CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER INSTRUCTION MANUAL REVISION: 3/98 COPYRIGHT (c) 1996-1998 CAMPBELL SCIENTIFIC, INC.
WARRANTY AND ASSISTANCE The CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER is warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and workmanship under normal use and service for twelve (12) months from date of shipment unless specified otherwise. Batteries have no warranty. CAMPBELL SCIENTIFIC, INC.'s obligation under this warranty is limited to repairing or replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER INSTRUCTION MANUAL TABLE OF CONTENTS 1. PAGE GENERAL .................................................................................................................................... 1 2. SPECIFICATIONS ..................................................................................................................... 1 3. INITIAL SETUP ..........................................................................................................................
TABLE OF CONTENTS APPENDICES A. EXAMPLE FLUX PROGRAM .............................................................................................A-1 B. SERIAL COMMUNICATIONS WITH THE CSAT3 .......................................................B-1 B.1 B.2 B.3 B.4 B.5 CSAT3 RS-232 Commands ...................................................................................................B-1 CSAT3 Binary Data Output Format ................................................................................
TABLE OF CONTENTS B-5 B-6 B-7 B-8 B-9 D-1 D-2 Converting uz Wind from Word 2............................................................................................B-4 Converting Speed of Sound from Word 3 ..............................................................................B-4 Decoding the Diagnostic Flags from Word 4..........................................................................B-4 Special Case - Not a Number........................................................................
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER 1. GENERAL The CSAT3 is a three dimensional sonic anemometer. It measures wind speed and the speed of sound on three nonorthogonal axes. From these measurements, orthogonal wind speed and sonic temperature is computed. The CSAT3 can be used to measure average horizontal wind speed and direction or the turbulent fluctuations of horizontal and vertical wind. From the turbulent wind fluctuations, momentum flux is calculated.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER DIGITAL RS-232: Baud rate: 9600 Data type: 2-byte integer SDM AND RS-232 DIGITAL RANGE AND RESOLUTION: -1 Full scale wind: ±65.535 m s autoranging between four ranges; least significant bit -1 is 0.25 to 2 mm s . -1 Speed of sound: 300 to 366 m s (-50° to -1 +60°C); least significant bit is 1 mm s (0.002°C). ANALOG: Number of outputs: 4 Voltage range: ±5 V Resolution: 2.4 mV ANALOG RANGE AND RESOLUTION: Full scale wind: User selectable for ux and -1 uy; ±32.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER TABLE 3-1. SDM Addressing Scheme Datalogger Address (base 4) 00 01 02 03 10 11 12 13 20 21 22 23 30 31 32 CSAT3 Thumb Switch (HEX) 0 1 2 3 4 5 6 7 8 9 A B C D E Address (base 10) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 4. INSTALLATION 4.1 ORIENTATION The three components of wind are defined by a right handed orthogonal coordinate system. The CSAT3 points into the negative x direction (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 X Y FIGURE 4-1. CSAT3 Coordinate System and Mounting Hardware 10 to m 15c FIGURE 4-2. CSAT3 Sonic Anemometer, KH20 Krypton Hygrometer, and FW05 Fine Wire Thermocouple.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER TABLE 5-1. CSAT3 Power 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. Firmly grasp the sonic anemometer block, loosen the bolt underneath the block, and adjust the head accordingly. Finally, tighten the bolt with a 9/16” wrench. 4.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER TABLE 5-6. CSAT3 Analog Output Wiring Description ux sig high ux sig low uy sig high uy sig low uz sig high uz sig low c sig high c sig low shield 6.1.1 CR23X, 21X, CR10(X) Color Brown Black Red Black Green Black White Black Clear TABLE 5-7. FW05/FWC-L35 Fine Wire Thermocouple Description Signal High Signal Low 6.1 SDM SDM is a Campbell Scientific communication protocol used between a Campbell Scientific datalogger and a smart sensor.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER TABLE 6-2. Calibration for Analog Outputs ux Slope Low Range -1 -1 (m s V ) 6.5536 Slope High Range -1 -1 (m s V ) 13.1072 Offset -1 (m s ) 0 uy 6.5536 13.1072 0 uz 1.6384 1.6384 0 c 6.5536 6.5536 340 When the analog outputs are used, the anemometer uses its internal timer to trigger the wind measurements. Thus, the wind measurements can be skewed in time ±1/2 the data acquisition system’s scan interval from other analog measurements, e.g.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER internal trigger then it will take measurements at this rate until it is changed. Note that the power consumption of the anemometer is dependent on the Execution Parameter and the trigger rate (see Figure 8-1). Where an external trigger source is used it is important to make sure the trigger rate is greater than or equal to the Execution Parameter.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER FIGURE 8-1. Typical Average CSAT3 Power Requirements 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 9-1. CSAT3 Pipeline Delay 9. DATA PIPELINE DELAY When the CSAT3 is triggered to take a measurement, it determines the times of flight for all three transducer pairs.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER hygrometer, the thermocouple and hygrometer data must be shifted back in time two triggers. This can be done on-line with a datalogger. 10. DATALOGGER PROGRAMMING USING SDM 10.1 SDM-CSAT3 (P107) USED WITH CR23X, 21X, OR CR10(X) SDM-CSAT3 (P107) is an Input/Output instruction that controls and retrieves data from the CSAT3 (see Table 10-1).
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER TABLE 10-2. CR23X and 21X Execution Interval and CSAT3 Execution Parameter CR23X/21X Execution Interval (seconds) 0.05 0.0625 0.075 0.0875 to 0.1 0.1125 to 0.1625 0.175 to 0.2 0.2125 to 0.325 0.3375 to 0.5 0.5125 to 1 CR23X/21X Execution Frequency (Hz) 20 16 13.333 11.429 to 10 8.889 to 6.154 5.714 to 5 4.706 to 3.077 2.963 to 2 1.951 to 1 CSAT3 Execution Parameter 20 15 12 10 6 5 3 2 1 TABLE 10-3.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER -99999, Anemometer does not Respond. This is the special case when the datalogger attempts to address an anemometer and the anemometer does not answer. This occurs if the anemometer is not connected to the SDM bus, the anemometer is not connected to a 12 VDC power supply, or none of the anemometers on the SDM bus are set to the SDM address in the SDM-CSAT3 (P107) instruction. 61440, Lost Trigger.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER EXAMPLE 1. Measuring the CSAT3 Using the SDM Output and a CR23X Datalogger ;{CR23X} ; ;Flag 1 - Set low to configure the CSAT3. *Table 1 Program 01: .1 Execution Interval (seconds) ;Get the data from the CSAT3. ; 01: SDM-CSAT3 (P107) 1: 1 Reps 2: 3 SDM Address 3: 91 Trigger and Get wind & Ts data 4: 1 Ux Input Location [ Ux_in ] ;Check the diagnostic word for lost trigger ;condition. Set Flag 1 low to reconfigure the ;CSAT3 if it is in a lost trigger state.
CSAT3 THREE DIMENSIONAL SONIC ANEMOMETER There are no user serviceable components on the CSAT3. The only time the electronics box must be opened is to change the SDM address. Should the CSAT3 need to be serviced, call (435) 752-3268, to obtain an RMA number. 12. CALIBRATION The CSAT3 is calibrated over the temperature range of -30° to +50°C. The CSAT3 will not operate outside that temperature range.
APPENDIX A. EXAMPLE FLUX PROGRAM A copy of the example CR23X program is available on the Campbell Scientific ftp site at ftp://ftp.campbellsci.com/pub/outgoing/files/ec_csat3.exe. The file ec_csat3.exe is a self extracting DOS file. At a DOS prompt type in ec_csat3.exe and press the key. The example flux program measures the CSAT3, a FW05 fine wire thermocouple, and a KH20 as well as a net radiation soil heat flux and soil moisture.
APPENDIX A. EXAMPLE FLUX PROGRAM TABLE A-1. CR23X Sensor Connections Channel 1H 1L Sensor HMP45C (temperature) HMP45C (temperature) Color Yellow Purple 2H 2L HMP45C (RH) HMP45C (RH) HMP45C KH20 KH20 KH20 FW05 FW05 FW05 CS615 CS615 CS615 Q7.1 Q7.1 Q7.
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 1 The CSAT3 will ignore this command if a datalogger (SDM) is triggering the anemometer. 2 After the PC takes over as the trigger source it must continue to trigger the CSAT3 at the rate specified in the Execution Parameter (An). If the CSAT3 does not receive a trigger for three seconds it will enter the Lost Trigger state. The acquire signal (An) command will have to be issued in order for the anemometer to exit the Lost Trigger state.
APPENDIX B. SERIAL COMMUNICATIONS WITH THE CSAT3 set RTS line high read CTS line until CTS line is high send the An command to acquire signals send W or S command check for data serial port keep checking until there is data on the serial port read wind data (W) or long status (S) from serial port send W or S command process data repeat until finished collecting data set RTS line low FIGURE B-2. CSAT3 as the Trigger Source. B.
APPENDIX B. SERIAL COMMUNICATIONS WITH THE CSAT3 TABLE B-5. Converting uz Wind from Word 2 Range Word 4 Range Code b07 b06 0 1 1 1 1 0 2 0 1 3 0 0 Conversion uz wind (m s ) = word 2 ∗ 0.001 ∗ 0.25 -1 uz wind (m s ) = word 2 ∗ 0.001 ∗ 0.50 -1 uz wind (m s ) = word 2 ∗ 0.001 ∗ 1.00 -1 uz wind (m s ) = word 2 ∗ 0.001 ∗ 2.00 -1 Output Resolution -1 (mm s ) 0.25 0.50 1.00 2.00 The speed of sound reported by the CSAT3 is the average between the three sonic paths.
APPENDIX B. SERIAL COMMUNICATIONS WITH THE CSAT3 B.5 CSAT3 RS-232 STATUS FORMAT The CSAT3 returns a 10 ASCII byte status in response to an S or P command. This status provides information on the CSAT3’s Trigger Source and the Execution Parameter. It also indicates if the analog outputs are on/off, if the CSAT3 is reporting good data, and serial number of the CSAT3. This software serial number matches those on the anemometer head and electronics box. TABLE B-9. RS-232 Status, Response to the S or P command.
APPENDIX C. CSAT3 MEASUREMENT THEORY C.1.2 TEMPERATURE C.1 THEORY OF OPERATION C.1.1 WIND SPEED Each axis of the CSAT3 pulses two ultrasonic signals in opposite directions. The time of flight of the first signal (out) is given by: to = d c + ua c= (1) and the time of flight of the second signal (back) is given by: tb = d The sonically determined speed of sound can be found from the sum of the inverses of Eq. (1) and (2).
APPENDIX C. CSAT3 MEASUREMENT THEORY where Ts is sonic virtual temperature and γd is the ratio of specific heat of dry air at constant pressure to that at constant volume (Fleagle and Businger, 1980; Kaimal and Gaynor, 1991; Kaimal and Businger, 1963; Schotanus et al., 1983). With Eq. (8), the effect of humidity, on the speed of sound, is included in the sonic virtual temperature. The sonic virtual temperature, in degrees Celsius, is given by Eq. (9), where γd = 1.4 and -1 -1 Rd = 287.04 JK kg .
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 and properties of the cable used to connect the sensors. 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 parameters that were tested and their failure rate as a percent of attempts. The following report was created from the above SPLIT parameter file, SDM.PAR. TABLE D-2.