CSAT3 Three Dimensional Sonic Anemometer Revision: 9/12 C o p y r i g h t © 1 9 9 8 - 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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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. General ........................................................................1 2. Specifications .............................................................1 2.1 2.2 2.3 2.4 Measurements ......................................................................................1 Output Signals...................................................
Table of Contents 10. Datalogger Programming using SDM .....................19 10.1 10.2 10.3 10.4 10.5 10.6 10.7 CRBasic CSAT3 () Instruction.......................................................... 19 EDLOG SDM-CSAT3 (P107) Instruction ........................................ 19 Datalogger Instruction Parameters .................................................... 19 Diagnostic Word................................................................................
Table of Contents 4-4. 8-1. 8-2. 11-1. 11-2. 11-3. 11-4. 11-5. 11-6. A-1. A-2. A-3. A-4. B-1. B-2. CSAT3 coordinate system and original noncaptive mounting hardware (s/n 0107 to 0630) .............................................................8 Typical average CSAT3 current drain at +12 VDC ...........................17 CSAT3 pipeline delay ........................................................................17 Proper location of the top (p/n 17388) and bottom (p/n 17389) wicks........................
Table of Contents D-1. D-2. D-3. Data from Example CR3000 SDM Clock Rate Search Program..... D-2 Data from Example CR23X SDM Clock Rate Search Program...... D-3 SDM Clock Rate Report..................................................................
CSAT3 Three Dimensional Sonic Anemometer 1. General The CSAT3 is an ultrasonic anemometer for measuring wind speed in three dimensions. It uses three pairs of non-orthogonally oriented transducers to sense the horizontal wind. Each pair of transducers transmits and receives the ultrasonic signal. The time of flight is directly related to the wind speed along the sonic transducer axis. The speed of sound is directly related of the air density, e.g. temperature and humidity.
CSAT3 Three Dimensional Sonic Anemometer to apply the speed of sound correction described by Liu et al., 2001. The CSAT3 can be configured to make a single measurement per trigger or multiple measurements that are centered around the trigger (oversampled).
CSAT3 Three Dimensional Sonic Anemometer REPORTING RANGE: SDM and RS-232 digital Outputs: Full scale wind: ±65.535 m s-1 autoranging between four ranges; least significant bit is 0.25 to 2 mm s-1 Speed of sound: 300 to 366 m s-1 (-50° to +60°C); least significant bit is 1 mm s-1 (0.025°C embedded code version 4; 0.002°C embedded code version 3) ANALOG OUTPUTS: Range Output ux, uy ±32.768 m s-1 ±65.536 m s-1 uz ±8.192 m s-1 c 300 to 366 m s-1 (-50° to +60°C) 2.
CSAT3 Three Dimensional Sonic Anemometer 2.4 Power Requirements VOLTAGE SUPPLY: 10 to 16 Vdc POWER: 2.4 W @ 60 Hz measurement frequency 1.2 W @ 20 Hz measurement frequency 3. Initial Setup 3.1 Factory Settings • • • • • • • Analog Outputs – Off Execution Parameter – 10 Hz (see Section 10.3 and B.1) Trigger Source – Internal Clock (see Section 8, 9, and B.1) SDM Address – 3 (see Section 3.2, 6.1, and 10.
CSAT3 Three Dimensional Sonic Anemometer 3.2 DM Address Each CSAT3 on the SDM bus must have a unique address. A hex thumb switch within the electronics box is used to change the SDM address. Remove the lid and orient the electronics box with the connectors pointing down. The hex thumb switch is now located in the lower right hand side of the electronics box (see TABLE 3-1 for SDM addresses). CAUTION SDM address F (hex) is a special address used during a Group Trigger.
CSAT3 Three Dimensional Sonic Anemometer 4.2 Mounting The current mounting configuration for the CSAT3 includes a CM250 Leveling Mount, which should be mounted on the end of a 1.31" diameter crossarm such as the CM20X. Mount it so that the bolt on the end points upward, and secure it in place by tightening the set screws with the 3/16" Allen wrench that came with the CM250. The CSAT3 is then mounted to the CM250 by screwing the bolt into the anemometer block. See FIGURE 4-1.
CSAT3 Three Dimensional Sonic Anemometer Logan, Utah CSAT3 3-D SONIC ANEMOMETER 10.00 cm 60 o S/N: 102 MADE IN USA Z 8915 CSAT3 Boom Y X FIGURE 4-2. CSAT3 coordinate system and captive mounting hardware (s/n 0631 to current) Logan, Utah CSAT3 3-D SONIC ANEMOMETER 10.00 cm 60 o S/N: 102 MADE IN USA Z X Y FIGURE 4-3.
CSAT3 Three Dimensional Sonic Anemometer Logan, Utah CSAT3 3-D SONIC ANEMOMETER 10.00 cm 60 o S/N: 102 MADE IN USA Z X Y FIGURE 4-4. CSAT3 coordinate system and original noncaptive mounting hardware (s/n 0107 to 0630) 4.3 Leveling Over flat level terrain, adjust the anemometer head so that the bubble within the level is in the bullseye. Over sloping terrain, adjust the anemometer head so that the horizontal surface that the bubble level is mounted on is parallel to the terrain.
CSAT3 Three Dimensional Sonic Anemometer CAUTION The CSAT3 electronics box contains unique calibration information for its respective sensor head. Do not mismatch CSAT3 sensor heads and electronics. Doing so will result in erroneous wind and speed of sound measurements. NOTE Before extending the SDM signal cable, read Appendix D. NOTE Short haul modems, wire or fiber optic, may be used to lengthen the RS-232 communications cable. Short haul modems do not include an RTS signal.
CSAT3 Three Dimensional Sonic Anemometer TABLE 5-4. CSAT3 SDM Output to a 21X Datalogger Channel 1H C1 C2 C3 Description Color SDM Data Green 10 K resistor to 1H SDM Clock White SDM Enable Brown Digital Ground Black Shield Clear Pin D C E F nc TABLE 5-5. CSAT3 SDM Output to a CR9000 Datalogger CR9000 9080 DB9 Pin 8 7 6 2 Datalogger Description SDM Data SDM Clock SDM Enable Digital Ground Color Green White Brown Black/Clear Pin D C E F/nc TABLE 5-6.
CSAT3 Three Dimensional Sonic Anemometer TABLE 5-8. FW05/FWC-L35 Fine Wire Thermocouple Description Signal High Signal Low 6. Color Purple Red CSAT3 Outputs The CSAT3 has three signal outputs: SDM, RS-232, and analog. Campbell Scientific recommends that the SDM output be used when ever possible, followed by RS-232, and finally analog. TABLE 6-1 summarizes the difference between the three output options.
CSAT3 Three Dimensional Sonic Anemometer TABLE 6-2. SDM Compatible Dataloggers Datalogger Model 21X 1K 21X 2K CR10 2K CR10 4K CR10X CR23X CR9000 CR5000 CR9000X CR1000 CR3000 CR800/850 Datalogger PROMs or Operating System (OS) 6145-3, 6146-5, 10006-1 6148-5, 6149-7, 6070-64 5954-396 Library Special OS 1.4 or > All OS 2.01 or > All OS All OS All OS All OS All OS Requires CSAT3 embedded code 2.1 or > 2.1 or > 2.1 or > 2.1 or > 2.1 or > 2.1 or > 2.1 or > 3.0 or > 3.0 or > 3.0 or > 3.0 or > 3.0 or > 6.1.
CSAT3 Three Dimensional Sonic Anemometer 6.2 RS-232 Output The Windows PC support software (CSAT32.EXE) can be used to graph the CSAT3 data in real time or collect time series via the RS-232 serial port. A copy of the CSAT3 PC software is available from the Campbell Scientific web site in the Support|Downloads section. This software is intended as a diagnostic tool, rather than part of a long term data acquisition system. Appendix B contains detailed information on the CSAT3 RS-232 commands.
CSAT3 Three Dimensional Sonic Anemometer signal processing techniques result in more accurate, lower noise measurements. Unlike CSAT3s running embedded code version 3, embedded code version 4 does not use a library of calibration templates and pattern recognition to determine the ultrasonic time of flight. Embedded code versions 4 and 3 have the same wind resolution. The resolution of the speed of sound measurement using embedded code version 4 is 15 times worse than embedded code version 3 (0.002°C to 0.
CSAT3 Three Dimensional Sonic Anemometer only by the spacing between transducers but also by the current wind speed and speed of sound conditions. After power-up or loss of signal, the CSAT3 enters a mode where it tests the forward and return paths for each of the pairs of ultrasonic transducers. This is called the “acquire” mode and takes about 10 seconds before normal output is available from the anemometer.
CSAT3 Three Dimensional Sonic Anemometer 8. CSAT3 Trigger The CSAT3 takes a measurement of wind speed and the speed of sound when triggered from one of three different sources. The trigger sources are the internal CSAT3 timer, SDM communications, or RS-232 communications. In the case of the CSAT3 internal timer, the Execution Parameter exactly defines the trigger rate. The Execution Parameter is set either via a SDM or RS-232 command.
CSAT3 Three Dimensional Sonic Anemometer FIGURE 8-1. Typical average CSAT3 current drain at +12 VDC ti t i+1 t i+2 t i+3 Trigger Measure Times Of Flight Mi Mi+1 M i+2 M i+3 Process Data Pi - 1 Pi Pi + 1 Pi + 2 Output Data Si - 2 Si - 1 Si Si + 1 Time FIGURE 8-2. CSAT3 pipeline delay 8.1 Sampling Modes The CSAT3 can be configured to make measurements in either a singlemeasurement mode or an oversampled mode.
CSAT3 Three Dimensional Sonic Anemometer 8.1.1 Single-Measurement Mode In the single-measurement mode, the anemometer makes one measurement per trigger. With this approach, the anemometer’s high frequency response is limited only by the geometry of the anemometer head, thus minimizing the possibility of under-estimating high-frequency signal variations and covariations. However, this approach also aliases high-frequency information to lower frequencies.
CSAT3 Three Dimensional Sonic Anemometer 10. Datalogger Programming using SDM The CRBasic CSAT3 () and EDLOG SDM-CSAT3 (P107) instructions are Input/Output instructions that control and retrieve data from the CSAT3. These instructions are available on the CR3000, CR1000, CR5000, CR800/850, CR9000(X), and CR23X, 21X (with CSAT3 PROMs), CR10X, and CR10 (with CSAT3 PROMs or library special PROMs). 10.
CSAT3 Three Dimensional Sonic Anemometer SDMAddress/SDM Address: The unique SDM Address of the CSAT3 connected to the datalogger. In CRBasic dataloggers, the CSAT3 address is entered as a base ten number. In EDLOG dataloggers, the CSAT3 address is entered as a base four number (see TABLE 3-1). The SDM Address is sequentially incremented if the Reps option is greater than 1. The wind data and the speed of sound (sonic virtual temperature) is scaled by the instruction into m s-1 and degrees Celsius.
CSAT3 Three Dimensional Sonic Anemometer CAUTION Command/Option 90, 91, 98, or 99 must not be used to collect data from a CSAT3 running a cold shifted calibration, see Section 11.2.1. Option 1, 2, 3, 5, 6, 10, 12, 15, 20, 30, and 60: “Set Execution Parameter” tells the CSAT3 which measurement parameters to use and what frequency to expect the measurement trigger from the datalogger. The datalogger Execution Interval and the appropriate CSAT3 Execution Parameter is summarized in TABLE 10-3 and TABLE 10-4.
CSAT3 Three Dimensional Sonic Anemometer Ux Input Location: The Input Location to store the first of five data values to an EDLOG datalogger.
CSAT3 Three Dimensional Sonic Anemometer data condition also occurs when the datalogger’s execution frequency (inverse of the execution interval) is much greater than the execution parameter the anemometer was told to use. 61441, SDM Communications Error. The datalogger and CSAT3 are unable to communicate correctly. Extending the SDM cable beyond the standard 7.62 m (25 ft.
CSAT3 Three Dimensional Sonic Anemometer TABLE 10-7. Wiring for Program Example 1 Description Color CR3000 SDM Data Green SDM-C1 SDM Clock White SDM-C2 SDM Enable Brown SDM-C3 Digital Ground Black G SDM Signal Shield Clear G Power Red +12 Vdc Power Refernece Black G Power Shield Clear G EXAMPLE 1. Measuring the CSAT3 Using the SDM Output and a CR3000 Datalogger 'CR3000 Series Datalogger '28 December 2006 'Copyright (c) 2006 Campbell Scientific, Inc. All rights reserved.
CSAT3 Three Dimensional Sonic Anemometer ' ' ' (N) ' {-y} ' | ' | ' | ' | ' | ' (W) {+x} <-------[ ]----X--- {-x} (E) ' / | \ ' CSAT3 Block | CSAT3 Transducers ' | ' | ' v ' {+y} ' (S) ' 'The program computes the compass wind direction, using the constant 'CSAT3_AZIMUTH, and a CSAT3 wind direction. Good CSAT3 wind directions 'are between -90 to 0 and 0 to 90 degrees, e.g. the wind is blowing into 'the CSAT3 sensor head.
CSAT3 Three Dimensional Sonic Anemometer 'Wind directions and speed. Dim wnd_out(8) 'Alias wnd_out(1) = wnd_spd - in compass coordinate system, same as CSAT3. 'Alias wnd_out(2) = rslt_wnd_spd - in compass coordinate system, same as CSAT3. Alias wnd_out(3) = wnd_dir_compass 'Alias wnd_out(4) = std_wnd_dir - in compass coordinate system, same as CSAT3.
CSAT3 Three Dimensional Sonic Anemometer Totalize (1,n,IEEE4,NOT (del_T_f) OR NOT (disable_flag_on(2))) FieldNames ("del_T_f_Tot") Totalize (1,n,IEEE4,NOT (sig_lck_f) OR NOT (disable_flag_on(2))) FieldNames ("sig_lck_f_Tot") Totalize (1,n,IEEE4,NOT (amp_h_f) OR NOT (disable_flag_on(2))) FieldNames ("amp_h_f_Tot") Totalize (1,n,IEEE4,NOT (amp_l_f) OR NOT (disable_flag_on(2))) FieldNames ("amp_l_f_Tot") Average (1,panel_temp,IEEE4,FALSE) Average (1,batt_volt,IEEE4,FALSE) EndTable '*** Working Data Tables ***
CSAT3 Three Dimensional Sonic Anemometer 'Break up the four CSAT3 warning flags into four separate bits. diag_csat_work = diag_csat del_T_f = diag_csat_work AND &h8000 sig_lck_f = diag_csat_work AND &h4000 amp_h_f = diag_csat_work AND &h2000 amp_l_f = diag_csat_work AND &h1000 'Turn on the intermediate processing disable flag when any CSAT3 warning flag is 'high, including the special cases NaN (61502), a Lost Trigger (61440), No Data '(61503), an SDM error (61441), or wrong CSAT3 embedded code (61442).
CSAT3 Three Dimensional Sonic Anemometer TABLE 10-8. Wiring for Program Example 2 Description Color CR3000 SDM Data Green SDM-C1 SDM Clock White SDM-C2 SDM Enable Brown SDM-C3 Digital Ground Black G SDM Signal Shield Clear G Power Red +12 Vdc Power Refernece Black G Power Shield Clear G EXAMPLE 2. Measuring the CSAT3 Using the SDM Output and a CR23X Datalogger ;{CR23X} ; ;22 April 2001 ;Copyright (c) 2001 Campbell Scientific, Inc. All rights reserved.
CSAT3 Three Dimensional Sonic Anemometer ;If the CSAT3 head is pointing West of North (above figure), ;theta is negative. If the CSAT3 head is pointing East of ;North, theta is positive. ; ;The site attendant must enter the value of theta. Search ;for the text string "unique value" to find the location where ;theta is entered. *Table 1 Program 01: .1 Execution Interval (seconds) ;Get the data from the CSAT3.
CSAT3 Three Dimensional Sonic Anemometer ;Disable Intermediate Processing if any of the diagnostic flags are ;on,vi.e. diag >= 4096 or any of the science data is "Not a ;Number", (-99999). ; 8: If (X<=>F) (P89) 1: 36 X Loc [ diag_abs ] 2: 3 >= 3: 4096 F 4: 19 Set Intermed. Proc. Disable Flag High (Flag 9) ;Decode CSAT3 diagnostic flags. ; 9: Do (P86) 1: 2 Call Subroutine 2 ;Process CSAT3 output data every minute.
CSAT3 Three Dimensional Sonic Anemometer 17: Real Time (P77) 1: 110 Day,Hour/Minute (midnight = 0000) 18: Resolution (P78) 1: 1 High Resolution 19: Sample (P70) 1: 3 Reps 2: 13 Loc [ wnd_spd_a ] 20: Sample (P70) 1: 1 Reps 2: 17 Loc [ csat_dir ] 21: Average (P71) 1: 4 Reps 2: 1 Loc [ Ux ] 22: Standard Deviation (P82) 1: 4 Reps 2: 1 Sample Loc [ Ux 23: Totalize (P72) 1: 7 Reps 2: 20 Loc [ smpls ] ] *Table 2 Program 02: 0 Execution Interval (seconds) *Table 3 Subroutines ;Configure CSAT3.
CSAT3 Three Dimensional Sonic Anemometer ;Load the angle between North and the CSAT3 head. ;The station operator must enter the angle theta. ; 4: Z=F (P30) 1: 0 F ;<- unique value 2: 0 Exponent of 10 3: 35 Z Loc [ theta ] ;Load the constants used in recording the number of times the ; diagnostic flags were on.
CSAT3 Three Dimensional Sonic Anemometer ;Configure CSAT3 with 10 Hz parameters. ; 12: SDM-CSAT3 (P107) 1: 1 Reps 2: 3 SDM Address 3: 10 Set Execution Parameter 4: 1 Ux Input Location [ Ux ] 13: End (P95) 14: End (P95) 15: End (P95) 16: End (P95) ;Each diagnostic flag, that is encoded in the diagnostic word ;(diag), is assigned an Input Location. These Input Locations ;serve as flags and take on values of one or zero.
CSAT3 Three Dimensional Sonic Anemometer 24: Z=X (P31) 1: 5 2: 30 X Loc [ diag ] Z Loc [ diag_work ] 25: If (X<=>F) (P89) 1: 30 X Loc [ diag_work ] 2: 2 <> 3: 61440 F 4: 30 Then Do 26: If (X<=>F) (P89) 1: 30 X Loc [ diag_work ] 2: 1 = 3: 61503 F 4: 30 Then Do ;Set the F03F (no data available) flag.
CSAT3 Three Dimensional Sonic Anemometer 36: End (P95) 37: End (P95) ;Process CSAT3 Output data. ; 38: Beginning of Subroutine (P85) 1: 3 Subroutine 3 ;Add the offset (theta) between the CSAT3 negative x-axis and ;North. ; 39: Z=X+Y (P33) 1: 14 X Loc [ cmpss_dir ] 2: 35 Y Loc [ theta ] 3: 14 Z Loc [ cmpss_dir ] ;Ensure that the compass wind direction is positive.
CSAT3 Three Dimensional Sonic Anemometer 46: End (P95) 47: End (P95) End Program -Input Locations1 Ux 2 Uy 3 Uz 4 Ts 5 diag 6 _________ 7 _________ 8 _________ 9 Prop_E 10 Ux_copy 11 Prop_N 12 Uy_copy 13 wnd_spd_a 14 cmpss_dir 15 dir_std_a 16 wnd_spd_b 17 csat_dir 18 dir_std_b 19 zero 20 smpls 21 NaN_csat 22 del_T_f 23 track_f 24 amp_h_f 25 amp_l_f 26 F03F_f 27 _________ 28 _________ 29 _________ 30 diag_work 31 _8000h 32 _4000h 33 _2000h 34 _1000h 35 theta 36 diag_abs 11.
CSAT3 Three Dimensional Sonic Anemometer CAUTION Lightly dab the face of the transducers to remove water droplets. Applying excessive force on the face of the transducer may separate the matching layer from the brass housing. There are no user serviceable components on the CSAT3. The only time the electronics box must be opened is to change the SDM address. 11.1 Wicks CSAT3 embedded code version 4 and the wicks work together to improve the performance of the CSAT3 in rainy conditions.
CSAT3 Three Dimensional Sonic Anemometer I N S TA N T A D H E S I V E FIGURE 11-2. P/N 28902 CSAT3 Sonic Wick Spares Kit contents 11.2 Calibration The CSAT3 is calibrated over the temperature range of -30° to +50°C (standard) or -40° to +40°C (cold shifted). The CSAT3 may or may not make measurements outside the calibration range. Any measurements taken outside the calibration range will be suspect. The CSAT3 does not require any field calibration.
CSAT3 Three Dimensional Sonic Anemometer The standard datalogger instruction reports either the speed of sound (c), option 90 or 99, or the sonic temperature (Ts), Command/Option 91 or 98, can not be used with a CSAT3 running a cold shifted calibration. Instead, use option 92 “Trigger and Get Wind & c-340 Data” or option 97 “Get Wind and c-340 Data After a Group Trigger” and then add 337 m s-1. To find Ts, use Equation 9 in Appendix C. 11.2.
CSAT3 Three Dimensional Sonic Anemometer FIGURE 11-4. Recommended settings for the wind vertical axis FIGURE 11-5. Recommended settings for the wind vertical axis labels Collect and graph 1 minute of wind data from the CSAT3 while it is in the zero wind environment (FIGURE 11-6). The wind offset should be less than ± 4 cm s-1 (0.04 m s-1) for ux and uy, and less than ± 2 cm s-1 (0.02 m s-1) for uz. If the CSAT3 wind offset is greater than these specifications, contact Campbell Scientific, Inc.
CSAT3 Three Dimensional Sonic Anemometer FIGURE 11-6. Wind data from CSAT3 s/n 315; wind offsets within specifications at 19°C 12. Select Backdoor Commands The CSAT3 supports a variety of Backdoor Commands used to configure the CSAT3 for use with a RS-232 data collection system. Connect the CSAT3 to a PC using the RS-232 serial cable that was shipped with the CSAT3. Connect a 12 Vdc power supply to the CSAT3 using the SDM/Power cable. Start the CSAT3 PC support software (CSAT32.EXE).
CSAT3 Three Dimensional Sonic Anemometer After receiving the “??” command, the CSAT3 will respond with text similar to that below for CSAT3s running embedded code version 3 or less, ET= 10 ts=i XD=d GN=111a TK=1 UP=5 FK=0 RN=1 IT=1 DR=102 rx=2 fx=038 BX=0 AH=1 AT=0 RS=0 BR=0 RI=0 GO=00000 HA=0 6X=3 3X=2 PD=2 SD=0 ?d sa=1 WM=o ar=0 ZZ=0 DC=6 ELo=021 021 021 ELb=021 021 021 TNo=dbb d TNb=ccc JD= 007 C0o=-2-2-2 C0b=-2-2-2 RC=0 tlo=9 9 9 tlb=9 9 9 DTR=01740 CA=0 TD= duty=026 AQ= 10 AC=1 CD=0 SR=1 UX=0 MX=0 DTU=
CSAT3 Three Dimensional Sonic Anemometer be changed if RI=1 (always power the RS-232 drivers). Check the setting of RI in the Long Status Message. “ri n” – Toggle Rts Independent; where n = 0 means power the RS-232 drivers if RTS is asserted and n = 1 means always power the RS-232 drivers. Always powering the RS-232 drivers allows the use of short haul modems between the CSAT3 and PC. “sr2718” – Save RAM contents, with modified calibration parameters, to nonvolatile EEPROM.
Appendix A. CSAT3 Orientation A.1 Determining True North and Sensor Orientation The orientation of the CSAT3 negative x-axis is found by reading a magnetic compass and applying the site-specific correction for magnetic declination; where the magnetic declination is the number of degrees between True North and Magnetic North. Magnetic declination for a specific site can be obtained from a USGS map, local airport, or through a NOAA web calculator (Section A.2).
Appendix A. CSAT3 Orientation Declination angles are always subtracted from the compass reading to find True North. A declination angle East of True North is reported as positive a value and is subtracted from 360 (0) degrees to find True North as shown FIGURE A-2. A declination angle West of True North is reported as a negative value and is also subtracted from 0 (360) degrees to find True North as shown in FIGURE A-3.
Appendix A. CSAT3 Orientation A.2 Online Magnetic Declination Calculator The magnetic declination calculator web calculator published by NOAA’s Geophysical Data Center is available at the following url: www.ngdc.noaa.gov/geomagmodels/Declination.jsp. After the web page loads, enter the site zip code, or longitude and latitude, then click on the “Compute Declination” button (FIGURE A-4). FIGURE A-4. USGS web calculator The declination for Logan, UT is 12.4 degrees (3 June 2010).
Appendix A.
Appendix B. Serial Communications with the CSAT3 B.1 CSAT3 RS-232 Commands The CSAT3 powers up its RS-232 drivers when it detects that the RTS (request to send) line has been asserted by the PC. All RS-232 communications begin with the PC asserting the RTS line, the CSAT3 responds by asserting the CTS (clear to send) line. The PC must keep the RTS line asserted as long as it is communicating with the CSAT3. RS-422 communications and short-haul modems do not include an RTS signal.
Appendix B. Serial Communications with the CSAT3 TABLE B-1. RS-232 Command Codes Command & P1 U1 S W A(1..e)1,3,4 O L H Trigger before Command PC or CSAT3 timer CSAT3 timer or PC CSAT3 timer or PC PC or CSAT3 timer PC or CSAT3 timer PC or CSAT3 timer SDM, PC, or CSAT3 timer SDM, PC, or CSAT3 timer SDM, PC, or CSAT3 timer Description Unprompted data output mode. Send data and make measurements at the rate specified by the An command. Send the RS-232 status (TABLE B-9) and trigger the next measurement now.
Appendix B. Serial Communications with the CSAT3 Nassi-Shneiderman diagrams are given in FIGURE B-1and FIGURE B-2 for collecting data using a PC and the RS-232 port. In FIGURE B-1, the PC is the Trigger Source and the data acquisition system. In FIGURE B-2, the anemometer is triggered by its internal timer and a PC is the data acquisition system. Use the logic in FIGURE B-1 when the CSAT3 is measured along with other analog/digital signals.
Appendix B. Serial Communications with the CSAT3 TABLE B-2. RS-232 Output Word 0 b15 - b0 ux wind Word 1 b15 - b0 uy wind Word 2 b15 - b0 uz wind Word 3 b15 - b0 c b15 b14 b13 b12 diagnostic flags b11 b10 ux range Word 4 b09 b08 uy range b07 b06 uz range b05 - b00 counter B.3 Words 0 through 3 The ux, uy, and uz wind speeds are reported on one of four different ranges. This range is given by bits b11 through b06 in word 4.
Appendix B. Serial Communications with the CSAT3 TABLE B-6. Converting Speed of Sound from Word 3 Conversion Output Resolution (mm s-1) (°C @ 25°C) 1 0.0017 speed of sound (m s-1) = word 3 ∗ 0.001 + 340.0 B.4 Word 4 Word 4 contains diagnostic information and the reporting range of ux, uy, and uz wind speed. The diagnostic flags, bits b15 through b12, describe the status of the anemometer (TABLE B-7). A flag is on if the bit is set high.
Appendix B. Serial Communications with the CSAT3 TABLE B-9.
Appendix C. CSAT3 Measurement Theory C.1 Theory of Operation C.1.1 Wind Speed Each axis of the CSAT3 pulses two ultrasonic signals in opposite directions.
Appendix C. CSAT3 Measurement Theory blowing perpendicular to the sonic path. No additional off-line corrections are required as suggested by Liu et al., 2001. c= 1⎤ d⎡ 1 ⎢ + ⎥ 2 ⎢⎣ t o t b ⎥⎦ (5) The speed of sound in moist air is a function of temperature and humidity and is given by: c = γP ρ = γRd Tv = γRd T( 1 + 0.
Appendix C. CSAT3 Measurement 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 C.
Appendix D. SDM Communications and Long Signal Cables D.1 Brief Description of SDM Clock Rates The fastest rate that a datalogger and SDM sensors can communicate via the SDM bus is determined by the number of SDM sensors connected to the SDM bus, properties of the cable used to connect the sensors (resistance and capacitance), and the scan interval. This rate, called the SDM clock rate, has been optimized for the standard 7.62 m (25 ft.) SDM signal and power cable supplied with the CSAT3.
Appendix D. SDM Communications and Long Signal Cables D.2 CR3000 Example Connect all the SDM devices to the datalogger with the cable in question. Download the example CRBasic SDM search program to the datalogger. This program will test the SDM communications between a CRBasic datalogger and a CSAT3, LI-7500, or both a CSAT3 and LI-7500. After the program compiles, use the CRBasic keyboard and set the menu items “Test CSAT3?” and “Test LI-7500?” to the appropriate values.
Appendix D. SDM Communications and Long Signal Cables Take the following case, a 575 foot SDM signal and power cable is used to connect a CR23X datalogger and a single CSAT3 anemometer. Communication between the CR23X and CSAT3 fails at the default SDM clock rate. Thus, a slower SDM clock rate must be used. The example CR3X SDM clock rate search program generated the data in TABLE D-2. TABLE D-2. Data from Example CR23X SDM Clock Rate Search Program 150,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16, ...
Appendix D.
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