Fast Greenhouse Gas Analyzer

Transcript

LOS GATOS RESEARCH  Fast Greenhouse Gas Analyzer Model Number 907-0010 Los Gatos Research 67 East Evelyn Avenue, Suite 3 Mountain View, CA 94041 Phone: 650-965-7772 Fax: 650-965-7074 http://www.lgrinc.com/ Los Gatos Research Table of Contents Table of Contents ................................................................................................................ 2 Installation........................................................................................................................... 3 Electrical Power Connection....................................................................................... 3 Keyboard / Video / Mouse (KVM) Connections ........................................................ 3 Data Interface Connections ......................................................................................... 4 Gas Inlet / Outlet Connections .................................................................................... 4 Instrument Startup / Shutdown ................................................................................... 5 Operation............................................................................................................................. 5 Main Panel ...................................................................................................................... 5 Display Modes ............................................................................................................ 5 File Transfer Menu ..................................................................................................... 7 Startup / Shutdown.................................................................................................... 12 Setup Panel.................................................................................................................... 15 Flux Mode ................................................................................................................. 15 File Settings Menu .................................................................................................... 16 Calibration Menu and Mirror Ringdown Time ......................................................... 16 Serial Configuration Menu ....................................................................................... 18 Service Mode Menu .................................................................................................. 19 Time Menu ................................................................................................................ 19 Data Analog Output Menu ........................................................................................ 20 Manifold Menu (for Optional Multi-port Inlet Unit) ................................................ 21 Laser Offset Menu .................................................................................................... 22 Appendix ........................................................................................................................... 26 Appendix A - Instrument Flow Schematic ............................................................... 26 Appendix B – High Flow Throttle Valve Operation (Fast Flow Only) .................... 27 Appendix C – Accessing data via a LAN Ethernet Connection ............................... 29 Appendix D: Multi-port Inlet Unit (Optional) ......................................................... 31 LGR Contact Information: ................................................................................................ 35 Rev. 10-A 2 of 35 Los Gatos Research Installation The Fast Greenhouse Gas Analyzer (model 907-0010) is comprised of several components. Be sure to check that each of the system components has arrived before beginning the installation procedure. You should have received:       Fast Greenhouse Gas Analyzer (FGGA) Instrument Power Cord FGGA Users Guide (this document) Null Modem type Serial Data Cable USB Flash Drive Muffler for Internal Pump Exhaust If you have not received all of these components, please contact LGR (650-965-7772 or [email protected]). Electrical Power Connection In order to operate the Fast Greenhouse Gas Analyzer, it must be connected to mains power via the fused power entry module on the back of the unit. The unit can be switched from 115 VAC to 230 VAC via a voltage selection switch on the rear panel near the power entry module (Figure 1). If operation from any other voltage source or frequency is desired, please contact LGR. Figure 1: AC power entry module with fuse and AC voltage selection switch Keyboard / Video / Mouse (KVM) Connections The Fast Greenhouse Gas Analyzer (model 907-0010) has connections for an external keyboard, monitor, and mouse on the back panel (see Figure 2). A standard PS/2 mouse and keyboard should be used, and an analog monitor capable of supporting 800 x 600 pixel mode should be connected. Figure 2: Keyboard, Video, and Mouse connections. Rev. 10-A 3 of 35 Los Gatos Research Data Interface Connections The RMT-200 Fast Greenhouse Gas Analyzer has eight data interface connection ports (see Figure 3). The “USB” ports (one on the rear panel, one on the front panel) can be utilized for file transfer to USB memory devices, or connection of other USB devices (keyboard, mouse). The “Serial” port is utilized for real-time measurement output directly to a computer. The “Ethernet” connection allows the instrument to be connected to a Local Area Network (LAN) and the data directory is made available as a Windows™ network shared directory. The “CH4” and “CO2” and “H2O” analog ports provide a DC voltage that is proportional to the measured methane, carbon dioxide, or water vapor concentration. If these outputs are connected to an external device, it should be terminated into a moderate / high impedance (>1 kOhm). The “MIU” connection is utilized to control the optional Multiport Inlet Unit. The functionality of the data interface connections is described in relevant sections later in this manual. Figure 3: Data interface connections. Gas Inlet / Outlet Connections The gas inlet and outlet ports of the instrument are on the rear panel (see Figure 4). The unit is shipped with all inlets and outlets plugged for protection during transit. In the normal mode of operation (internal pump), the gas to be measured should be connected to the inlet port (3/8” Swagelok), the internal pump exhaust port (1/4” Swagelok) should be open, and the outlet to the scroll pump (1/2” Swagelok) should be capped with the provided plug. The acceptable inlet gas pressure range is 0 to 20 psig. In the normal mode of operation, the internal pump draws sample through the instrument from the inlet, and the pump is exhausted through a small (1/4” Swagelok) port. This exhaust port can either be connected to the provided muffler to expel the instrument exhaust into the room air or the exhaust can be routed to an appropriate ventilation system via ¼” tubing. For high flow mode operation, the outlet to the scroll pump should be connected to a high flow dry scroll pump (LGR recommends the Iwata ISP-500B, or BOC Edwards XDS35i). These operational modes are described in more detail later in the manual. Figure 4: Gas inlet (3/8”) / internal pump exhaust (1/4”) / external pump (1/2”) connections. Rev. 10-A 4 of 35 Los Gatos Research Instrument Startup / Shutdown When the appropriate electrical, gas, and data connections are in place, the instrument may be started via the power switch on the front panel. The internal computer will boot, and automatically load and start the instrument control software. The startup process takes approximately 1 minute. Operation of the instrument is described in the next section. Shutdown of the instrument is accomplished by exiting the operating software, waiting for the instrument to shut down, and turning off the power switch. Please refer to the more detailed Startup/Shutdown section on Pages 12-14. Operation The Fast Greenhouse Gas Analyzer is easily operated via the user interface as described in this section. Main Panel Display Modes When the instrument is turned on, it will automatically go through a 90-second initialization cycle with the Los Gatos Research logo and “Please Wait” message on the screen. After initialization is complete, the instrument will begin to draw in air and to display methane, water, and carbon dioxide concentrations in the air in parts per million (ppm) mixing ratio units, as shown in Figure 5. Figure 5. The methane, water, and carbon dioxide measurements are reported in parts per million (ppm) mixing ratio units. The parameter display window shows the current time and current filename on the upper line, and the measurement cell temperature, cell pressure, mirror ringdown time, and remaining hard drive capacity on the lower line. Rev. 10-A 5 of 35 Los Gatos Research The user may click on the Display button to advance to the timechart display, as shown in Figure 6. The dropdown selector in the lower right portion of the screen allows the user to select a timechart of the methane, water, or carbon dioxide concentration. These data are also being saved to the file indicated in the parameter window, along with a continuous record of the pressure, temperature, and mirror ringdown time. The user may change the rate at which data are written to the log file by selecting the arrows on either side of the Rate indicator. In HI flow mode, rates from 1 Hz to 20 Hz may be selected. In LO flow mode, data will be acquired at a 1 Hz rate and averaged for a selected interval (1 to 100 seconds) before being written to the data file and plotted on the time chart. Longer averaging periods (or equivalently, slower data acquisition rates) will yield better measurement precision than shorter averaging periods; so the user may trade off precision in concentration for precision in time. At data rates faster than 2 Hz, the screen will not update faster than 3 Hz to maintain readability, but the data file will be written at the faster rate selected by the user. Figure 6. The time chart shows changes in the methane measurements over time. A 10-point running average (black line) is shown going through the raw data (circles and blue line). The user may click on the Display button again to advance to the Spectrum display, which allows the user to see the laser transmission through the ICOS measurement cell (Figure 7, top frame) recorded as the laser wavelength is tuned across the various absorption features, and the fitted absorption lineshapes that results from a detailed analysis of a section of the measured transmission signal (Figure 7, bottom frame). The dropdown selector in the lower right portion of the screen allows the user to select a display of the methane and water spectrum, or the carbon dioxide spectrum. Rev. 10-A 6 of 35 Los Gatos Research Figure 7. The top graph shows the voltage from the photodetector as the laser scans across the methane and water absorption features. The bottom graph shows the corresponding optical absorption displayed as black circles, and the peak fit resulting from signal analysis as a blue line. The computationally intensive signal analysis imposes some rate limitations on the graphical display of data. As a result, measurements at 10 or 20 Hz acquisition rates while displaying the spectrum or the time chart are not recommended. Please use the Numeric display to ensure the highest signal-to-noise ratios for these fast data rates. If the user attempts to display graphics while acquiring data at 10 or 20 Hz, the display will warn the user that the true data acquisition rate may be reduced due to graphical processing overhead. File Transfer Menu Each time the instrument is re-started, and each time the user enters and then exits the File Transfer Menu or Setup Panel, a new data file is created with a file name in the form of fgga10Apr2010_f0001.txt, where the first 4 characters represent the instrument model (FGGA) and the next 9 characters represent the date (ddMonyyyy) and the last four numbers are a serial number. The serial number counts upward to provide up to 10,000 unique file names each day. If the instrument is left in continuous operation, a new data file will automatically be created every 24 hours in order to keep data file sizes manageable. This interval is adjustable in the “File Settings” dialog of the Setup Menu (described later in this manual). The data files are written in text (ASCII) format and contain labeled columns as shown in Figure 8. Rev. 10-A 7 of 35 Los Gatos Research Figure 8. The beginning of a typical data file, showing data columns with time, methane concentration, cell pressure, cell temperature, etc. Instrument settings are encoded after the end of the data columns. The “Time” column reports the time stamp of each recorded measurement; its format is set by the user in the “File Settings” menu of the “Setup” panels (see page 16). Also reported are:       [CH4] (ppm) [H2O] (ppm) [CO2] (ppm) Cell pressure (Torr) Cell temperature (Celsius) Ambient Temperature (Celsius)  Ring-Down Time (microseconds) For each of these measurements there is an additional adjacent column reporting the standard error of the measurement (designated with ‘_se’ tag). The standard error is zero when the instrument is running at 1 Hz, as no averaging of data has taken place. At speeds slower than 1 Hz, the standard error of the average is reported. At the end of each data file are encoded listings of settings used by the instrument for that data file. The settings are typically not needed by the user, but are stored for diagnostic or troubleshooting purposes. The user may transfer data files from the instrument hard disk to a USB memory device by selecting the File Transfer button. The instrument will remind the user to insert a USB memory device into the instrument USB port before proceeding (Figure 9). After pressing OK, data acquisition will halt, and the user will see two file directory windows as shown in Figure 10. The directory windows default to the local drive on the left screen and the USB memory device on the right. Clicking the “Local Drive” or “USB Key” radio buttons at the top of each pane can change the individual directory windows. The user may navigate through folders, create directories, and delete files and directories. The user may also use the left mouse button to highlight one or multiple files in the windows and the arrow buttons to copy the files between the directories. Rev. 10-A 8 of 35 Los Gatos Research Figure 9. Reminder to insert USB memory device. Figure 10. File transfer windows. Highlight the files to copy and click the appropriate arrow. Click the new folder icon (yellow folder with red star) to create directories and click the trash can to delete files. The instrument data directory (left pane of Figure 10) is composed of two types of directories – the archive directory and daily directories. Inside the archive directory Rev. 10-A 9 of 35 Los Gatos Research (shown in Figure 11) the instrument automatically generates a single zip archive file that contains all the data files recorded on a given day (named ddMonYYYY.zip). The daily directories (shown in Figure 12) are automatically created every day that the instrument operates, and contain two subdirectories – batch and flow. The flow directory contains all data files taken that day in flow through mode (Figure 13), and the batch directory contains all data files taken that day in the optional batch mode. The serial number of the data file is preceded by an “f” for flow through mode data files, and by a “b” for (optional) batch mode data files. Figure 11. Archive directory. For convenient data transfer and archiving, a single zip archive file is created to contain all the data from each day of operation. Rev. 10-A 10 of 35 Los Gatos Research Figure 12. Daily directory. Separate subdirectories are automatically created by the instrument for flow through data files and (optional) batch operation data files. Figure 13. Flow through data directory. The serial number is preceded by an f for flow through mode data files, and by a b for (optional) batch mode data files. Rev. 10-A 11 of 35 Los Gatos Research NOTE: Files may be managed within the local drive by selecting the “Local Drive” radio button above both directory windows. Files can then be organized into directories by creating a folder, copying the desired files to that folder, then deleting the original files. When finished transferring files, the user must click the Exit button and wait for the “Safe to Remove USB Memory Device” message prior to removing the USB memory device to ensure proper un-mounting of the file system. WARNING: Removal of the USB memory device before prompted to do so may result in loss of data. If the user forgets to insert a USB device before entering the File Transfer mode, or if the USB device is not recognized, the instrument will display a warning and will automatically restart data acquisition (Figure 14). Figure 14. File Transfer Error. User forgot to insert a USB device, or the device was not recognized. Please try again with a USB device correctly inserted or with a different USB device. Startup / Shutdown The internal computer will boot and automatically load / start the instrument control software once the proper power connections are made and the switch is set to the ON position. The startup process takes approximately 1 minute. Once a month, the instrument automatically performs a thorough file system integrity check during boot up. The following figure appears and the instrument will take approximately 1-2 minutes to complete the integrity check before continuing with loading the software. Do not turn off the computer during this maintenance. Rev. 10-A 12 of 35 Los Gatos Research Figure 15: The Routine Maintenance Screen appears during boot up once a month. Normal operation will automatically continue after maintenance is complete. Please do not turn off instrument during maintenance. The Exit button will prompt the user for verification prior to shutting down the instrument as shown in Figure 16. This prevents accidental button presses from causing interruption in data acquisition. The OK button will halt data acquisition, close the current data file, will display the shutdown screen. After the progress bar completes, the instrument will switch to a text-based output as it completes shutting down. The user must wait until after the “Power Down” command is displayed as shown in Figure 17 before turning off the instrument. Failure to do so may result in file system instability. Rev. 10-A 13 of 35 Los Gatos Research Figure 16: Instrument shutdown screen. Figure 17: Final shutdown screen. Rev. 10-A 14 of 35 Los Gatos Research Setup Panel The Setup button will prompt the user for verification prior to entering Setup mode as shown in Figure 18. This prevents accidental button presses from causing interruption in data acquisition. The OK button will halt data acquisition, close the current data file, and display the Setup Panel shown in Figure 19. From this panel the user may select the instrument mode, configure file settings, calibrate, configure the serial output, enter service mode, configure the instrument time, configure the analog output, configure the optional Multi-port Inlet Unit (Manifold), or enable manual laser offset adjustment. Figure 18. Pressing the Setup button prompts the user for further input. Figure 19. The Setup panel allows the user to select the instrument mode, configure file settings, calibrate, configure the serial output, enter service mode, configure the instrument time, configure the analog output, configure the optional Multi-port Inlet Unit (Manifold), or enable manual laser offset adjustment. Flux Mode When the user presses the Flux Mode button, the instrument toggles between normal (LO) and fast flux (HI) modes. (An instrument internal flow schematic and adjustments to the high flow throttle valve can be found in the Appendix). In fast flux (HI) mode, the internal pump of the instrument shuts off and the external pump power outlet will activate. In normal (LO) mode, the high-flow valve on the optical cell will close, the external pump power outlet will deactivate, and the internal pump turns back on. Rev. 10-A 15 of 35 Los Gatos Research File Settings Menu The File Settings Menu (Figure 20) allows the user to adjust the timestamp format of the data files and the new file creation interval (when running continuously). The available timestamp formats are shown below in Table 1. Absolute Local American mm/dd/yyy, hh.:mm:ss.sss Absolute Local European dd/mm/yyyy, hh:mm:ss.sss Absolute GMT American mm/dd/yyy, hh.:mm:ss.sss Absolute GMT European dd/mm/yyyy, hh:mm:ss.sss Relative Seconds After Power On ssssss.sss Relative Seconds in Hours, Minutes, Seconds hh:mm:ss.sss Table 1. Available Time Stamp Formats. Figure 20: The File Settings menu. Calibration Menu and Mirror Ringdown Time The Fast Greenhouse Gas Analyzer is equipped with a calibration routine. Los Gatos Research recommends regular calibration to ensure measurement accuracy and consistency. Calibration can be achieved by attaching a tube, regulated at a pressure just slightly above ambient atmosphere (< 10 psig), from a local gas standard to the instrument inlet. The sequence of calibration steps is illustrated below. Click the “Calibrate” button on the “Setup” panel to bring up information on the most recent calibration. Click the “Calibrate” button on the pop-up window and another screen will pop up indicating that calibration will begin when the “Setup” menu is exited. Exit “Setup” mode and another screen will confirm that calibration is desired. Enter the known total concentration (in ppm) of the individual gas to be calibrated (CH4, H2O, or CO2) into the corresponding field and select the box next to the species to be calibrated. Rev. 10-A 16 of 35 Los Gatos Research A screen will pop up indicating that the instrument is ready to calibrate. Click “OK” when consistent flow has been established, the transfer tube is fully flushed with the calibration gas, and you are ready to begin calibration. (If “OK” is not clicked within 60 seconds, calibration will be aborted and standard gas measurement will continue). The instrument will run the calibration routine for approximately two minutes. A screen will pop up indicating when the calibration is finished and that the user should disconnect the calibration gas. (Note - the user may instead leave the local standard gas connected for a short time to verify a successful calibration – to do so press OK and the instrument will resume normal measurement mode. The user can then verify that the displayed concentration correctly corresponds to the standard gas). The time of latest calibration is also stored in the instrument configuration files for future reference. Figure 21. Screenshots of the User Interface calibration sequence. Rev. 10-A 17 of 35 Los Gatos Research The mirrors of the internal measurement cell are protected from contamination by an inlet filter and pump check valves. However, it is possible over time and with continued use that the mirrors may gradually decline in reflectivity. This will not create errors in the measured methane concentration, as the mirror reflectivity is continually monitored and the measurement is fully compensated. However, if a significant change occurs in the mirror ringdown time (for example, greater than 20% reduction in ringdown time), the precision of the instrument may be reduced. Users should occasionally take note of the ringdown time and request instruction from LGR on mirror cleaning if a significant reduction in ringdown time occurs. Serial Configuration Menu The Serial Configuration Menu allows the user to change how the data reported at the RS-232 port is configured. Standard settings for Baud Rate, Parity, and Stop Bits are provided. The format of the Time Stamp can be selected (see Table 1 above), the Delimiter chosen (comma, tab, space), and the Rate (1-10) specified. Note that the actual rate of serial output is equal to the Logged File Rate (i.e. 1Hz) divided by the Rate specified in the Serial Configuration Menu. NOTE: When connecting the serial port of the instrument to an external computer, a null modem type serial cable should be used. Figure 22. The Serial Configuration Menu. Rev. 10-A 18 of 35 Los Gatos Research Service Mode Menu A password protected Service Mode is available only for qualified technicians to make software upgrades or run instrument diagnostics. Figure 23. The Service Menu. Time Menu The Time Menu lets the user adjust the current time and date settings of the instrument (Figure 24). The time zone and daylight savings enable / disable may also be set here. Figure 24: The Time menu. Rev. 10-A 19 of 35 Los Gatos Research Data Analog Output Menu When the user selects the Analog Out button, the Data Analog Output Menu is displayed as shown in Figure 25. The Data Analog Output port has a 16-bit voltage range from 0 to 5 volts. The user may specify a conversion between the methane ppm measurement and the analog output voltage using the Up-Down arrow controls in the Data Analog Output box. The arrows allow the user to select what concentration value will correspond to the maximum 5 VDC analog output. For example, the user may wish to set 5 Volts = 10 ppm on the expectation that the gases measured will be in the ambient range near 2 ppm, with occasional bursts up to almost 10 ppm. On the other hand, if the user wants exactly two times greater sensitivity on the analog output, with the expectation that the concentration will not go above 5 ppm, the user may set 5 Volts = 5 ppm. If the measured concentration goes above the maximum expected value for the Data Analog Output, the on-screen displays and data files will continue to record the correct concentration, but the Data Analog Output will simply saturate at its maximum value of 5.0 volts until the concentration drops back into the expected range. Figure 25. The Data Analog Output Menu. Rev. 10-A 20 of 35 Los Gatos Research Manifold Menu (for Optional Multi-port Inlet Unit) This panel configures the control of the optional Multi-port Inlet Unit (MIU) if present. Details of its operation are further described in the corresponding section in the Appendix. If the MIU is not present, it should be ‘disabled’ in this menu. Figure 26: operation) Rev. 10-A Gas Manifold Control panel for the (optional) Multi-Port Inlet Unit (see Appendix for 21 of 35 Los Gatos Research Laser Offset Menu This panel allows activation of manual laser offset control. The manual adjustment of laser offset may be required under conditions where the laser wavelength has drifted beyond the automatic control range of the instrument, or if the instrument is operated outside the specified environmental temperature range. Figure 27: Laser Offset control panel. If the user encounters a situation where (after at least a 1 hour warm-up period) an absorption peak is observed to be outside the grey target area in the spectrum display (as shown below), this indicates that the laser wavelength has drifted beyond the automatic control range of the instrument, and needs to be reset manually. Rev. 10-A 22 of 35 Los Gatos Research Figure 28: Spectrum display showing the methane absorption feature outside of the grey target area. In order to manually adjust the laser offset, enter the setup menu, choose the laser offset control panel, and check the indicator box to “enable manual control of laser offset” as shown in the figure below. Figure 29: Manual control of laser offset enabled. Rev. 10-A 23 of 35 Los Gatos Research After enabling manual control of the laser offset, click OK to exit the menu, click Return to exit setup, and switch to spectrum view (shown below) by selecting the display icon. A control for the laser offset is now visible in the lower left portion of the screen. Figure 30: Spectrum display with manual control of the laser offset enabled. The user should now use the + and – controls on this spinner to manually center the methane absorption feature within the grey target area (as shown in the figure below). Once the absorption feature has been centered, the user should reenter setup, and disable the manual laser offset control. This will allow the software to resume automatic tracking and control of the laser wavelength. Rev. 10-A 24 of 35 Los Gatos Research Figure 31: Laser offset properly adjusted to center the methane absorption feature in the grey target area. NOTE: To adjust the offset of the methane / water laser scan, enter the setup menu with the methane / water spectrum displayed. To adjust the carbon dioxide laser scan, enter the setup menu with the carbon dioxide spectrum displayed. Rev. 10-A 25 of 35 Los Gatos Research Appendix The following Appendices give additional information on the instrument configuration and operation. Appendix A - Instrument Flow Schematic The internal flow of gas through the instrument is shown schematically below in Figure 32. Gas from the instrument inlet flows through one or both of the inlet paths shown, depending on whether the instrument is in normal flow (LO) mode or fast flow (HI) mode. In normal flow mode, the high flow solenoid valve is closed, and all of the inlet gas flows through the electronic pressure controller. This controller throttles the flow to maintain the cell at its target pressure (~138 Torr) under variable ambient inlet pressure and any variations in the pumping speed. In fast flow mode, the high flow solenoid valve opens, and the inlet gas flows through both of the inlet paths. The high flow throttle valve (whose operation is described in the Appendix B) provides coarse manual control of the flow to adjust for various external inlet configurations, and the electronic pressure control provides trim control to again maintain the target cell pressure under variable conditions. The gas exiting the cell flows through either the internal pump (in normal flow mode) or through the ½” external pump connection (in fast flow mode). Both of these outlet flow paths are isolated by check valves to prevent leakage from the flow path that is not in use. The cell “flush” time (cell volume / flowrate) is approximately 7.4 seconds while operating with the internal pump, and approximately 0.042 seconds while operating with an external BOC Edwards XDS-35i scroll pump. Rev. 10-A 26 of 35 Los Gatos Research High Flow Throttle Valve 1/4” Orific e C v = 0.73 High Flow Solenoid Valve 1/4” Orific e C v = 0.61 Inlet 3/8” Elec tronic Pressure Controller Cell P 408 c c Cell ~ 138 Torr Chec k Valve 1/3 psi c rac k C v = 4.48 Outlet 1/2” High Flow 580 lpm (w/ XDS-35i) 9.7 l/sec 0.042 sec flush Chec k Valve 1/3 psi c rac k C v = 0.67 Lo Flow 3.3 lpm 55 c c /sec ~ 7.4 sec flush Internal 2-Head Diaphragm Pum p ~ 0.65 slpm @ 138 Torr Figure 32: Internal flow schematic of the instrument. Appendix B – High Flow Throttle Valve Operation (Fast Flow Only) The function of the high flow throttle valve is to provide coarse manual control of the flow to compensate for various external inlet configurations. Depending on the pressure drop of the customer inlet system that is coupled to the instrument, this valve may have to be adjusted to allow the internal pressure controller to function properly. If the instrument is not operating at the target setpoint (approximately 138 Torr) during high flow operation, the high flow throttle valve may need to be adjusted. The high flow throttle valve is located within the instrument (and labeled), and is accessible by removing the High Flow Throttle Valve cover on the rear of the instrument. The operation / adjustment of the high flow throttle valve is shown schematically in Figure 33. With the instrument operating in fast flow mode, and the high flow throttle valve nearly closed, the flow is routed primarily through the electronic pressure controller (see Figure 32). In this condition, the electronic pressure controller is fully open but not able to pass sufficient flow to maintain the cell at its target pressure. As the high flow throttle Rev. 10-A 27 of 35 Los Gatos Research valve is opened, a point is reached where the flow through the valve combined with the flow through the fully open pressure controller is sufficient to maintain the target cell pressure. As the high flow throttle valve is opened further (through approximately ½ more turn), the electronic pressure controller is within its control range and able to throttle down its flow to compensate for the additional flow through the valve. As the high flow throttle valve is opened even further, the electronic pressure controller is now fully closed and unable to control the cell pressure. The ideal operating point is for the high flow throttle valve to be set in the middle of the electronic pressure control range. This midpoint can be found by slowly opening and closing the high flow throttle valve while observing the reported cell pressure (5 Hz mode works well for this), and noting the points at which the control range starts and ends. This control range typically spans approximately ½ turn of the high flow throttle valve; once the range is found, set the valve position to the middle of this range. NOTE – the maximum range and reading display of the pressure transducer is approximately 155 Torr – anytime the cell pressure is above 155 Torr the display will remain locked at 155 Torr. Pressure Transduc er Max Reading ~ 155 Torr Cell Pressure [Torr] Setpoint ~ 138 Torr Control Range High Flow Throttle Valve Figure 33: Operational behavior of the high flow throttle valve. Rev. 10-A 28 of 35 Los Gatos Research Appendix C – Accessing data via a LAN Ethernet Connection This procedure describes how to access the analyzer data directory as a Windows™ Share via a Local Area Network (LAN) ethernet connection. The data files stored on the internal hard disk drive of the analyzer may be accessed as a Windows™ Share via a Local Area Network (LAN) ethernet connection. The following prerequisites are necessary for this function to operate: 1. The analyzer must be connected to a Local Area Network (LAN) via the RJ-45 ethernet connection on the rear panel. 2. The analyzer must receive a response to a DHCP (Dynamic Host Configuration Protocol) request when the instrument is booted. If the analyzer does not receive a reply, it will disable the ethernet port and not attempt another DHCP request until the analyzer is restarted. When these prerequisites are met, the data directory may be accessed via a Windows computer on the same LAN as follows: 1. Click “Start”, then “Run”, then type the following into the “Open” command field: \\LGR-XX-XXXX (where XX-XXXX is the serial number of the analyzer). 2. In a short time (usually between 10 and 60 seconds for the first access) a Windows share directory window will be displayed with a subdirectory named “lgrdata” displayed. 3. Double-click on the “lgrdata” directory, and you will see a listing of the data files stored on the internal hard disk drive of the analyzer. You may open or transfer any of the data files as you would with any Windows™ share drive. ADDITIONAL NOTES: 1. The analyzer shared data directory may (or may not) be visible by “browsing” for it in the Windows “Network Neighborhood”. If it is, it will be in the workgroup called “LGR” and the computer name will be “LGR-XX-XXXX” where XXXXXX is the analyzer serial number. 2. You can open the data file that is currently being written into by the analyzer without interrupting the analyzer operation (you will see a snapshot of the file as it was when you opened it). You will notice that the current data file is only updated occasionally (every 4 kB worth of data), so a new data file will appear empty until enough data is collected and written to disk. 3. If a LAN is not available, you may plug the analyzer into a simple standalone broadband router (such as a Netgear Model RP614 – approximately $45). This will enable the analyzer to obtain a DHCP address from the router when the analyzer is started. You may then plug any Windows™ computer into the same broadband router and access the data directory. 4. A “crossover” ethernet cable will NOT allow an external computer to access the shared data directory, as the analyzer will not obtain a DHCP address at boot and will shut down its ethernet interface. Rev. 10-A 29 of 35 Los Gatos Research 5. You may be able to access the shared analyzer data directory from computers running operating systems other than Windows™. The analyzer uses a Samba server to share the data directory, and it may be accessed by any appropriate Samba client application. Rev. 10-A 30 of 35 Los Gatos Research Appendix D: Multi-port Inlet Unit (Optional) The Multi-port Inlet Unit (MIU) is designed to allow the instrument to switch automatically between various inlets giving the user the opportunity to sample different unknowns in different locations as well as sampling different references. The unit contains a manifold of digitally controlled valves which are programmed to allow any one of the 16 input ports to be directed to the instrument inlet port. The Multi-port Inlet Unit is shown in Figure 34 and Figure 35. Figure 34: Multi-port Inlet Unit (front view). Figure 35: Multi-port Inlet Unit (back view) showing the various connections. The unit supports up to 16 inlet ports labeled numerically. The outlet port connects to the gas inlet of the analyzer. The included 25pin control cable connects the instrument to the Multi-port Inlet Unit. An additional power cable is included to power the Multi-port Inlet Unit. The power and control cable connections are shown in Figure 36 and Figure 37. Figure 36: Power and Control connections for the Multi-port Inlet Unit. Rev. 10-A 31 of 35 Los Gatos Research Figure 37: Connection of Multi-port Inlet Unit control cable to back of the Analyzer. Gas connections are made using ¼” Teflon tubing. Care should be taken to insure that the tubing has been pushed in entirely so as to avoid leaks in the seals. IMPORTANT NOTE – for tube removal you must first push in the outer ring around the connector to allow the tube to be released and pulled free. Figure 38: The ‘Outlet Port’ of the Multi-port Inlet Unit connects to the inlet port of the Analyzer. Rev. 10-A 32 of 35 Los Gatos Research Figure 39: Insertion of sample tube into inlet port '1' on the Multi-port Inlet Unit. IMPORTANT NOTE – for tube removal you must first push in the outer ring around the connector to allow the tube to be released and pulled free. The user can configure which ports are sampled and for how long. This is accessed through the ‘Manifold’ button on the ‘Setup’ menu (see page 21). Figure 40: Gas manifold control for the Multi-port Inlet Unit. The user configures which inlet ports are being used and for how long the instrument should sample each one (in seconds). The control allows two groupings of inlets: unknown and reference. The defined inlets are sampled sequentially with multiple unknown cycles allowed between a reference cycle. A short text description of the inlet can also be entered which is logged in the data file along with the valve number. Rev. 10-A 33 of 35 Los Gatos Research Figure 40 shows the gas manifold control for the Multi-port Inlet Unit. The user configures which inlet ports are being used and for how long the instrument should sample each one (in seconds). The ports are identified by a valve number ranging from 1 to 16 (if a valve is set to 0, the entry is ignored). The user can also input a short text description which is associated with the valve, saved in the data file, and displayed on the parameter window during the instrument run. The control allows two groupings of inlets: ‘unknown’ and ‘reference’. All defined inlets are sampled sequentially in their respective group. The user can decide how many cycles of the unknown group to sample before running a reference group. The user can also indicate whether to start with the reference group first. The enable/disable toggle button allows the user to specify whether the unit is being used. If it is enabled, the valve numbers and text descriptions are added to the data file to allow the user to identify which sections of the data run are associated with a particular valve. Figure 41: Selected columns from the data file showing the appended columns indicating active valve number and user description. While the Multi-port Inlet Unit is operating, the current valve being sampled (and its text description) is shown on the instrument parameter window (see Figure 42). Figure 42: Parameter window showing the Multi-port Inlet Unit (MIU) is enabled. The currently sampled valve number and user-defined description are shown (in this example, it is valve ‘2’ which has been labeled as ‘Inlet 2’). The Multi-port Inlet Unit allows the user to sample multiple sources, including references, allowing for a more automated deployment. By sampling suitable references periodically during an ongoing data run, the user can post-correct the data for long-term drift when active calibration cannot be done. Rev. 10-A 34 of 35 Los Gatos Research NOTE: The control of the Multi-port Inlet Unit is unidirectional. The instrument does not receive feedback on the MIU state. If the MIU is enabled in the ‘Set Up’ panel, the data file will be tagged with MIU valve descriptions whether or not the MIU is properly connected, powered, etc; the data file simply logs the condition of the control signal to the MIU. NOTE: The valves in the Multi-port Inlet Unit are normally closed with power off. However, upon instrument start-up, all the valves will receive an ‘open’ signal until the instrument software has properly booted and initiated the data collection. If pressurized tanks are connected to the instrument (such as reference tanks), there will be a short period of time (~ 1 to 2 minutes) where the tanks will be exposed to other inlet ports during this start-up time. LGR Contact Information: For questions regarding the operation of this instrument, please contact: Thomas Owano, Ph.D. Los Gatos Research 67 East Evelyn Ave., Suite 3 Mountain View, CA 94041 Ph. (650) 965-7772 x222 Fax (650) 965-7074 [email protected] Rev. 10-A Douglas Baer, Ph.D. Los Gatos Research 67 East Evelyn Ave., Suite 3 Mountain View, CA 94041 Ph. (650) 965-7772 x229 Fax (650) 965-7074 [email protected] 35 of 35