IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 2/12 C o p y r i g h t © 2 0 1 0 - 2 0 1 2 C a m p b e l l S c i e n t i f i c , I n c .
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IRGASON 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. Introduction..................................................................1 2. Cautionary Statements................................................1 3. Initial Inspection ..........................................................2 4. Overview.......................................................................2 5.
IRGASON Table of Contents 8. EC100 Outputs ...........................................................22 8.1 SDM Output........................................................................................... 22 8.2 USB or RS-485 Output .......................................................................... 22 8.3 Analog Outputs ...................................................................................... 24 9. Maintenance ...............................................................25 9.
IRGASON Table of Contents 6-4. Mounting the IRGASON Temperature Probe.......................................11 6-5. EC100 electronics front panel with enhanced barometer. At left, as received from Campbell Scientific. At right, all wiring and connections complete. ........................................................................12 6-6. Base of EC100 enclosure ......................................................................13 6-7. Sensor connections to EC100.....................................
IRGASON Table of Contents iv
IRGASON Integrated CO2/H2O OpenPath Gas Analyzer and 3D Sonic Anemometer 1. Introduction The IRGASON is an in-situ, open-path, mid-infrared absorption gas analyzer integrated with a three-dimensional sonic anemometer. The gas analyzer provides measurements of absolute densities of carbon dioxide and water vapor, while the sonic anemometer measures orthogonal wind components.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer o o o The SDM, USB, and RS-485 output options include IRGASON diagnostic data. Be aware that the absence of diagnostic data in the analog output option could make troubleshooting difficult and may lead to the user not being aware of potential problems with the instrumentation (see Section 8, EC100 Outputs). Resting the analyzer on its side during the zero-and-span procedure may result in measurement inaccuracy.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer • Standard outputs: o ux, uy, and uz orthogonal wind components o sonic temperature (based on the measurement of c, the speed of sound) o sonic diagnostic flags o CO2 density, H2O density o gas analyzer diagnostic flags o air temperature, air pressure o CO2 signal strength, H2O signal strength o Air temperature and air pressure are auxiliary sensor inputs.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer Sonic accuracy5 Offset error ux, uy: < ±8 cm·s-1 < 4 cm·s-1 u z: Gain error Wind vector ±5° horizontal: < ±2% of reading Wind vector ±10° horizontal: < ±3% of reading Wind vector ±20° horizontal: < ±6% of reading Sonic reporting range Full scale wind: Sonic temperature: ±65.553 m/s -50° to +60°C Auxiliary sensors6 Barometer Internal basic barometer Manufacturer: Freescale Model: MPXAZ6115A Accuracy: ±2.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 5.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer FIGURE 5-1(a). IRGASON dimensions, side view FIGURE 5-1(b).
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 5.4 Power Requirements During Power-up and Operation Power requirement Source: 10 to 16 Vdc Load at 25oC: 420 mA at 25oC in power-down mode1: 250 mA 1 sonic anemometer fully powered and gas analyzer in stand-by 6. Installation 6.1 Orientation During operation, the IRGASON should be leveled and pointed into the prevailing wind to minimize flow distortions from the instrument arms and other supporting structures.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer WARNING 8 Handle the IRGASON carefully. The optical source may be damaged by rough handling, especially while the analyzer is powered. 6. If the assembly is not level, slightly loosen the bolt that holds the mounting bracket on the boom adapter and adjust the assembly until the leveling bubble on top of the IRGASON block is within the bullseye. Retighten the bolt. 7.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer IRGASON IRGASON Mounting Bracket (p/n 27496) CM250 Leveling Mount (p/n 26559) CM20X (p/n 1790X) or equivalent crossarm FIGURE 6-1. Exploded view of mounting the IRGASON WARNING Over-tightening bolts will damage or deform the mounting hardware.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer FIGURE 6-2. EC100-enclosure mounting bracket mounted on a vertical mast (left) and a tripod leg (right) FIGURE 6-3.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 8. Mount the IRGASON temperature probe so that it measures temperature at the same height as the sample volume of the IRGASON. To do this, first attach the R.M. Young 41303-5A 6-Plate Solar Radiation Shield (p/n 4020) to the mast with the included u-bolt. Next, insert the end of the probe into the hole on the bottom of the shield. Tighten the screws to hold the probe in place. See Figure 6-4.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer tighten the thumbscrews (see Figure 6-5). The gas analyzer cable is approximately 3 meters in length. 2. Connect the IRGASON sonic cable. Similar to (a), begin by removing the black- rubber cable-entry plug found on the bottom left of the EC100 enclosure. Insert the cable entry plug on the cable into the slot and connect the male end to the female connector labeled Sonic Anemometer on the EC100 electronics (see Figure 6-5).
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer FIGURE 6-6. Base of EC100 enclosure NOTE Unique calibration information is stored in the gas and sonic connectors of the IRGASON rather than in the EC100. This means that any IRGASON may be used with any EC100. FIGURE 6-7.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 3. Connect the IRGASON temperature probe. Unscrew the temperature connector cover, which is found on the base of the EC100 enclosure (see Figure 6-6). Insert the 3-prong probe connector into the female connector on the enclosure and screw it firmly in place. The IRGASON temperature probe cable is approximately 3 meters in length. 4. Ground the EC100 by attaching a thick wire (e.g.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer o Analog output: use cable CABLE4CBL-L (p/n 21972) or CABLE2TP-L (p/n 26986-L). Once again, the customer specifies the length of this cable at time of order. The connector labeled Analog Outputs on the EC100 panel indicates where each wire should be connected (CO2 voltage signal, H2O voltage signal, and two ground connections). 6. Wire power and ground (i.e., power reference) cable CABLEPCBL-L (p/n 21969-L) to the EC100.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 7.1 Factory Defaults Table 7-1 shows the default value for each setting described in the following sections. TABLE 7-1.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer any integer value between 0 and 14. The value 15 is reserved as an SDM-group trigger. 7.4 Unprompted Output If the EC100 is to output data as USB or RS-485 (see Section 8.2, USB or RS-485 Output), this setting must be set to USB Port or RS485, respectively. The factory default is to disable the unprompted output and assume data are to be logged via SDM (see Section 8.1, SDM Output). Only one unprompted-output type (i.e.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer troubleshooting only. In normal operation, Temperature Sensor is set to Auto-Select, and this setting is not used. 7.11 Pressure Sensor This setting identifies which barometric pressure sensor is used. The EC100 always includes the basic barometer, but it may be ordered with the optional enhanced barometer (model CS106). This setting defaults to EC100 Enhanced if the CS106 is ordered and to EC100 Basic otherwise.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 7.14 ECMon Settings for the IRGASON are easily verified or changed using the Windows PC support software ECMon (Eddy Covariance Monitor), which is found on the IRGASON, EC150 & EC155 Support CD (p/n 27007) or at www.campbellsci.com. Before installing ECMon, read the file titled _Read_me.txt found on the IRGASON, EC150 & EC155 Support CD.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer FIGURE 7-1.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer FIGURE 7-2. Setup window in ECMon 7.15 Device Configuration Utility DevConfig software (Device Configuration Utility) may also be used to change settings, although ECMon is generally preferred because of its more user-friendly interface. DevConfig may be downloaded from the IRGASON, EC150 & EC155 Support CD (p/n 27007), or may be downloaded free of charge from the Campbell Scientific website www.campbellsci.com).
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 8. EC100 Outputs The EC100 is the IRGASON electronics module that measures the sensors and controls the system. It outputs data in one of four types: SDM, USB, RS-485, or analog. In general, Campbell Scientific recommends that SDM be used if a Campbell Scientific datalogger is responsible for data collection. However, RS-485 output is recommended if cable lengths exceed 100 meters.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer To use USB or RS-485 output, connect a USB or RS-485 cable from the EC100 to the receiving device (see Section 6.3, Wiring and Connections), and configure the settings (see Section 7, Settings). The Unprompted Output setting must be set to USB or RS-485. If RS-485 is selected, the RS485 Baud Rate must be set. The Unprompted Output Rate must be set to the desired output rate. All output data are formatted as comma delimited ASCII.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer The final data element in each row or output array is the signature. The signature is a four character hexadecimal value that is a function of the sequence and number of bytes in the output array. The recording device (i.e., PC or datalogger) calculates its own signature using each transmitted byte until encountering the transmitted signature. The computed signature and the transmitted signature are compared.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer TABLE 8-2. Multipliers and Offsets for Analog Outputs Density (mg m-3) Voltage Output Multiplier (mg m-3 V-1) Offset (mg m-3) CO2 386.32 -102.59 H2O 8.65 -2.26 9. Maintenance IRGASON operation requires six maintenance tasks: • • • • • • routine maintenance wick maintenance analyzer window cleaning zero and span replacing the analyzer desiccant / scrubber bottles factory recalibration 9.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer Remove the wicks during the winter. The wicks will accumulate snow or freezing rain, resulting in blockage of the sonic signals. When installing wicks, be sure they are located in the proper position. The top wick must be flush with the transducer face, with the wick tail located at the lowest point of the transducer (see Figure 9-1).
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer Wicks are available as listed in Table 9-1. TABLE 9-1. Rain Wick Replacement Parts Wick Campbell Scientific, Inc Part Number Campbell Scientific Description Bottom Wick 28652 FAB EC150/IRGASON RAIN WICK BOTTOM Top Wick 28653 FAB EC150/IRGASON RAIN WICK TOP The top wick has a short seam which has to be aligned with the short side of the top snout.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 9.3 Gas-Analyzer Window Cleaning The windows of the analyzer should be cleaned if the signal strength for CO2 or H2O drops below 0.7 or 70% of the original value. These values may be monitored in the output data, or they can be viewed with ECMon. To clean the windows, use isopropyl alcohol (2-propanol / isopropanol) and a cotton swab or a non-scratching tissue or cloth.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer rubber seals on the ends of the shroud are clean and in good condition. Position one end of the shroud over the lower snout and twist the top part of the shroud, allowing it to extend and cover the upper snout; while doing so, avoid making contact with the sonic transducers. Continue twisting the shroud until it is fully extended and covering both snouts.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 8. NOTE Connect a gas tank of known CO2 concentration to a pressure regulator, then to a flow controller, and finally to the intake of the shroud. Optimally, the concentration of span CO2 should be near the concentration of CO2 being measured in the field. Begin with both the pressure regulator and flow controller turned off.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 10. Remove the H2O span gas, and connect a zero air source (no CO2 or H2O) to the inlet tube of the shroud. As described in step 8, use a pressure regulator and flow controller so that zero air flows through the shroud between 0.4 and 0.6 l/min. Wait for the measurement readings to stabilize (this may require several minutes) and write down the reported values for CO2 and H2O concentrations.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 16. Enter the known dew point (in C°) in the box labeled Span Dew Point and press Span. 17. The zero-and-span procedure is now complete. Remove the shroud, reconnect the IRGASON temperature probe, and prepare the site for normal operation. 9.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer Scrubber bottle cover Scrubber bottle cover FIGURE 9-5. Replacing the desiccant and CO2 scrubber bottles 9.6 Factory Recalibration When the IRGASON is manufactured, the gas analyzer calibrated over a wide range of temperatures, pressures, and gas concentrations.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 10. Datalogger Programming The datalogger is programmed in the CRBasic language, which features two instructions for communication with the EC100 via SDM. The first instruction is EC100(), which reads measurement data from the EC100. The second is the EC100Configure(), which receives and sends configuration settings. 10.1 EC100() Instruction The EC100() instruction is used to retrieve data from the IRGASON via SDM.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer TABLE 10-1. Output Modes for EC100 Instruction Output Mode 0, 1, 2, 1, 2 Data Field Description Units 1 Ux m/s 2 Uy m/s 3 Uz m/s 4 Sonic Temperature ºC 5 Sonic Diagnostic Flag 6 CO2 Density mg/m3 7 H2O Density g/m3 8 Gas Diagnostic Flag 9 Air Temperature ºC 10 Air Pressure kPa CO2 Signal Strength nominally 0.0 ≤ strength ≤1.0 H2O Signal Strength nominally 0.0 ≤ strength ≤1.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer TABLE 10-3.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 10.2 EC100Configure() Instruction EC100Configure() provides a third option, beside the ECMon software and DevConfig utility, for retrieving and modifying settings. ECmon and Device Configuration are user-interactive, whereas the EC100Configure() instruction allows automated control under CRBasic datalogger programming. EC100Configure() is a processing instruction.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer TABLE 10-4. ConfigCmd Values for Setting and Retrieving Settings ConfigCmd Variable Set Retrieve Setting Description (some settings list possible values for the DestSource variable) 0 100 Bandwidth: 5 = 5 Hz, 10 = 10 Hz, 12 = 12.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 10.2.1 ConfigCmd 11 Zero-and-span Control To perform zeroing of CO2 and H2O , ConfigCmd 11 is set to 1. After the IRGASON completes the zero, it will write the value to -1. The datalogger program can poll this value or simply wait for a period of time to allow the zeroing to complete.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer output indicates moisture is present, the datalogger can send the EC100Configure() instruction to the IRGASON and enable the heaters. 10.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 11. Theory of Operation 11.1 IRGASON Sonic Anemometer The CSAT3 measures wind speeds and the speed of sound by determining the time of flight of sound between pairs of transducers. However, unlike many other commercial anemometers, it does not use simple threshold detection to determine the ultrasonic times of flight.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 11.1.2 Temperature The sonically determined speed of sound can be found from the sum of the inverses of Eq. (1) and (2). The CSAT3 corrects online for the effect of wind blowing perpendicular to the sonic path. No additional off-line corrections are required as suggested by Liu et al., 2001.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer The sonic virtual temperature, in degrees Celsius, is given by Eq. (9), where γd = 1.4 and Rd = 287.04 J·K-1·kg-1. Ts = c 2 γ dRd − 273.15 (9) 11.2 IRGASON Gas Analyzer The IRGASON gas analyzer is a non-dispersive mid-infrared absorption analyzer. Infrared radiation is generated in the upper arm of the analyzer head before propagating along a 15 cm optical path.
IRGASON Integrated CO2/H2O Open-Path Gas Analyzer and 3D Sonic Anemometer 11.3 Theory References Kaimal, J. C. and Businger, J. A.: 1963, “A Continuous Wave Sonic Anemometer-Thermometer”, J. Applied Meteorol., 2, 156-164. Kaimal, J. C. and Gaynor, J. E.: 1991, “Another Look at Sonic Thermometry”, Boundary-Layer Meteorol., 56, 401-410. Fleagle, R. G. and Businger, J. A.: 1980, An Introduction to Atmospheric Physics, Academic Press, Inc., New York. Liu, H., Peters, G., and Foken, T.
Appendix A. Filter Bandwidth and Time Delay The EC100 measures CO2, H2O, 3-D wind components, and sonic temperature from the IRGASON at 100 Hz and then applies a user-selectable low-pass filter. The available filter bandwidths are 5, 10, 12.5, 20, and 25 Hz. Figure A-1 shows the amplitude response of these filters. The EC100 filters provide a flat pass band, a steep transition from pass band to stop band, and a wellattenuated stop band.
Appendix A. Filter Bandwidth and Time Delay The EC100 measures gas and wind data at 100 Hz, and 100 Hz data are downsampled to the datalogger scan rate through SDM communications (see Section 8, EC100 Outputs). This process synchronizes EC100 gas and wind data with other signals measured by the datalogger to within ±5 ms (plus or minus onehalf of the inverse of 100 Hz).
Appendix A. Filter Bandwidth and Time Delay EC100 10-Hz Filter Compared to 20-msec Moving Average (Amplitude Responses) 10 1 No Units 0.1 EC100 10-Hz Bandwidth Filter 10-Hz Bandwidth from a 50-msec Moving Average 0.01 0.001 0.0001 1 10 70 Hertz FIGURE A-2. Frequency response comparison of the EC100 10 Hz bandwidth and a 50 ms moving average TABLE A-1. Filter Time Delays for Various Bandwidths Bandwidth (Hz) Time Delay (ms) 5 800 10 400 12.
Appendix A.
Appendix B. Equations Table B-1 lists variables and constants used in the following equations. TABLE B-1. Table of Equation Variables and Constants Variable or Constant Description Units ρc CO2 Mass Density mg·m-3 ρv H2O Mass Density g·m-3 ρd Mass Density of Dry Air g·m-3 Xc µmol·mol-1 Xv CO2 Molar Mixing Ratio (concentration relative to dry air) H2O Molar Mixing Ratio (concentration relative to dry air) Mc Molecular Weight of CO2 44 mg·mmol-1 Md Molecular weight of dry air 0.
Appendix B. Equations ⎛ PM ⎞⎛ ⎞ X d v ⎟ ⎟⎟⎜⎜1 − ρ d = ⎜⎜ ( ) R T 273 . 15 1000 X v ⎟⎠ + + ⎠⎝ ⎝ (B-5) Dew Point from Molar Mixing Ratio Td = 240.97 Td _ tmp (B-62) 17.502 − Td _ tmp ⎛ ⎞ XvP ⎟⎟ Td _ tmp = ln⎜⎜ ( ) ⋅ + 0 . 61121 f 1000 X v ⎠ ⎝ (B-72) f = 1.00072 + (3.2 ×10 −5 )P + (5.9 ×10 −9 )PT 2 (B-82) Water Vapor Molar Mixing Ratio from Dew Point Xv = e 1000 P−e (B-9) ⎛ 17.502Td e = 0.61121 ⋅ f ⋅ EXP⎜⎜ ⎝ 240.97 + Td ⎞ ⎟⎟ ⎠ (B-102) Water Vapor Mass Density from Dew Point ρv = (0.
Appendix C. Material Safety Data Sheets (MSDS) MSDS are available for chemicals used in IRGASON filters. The MSDS samples below are made available for convenience. However, chemical manufacturers may change MSDS at any time. Up-to-date MSDS are available at www.campbellsci.com. C.
Appendix C. Material Safety Data Sheets (MSDS) C.
Appendix C.
Appendix C.
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