TGA200A use a set of four cam clamps to lock the optical bench down for transport Flip the cam clamps to the loose position for operation Also loosen the four bolt clamps that lift the optical assembly off the optical bench and the additional bolt clamp that holds the alignment mechanism down The cam and bolt clamps are shown in FIGURE 6 5 The cam and bolt clamps should be tightened only for transport They should be loose during operation to allow the optical bench to move within its enclosure with changes in temperature TGA Series Trace Gas Analyzers Cam Clamps FIGURE 6 5 TGA200 and TGA200A shipping clamps Once the enclosure is properly positioned the analyzer needs sample input connections and data output connections The analyzer should be connected to other system components as follows 6 1 1 Plumbing Connections A TGA requires only a few additional components to draw samples into the system to be analyzed The connec
107. ent pn 9838 is a box of 100 replacement filter elements This element must be replaced when it plugs enough to cause a significant decrease in the sample cell pressure The replacement interval is typically monthly but could be longer or shorter depending on conditions Atmospheric Profiles Low flow applications such as atmospheric profiles often use the pn 18072 heated filter orifice assembly This assembly uses a heated filter holder pn 18058 which uses a replaceable filter element pn 17575 This element will typically require replacement annually but this interval could be longer or shorter depending on site conditions See Section 4 1 6 Replacement Parts for details on these filter holders and replacement filter elements The TGA sample cell and optics do not require routine cleaning Historically the only TGAs returned to CSI for cleaning were heavily contaminated by inadvertently pulling large amounts of dirty water through the analyzer 8 4 Sample Pumps The TGA requires a vacuum pump to pull the air sample through the analyzer The sample pump is not included as part of the TGA so the details of pump maintenance depend on the choice of pump Two sample pumps available from Campbell Scientific are given as examples RB0021 L The RB0021 L sample pump is a large capacity pump used for eddy covariance It is an oil sealed rotary vane pump that requires periodic replacement of the oil typically monthly Oil for the RB0021
108. erial cable connecting PC to RS232 port of TGA CPU module 40 TGA100A TGA200 OS download instruction sess 41 Device configuration utility Logger Control tab 42 Device Configuration utility Settings Editor tab ssse 43 Web based decimal to hexadecimal converter 44 Device configuration utility Terminal tab esses 45 TGA tool bar functions ee eeceseceecnceneesseceeeecaeeeeceaserceaeeaeeaeeneeees 49 Connect window of TGA software interface sss 50 TGA error message for incompatible serial numbers 51 Toolbar before top and after bottom connection 51 TGA Status with a detected error bottom ssssssse 52 TGA Status window without error left and with error right and line lock manually disabled sss 52 Expanded view of the menu in the TGA s Settings window 53 TGA Windows laser settings sse 54 TGA TEC laser setting Sreser ren r A enne 54 Laser current parameter settings for TGA Windows 55 Laser current parameter settings for TGA TEC seee 56 Typical Line Lock parameter settings een 57 Settings of the Settings gt Laser gt Other screen ssssse 58 Ramp synchronization prompt eese 5
109. ers 3000 E About TGA Duty Cycle Heater 1 1 00 TGA Temperature 2 Temperature set point 3000 5 23 38 C Duty Cycle Heater 2 1 00 FIGURE 7 22 TGA temperature control window for the two TGA enclosure heaters Data Output The Settings gt Other gt Data Output window is shown in FIGURE 7 23 Check the SDM output button for normal operation This will configure the TGA as an SDM sensor allowing a datalogger to request and receive data via an SDM cable Set the SDM address for the TGA from 0 to 14 and make sure the datalogger program uses the same address to request data see Section 7 3 1 SDM Output The TGA may be configured for analog output but this option requires the use of a separate analog output module It is not possible to configure a TGA for both SDM and analog output Contact Campbell Scientific for details 67 TGA Series Trace Gas Analyzers 68 CAUTION TGA TEC Parameter Settings X Laser SDM output Line Lock SDM address for TGA OF Other Detectors eeuna Temperature PreAmp Calculations Concentration Analog Input Other N20 Conc TGA Temperatures Scaing Serial Numbers 0 00 About TGA Channel 1 l2 3 4 1 00 FIGURE 7 23 Data output setting window for SDM Serial Numbers The Settings gt Other gt Serial Numbers window is shown in FIGURE 7 24 The TGA is identified by a serial number and by a description The TGA serial number is
110. ers To install a TE cooled laser in a TGA200 1 Turn off power to the TGA200 2 Disconnect the dewar cable from the laser dewar and the electronics and remove the cable from the TGA200 This cable will not be used with the new TE cooled laser assembly which has the cable permanently attached 3 Remove the four screws that fasten the laser dewar to the TGA200 optical bench Remove the dewar from the TGA200 but keep the mounting screws 4 Mount the TE cooled laser assembly to the optical bench using the dewar mounting screws H 3 Appendix H Upgrading Early Generation TGAs to TE cooled Laser NOTE 5 Replace the input and output modules with the ones that have been modified for use with TE cooled lasers 6 Connect all of the cables to the input and output modules except the Laser Current connector Do not connect the Laser Current connector to the output module at this time 7 Install the TGA TEC software on a Windows PC See Section 6 2 1 Installation of PC Software 8 Update the TGA operating See Section 6 2 2 Updating TGA Operating System 9 Complete the configuration for a new laser See Section 6 3 Detailed Setup Instructions H 1 2 Detectors If the TGA200 was equipped with liquid nitrogen cooled detectors the detectors may be replaced with TE cooled detectors This requires the additional assembly pn 21577 TGA200 TE cooled detectors Contact Campbell Scientific for details on this upgrade
111. ers Upgrading a TGA100 is similar to upgrading a TGA200 or TGA100A It requires the same laser assembly input and output modules and software Most of the additional upgrade issues are also common to the TGA100A See the section on upgrading a TGA100A for details Some TGA100s may require additional upgrades as detailed in the following sections H 3 2 CPU Module TGA100s shipped with a CPU module that required a real time connection to a PC running DOS This was replaced with the introduction of the TGA100A by a new design that does not require a real time connection to a computer The newer style CPU module can be distinguished from the older style visually by the color of the module cover The older style has a black module cover while the newer style has a shiny nickel plated module cover The newer style CPU module is required for the TE cooled laser Most early TGAs have already been upgraded to the new CPU module Contact Campbell Scientific for details H 3 3 Input and Output Modules H 6 TGA100s shipped with an older style module cover and connectors for the input and output modules The older modules have black module covers instead of the newer nickel plated covers Compare the TGA100 modules shown below to the TGA200A modules shown in Appendix H 3 1 Basic Upgrade Modules shipped with TGA100As and TGA200s and TGA100 modules that have been upgraded will look like the upgraded modules but Appendix H Upgrading Early Generat
112. es are approximately equal within 0 2 If one duty cycle is significantly higher than the other adjust the corresponding temperature setpoint downward Try a 0 5 C change This will compensate for any average difference in thermistor readings etc It is not necessary for the duty cycles to be perfectly matched Appendix I Install Temperature Control Upgrade Campbell Scientific Companies Campbell Scientific Inc CSD 815 West 1800 North Logan Utah 84321 UNITED STATES www campbellsci com info campbellsci com Campbell Scientific Africa Pty Ltd CSAf PO Box 2450 Somerset West 7129 SOUTH AFRICA www csafrica co za cleroux a csafrica co za Campbell Scientific Australia Pty Ltd CSA PO Box 8108 Garbutt Post Shop QLD 4814 AUSTRALIA www campbellsci com au info campbellsci com au Campbell Scientific Beijing Co Ltd 8B16 Floor 8 Tower B Hanwei Plaza 7 Guanghua Road Chaoyang Beijing 100004 P R CHINA www campbellsci com info campbellsci com cn Campbell Scientific do Brasil Ltda CSB Rua Apinag s nbr 2018 Perdizes CEP 01258 00 Sao Paulo SP BRASIL www campbellsci com br vendas campbellsci com br Campbell Scientific Canada Corp CSC 14532 131 Avenue NW Edmonton AB T5L 4X4 CANADA www campbellsci ca dataloggers campbellsci ca Campbell Scientific Centro Caribe S A CSCC 300 N Cementerio Edificio Breller Santo Domingo Heredia 40305 COSTA RICA www campbellsci cc info a cam
113. ew provides a finer adjustment of the horizontal alignment than the one at the laser end allowing the signal to be more easily maximized Newer systems have a fine pitch horizontal adjustment screw at the laser end and require no adjustment at the detector end B 5 Appendix B Optical Alignment Adjust the vertical alignment screw see FIGURE B 3 to maximize the sample detector signal in the same way as for the horizontal alignment Iterate the horizontal and vertical alignment until the sample detector signal is maximized If there is a single narrow peak horizontally and vertically the system is also in good focus If the response peak is broad or if it has multiple peaks adjust the focus as outlined in the following section B 1 3 Focus Adjustment B 1 3 Focus Adjustment The optical system includes the long sample cell with the lens holder at the laser end and the beamsplitter and detectors at the other end To focus the system this entire assembly is moved closer or farther away from the laser 1 To adjust the focus first note the sample detector signal at the current focus position Loosen the axial clamping screw slide the optical assembly either forward or back a short distance 2 mm and retighten the axial clamping screw Readjust the horizontal and vertical alignment to find the maximum sample detector signal at this new focus position Compare the sample detector signal at this focus position to the signa
114. ference Gas for more details on the reference gas Connect the sample intake to the sample gas inlet The sample intake should be filtered to remove particulates 10 um maximum pore size and should have an appropriate needle valve or fixed orifice to control the sample gas flow The test intake pn 15838 is shipped with the TGA to make the initial setup easier for the user The test intake includes a filter needle valve and tubing to allow the TGA to operate without fully installing the eddy covariance EC intake and dryer or other intake assembly or sampling system that will be used in a field installation If the application requires very high accuracy connect a purge gas supply to the TGA purge inlet The purge gas supply should have an appropriate regulator flow meter and needle valve to supply approximately 10 ml min The reference gas assembly pn 15837 is available from Campbell Scientific for this connection refer to Section 4 1 3 1 TGA Reference Gas Connection 6 1 2 Data Output Connections NOTE Connect the SDM cable to the CPU module in the TGA and the datalogger A 20 ft SDM cable pn 22178 is included for this purpose If a longer SDM cable is needed use pn CABLEACBL L See Section 7 3 1 SDM Output for details on SDM data output If using the CABLE4CBL L the colors of the wires are different Remove the cable feedthrough cap from side of the TGA enclosure and insert the end of the SDM cable The connection
115. figuration Both the TGA100 and TGA100A have a long sample cell 153 08 cm 60 27 in in front of the beamsplitter and a pair of short cells reference and sample each 4 52 cm 1 78 in behind the beamsplitter see FIGURE 4 25 The normal configuration for the TGA100 and TGA100A is to use only the long sample cell and the short reference cell In this case Ls is set to zero and the values of L4 and Le are entered The concentration calculation simplifies to C XL4XD _ 0 02959 C XD L D D Q 27 TGA Series Trace Gas Analyzers 5 28 It is possible to measure very high concentrations of the target gas in the TGA100 and TGA100A by changing the plumbing connections to flow the sample air through the short sample cell instead of the long sample cell In this case L 4is set to zero and the actual values of Ls and Lp are entered The concentration calculation simplifies to C C D 3 The TGA200 and TGA200A have only one sample cell and one reference cell These are both long 146 6 cm 57 72 and located behind the beamsplitter Because they are behind the beamsplitter their lengths are entered as Ls and Lg and L is set to zero The concentration calculation simplifies to Equation 3 above Specifications Measurement Specifications The typical concentration measurement noise is calculated as the square root of the Allan variance Allan deviation with 100 ms averaging which is comparable to the stan
116. from the fitting It is strongly recommended to cap all disconnected tubes to keep them clean Spare caps may be needed if they become lost or damaged FIGURE G 4 Swagelok cap TABLE G 5 Dimensions and Part Numbers for Swagelok Caps Tubing OD in Swagelok pn CSI pn 1 8 B 200 C 19219 1 4 B 400 C 15831 3 8 B 600 C 15547 1 2 B 810 C 17335 5 8 B 1010 C 19496 Appendix H Upgrading Early Generation TGAs to TE cooled Laser Most TGAs shipped since 2000 can be upgraded to use TE cooled lasers Earlier TGAs will require more upgrades than the more recent TGA200s The following sections give details for each TGA model H 1 TGA200 H 1 1 Basic Upgrade Upgrading a TGA200 to use a TE cooled laser requires the following parts TE cooled laser assembly TGA200A Input Module TGA200A Output Module TGA TEC software The TE cooled laser assembly includes the laser mounting hardware and cable The assembly is shown in FIGURE H 1 installed in a TGA200A There are five different laser assemblies available to measure different gases pn 30477 Methane CH4 pn 30478 Nitrous Oxide N20 pn 31121 Nitrous Oxide and Carbon Dioxide N20 and CO CO is based on the PC 60 60 isotopolog pn 31119 Carbon Dioxide CO2 and 613C pn 30877 Carbon Dioxide CO2 6180 and 613C FIGURE H 1 TE cooled laser assembly installed in a TGA 200A H 1 Appendix H Upgrading Early Generation TGAs to TE cooled Laser
117. fy the detector signals are consistent with previous operation of the TGA If they have changed check the operational parameters see Appendices B through D Verify that the reference transmittance at the center of the absorption line is consistent with previous operation of the TGA This transmittance is dependent on which absorption line is selected the concentration in the reference cell the pressure in the reference cell and the laser performance A significant change indicates a problem Check the concentration and the concentration standard deviation to verify proper performance The TGA is now fully functional 7 1 2 Routine System Checks The TGA is often used for long term continuous measurements It is necessary to periodically check the status of the system and perform routine maintenance The status can be checked either with the TGA software running on the user s PC or through a datalogger connected to the TGA Ifthe TGA is in multiple ramp mode check the values for each ramp Parameters should be tracked in a log book to establish normal values and variability This will help the user to recognize when a parameter changes beyond its normal variability 1 Verify the status flags If using a datalogger make sure the value of the TGAStatus variable is zero A nonzero value indicates a problem See Section 7 3 1 SDM Output for details on the TGA status flags If using the PC software check for error messages in the
118. ghtly different for TGA Windows and TGA TEC TGA Windows FIGURE 7 10 supports a rapid warm up function to bring the laser more quickly to room temperature This is helpful for periodic typically annual evacuation of the LN dewar TE cooled lasers do not require this feature Therefore the Laser gt Current screen of the TGA TEC does not show the option to heat the laser FIGURE 7 11 Both versions have a box to turn the laser on off Check this box for normal operation Uncheck this box to disable the laser current The laser DC Mod modulation Zero and High currents determine the laser scan sequence They should be set and optimized for the individual laser The DC Mod Zero and High current parameters may also be set from the Laser window See Appendix C Optimizing Laser Parameters for details on how to set the laser current parameters This section also discusses the Line Lock and Auto buttons next to the DC Mod and Zero currents The Maximum laser current mA provides a safety limit The TGA software will not allow the DC Mod Zero or High current to be set to a value that would apply a current through the laser greater than this limit Set this limit for the individual laser Setting the maximum laser current parameter above a laser s safe operation current greatly increases the risk of damaging the laser i p Y TGA Parameter Settings al E Laser Temperature E V Laser on Line Lock Heat laser up to 310
119. h Window Aaa El Vj EI bb LE Ramp A C02 Conc 150 20323 ppm Mean C02 Conc 164 219772 ppm C02 Conc StdDev 48 20964 ppm Smp Det Signal CO2 30 5060 mV Ref Det Signal CO2 1 0053 mV Laser DC Current CO2 403 44 mA Smp Transmittance CO2 98 6258 Ref Transmittance CO2 97 7745 Ramp B Ramp C Isotope Ratios Miscellaneous Detectors Smp Det Temp 45 000 C Ref Det Temp 45 000 C Smp Det Cooler 1392 Ref Det Cooler 1451 Smp Det Gain 3 Smp Det Offset 58 Ref Det Gain 5 Ref Det Offset 0 FIGURE 7 43 Data outputs of TGA TEC 7 2 8 Files TGA data are usually collected using a datalogger However the data can also be collected using the PC The Files tool of the TGA toolbar is used to set up the values to be collected and to turn data collection on and off Clicking on the Files icon of the TGA toolbar will bring up the Data Files screen shown in FIGURE 7 44 88 Data Files EE x Turn Data Collection On Settings Files Data Files mm dd yyyy hhmm dat File Format Binary Y Col 1 Time of Day Housekeep Data File TGA Series Trace Gas Analyzers mm dd yyvy hhmm all File Format ascii Y Day of Year Col 2 C02 Conc Col 2 Time of Day Data File Col 3 Ref Det Signal CO2 Col 3 C02 Conc LH keep Fil Col 4 Smp Det Signal CO2 Col 4 Mean CO2 Conc Quse Seine Col 5
120. he ramp at lower DC current Ifa negative high current pulse is required it may be helpful to also reduce the zero current below its normal setting C 3 1 High Current Count The High current count parameter may be adjusted in conjunction with the high current The High current count parameter sets the duration of the high current pulse from 0 to 8 counts where each count represents a 20 us interval giving a total duration of 0 to 160 us Generally it is best to start with the high current counts at its maximum value which will give a low amplitude long duration pulse However if the high current is set to a small value less than 20 mA for LN cooled lasers or less than 2 mA for TEC lasers it may be helpful to reduce the high current counts and increase the high current This will allow more of the samples to be used in the concentration calculation This parameter can be adjusted from the Settings gt Laser gt Other window see Section 7 2 3 1 Laser Adjusting this parameter usually makes little difference in the TGA s performance so when in doubt this parameter should simply be left at the default which is 8 counts For multiple ramp mode the high current count is common to all ramps and should generally be left at the default 8 counts Appendix C Optimizing Laser Parameters C 4 Omitted Data Count Some additional data must be omitted from the concentration calculation to allow the laser temperature to stabilize fully
121. he tabs Typical names for the more commonly measured gases are given in TABLE 7 2 Text of the user s choice up to 23 characters may be entered as an alternative TABLE 7 2 Suggested Naming for Gas Names Setting Target Gas Suggested Naming Methane CH4 Nitrous Oxide N20 Carbon Dioxide C 50 60 12C Carbon Dioxide C 50 60 13C Carbon Dioxide C 50 60 180 Ammonia NH3 The Multimode power parameter is the percentage of the laser s power in unwanted side modes See Appendix C 7 Laser Multimode Correction for details on how to set this parameter At the bottom of the window are two ramp timing parameters that are common to all ramps High current count is the duration of the high current phase of the ramp in counts Omitted count is the number of counts to omit from concentration calculations The defaults are 8 and 20 For more information on these parameters see Appendix C 3 1 High Current Count and Appendix C 4 Omitted Data Count Temperature From the Settings gt Detectors gt Temperature window parameters can be set to control the temperature of the detectors This window is the same for both versions of the software TGA Windows and TGA TEC and is shown in FIGURE 7 15 59 TGA Series Trace Gas Analyzers 60 arameter Se E Laser Temperature Ourent V Control detector temperatures i Line Lock i Other B Detectors Cooler control update interval 10
122. iation time parameter displayed at the bottom of the window shown in FIGURE 7 17 determines the time over which these statistics are calculated Analog Input The Settings gt Calculations gt Analog Input parameters are the same for both versions of the software The TGA has four differential analog input channels Channel 2 and 3 measure temperatures inside the TGA enclosure for controlling the heaters see Appendix I Install Temperature Control Upgrade Channel 4 measures the TGA Series Trace Gas Analyzers sample cell pressure Channel is available for the user to add a sensor Each of these channels has a tab to configure it Pressure is the label given to the tab for channel 4 The default configuration for Channel 1 is shown in FIGURE 7 18 Laser Temperature Current Channel 1 Channel 2 Channel 3 Pressure Line Lock i Other Detectors Name i Es Ex TGA analog input PreAmp C PRT sensor TGA100A B Calculations A200 Concentration V Mera i f Analog Input Manual scale offset B Other TGA Temperatures Scale 1 00 Data Output Serial Numbers ee About TGA Measured data 0 02 FIGURE 7 18 Default settings for Channel 1 in analog input screen Channels 2 and 3 measure temperatures inside the TGA enclosure Early TGA used platinum resistance thermometer PRT sensors but the TGA200 and TGA200A use thermistor probes TGA100s and TGA100A may be upgr
123. iew mode of laser display sess 76 Magnified mode of laser display sss 77 Detrended mode of laser display csscesseesseeeeeseeesceeeeeteeeeeenseenes 78 Folded mode of laser display sss 79 Absorbance mode of laser display ssssssssssssss 80 Setting options for laser window display sess 81 Laser line find window eese 82 Interactive Laser Find window for a CO2 isotope laser 83 Noninteractive Laser Find window eee 84 Options for graphical display of data in TGA Windows 85 Adding parameters to a graph in TGA TEC eee 86 Example graph showing N20 concentration and standard deVIatlOTL otn CR EC ROO E 86 Data outputs of TGA TEC isses 88 Controlling PC recorded data options in the TGA 89 Example of log file messages sseeeeeeenere 90 Setting TGA for SDM output from TGA Parameter Settings Window etae tpe REOR P eO Un 91 TGA100 or TGA100A optical layout with air gap purge A 8 TGA200 or TGA200A optical layout with air gap purge A 8 TGA100 and TGA100A optical layout esee B 1 Alignment hardware of detector end of TGA100 and TGA100A B 2 Alignment hardware of laser end of TGA100 and TGA100A B 3 TGA200 and TGA200A optical
124. igned well enough to see a response in the sample detector follow these steps to optimize the horizontal and vertical alignment 1 Adjust the horizontal position see FIGURE B 5 to maximize the sample detector signal NOTE The sample and reference signals may not reach their maxima simultaneously If so ignore the reference detector signal and adjust the alignment to maximize the sample detector signal Adjust the horizontal position past the peak in each direction far enough to make sure there is a single response peak If there is a single peak leave it at the center of the peak If there are multiple peaks leave the horizontal alignment at the center of the group of peaks 2 Adjust the vertical position see FIGURE B 5 to maximize the sample detector signal in the same way as for the horizontal alignment 3 Adjust the sample detector mirror tip and tilt knobs to maximize the sample detector signal 4 Adjust the beamsplitter mirror tip and tilt knobs to maximize the reference detector signal Appendix B Optical Alignment 5 Adjust the reference detector mirror tip and tilt knobs to maximize the reference detector signal 6 Iterate these steps until both detector signals are maximized If there is a single narrow peak horizontally and vertically the system is also in good alignment If the response peak is broad or if it has multiple peaks contact Campbell Scientific for assistance B 2 4 Focus Adjustment The TGA2
125. in go to optimum temperature 103 6 485 0 65 5 6 0 31 0 12 Increase the laser operating temperature by 0 1 or 0 2 K Some lasers will allow a larger temperature increment but when in doubt use 0 1 K The line locking algorithm will decrease the DC current as needed to keep the absorption line in the center of the ramp Appendix C Optimizing Laser Parameters 13 Wait until the laser temperature and DC current stabilize and then record the values 14 Iterate this process until the transmittance or concentration noise increases noticeably 15 Return to the starting laser temperature and then step the temperature downward until the transmittance or concentration noise again increases noticeably Record the laser temperature DC current reference transmittance concentration noise and sample signal at each step To evaluate the results first verify the DC current decreases approximately linearly with increasing temperature A discontinuity indicates the line locking algorithm may have switched to a different absorption line This can be caused by other strong absorption lines nearby or by a laser mode hop If this happens repeat parts of this test near the discontinuity using a smaller step in laser temperature Watch the reference detector transmittance carefully If the discontinuity was caused by another strong absorption line nearby using a smaller temperature step may solve the problem If the
126. in carbon dioxide or water by tuning each ramp to a different isotopolog The multiple ramp mode may also be used to measure some other pairs of gases such as nitrous oxide and carbon dioxide or nitrous oxide and methane The measurement noise however will generally be higher than if a single gas is measured For measurements of a single gas the laser wavelength is chosen for the strongest absorption lines of that gas Choosing a laser that can measure two gases simultaneously involves a compromise Weaker absorption lines must be used in order to find a line for each gas within the laser s narrow tuning range 4 2 6 Concentration Calculation The reference and sample detector signals are digitized corrected for detector offset and nonlinearity and converted to absorbance A linear regression of sample absorbance vs reference absorbance gives the ratio of sample absorbance to reference absorbance The assumption that temperature and pressure are the same for the sample and reference gases is fundamental to the design of the TGA It allows the concentration of the sample Cs to be calculated by c CDD a Esso LL D where Cr concentration of reference gas ppm Lr length of the short reference cell cm Ls length of the short sample cell cm L4 length of the long sample cell cm D ratio of sample to reference absorbance The terminology long short cell is historical based on the original TGA100 and TGA100A optical con
127. intenance 8 1 Lasers and Detectors TGAs equipped with cryogenic lasers and or detectors required extensive routine maintenance refilling the dewar with LN daily to weekly and periodically typically annually evacuating the dewar to maintain its insulating vacuum TGAs equipped with TE cooled lasers and detectors require no routine maintenance Troubleshooting both types of lasers and detectors involves the routine system checks described in Section 7 1 Routine Operation and the detailed setup described in Appendices A through E TGA Series Trace Gas Analyzers 8 2 Reference Gas All TGAs require a constant flow of reference gas from a high pressure cylinder of prepared gas A typical cylinder will last approximately one year before it must be replaced See Appendix A 2 Reference Gas for details 8 3 Filtration and Sample Cell Cleaning The air sample to be measured must be filtered to remove particulates 10 um maximum pore size The filter will eventually plug requiring cleaning or replacement The filter is not included as part of the TGA so the details will depend on the choice of filter and the application flow rate Two popular configurations are given as examples Eddy Covariance Most TGA eddy covariance applications use a PD200T dryer that includes a pn 20553 47 mm filter holder Earlier TGAs used the PD1000 which had a similar filter holder These filter holders use a 47 mm diameter 10 um pore size filter elem
128. ion TGAs to TE cooled Laser without the blue sticker Some of the older modules may have been upgraded to the newer design to improve immunity to radio frequency RF interference Modules with the nickel pated module cover require only the basic upgrade described in Appendix H 3 1 Basic Upgrade Modules with the older black module cover may be upgraded at increased cost for the new module cover and connectors 9058 TGA TRACE GAS INPUT Ree SA a FIGURE H 7 Older style TGA output module shipped with TGA100s TGA100s that are still using the original black input and output modules will also be using an older style cable for the detectors See Appendix H 3 4 Detectors and Detector Cables for details on upgrading the detector cable H 3 4 Detectors and Detector Cables Similar to the TGA100A most TGA100s were supplied with TE cooled detectors However if the TGA100 was supplied with LN2 cooled detectors these should be replaced with TE cooled detector assemblies Contact Campbell Scientific for availability TGA100s used detector cables with three pairs of wires within a gray cable sheath This cable terminated at the electronics end with green screw terminal blocks In 2005 with the introduction of the TGA 100A this design was replaced with a bundle of three separate blue cables terminated with circular metal connectors The input and output modules were modified to use the H 7 Appendix H Upgrading Early Ge
129. ion and the other calibration tank should have zero concentration For applications measuring very high concentrations however it is preferable to bracket the expected measurement range For example if measuring isotope ratios in ambient CO calibration tanks with 300 ppm and 600 ppm may be preferred Configure the calibration tank connections to supply the same flow rate and to give the same sample cell pressure as for the trace gas measurements The difference in the measured concentrations for the two tanks should be equal to the true difference between the two calibration tanks If it is not adjust the Reference gas concentration ppm parameter on the Concentration Calculation window proportional to the measured error T T Cy PA Corig C 1 2 where Cue the corrected reference gas concentration Corig the original reference gas concentration T and T the true concentrations in the calibration tanks Mi and M the calibration tank concentrations measured by the TGA E 1 Appendix F TGA Frequency Response There are several issues related to the frequency response of the TGA including measurement rate sample rate digital filtering synchronicity and volume flow and pressure of the sample cell This discussion applies to all TGA variants running either the TGA Windows LN cooled lasers or TGA TEC TE cooled lasers software F 1 Measurement Rate The TGA scans a selected absorption line of a specific gas
130. is available from CSI as pn 8143 See RB0021 user manual for troubleshooting suggestions XDDI The XDD1 sample pump is a multi stage diaphragm pump used for low flow applications such as atmospheric profiles This pump requires no routine maintenance 95 TGA Series Trace Gas Analyzers See the XDD1 user manual for troubleshooting suggestions See Section 4 1 4 4 Sample Vacuum Pump for additional information about both of these pumps 96 Appendix A Configuring TGAs for Specific Gas Species Campbell Scientific TGAs can be configured to measure one of several gases by selecting an appropriate laser reference gas and detectors In some cases multiple gases can be measured simultaneously The following sections give details on how to configure the TGA for the more commonly measured gases A 1 Laser Selection CAUTION Each gas species has a unique set of absorption lines and tunable diode lasers have limited tuning ranges Therefore in most cases a different laser is required for each gas species to be measured Two types of lasers have been used in TGAs LN cooled lasers and thermoelectrically cooled TEC lasers The TGA uses a Class 1M laser Do not view the laser directly with optical instruments A 1 1 LN cooled lasers The TGA100 TGA100A and TGA200 used cryogenic lead salt lasers that were available at wavelengths from 3 to 10 um This wide range of wavelengths allowed the TGA to measure a large numbe
131. is is the estimate of the laser s multimode power Enter this value as the Multimode power parameter in the Settings gt Laser gt Other window Verify the reference transmittance is near zero C 13 Appendix C Optimizing Laser Parameters TGA200 The process for determining Multimode power in the TGA200 is slightly different than for the TGA100 and TGA100A because the TGA200 design has the reference and sample cells of similar length Therefore the absorption cannot be increased by putting the reference gas in the sample cell Instead the reference gas must be replaced by a higher concentration of the target gas If the reference transmittance is 50 or lower with the normal reference gas the second gas concentration must be at least 10 times greater than the reference gas 15 x for 50 to 60 or 20 x for 60 to 70 Otherwise the procedure is the same as for the TGA100 and TGA100A For multiple ramp operation the laser multimode power may be different for each absorption line Repeat the process described above for each ramp Appendix D Optimizing Detector Parameters Set the detector parameters after the laser parameters are adjusted D 1 Detector Gain and Offset The detector signals are processed in the TGA electronics which include an amplifier with programmable gain and offset in the input module and a second programmable gain amplifier in the analog module The detector gains and offsets are normally controlled auto
132. l at the previous focus position Step the focus again in the same direction if the signal improved or move it the other direction if the signal decreased Repeat this process until the sample detector signal has a single narrow peak of maximum height It may be helpful to record the focus position and sample signal in a table along with a qualitative assessment of the focus whether there is one or multiple peaks and if the peak seems broad or narrow Generally the goal is to set the focus for a single narrow peak giving the maximum sample signal In some cases it may be desirable to intentionally defocus the system as in some of the following scenarios e Isotope ratio measurement accuracy may be improved by defocusing to reduce detector nonlinearity e Ifthe laser signal is large enough that the detector temperatures must be raised above 0 C to avoid detector saturation defocusing will reduce the signal and it will also reduce detector nonlinearity e If it is difficult to coalign the reference and sample detector see Appendix B 1 4 Reference Detector Coalignment it may be helpful to defocus the system In cases where the optics are to be intentionally defocused start at the position of best focus and move the optical system away from the laser by no more than B 6 Appendix B Optical Alignment 5 mm It is generally best to defocus just enough to give a single relatively broad flat peak B 1 4 Reference Detector C
133. l shows the expanded window of the View More mode View More is the default mode 71 TGA Series Trace Gas Analyzers 72 amp Laser Settings EJ Laser Settings View More Expand Detrended Co View Less Expand Detrended v Colors DC current 88 14 5 amp 17 00 17 00 C FIGURE 7 27 View Less View More function of the Laser Settings window 7 2 4 2 Tabbed Expand The Tabbed or Expand button 1s used to switch between individual displays for each ramp or displaying only one ramp and having tabs to switch the displayed ramp The two display modes are shown in as shown in FIGURE 7 28 The difference between the two modes is irrelevant for single ramp mode TGA Series Trace Gas Analyzers r View Less Tabbed Detrended Colors CH4 DCcurent 88 144 H Mod curent 1 30 Ej Zero current 50 00 2 Auto High current 0 00 t 17 00 2 17 00 C 7 2 4 3 Display Mode E Laser Settings View Less Expand Detrended Colors CH4 Gase DC current 8814 HO Mod current 1 30 futo Zero current 50 00 Highcurent 0 005 FIGURE 7 28 Tabbed Expand function of the Laser Settings window The Display Mode of the Laser Settings window 1s the third button from the left There are five display modes that can be set from here The default mode is Detrended Raw Maximum Magnified Detrended Folded Absorbance A side by side comparison of the modes is gi
134. l conditions of normal use except when passed through magnifying optics such as microscopes and telescopes Do not view the laser directly with optical instruments The power cords supplied with the TGA may not be of sufficient length for a given site application If longer AC power cords are required always have a qualified electrician perform the work e WARNING o Before attempting to install or change a laser in the TGA read all documentation accompanying the laser and thoroughly review Appendix A 1 4 Changing Lasers before attempting to change or use a new laser Laser settings and proper parameters must be set according to the laser s requirements and a defined order of events must occur to initiate a new laser in the TGA Failing to do so could irretrievably damage the laser The cam and bolt clamps of the TGA should be tightened during transport Failure to do so could damage the analyzer e CAUTION O The cam and bolt clamps of the TGA should only be tightened during transport They should always be loose during operation of the TGA The optical bench of the TGA should be free to move within its enclosure with changes in temperature Failure to do so could result in inaccurate measurements TGA Series Trace Gas Analyzers 3 Initial Inspection 4 Overview e Upon receipt of a Campbell Scientific TGA inspect the packaging and contents for damage File damage claims with the shipping company Contact Campbell Scie
135. l mode and then uncheck the All Caps box at the bottom of the window as shown in in FIGURE 6 20 6 Enter C to view the Configuration Options 7 Enter 1 Ethernet Address At the prompt enter 0x followed by a four digit hexadecimal value If the serial number in hex is less than four digits use leading zeros to create a four digit hex number In the example shown in FIGURE 6 19 the serial number entered would be 0x05b2 NOTE The Ox preceding the four digit hex must be a lowercase x 44 TGA Series Trace Gas Analyzers 8 Enter 6 to Save and Exit EE O Der oraa a umm WC iei Camera Datalogger Datalogger Other Network Peripheral Peripheral Phone Modem Radio El Sensor CRS450 Series CS120 CS125 C5140 CS450 Series CS451 Series CS650 Series EC100 OBS500 TGA 100A TGA200 E Unknown Wireless Sensor Communication Port COM1 Use IP Connection Baud Rate 115200 v x TGA200A C Configuration Options 1 Ethernet Address 0x00D02C030022A 2 IP Port 3000 3 IP Address 192 168 28 91 IP Default Gateway 192 168 28 1 5 IP Network Mask 255 255 252 0 Save and Exit Exit with no Save Current Ethernet Address 0x00D02C03002A Enter New Address lower 2 bytes only Ox05b2 Configuration Options 1 Ethernet Address 0x00D02C0305B2 2 IP Port 3000 IP Address 192 168 28 91 IP Default Gateway 192 168 28 1 IP Network Mask 255 255 252 0 Save and Exit Exit with no Save
136. laser dewar to be filled Connect the side flaps to the end flaps with the hook and loop fastener strips and then attach the top to the bottom 13 TGA Series Trace Gas Analyzers 14 4 1 4 Other Accessories 4 1 4 1 TGA Air Sample Intake The TGA air sample intake assembly pn 17882 includes a rain diverter insect screen stainless steel tubing and mounting bracket The assembly can be mounted on a pipe as shown in FIGURE 4 10 with an outer diameter from 1 3 cm 0 5 in to 5 cm 2 in This intake is suitable for low or high flow applications ll a bi n FIGURE 4 10 TGA air sample intake 4 1 4 2 TGA Heated Intake Filter amp Orifice The heated intake filter and orifice pn 18072 is used with trace gas analyzer systems in low flow applications such as atmospheric profiles or chamber measurements The assembly consists of a plastic housing that covers and insulates a heated filter and orifice The filter and orifice is shown in FIGURE 4 11 The heater requires 12 Vdc 0 5 W of power and includes a connector to attach a pn 18073 L cable from a 12 Vdc source Nominal flow for the three standard orifice sizes 0 007 in 0 010 in and 0 013 in is 0 26 0 56 and 0 90 slpm at sea level Ei Una FIGURE 4 11 TGA heated intake filter and orifice 4 1 4 3 TGA High Flow Filter Holder The TGA high flow filter holder pn 20553 uses a 47 mm filter membrane to remove particulates from an air stream a
137. layout sess B 8 Alignment hardware of laser end of TGA200 variants B 8 Alignment hardware of detector end of TGA200 variants B 9 Use of alignment tool for aligning mirror in TGA beamsplitter DIOCK qp B 11 Use of alignment tool for aligning mirror in TGA beamsplitter block alternate angle B 11 Use of alignment tool to position tip tilt screws for aligning detector side mirrors esee B 12 Typical laser DC current as a function of temperature C 3 Typical reference transmittance as a function of laser ie mperatute uto etie eter testis leise e e C 4 Typical concentration noise as a function of laser temperature C 4 Typical sample detector signal as a function of laser temperature C 5 Example of using Laser Line Find function to determine laser threshold c rrent tese Set eio UOS C 6 Effects of temperature perturbation eee C 7 High current adjustment procedure see C 8 Adjustment of omitted data counts sess C 11 Adjustment of modulation current eese C 12 ECfilt r coefficients once ete etre rS F 2 EC filter frequency response linear scale F 3 EC filter frequency response logarithmic scale F 3 vi Table of Contents G I Swagelok insert saos ee RR t e r
138. le Gas Species Lasers sssss 11 4 2 Available AC Mains Power Cords by Region sss 12 4 3 Power Module Mounting Brackets sse 12 4 4 Sample Air Dryer Specifications sse 19 5 1 Typical Measurement Noise sss 29 5 2 Physical Specifications of TGA Variants esee 29 7 1 Appearance and Function of Line Lock Icons esss 57 7 2 Suggested Naming for Gas Names Setting ssssssssssss 59 Js FEC ASMSHUCE OM 4 err eee eet deett 92 7 4 Descriptions of TGAStatus Values esses 94 A 1 Discontinued Cryogenic Lead salt Lasers sess A 1 A2 TE codled Lasers a a a atea ORO o D Rat A 2 A 3 Replacement Cables for TGA Dewars sese A 2 A 4 Suggested Reference Gas Concentrations sss A 5 C 1 Example Laser Temperature Optimization Data eee C 2 F 1 Recommended Passband Settings sss F 4 F 2 Processing Lags for EC filters sse F 5 F 3 Summary of TGA Update Times sse F 5 F 4 Sample Cell Residence Time as a Function of Sample Cell Volume and TGA Model senten F 6 G 1 Available Plastic Tubing Sizes Construction and Usage Cuidelines 1iuo ehe tie e eee eet t G 2 G 2 Dimensions and Part Numbers for Swagelok Inserts G 3 G 3 Dimensions and Part Numbers for Swagelok Fe
139. lignment FIGURE B 6 illustrates the alignment hardware at the detector end NOTE This illustration is a view looking up from underneath The adjustment screws are not visible from above Sample Detector j Mirror Tip Tilt Reference Detector Mirror Tip Tilt FIGURE B 6 Alignment hardware of detector end of TGA200 variants B 2 1 Configure the TGA PC Software 1 Start the TGA program and make sure the laser and detector parameters are set appropriately for the laser 2 Display the reference detector signal and the sample detector signal in agraph The goal of the alignment procedure is to maximize these signals 3 Edit the graph options to move one of the traces to the right axis set the minimum value of each Y axis to zero and let the maximum of each Y axis scale automatically 4 Setthe reference and sample detector gains to zero This will disable automatic gain and offset adjustment which can cause confusion during the alignment process when enabled 5 Setthe detector temperatures as needed to avoid saturation This adjustment may need to be repeated during the alignment process 1f the signal level increases too much It is not important to have large signals during alignment When in doubt set the detector temperatures relatively high for relatively low signals B 2 2 Initial Alignment If the optical system is significantly misaligned there may be no observable detector response This initial alignment proc
140. line In this case it may be necessary to choose a laser temperature that gives a compromise between reference transmittance and concentration noise If there is no laser temperature that gives satisfactory performance it may be necessary to choose another absorption line For multiple ramp operation follow the process described above but also record the DC current reference transmittance and concentration noise for the additional ramps Ideally all ramps will have the same optimum laser temperature In some cases it may be necessary to set the laser temperature between the optimum temperatures for the ramps to achieve acceptable performance for all ramps C 2 Zero Current The laser current must be reduced below the lasing threshold briefly at the start of each spectral scan described in Section 4 2 5 Laser Scan Sequence to measure the detector response with no laser emission If the zero current is set too high the laser will emit some energy when it should be off and the TGA will calculate the wrong transmittance This will cause an error in the reported concentration This problem could be avoided by simply setting the zero current to 0 mA to guarantee the laser is off However both current and temperature affect the laser s emission frequency and the laser s temperature is C 5 Appendix C Optimizing Laser Parameters C 6 NOTE affected by its current The laser s temperature falls slightly when the current is reduced
141. ller H 9 l Install Temperature Control Upgrade l 1 I 1 Install Thermistor Probes 0 cccccessessseesceesceeeeeeeceeceseceseenseeneeeeeenes I 1 L2 Connect the Control Cables iaieineea i I 3 L3 Enter Control Parameters sse I 4 L4 HEISE I 4 I 1 Operations sc so cnet est ea tli ure Ge eade ash wl I 5 Figures 4 1 Screen of TGA Windows software 5 4 2 TGA200A system components 0 0 0 ceeeeesteceeeeeeseeceeeeecsaeceeeeeenaeceenees 7 4 3 TGA200A power module sese 8 AA OLGA testantake s etd Oe DR RS GIN GU 8 4 5 TGA leak check nozzle seeeeeens 9 4 6 TGA CATS Ethernet Crossover Cable sssssssss 10 4 7 Serial data Cable sss ideae mes 10 4 8 TGA reference gas connection 13 4 9 TGA with insulated cover enclosure sss 13 4 10 TGA air sample intake ssssssssssseeeeneenee 14 4 11 TGA heated intake filter and orifice 14 4 12 TGA High Flow Filter holder see 15 4 13 RB0021 sample pump sse 15 4 14 XDDI sample pump sese ene 16 4 5 DOAV502 vacuum pump nennen enne enne enne 17 4 16 DAAV505 vacuum pump nennen nennen nennen 18 4 17 PDIT air sample dryer ssssssseeeeenee 20 4 18 PDIT 1 5 air sample dryer 20 Table of Contents PD200T air sample dryer naan ken eene ROI erre 21 PD625 air sample diyet nenne e e E E aR 21
142. losure and in the TGA200A enclosure AC power input is required and the appropriate input cable type should be specified at the time of order The type of mounting hardware for the module is also specified at the time of order TGA Series Trace Gas Analyzers FIGURE 4 3 TGA200A power module 4 1 1 2 TGA Accessory amp Tool Kit The TGA200A comes with an accessory and tool pack pn 15895 containing a tube cutter analyzer mirror position gauge and screwdriver as well as an assortment of Swagelok fittings end wrenches hex keys and hose clamps Many of these items are required during the installation of a trace gas analyzer 4 1 1 3 TGA Test Intake The test intake for the TGA200A pn 15838 includes a filter needle valve and 7 6 m 25 ft of tubing for use as a sample intake It is shipped with trace gas systems and may also be purchased as a replacement part The test intake is shown in FIGURE 4 4 FIGURE 4 4 TGA test intake 4 1 1 4 TGA Leak Check Nozzle A leak check nozzle for the TGA200A pn 15836 includes 7 6 m 25 ft of tubing and a needle valve and nozzle for detecting leaks around fittings and tubing of a trace gas analyzer Detecting leaks requires the user to supply a TGA Series Trace Gas Analyzers pressure regulator and gas tank where the tank should contain a relatively high concentration of the gas being measured The leak check nozzle is shipped with each trace gas analyzer and may be purchased as a re
143. many times but the assembly process is slightly different than the first assembly 1 Insert the tube with pre swaged ferrules into the fitting until the front ferrule seats against the fitting body 2 Rotate the nut finger tight 3 While holding the fitting body steady tighten the nut slightly with a wrench G 3 Common Replacement Parts Tubing Campbell Scientific can provide several types and sizes of plastic tubing as shown in TABLE G 1 A tubing cutter pn 7680 can be used to cut these tubes TABLE G 1 Available Plastic Tubing Sizes Construction and Usage Guidelines CSI pn Tubing Type OD in ID in Length ft Construction Notes 15702 Synflex 1300 1 4 0 17 500 Black HDPE Aluminum jacket overlapped layer limits 15703 38 1 4 250 aluminum tape diffusion best 19164 1 2 3 8 250 ethylene for sample copolymer liner tubes 26506 LLDPE 3 8 1 4 500 Black linear low More flexible density than HDPE 25539 1 2 3 8 500 polyethylene 19499 HDPE 5 8 1 2 100 Black High Required for density larger polyethylene diameter Tubing inserts Appendix G Using Swagelok Fittings Inserts are recommended for use in plastic tubing These inserts become permanently attached to the tubing at the first assembly so spare inserts may be needed for replacing the ends of tubing X C FIGURE G 1 Swagelok insert TABLE G 2
144. matically by the TGA software To enable this automatic control click the Auto gain offset box on the Settings gt Detectors gt Preamp window To set the offsets and gains manually adjust one of the values to disable the automatic function The detector gains and offsets should usually be controlled automatically However there are two exceptions First automatic control should be disabled while performing some of the setup steps such as optical alignment Second the automatic gain algorithm will not increase the sample gain beyond gain 7 Therefore if the detector signals are extremely weak it may be necessary to set the detector gains and offsets manually D 2 Detector Preamp Gain The detector electronics have a fixed gain in the first preamplifier stage Early TGAs used a gain of 200 but this was changed to 45 for TGA200s and TGA200As This reduced gain allows the detector signals to be larger without saturating the input range This is an advantage for higher power lasers and for LN2 cooled detectors used for longer wavelengths Some early input modules have been modified to use a gain of 45 in the preamp These instruments are identified by a label on the printed circuit board Gain 45 Input modules upgraded for use with TE cooled lasers have a gain of 45 These modules have a blue label on the top that designates them for use with TE cooled lasers see Appendix H 3 1 Basic Upgrade The preamp gain either 45 or 200 must be en
145. mum current To avoid damaging the laser make sure the laser cable is not connected 5 Turn the analyzer electronics on 6 Sendthe new parameters to the TGA as you connect the TGA software 7 Savethe new parameters in the TGA 8 Turn the analyzer electronics off A 3 Appendix A Configuring TGAs for Specific Gas Species 9 Connect the Laser Temperature Laser Heater Cooler and the dewar LN gt cooled laser connectors To avoid damaging the laser do not connect the Laser Current connector at this time 10 Turn the analyzer on 11 Connect to the TGA with the TGA software Receive the parameters as you connect This allows you to view the parameters stored in the TGA 12 Verify all of the parameters are correct for the new laser If any parameters are incorrect adjust the parameters as needed and repeat steps 7 to 12 Do not proceed until you verify the correct parameters are stored in the TGA s non volatile memory 13 Turn the analyzer off and connect the Laser Current connector 14 Turn the analyzer on 15 Connect to the TGA with the TGA software Receive the parameters as you connect The new laser will now be active To complete the installation change the reference gas Appendix A 2 Reference Gas and detectors Appendix A 3 Detectors if necessary and then follow the steps in Appendix B Optical Alignment Appendix A 4 Finding the Absorption Line Appendix C Optimizing Laser Paramete
146. ncentration oncentration i Analog Input B Other TGA Temperatures Data Output Serial Numbers Absorption Cell Lengths About TGA Length of long sample cell cm 0 00 Length of short sample cell cm 146 60 Length of reference cell cm 146 60 Standard Deviation Standard deviation time 5 00 FIGURE 7 17 Calculation concentrations settings The center section of this window displays information about the Reference Gas Concentration Enter the concentration of the reference gas in ppm This parameter is used as detailed in Section 4 2 6 Concentration Calculation to derive the concentration of the air in the sample cell This parameter may be adjusted as described in Appendix E Calibration to improve the accuracy of the TGA If the number of ramps is greater than one each ramp will have a reference gas concentration parameter The Absorption cell lengths are also used to calculate the concentration of the air in the sample cell See Section 4 2 6 Concentration Calculation for a discussion of how these parameters are used in the calculation and see Section 5 2 Physical Specifications for the correct lengths to enter for each of the TGA models The TGA software calculates a mean and a standard deviation of the concentration measurements These statistics can be displayed either graphically Section 7 2 6 Graph or numerically Section 7 2 7 Data or they may be saved to the data files Section 7 2 8 Files The standard dev
147. nd has been designed with minimal dead volume to maintain frequency response when performing eddy covariance measurements Itis included as part of the PD200T sample air dryer and may be used in any application that requires a large capacity filter with minimal dead volume The filter holder is shown in FIGURE 4 12 This filter holder replaces pn 9839 which was used with the PD1000 sample dryer TGA Series Trace Gas Analyzers FIGURE 4 12 TGA High Flow Filter holder 4 1 4 4 Sample Vacuum Pump The TGA requires a sample pump to pull the sample and reference gases through the TGA at low pressure The actual flow rate and pressure required will depend on the application Two sample pump options are available from Campbell Scientific The XDDI has a capacity of 1 slpm at 50 mb 0 8 slpm with 50 Hz power and is adequate for low flow applications The RB0021 L has a capacity of 18 slpm at 50 mb 15 slpm with 50 Hz power and is used for high flow applications The pumps are supplied with the tubing and fittings needed to connect to the TGA A brief overview of each of the pumps is given in the following descriptions RB0021 L Sample Pump The RB0021 sample pump is an air cooled direct drive oil sealed rotary vane pump It is modified with a special oil return line that allows continuous operation with minimal loss of pumping capacity and a 2 54 cm 1 0 in inlet connection Specifications are given for 115 Vac 60 Hz single phase power
148. ned by the settings in the PC software TGA Windows or TGA TEC Analog The TGA can be equipped with an optional SDM to analog converter to provide an analog version of the digitally filtered concentration measurements for analog data acquisition systems These analog outputs will be updated at different rates depending on whether the TGA 1s measuring 1 2 or 3 gases The analog outputs are updated every 6 ms 167 Hz 4 ms 250 Hz and 6 ms 167 Hz for single double and triple ramp operation respectively The sample rate will be determined by the user supplied analog data acquisition system F 1 Appendix F TGA Frequency Response F 3 Digital Filters No units The TGA has two types of digital filter available a moving average and an EC filter optimized for eddy covariance measurements The moving average filter option is generally used for low flow rate applications such as atmospheric profiles or soil chambers The user selects the averaging time from 2 to 2000 ms The TGA s actual measurement time is 2 ms so setting the averaging time to 2 ms gives the original unfiltered data The averaging time is normally set to the sampling interval For example if data are collected by a datalogger at 10 Hz 100 ms sampling interval the moving average should be set to 100 ms All of the original 500 Hz measurements are thus represented in the averages saved by the datalogger The EC filter is a finite impulse response FIR
149. needed TGA Series Trace Gas Analyzers Parameters could not be sent l x Connection Refused Incompatible Serial Numbers The TGA serial number in the parameter file 1112 does not match the serial number of the TGA 1113 at IP address 192 168 76 31 Parameters are not sent FIGURE 7 3 TGA error message for incompatible serial numbers CAUTION Use extreme caution when sending parameters to the TGA to make sure the correct parameters are being sent If the wrong parameters are sent for the laser in the TGA the laser may be damaged After sending parameters parameter synchronization will automatically default back to Receive Parameters from TGA Choose an update interval which defines how often data are sent from the TGA to the PC The default is 100 ms If the connection is slow the connection may be unreliable In this case a longer interval such as 1000 ms may help to maintain the connection The update interval may be changed while the TGA is disconnected or connected Once the TGA is connected the Connect icon will change to reflect this as shown in the bottom panel of FIGURE 7 4 If defined previously see Section 6 2 3 Configure Ethernet Connection the identification string will appear at the top of the toolbar eee e a We 0X mw EE E ld Connect Status Settings Laser Find Graph Dat Files KO TGA TEC Connected to Lab TGA200 Ea WD A ov Ez 8 id Connection
150. neration TGAs to TE cooled Laser mating connector for these cables see Appendix H 3 3 Input and Output Modules This newer cable provides better immunity to RF interference Some TGA100s have already been upgraded to this style cable to improve RF immunity This newer style cable is required for TE cooled lasers because it has the proper connectors to mate with the updated input and output modules The older TGA100 cable may be replaced with the TGA100A Detector Cable Set pn 17897 Mounting this cable also requires new screws and washers pn 18000 qty 6 and pn 2146 qty 6 This cable also requires that the detector holder be of the later design Early TGA100s had a two piece design for the short absorption cells and the detector holders This was replaced in 2002 by a one piece design that allowed easier coalignment of the reference detector to the sample detector The newer style absorption cell detector holder is required for the TE cooled laser because it is compatible with the TGA100A detector cable assembly See FIGURE H 8 and FIGURE H 9 to see the difference between these two designs Contact Campbell Scientific for availability of the newer design FIGURE H 8 Older style two piece detector holder and short cell H 8 Appendix H Upgrading Early Generation TGAs to TE cooled Laser gt FIGURE H 9 Newer style combined detector holder short cell shown with newer style cable H 3 5 Temperature Controller Early TGA
151. nfiguration should result in both detectors seeing the same amount of absorption Appendix D Optimizing Detector Parameters TGA200 and TGA200A Change the tubing connection outside the TGA enclosure to flow the reference gas through both the sample cell and the reference cell in parallel Disconnect the sample and reference tubes Insert a tee and two short tubes to connect the reference gas to both the reference inlet and the sample inlet This will split the reference flow to go through both absorption cells in parallel resulting in both detectors seeing the same amount of absorption Adjust the pressure in the TGA to give reference transmittance near 90 70 to 95 is also acceptable Usually this is accomplished by changing the sample flow or by adjusting a bleeder valve at the pump Adjust the reference flow to make sure there are no leaks View the reference and sample transmittance as you adjust the reference flow from 10 to 50 ml min A significant change indicates there may be a leak Temporarily change some parameter settings for this test e Reference gas concentration ppm 1000 each ramp if in multiple mode e Length of long sample cell cm 0 e Length of short sample cell cm 100 e Length of reference cell cm 100 Start a Graph window to observe the mean concentration The reference and sample detectors are measuring absorption of the same reference gas through the same path length Therefore the measured
152. nsmittance measurement is affected by detector nonlinearity see Appendix D 4 Detector Linearity Coefficients The reference detector is more linear because it has a smaller signal Therefore this measurement should be based on the reference detector not the sample detector To achieve the optimum amount of absorption first note the reference transmittance with reference gas in the reference cell only the normal configuration Normally the reference gas concentration is chosen to give approximately 50 absorption For this test however it is best to have between 70 and 80 absorption Usually this can be accomplished by reducing the sample flow to reduce the pressure in the analyzer When the proper absorption is achieved record the sample cell pressure It is acceptable for the transmittance to be less than 70 but it must NOT be greater than 80 To configure the instrument for the multimode test turn off the sample pump swap the reference gas and sample connections and turn the pump back on This will put the reference gas in the long sample cell and the air sample in the short reference cell The total flow to the sample pump should be the same as before so the pressure should also be the same Verify the pressure is within 10 of the previous pressure Adjust the laser modulation current as needed the increased absorption may make the line wider Record the reference transmittance shown in the Laser Settings window Th
153. nt length of tubing inside the analyzer enclosure This brings both sample and reference gas to the temperature of the inside of the enclosure The absorbance of the reference gas depends primarily on the line strength of the selected absorption line the concentration of the reference gas and the path length Pressure and temperature also affect the reference absorbance The reference gas concentration should be chosen to give an absorbance in the center of the absorption line of 0 3 to 0 9 transmittance of 75 to 40 If the absorbance is significantly more or less than this the concentration noise may increase Suggested reference gas concentrations for the most commonly measured gases are listed in TABLE A 4 NOTE A higher reference gas concentration is required for the TGA100 and TGA100A because they have a shorter path length for the reference cell TABLE A 4 Suggested Reference Gas Concentrations Gas Species TGA100 or TGA200 or Balance of P TGA100A TGA200A Tank Methane CHa 15 000 1 5 500 N2 Nitrous Oxide N20 2 000 60 Air or N2 N20 CO2 N20 2 000 90 Air or N2 CO2 300 000 30 15 000 1 5 N20 CH4 N20 10 000 350 m 2 CH4 20 000 850 Croon Dioxide CO2 isotopic ratios 100 000 10 2500 Air C only Carbon Dioxide CO isotopic ratios x d f 5180 and 83C 300 000 30 10 000 1 Air Ammonia NH3 5 000 160 Air or N2 Water or other Contact Campbell Scientific
154. ntific to facilitate repair or replacement e Immediately check package contents against shipping documentation Thoroughly check all packaging material for product that may be trapped inside Contact Campbell Scientific about any discrepancies Model numbers are found on each product On cables the model number is often found at the connection end of the cable Check that correct lengths of cables are received e The TGA200A ships with the separate items listed in TABLE 3 1 TABLE 3 1 Parts Included with the TGA200A Part Number Description 15895 TGA Accessory amp Tool Pack 15836 TGA Leak Check Nozzle 25ft tubing 15838 TGA Test Intake 5ft tubing 22178 TGA200A SDM Cable 20ft Raw Plastic Tubing 1 4 in OD X 040 Wall pee Polyethylene Alum 18148 10Base T CATS Ethernet Crossover Cable 25ft 20730 9 Pin Female to 9 Pin Male Serial Data Cable 25ft 30723 TGA TEC Support Software amp OS 30981 TGA200A Power Module The optical source of Campbell Scientific TGAs is a tunable diode laser that is simultaneously temperature and current controlled to produce a linear wavelength scan centered on a selected absorption line of the trace gas A beamsplitter allows most of the energy from the laser to pass through a 1 5 m 4 9 ft sample cell where it is absorbed proportional to the concentration of the target gas The portion of the beam that is reflected by the beamsplitter passes through a reference
155. oalignment Once the optical alignment has been optimized for the sample detector check the coalignment of the reference and sample detectors Ideally the sample and reference detectors are optically coincident and adjusting the horizontal and vertical alignment gives a maximum response for both detectors at the same position Evaluate this by watching both detector signals while adjusting the horizontal and vertical alignment If they are not coincident the reference detector alignment must now be adjusted The process is different for older and newer systems Older systems The beamsplitter mount can be rotated to adjust the vertical coalignment of the reference detector to the sample detector Loosen the three beamsplitter clamping screws rotate the beamsplitter mount to maximize the reference detector signal and retighten the beamsplitter clamping screws It is recommended that the system be at normal operating pressure vacuum pump on for this step If it is not possible to achieve adequate signal on the reference detector signal by rotating the beamsplitter it may be necessary to make a small adjustment to the horizontal vertical and axial alignment to reach a compromise between the reference detector signal and the sample detector signal Newer systems These systems have a combined reference cell detector holder that includes horizontal and vertical alignment cams For these systems the beamsplitter mount should be rotated to
156. of the laser s power at the center of the absorption line The side mode power at NOTE NOTE Appendix C Optimizing Laser Parameters other frequencies will generally not be absorbed The measured transmittance at the center of the absorption line gives an estimate of the laser multimode power Two different methods are used depending on the TGA model TGA100 and TGA100A TGA100s and TGA100As have a long sample cell and a short reference cell The laser s multimode power can be estimated by temporarily putting reference gas in the long sample cell This increases the path length by a factor of almost 34 This test is best performed in conditions in which there is not an excessive amount of absorption as this can lead to two possible problems First the absorption lines become broader and absorption in the tails of the absorption line can reduce the response at the edges of the spectral scan that are assumed to be 100 transmittance This will give an error in the estimate of multimode power especially if there is another absorption line nearby Second too much absorption will increase the chances of absorbing the multimode power in some other absorption lines of the gas The correct absorption can usually be achieved by adjusting the pressure in the sample cell To begin go to the Settings gt Laser gt Other window and set the Multimode power to zero Then note the reference transmittance in the Laser Settings window The tra
157. of the keyboard to increase or decrease the value The DC current and Mod current have automatic functions that can adjust the value Click the button to the right of the up down arrow buttons to enable these automatic functions NOTE The TGA Windows software also has an Auto button for Zero current The suggested procedure for setting the Zero current does not use the function see Appendix C 2 Zero Current This button has been removed from TGA TEC 70 TGA Series Trace Gas Analyzers The DC current and modulation current can be adjusted by clicking inside the graph in the window and then using the left and right arrow keys to adjust the DC current pan right left and using the up down arrow keys to adjust the modulation current zoom in out The Laser window for TGA Windows and TGA TEC are nearly identical only the units for the laser temperature are different The TGA TEC window is shown in FIGURE 7 26 Laser Settings View Less Tabbed Detrended v Colors CH4 DCcurent 8814 9y Mod current Lasertemp 17 00 17 00 C FIGURE 7 26 The TGA TEC screen for setting laser parameters 7 2 4 1 View Less View More The View Less View More toggle allows the expansion of what is shown in the window View Less shows only the DC current for each ramp View More also shows the modulation current zero current high current and laser temperature settings The left panel of FIGURE 7 27 shows View Less the right pane
158. or 2 on the laser side 4 Set both setpoints well below the measured values Use a voltmeter to measure the voltage across each heater The voltage should be approximately 0 V NOTE The temperature control module works by switching the low side to ground When the heater is off both terminals will be at approximately 48 V with respect to ground 5 Set the TGA Temperature 1 setpoint well above the measured temperature Verify the corresponding duty cycle increases to 1 Appendix I Install Temperature Control Upgrade 6 Measure the voltage across Heater 1 It should now be approximately 48 V NOTE The heater does not greatly increase the temperature of the air flowing through the fan It is usually not possible to feel this temperature increase by hand 7 Repeatthis test with TGA Temperature 2 setpoint and Heater 2 Operation Set the temperature setpoints to the desired value typically 35 C They will normally be set to the same value The Duty Cycle Heater 1 and Duty Cycle Heater 2 parameters will be automatically adjusted to control the temperatures These duty cycles determine the fraction of the time the heaters will be turned on for each pulse The pulse repetition rate is determined by the Pulse Period parameter Put the enclosure lid on the TGA The temperature should warm up to the setpoint and stay there This warm up typically takes approximately one hour When the temperature is stable verify that the two duty cycl
159. ough water vapor at a sample intake to avoid condensation in the downstream tubing raer FIGURE 4 18 PD1T 1 5 air sample dryer The Nafion tube in the PD1T 1 5 is 1 5 ft long instead of the 6 ft length used in the PDIT It will dry 0 5 Ipm to 0 C dewpoint compared to 15 C for the PDIT The sample inlet and outlet tubes are the same 1 8 in OD SS tubes as for the PDIT but are shorter than on the PDIT The same design for the internal connection to the Nafion tube eliminates dead volume The purge connections are 3 8 in Swagelok and the dryer shell is 3 8 in OD stainless steel tubing The smaller shell reduces cost and the stainless steel tube is more rugged for mounting at the sample intake TGA Series Trace Gas Analyzers PD200T The PD200T consists of a 200 tube 48 in Nafion dryer element manufactured by Perma Pure Inc that is housed in a rugged dryer shell designed and manufactured by Campbell Scientific The PD200T includes a filter holder a flow meter to measure purge flow needle valves to adjust the sample and purge flow rates and mounting hardware Common accessories are spare filter membranes pn 9838 and a 4 40 lpm flow meter pn19541 to measure the sample flow The PD200T is shown in FIGURE 4 19 FIGURE 4 19 PD200T air sample dryer PD625 The PD625 is similar to the PD200T but is designed for lower flow rates Its 50 tube 24 in Nafion dryer element has a drying capacity one eighth th
160. ower Module Mounting Brackets Remove the cable feedthrough cap from side of the TGA enclosure and insert one end of the DC power cable Plug the DC power cable into the mating connector on the electronics box and secure the cable to the corner of the electronics box as shown in FIGURE 6 11 FIGURE 6 11 DC power cable connected to TGA200A and secured on electronics box Replace the cap of the cable feedthrough by pushing it on rotating it to fit snugly against the cables and tightening the thumbscrew Secure the SDM and power cabling by routing along the bottom of the feedthrough bracket and securing with cable ties as shown in FIGURE 6 12 37 TGA Series Trace Gas Analyzers FIGURE 6 12 Routing of SDM and power cable through TGA200A feedthrough bracket 5 Remove the feedthrough cap from the bottom of the power module Insert the other end of the DC power cable into the power module and connect it to its mating connector 6 Connect the power module to AC mains power 90 to 264 Vac 47 to 63 Hz using the detachable power cord NOTE If a long AC power cord is required have a qualified electrician connect the field wireable plug pn 28771 to a user supplied cord 7 Replace the cap of the cable feedthrough by pushing it on rotating it to fit snugly against the cables and tightening the thumbscrew The connected power module enclosure is shown in FIGURE 6 13 38 TGA Series Trace Gas Analyzers FIGURE 6 1
161. ower and the mode hop characteristics of a laser may change dramatically with temperature Because both temperature and current determine the emission frequency changing the current can compensate for a change in temperature The goal in setting the laser temperature is to find the combination of temperature and current that minimizes multimode operation and avoids mode hops The following discussion uses an LN2 cooled laser as an example but the process is the same for all lasers TE cooled laser temperatures are given in units of C instead of K In principle this is straightforward but it is complicated by the iterative nature of the process All of the other laser parameters must be set to reasonably appropriate values in order to evaluate the laser temperature but the optimum value of some of those parameters depend on temperature To begin set the other laser parameters as follows 1 Set the zero current as described in Appendix C 2 Zero Current but then reduce it by approximately 20 before setting the other parameters This will help to avoid confusion caused by the laser s lower threshold current at lower temperature 2 Set the high current count and the omitted data count to their maximum values 3 Set the high current as described in Appendix C 3 High Current 4 Set the modulation current as described in Appendix C 5 Modulation Current 5 Ifthe laser is used in multiple ramp mode set the parameters for each r
162. p Options Help Device Type E E mE E TGA100A TGA200 Communication Port v Settings Editor i Terminal TGA100A TGA200 OS Download Instructions This page is used to download an operating system to the TGA9032 CPU module in the TGAIO0A TGA200 trace gas analyzer 1 Remove power from the TGAIOOA TGA2O0 2 Connect a cable between one of your computer s serial ports and the RS 232 port on the TGA3032 CPU module Make sure that the appropriate serial port is selected in the left panel Click the Start button below In the resulting file open dialogue box select the 003 file that should be sent as an operating system After you have pressed the Open button in the file open dialogue press and hold the white card eject button on the TGA9032 module see the image below while applying power to the TGATO0DA TGA200 Press and hold white button While turning power on Baud Rate Start Print Instructions FIGURE 6 16 TGA100A TGA200 OS download instruction The TGA runs a program similar to a CR9000X datalogger program This program is installed at the factory and normally does not need to be updated when the operating system is updated However if this file becomes corrupted or needs to be updated connect to the TGA with the Device Configuration Utility which will bring up the screen shown in FIGURE 6 17 From there select the Logger Control tab Click the Send Program button and send the file tga cr9 4
163. p Timing High current count 8 5 Omitted count 20 2 FIGURE 7 13 Settings of the Settings Laser Other screen Number of ramps may be set to 1 2 or 3 corresponding to how many gases are to be measured see Section 4 2 5 Laser Scan Sequence If the number of ramps is decreased the laser current parameters DC Mod Zero and High current for the unused ramp remain in the parameter file Increasing the number of ramps gives the ramp synchronization prompt shown in FIGURE 7 14 To use the parameters that were previously stored in the parameter file for RAMP B click No Click Yes to overwrite the new ramp s laser current parameters with those of ramp A This synchronizes the new ramp to RAMP A This is a good choice for initial set up of the laser for multiple ramp mode or if it is not clear to the user what parameters are in the file for the new ramp 7 2 3 2 Detectors TGA Series Trace Gas Analyzers Increasing Number of Ramps WB Would you like to syncrhonize RAMP B with RAMP A FIGURE 7 14 Ramp synchronization prompt The middle section of the Settings gt Laser gt Other window FIGURE 7 13 will have a tab for each ramp Click the tab to bring it to the foreground Each tab has two parameters Gas name and Multimode power Gas name is a label that is used throughout the TGA software to designate what gas 1s measured for example after defining these settings the TGA will automatically label t
164. pbellsci cc Campbell Scientific Ltd CSL Campbell Park 80 Hathern Road Shepshed Loughborough LE12 9GX UNITED KINGDOM www campbellsci co uk sales campbellsci co uk Campbell Scientific Ltd CSL France 3 Avenue de la Division Leclerc 92160 ANTONY FRANCE www campbellsci fr info campbellsci fr Campbell Scientific Ltd CSL Germany FahrenheitstraBe 13 28359 Bremen GERMANY www campbellsci de info campbellsci de Campbell Scientific Spain S L CSL Spain Avda Pompeu Fabra 7 9 local 1 08024 Barcelona SPAIN www campbellsci es info campbellsci es Please visit www campbellsci com to obtain contact information for your local US or international representative
165. placement part as well The leak check nozzle assembly is shown in FIGURE 4 5 FIGURE 4 5 TGA leak check nozzle 4 1 1 5 TGA SDM Cable The TG200A includes a 6 m 20 ft cable pn 22178 used to connect the SDM ports on a trace gas analyzer to the SDM ports on a datalogger The cable includes three wires for SDM signals one wire for ground and a shield One end has untinned pigtail wires used to connect semi permanently to the trace gas analyzer s SDM connector The other end has tinned pigtail wires used to connect to the ports on a datalogger or SDM hub 4 1 1 6 Plastic Tubing The TGA200A includes 6 m 20 ft of 1 4 in OD Synflex 1300 tubing pn 15702 which has a high density polyethylene jacket overlapped aluminum tape and ethylene copolymer liner The aluminum layer limits diffusion of gases through the wall of the tube making it the best option for delivering sample air from an intake to a gas analyzer 4 1 1 7 CAT5 Ethernet Crossover Cable A 7 6 m 25 ft unshielded CATSe crossover Ethernet cable pn 18148 is included The Ethernet cable should be used when connecting two Ethernet capable products directly together or when connecting one directly to a PC It is not intended for use with hubs switches or routers A CATSe crossover Ethernet cable is shown in FIGURE 4 6 TGA Series Trace Gas Analyzers cy FIGURE 4 6 TGA CAT5 Ethernet Crossover Cable 4 1 1 8 Serial Data Cable A 7 6 m 25 ft 9 pin female to
166. pn 15837 or similar hardware In the TGA100A or TGA100A the purge connection is at the end of the enclosure The purge gas flows through the short sample cell and into a purge boot around the air gap between the laser and lens holder as shown in FIGURE A 1 A 7 Appendix A Configuring TGAs for Specific Gas Species Reference defector m No To pump E i Reference gas in Dewar LE AN EN Sample cell J N f N p s Y Sample gy wm Laser detector J S j Jj N J N2 CURT To pump Sample in FIGURE A 1 TGA100 or TGA100A optical layout with air gap purge In the TGA200 or TGA200A the purge connection is in the middle of the enclosure The purge gas splits flowing to the detector block and the beamsplitter block The flow through the beamsplitter block purges the air gap between the lens holder and the laser This configuration is shown in FIGURE A 2 detector Detector alignment mirrors Reference alignment mirror Reference detector FIGURE A 2 TGA200 or TGA200A optical layout with air gap purge A 8 Appendix B Optical Alignment Campbell Scientific TGAs have simple robust optical designs that do not require adjustments in normal use The optical alignment may need minor adjustments after transporting the system or if the laser is replaced The optical design of the earlier models TGA100 and TG100A is different than that of the later models TGA200 and TGA200A See
167. r of different gases Unfortunately these lasers were discontinued by the manufacturer in 2012 For reference the part numbers and gases measured are listed in TABLE A 1 TABLE A 1 Discontinued Cryogenic Lead salt Lasers Part Number pn Target Gas es Molecular Formula 7979 Methane CH4 7113 Nitrous Oxide N20 21400 Methane and Nitrous Oxide CH and N20 21401 Nitrous Oxide and Carbon Dioxide N20 and PC 60 90 17466 Carbon Dioxide and 8 C 2C160 60 and C 60 60 17469 Carbon Dioxide 8C and 5 8O 20160160 130160160 and 120180160 21398 Water Vapor 5D and 8 O H H O 7H H O and H H 8O 21399 Ammonia NH3 A 1 2 TE cooled Lasers The TGA200A uses TE cooled lasers that became available in 2014 These lasers are available at wavelengths from 3 to 6 um allowing the TGA200A to measure the gases most commonly measured with earlier TGAs In most cases earlier TGAs may be upgraded with a new TE cooled laser to avoid the need A 1 Appendix A Configuring TGAs for Specific Gas Species for cryogens See Appendix H Upgrading Early Generation TGAs to TE cooled Laser for details Part numbers for these lasers are listed in TABLE A 2 TABLE A 2 TE cooled Lasers Part Number pn Target Gas es Molecular Formula 30477 Methane CH4 30478 Nitrous Oxide N20 31121 Nitrous Oxide and Carbon Dioxide N20 and PC 60 50 31119 Carbon Dioxide and 68 C 12C160 60 and PBCISO 60 3
168. r temperature stability Some TGA100As have already been upgraded in conjunction with upgrades to the TGA Windows software This upgrade is not required for using TE cooled H 5 Appendix H Upgrading Early Generation TGAs to TE cooled Laser lasers but it is recommended for all TGA100As See Appendix I nstall Temperature Control Upgrade for details H 2 5 Power Module TGA100As shipped with two AC DC power adapters mounted under the electronics mounting bracket One of these power adapters supplies 12 Vdc power to the electronics and the other supplies 48 Vdc power to the temperature controller In the event that a TGA100A power supply fails an upgrade is available This upgrade includes a special version of the pn 30981 power module that has been modified to supply 48 Vdc for the heaters instead of the 24 Vdc used be later TGA models TGA200 and TGA200A Contact Campbell Scientific for details H 2 6 Purge Boot H 3 TGA100 Some TGA100As included an optional purge boot between the laser dewar and the optical assembly The purge boot mounted to the laser dewar and sealed around the front lens holder to enclose the air gap between the laser dewar and thelens The purge boot can be mounted to the TE cooled laser assembly in the same way as for the laser dewar If the purge boot becomes damaged contact Campbell Scientific and request pn 15902 H 3 1 Basic Upgrade Most TGA100s shipped since 2000 may be upgraded to use TE cooled las
169. reference and sample cells have the same length see TABLE 5 2 for a summary of these specifications for all systems The back end of each cell has a focusing lens alignment mirror and detector Sample detector Detector alignment mirrors Reference alignment mirror Reference detector FIGURE 4 26 TGA200 and TGA200A optical configuration 24 4 2 2 Laser DANGER 4 2 3 Dewars 4 2 4 Detectors TGA Series Trace Gas Analyzers The lead salt diode lasers used in the TGA100 TGA100A and TGA200 required cryogenic cooling These lasers were available at any wavelength from 3 to 10 um which could be specified to detect any one of many distinct species of different gases Lead salt tunable diode lasers have a limited tuning range typically 1 to 3 cm within a continuous tuning mode In some cases more than one gas can be measured with the same laser but usually each gas requires its own laser Most of these early TGAs used liquid nitrogen LN to cool the laser but some TGA100As used a cryocooler The laser dewars and cryocoolers have two laser positions available four with an optional second laser mount allowing selection of up to four different species by rotating the dewar installing the corresponding cable and performing a simple optical realignment In 2012 when the only manufacturer stopped production lead salt diode lasers became unavailable In 2014 however a thermoelectrically cooled interband c
170. rm is available from our web site at www campbellsci com repair A completed form must be either emailed to repair campbellsci com or faxed to 435 227 9106 Campbell Scientific is unable to process any returns until we receive this form If the form is not received within three days of product receipt or is incomplete the product will be returned to the customer at the customer s expense Campbell Scientific reserves the right to refuse service on products that were exposed to contaminants that may cause health or safety concerns for our employees Precautions DANGER MANY HAZARDS ARE ASSOCIATED WITH INSTALLING USING MAINTAINING AND WORKING ON OR AROUND TRIPODS TOWERS AND ANY ATTACHMENTS TO TRIPODS AND TOWERS SUCH AS SENSORS CROSSARMS ENCLOSURES ANTENNAS ETC FAILURE TO PROPERLY AND COMPLETELY ASSEMBLE INSTALL OPERATE USE AND MAINTAIN TRIPODS TOWERS AND ATTACHMENTS AND FAILURE TO HEED WARNINGS INCREASES THE RISK OF DEATH ACCIDENT SERIOUS INJURY PROPERTY DAMAGE AND PRODUCT FAILURE TAKE ALL REASONABLE PRECAUTIONS TO AVOID THESE HAZARDS CHECK WITH YOUR ORGANIZATION S SAFETY COORDINATOR OR POLICY FOR PROCEDURES AND REQUIRED PROTECTIVE EQUIPMENT PRIOR TO PERFORMING ANY WORK Use tripods towers and attachments to tripods and towers only for purposes for which they are designed Do not exceed design limits Be familiar and comply with all instructions provided in product manuals Manuals are available at www campbellsci com or
171. rrules G 3 G 4 Dimensions and Part Numbers for Swagelok Plugs G 4 G 5 Dimensions and Part Numbers for Swagelok Caps G 4 I 1 Control Parameters for TGA Thermistors sseeeeess I 4 vii Table of Contents viii TGA Series Trace Gas Analyzers 1 Introduction Campbell Scientific has been manufacturing tunable diode laser absorption spectrometer TDLAS trace gas analyzers TGAs since 1993 While the TGAs have improved through a succession of four different generations the core technology remains the same The TDLAS technique provides high sensitivity speed and selectivity All Campbell Scientific TGAs are rugged portable instruments designed for use in the field Common applications include gradient or eddy covariance flux measurements of methane or nitrous oxide and isotope ratio measurements of carbon dioxide Many of the important improvements are available as upgrades for older models These substantial upgrades blur the lines between the various models This manual covers all of the TGA models to some extent with emphasis on the later variants A brief summary of these TGA models and the most relevant improvements are summarized in TABLE 1 1 TABLE 1 1 Historical Summary of Campbell Scientific Trace Gas Analyzers TGA100 TGA100A TGA200 TGA200A Ship dates 1993 2004 2005 2009 2008 2012 2014 Transputer
172. rs Appendix D Optimizing Detector Parameters and Appendix E Calibration A 2 Reference Gas A prepared reference gas having a known concentration of the gas to be measured must flow through the reference cell The beamsplitter directs a fraction of the laser power through the reference cell to the reference detector This gives a reference signal with the spectral absorption signature of the reference gas The reference signal provides a template for the spectral shape and position of the absorption feature This allows the concentration of the sample gas to be derived without measuring the temperature or pressure of the sample gas or the spectral positions of the scan samples The reference signal provides feedback for a digital control algorithm to maintain the center of the spectral scan at the center of the absorption line line locking The reference signal also allows the user to identify the wavenumber of an absorption line by comparing it to the theoretical absorption spectrum of the gas The reference cell is kept at the same pressure as the sample cell by connecting the outlets of both cells to a common vacuum manifold A continuous flow of reference gas must be maintained to avoid dilution of the reference gas with the sample gas A flow of 10 ml min is recommended Appendix A Configuring TGAs for Specific Gas Species The reference gas and sample gas are brought to the same temperature by flowing each of them through a sufficie
173. s at the TGA use a five pin green connector as shown in FIGURE 6 8 12 not connected G SDM reference black and SDM shield clear C1 SDM data green C2 SDM clock blue C3 SDM enable yellow FIGURE 6 8 SDM connections of TGA 35 TGA Series Trace Gas Analyzers The SDM cable connector attaches to the CPU board in the TGA as shown in FIGURE 6 9 9010 FIDWER SUPPLY FIGURE 6 9 SDM cable connector on TGA CPU board Once the SDM cable is connected to the CPU board secure the cable to the outside of the electronics box at two places as shown in FIGURE 6 10 FIGURE 6 10 SDM cable tied to electronics box Connect the other end of the SDM cable to a datalogger To configure the TGA for SDM output connect a PC running TGA Windows TGA TEC Open the window Settings gt Other gt Data Output 36 6 1 3 Power TGA Series Trace Gas Analyzers Click SDM Output as shown in FIGURE 7 46 of Section 7 3 1 SDM Output and enter the SDM address for the TGA The TGA100 TGA100A and TGA200 used AC DC adapters inside the analyzer enclosure to provide power for the analyzer and the temperature controller Connect these to AC mains power using the detachable power cords supplied The TGA200A includes a TGA power module pn 30981 which is a separate enclosure to house the AC DC adapters 1 Mount the TGA power module near the TGA Various mounting options are available as described in Section 4 1 2 3 P
174. s heat is needed to maintain the laser at the set temperature and the laser heater voltage will gradually decrease Therefore monitoring the laser heater voltage may give an indication of when it is time to evacuate the dewar If the TGA is equipped with a TE cooled laser record the laser cooler voltage Verify that the concentration and concentration noise are as expected If the TGA is equipped with a LN2 cooled laser fill the laser dewar with liquid nitrogen as needed If the TGA is equipped with LN2 cooled detectors fill the detector dewar as needed Check the reference gas tank and regulator pressure Check other tanks air gap purge calibration etc as needed Monitor the change in pressure as these gases are consumed to gauge when to order replacement tanks and to identify possible leaks 7 1 3 Shutdown Procedure This section describes the routine shutdown procedure for the TGA l If a PC is connected to the TGA turn off data collection if data is being collected and quit the TGA program Shut off the TGA sample pump and bypass pump if applicable Shut off power to the TGA Shut off reference gas supply Shut off air gap purge supply if applicable Shut off calibration gas supplies 1f applicable TGA Series Trace Gas Analyzers If the TGA is equipped with a LN2 cooled laser there are two recommended shutdown states the TGA should be left in depending on how soon the TGA will be put back into use e
175. s through the insides of the tube or bundle of tubes and the purge air flows outside of the tubes in the opposite direction The water vapor is forced through the wall of the tubes by a difference in vapor pressure The sample becomes progressively drier as it travels down the dryer while the purge air becomes progressively more humid For best performance the purge flow should be very dry 40 C dewpoint and should have an actual flow rate of at least twice the sample flow Although the purge flow could be supplied by air from a compressed air tank or by ambient air dried with a chemical desiccant for most TGA applications it is provided by the dryer itself A portion of the sample flow is split off at the outlet of the dryer and pressure is reduced by connecting the purge outlet to the TGA sample pump Dropping the pressure reduces the partial pressure of the water vapor and increases the actual flow rate allowing the purge requirements to be met with just a fraction of the sample flow More information on the dryer can be found at www permapure com TABLE 4 4 Sample Air Dryer Specifications Specification Units PDIT 1 5 PDIT PD625 PD200T Campbell Scientific pn 21772 19206 16315 19200 Length cm in 72 28 239 94 76 30 137 54 Weight kg Ib 0 4 0 9 0 7 1 5 4 4 9 7 5 6 12 4 Connections e Sample Inlet 1 8 tube 1 8 tube 1 4 Swagelok 3 8 tube e Sample Outlet 1 8 tu
176. sband The EC filters reduce noise by three to four orders of magnitude The 100 ms moving average reduces noise by approximately one order of magnitude CYWY Yi AIL RANDE i 40 i 60 80 Hertz FIGURE F 3 EC filter frequency response logarithmic scale Appendix F TGA Frequency Response The EC filter passband should be chosen to preserve high frequencies that may be in the data while attenuating noise The optimum setting depends on the TGA frequency response which in turn depends on the sample cell residence time see Appendix F 5 Sample Cell Residence Time The recommended EC passband setting as a function of sample cell residence time is given in TABLE F 1 TABLE F 1 Recommended Passband Settings Residence Time ms Recommended Filter Bandwidth Hz 100 5 100 150 4 150 200 3 200 300 2 gt 300 1 F 4 Synchronicity NOTE NOTE For EC measurements it is very important to synchronize the wind vector data from the sonic anemometer with the scalar data from the TGA The FIR filters introduce significant time delay lag into the concentration measurements Because the lag is a constant it can easily be removed by EC post processing algorithms In single ramp mode the EC filter processing lag is 372 ms This lag is the same regardless of the passband selected but it is different for two ramp and three ramp mode The processing lags for the EC filters
177. served without absorption Adjust the detector temperature setpoints in the Settings gt Detectors gt Temperature window according to these criteria Sample Detector For input modules with a preamp gain of 200 The maximum detector signal is approximately 52 mV Set the sample detector temperature as needed to give a sample signal of approximately 45 mV to make sure the input will not saturate For input modules with a preamp gain of 45 The maximum detector signal is approximately 230 mV but there is generally little improvement in noise for signals above 50 mV Set the sample detector temperature for 50 to 100 mV sample signal Reference Detector Set the reference detector temperature to give a reference signal that is approximately 10 of the sample signal about 5 mV This usually will be a temperature close to that of the sample detector Keep in mind that the TE cooled detectors can cool the detectors a maximum of 80 to 90 C Make sure the detectors can be maintained at the setpoint even with the TGA enclosure warmed up to its operating temperature To first order detector nonlinearity can be compensated using the detector linearity coefficients described in Appendix D 4 Detector Linearity Coefficients However if concentration accuracy is more important than precision it is recommended to increase the sample detector temperature to give a signal level of 35 to 40 mV 3 to 4 mV for the reference detector This may incr
178. splay 75 TGA Series Trace Gas Analyzers Maximum View Maximum View displays the reference and sample transmittance scaled to the maximum and minimum of all of the data including the zero high and omitted data View Less Expand 17 00 r3 17 00 C FIGURE 7 31 Maximum View mode of laser display 76 TGA Series Trace Gas Analyzers Magnified The Magnified view displays the reference and sample transmittance scaled to the maximum and minimum of the data used in the concentration calculation including the zero high and omitted data This mode is used to set High current Laser Settings View Less Expand Magnified Colo CH4 17 00 17 00 C FIGURE 7 32 Magnified mode of laser display 77 TGA Series Trace Gas Analyzers 78 Detrended The Detrended display mode shows the data after they have been detrended by fitting a line to the data and dividing by this line The graph is scaled horizontally to show only the data used for concentration calculations This is the default display mode Laser Settings View Less Expand Detrended x Colo DC current 88 14 5 La Mod current 1 30 Zero current H High current 17 00 17 00 C FIGURE 7 33 Detrended mode of laser display TGA Series Trace Gas Analyzers Folded Folded display mode is similar to the Detrended display mode but the data have been detrended differently This mode shows data that are detren
179. t on the CPU module not the RS232 port and the RTD 1B and RTD 2A connectors on the temperature control module as shown in FIGURE I 5 a caf 3 aya S MODULE s LH di Te FIGURE l 5 Control cable connection Appendix I Install Temperature Control Upgrade 1 3 Enter Control Parameters 1 Inthe TGA software TGA Windows or TGA TEC bring up the Analog Input page in the Settings window 2 On the Channel 2 tab select Thermistor TGA200 3 On the Channel 3 tab select Thermistor TGA200 4 This will convert the measurements on analog inputs 2 and 3 to temperature using the conversion equation for thermistor probes 5 Inthe TGA software bring up the TGA Temperature page in the Settings window 6 Verify the temperature readings next to the temperature setpoints are approximately correct These are not intended to be high accuracy measurements but they should be within 1 or 2 C 7 Setthe control parameters to the default values shown in TABLE I 1 TABLE I 1 Control Parameters for TGA Thermistors Parameter Default Value Pulse period 0 1 Control coefficient P 2 0 Control coefficient I 0 01 Control coefficient D 20 l 4 Testing 1 Verify the TGA Temp 1 and TGA Temp 2 give reasonable values 2 Gently squeeze Thermistor 1 on the detector side between finger and thumb to warm the thermistor Verify that TGA Temperature 1 increases 3 Repeat this test for Thermist
180. tance at the Reese center of the spectral scan for ramp A 4 Reference detector transmittance at the Beier ose center of the spectral scan for ramp B i 2 Reference detector transmittance at the Reme Trane center of the spectral scan for ramp C RefDetTemp Reference detector temperature C 4 1 Current applied to the thermoelectric cooler RefDetCooler to maintain the reference detector at its 4 1 specified temperature arb RefDetGainOffset Gain and offset settings for the reference 4 1 detector preamplifier arb Sample detector signal at the center of the penpDerwienel spectral scan for ramp A mV 4 Sample detector signal at the center of the PIGDDSUDIBFAIB spectral scan for ramp B mV 2 Sample detector signal at the center of the pppoe mena spectral scan for ramp C mV 1 2 Sample detector transmittance at the center pip Deans of the spectral scan for ramp A 1 l Sample detector transmittance at the center Smp Dertigsh of the spectral scan for ramp B 5 2 Sample detector transmittance at the center POPPEL ANE of the spectral scan for ramp C 1 SmpDetTemp Sample detector temperature C 4 1 Current applied to the thermoelectric cooler SmpDetCooler to maintain the sample detector at its 4 1 specified temperature arb Gain and offset settings for the sample SEPP eatin detector preamplifier arb 1 l Fraction of full power applied to the TGA Deae enclosure heater detector end arb DutyCycle
181. tered in the parameters at the Settings gt Detectors gt Preamp window If it is unclear which gain is the correct one for a specific input module or if an input module upgrade is desired contact Campbell Scientific D 3 Detector Temperature Most TGAs are equipped with TE cooled detectors but some are equipped with LN cooled detectors to work with longer wavelength lasers LN2 cooled detectors have no temperature measurement or control They are designed to operate near LN s boiling point 77 K TE cooled detectors include a thermistor to measure the detector s temperature The TGA measures this temperature and adjusts the TE cooled current to cool the detector to the setpoint Generally a lower detector temperature will increase the detector signal and decrease the concentration noise However some lasers emit enough power to saturate the detectors 1f they are cooled to D 1 Appendix D Optimizing Detector Parameters their lowest temperature Cooling the laser can also increase detector nonlinearity Choosing the optimum temperature may involve a tradeoff between precision noise and accuracy nonlinearity To choose the optimum detector temperatures first set the reference and sample linearity coefficients at the Settings gt Detectors gt PreAmp window to zero Observe the detector signals in the Laser Settings window Increase the DC current to move away from the absorption line This allows the detector signals to be ob
182. teria must be considered e Ifthe high current is too high the laser s frequency will overshoot the absorption line at the beginning of the spectral scan quickly scan backwards through the absorption line and then scan forward through the absorption line This is visible in the reference detector display as a second narrow absorption line at the left edge of the spectral scan data See FIGURE C 6 and FIGURE C 7 This is acceptable as long as this ghost line is in the omitted part of the scan But if the signal falls off at the left edge of the scan as illustrated in the lower right of FIGURE C 6 the high current must be reduced even if the counting steps criterion indicates the high current is already too low e When incrementing the DC current it may not be possible to move the absorption line to the left edge because the two absorption lines the true line and its ghost may merge just inside the left vertical dotted line see FIGURE C 7 top right This also indicates the high current is too high For multiple ramp mode adjust the high current individually for each ramp In this case the laser temperature is perturbed by the entire previous scan not just the zero pulse of the present scan This means it will take a larger high current pulse for the ramp with the higher DC current because the laser will have cooled during the previous ramp at lower DC current It may require a negative value for the high current of t
183. tion Current The laser modulation current parameter controls the width of the spectral scan The edges of the spectral scan should extend slightly past the absorption lines to measure the laser s unabsorbed intensity 100 transmittance Adjust the modulation current until it occupies approximately one fourth of the spectral scan with a nearly flat portion on either side as illustrated in FIGURE C 9 The TGA software includes an automatic algorithm to set the modulation current To use this algorithm enable line locking and then click the Auto button next to the Mod current on the Laser Settings window Appendix C Optimizing Laser Parameters Modulation too low Modulation correct Modulation too high FIGURE C 9 Adjustment of modulation current For multiple ramp mode the modulation current must be set individually for each ramp It may need to be set to a different value for each ramp to compensate for residual temperature perturbation that cannot be completely removed by the high current pulse C 6 Laser Maximum Temperature and Laser Maximum Current The laser can be damaged by too much current or by operation at too high a temperature The TGA software will automatically disable the laser current if the laser s temperature is above an upper limit or if the laser current parameters are set to exceed an upper limit for any of the spectral scan points Set the laser maximum temperature and current to the values specified on th
184. tions for the TGA200A are located at the center of the TGA enclosure under the feedthrough cover FIGURE 6 6 Lift the cover following directions indicated on the cover to expose the connections Follow the steps below for this simple set up Refer to FIGURE 6 7 as needed for the physical connections TGA200A FIGURE 6 6 Feedthrough cover of TGA200A 33 TGA Series Trace Gas Analyzers 34 NOTE FIGURE 6 7 Plumbing connections located under feedthrough cover of TGA200A 1 Connect the vacuum exhaust outlet of the analyzer to the sample pump The sample pump must be able to pull the required flow rate at 75 mb or less The actual flow rate and pressure required will depend on the application Two sample pump options are available from Campbell Scientific The RB0021 is used for high flow applications and the XDD1 is adequate for low flow applications See Section 4 1 4 4 Sample Vacuum Pump for more details on sample pumps TGA Series Trace Gas Analyzers Connect a reference gas supply to the reference gas inlet The reference gas supply should have an appropriate regulator flow meter and needle valve so that it will supply the reference gas at approximately 10 ml min The reference gas assembly pn 15837 is available from Campbell Scientific to provide the flow meter needle valve and tubing for this connection See Section 4 1 3 1 TGA Reference Gas Connection for specifics about the assembly and Appendix A 2 Re
185. tive mode Save to File button checked will increment the laser temperature and collect and store a laser current scan at each temperature Each laser scan will be stored in a separate file The data are displayed in the laser map window as they are collected At the completion of the data collection any of the laser scans may be selected by clicking the button next to the temperature A typical screen is shown in FIGURE 7 39 83 TGA Series Trace Gas Analyzers gt E o a hi o gt o o c o o 4 o a 84 7 2 6 Graph Laser Map C 8 00 C 9 00 98 100 102 104 106 108 DC Current mA FIGURE 7 39 Noninteractive Laser Find window The Graph tool is used to graphically display real time data from the TGA The user interface is slightly different for TGA Windows and TGA TEC TGA Windows For TGA Windows click the Graph icon in the toolbar to bring up the Select Data window FIGURE 7 40 Click the parameters shown in bold to highlight which to include in the graph Ifa selection is highlighted by mistake click it a second time to toggle it off The sections for Ramp B Ramp C and Isotope Ratios are visible only if the TGA is in multiple ramp mode Once the choices are highlighted click OK to bring up the Graph window TGA Series Trace Gas Analyzers m Select Data o Select Data you would like to graph El Ramp amp C02 Conc Mean CO2 Conc CO2 Conc StdDev Smp Det Signal CO2 Ref
186. tor for two reasons First the flux density on the reference detector is low due to the beamsplitter transmitting most of the optical power to the sample detector and reflecting less than 10 onto the reference detector Second the reference detector is adjusted see Appendix D 3 Detector Temperature to give a relatively low response The reference detector may have a small amount of nonlinearity but this tends to be cancelled by setting the sample detector linearity coefficient so that the sample detector matches the reference detector as described below 1 Change the plumbing configuration to ensure the reference and sample detectors see the same absorption The step is different for the different TGA models TGA100 and TGA100A Change the tubing connections inside the TGA enclosure such that the reference gas flows through both short cells in parallel This can be accomplished by disconnecting the tubing at the inlet to the reference cell and inserting a tee and two short tubes connected to the inlets of the reference cell and the short sample cell Similarly disconnect the tubing at the outlet of the reference cell and insert another tee and two more tubes connected to the outlets of the reference cell and the short sample cell This will split the reference flow to go through the two short cells in parallel The sample inlet long sample cell should be connected in the normal way to a source of air or nitrogen This plumbing co
187. ure e reference detector signal e reference detector transmittance The TGA will disable the line lock function if it detects a problem with any of these values This prevents the line lock algorithm from misadjusting the DC current when the position of the absorption line cannot be determined reliably In this case the line locking algorithm is disabled temporarily When the error condition no longer exists the line locking is automatically re enabled The state of the line lock function is shown by three different icons on the button on the Settings gt Laser gt Current window and the Laser window The appearance and function of those icons is shown in TABLE 7 1 TGA Series Trace Gas Analyzers TABLE 7 1 Appearance and Function of Line Lock Icons Icon Function e Open yellow padlock indicates line locking has been turned off Closed yellow padlock indicates line locking is active Closed red padlock indicates line locking has been temporarily disabled by an error condition Set the Max pressure limit well above the typical operating pressure refer to FIGURE 7 12 A typical setting would be twice the operating pressure This will disable line locking when the sample pump is turned off Set the Min signal strength well below the normal value for the reference detector signal strength The default is 1 mV If the reference detector signal is less than 2 mV set this parameter to half the typical
188. ven in FIGURE 7 29 and a description of each of the modes follows 73 TGA Series Trace Gas Analyzers Laser Settings View Less Expand Raw v Colors Laser Settings View Less Expand Maximum v Colo Laser Settings x View Less Expand Magnified Color Laser Temp 17 00 17 00 C Laser Temp 17 00 17 00 C Laser Settings i Laser Settings View Less Expand Detrended Colo View Less Expand Folded Colors View Less Expand Absorbance v Col CH4 DC current Mod current Zero current High current 0 00 Laser Temp 17 00 7 17 00 C 17 00 FIGURE 7 29 Laser display modes 74 TGA Series Trace Gas Analyzers Raw Raw displays the raw detector signals with the Y axis scaled to match the input range of the electronics This mode is used to set the zero current and to verify the detector signals are within the range of the electronics not saturated Two colors are used on the right and left sides to show the range of data actually used to calculate concentration blue on right side The dashed vertical line shows the center of the spectral scan Laser Settings View Less Expand Raw v Colors CH4 DC current 88 4 gt 9 Mod current 1 30 H Zero current 50 00 High current ook Laser Temp 17 00 H J gt ee 17 00 C 1 1 FIGURE 7 30 Raw mode of laser di
189. zed measurement and rapid communication between a Campbell Scientific datalogger and multiple devices including the TGA100A TGA200 and TGA200A The TGA100 requires the CPU upgrade for SDM communication Although nearly all Campbell Scientific dataloggers support SDM only the CR1000 CR3000 CR5000 and CR6 dataloggers support communications with TGAs with the TGA instruction To configure the TGA for SDM output connect a PC running TGA Windows TGA TEC Open the window Settings Other Data Output Click the SDM output button as shown in FIGURE 7 46 and enter the SDM address for the TGA 7 3 1 1 Syntax 7 3 1 2 Remarks TGA Series Trace Gas Analyzers See the applicable user manual for details on these dataloggers TGA Parameter Settings x E Laser Temperature Current SDM output Line Lock SDM address for TGA 15 Other E Detectors Temperature PreAmp Calculations Channel 1 2 3 4 Concentration Analog Input B Other CH4 Conc Analog output TGA Temperatures Scaling Serial Numbers 0 00 About TGA FIGURE 7 46 Setting TGA for SDM output from TGA Parameter Settings Window The datalogger program must include the TGAQ instruction to retrieve data from the TGA The TGAQ instruction is used to measure a TGA100A TGA200 or TGA200A trace gas analyzer system It is also used for TGA100 with the upgraded CPU module TGA Dest SDMA ddress DataList ScanMod

TGA Series Trace Gas Analyzers

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