The Gill R3 and HS series of anemometers can be connected to the LI-7550 to collect data on a USB drive. This can facilitate remote data monitoring and collection through the available Ethernet connectivity.
The anemometer will have to be preconfigured to send data out in the required format. This can be achieved using any serial communication software like Windows HyperTerminal or Tera Term (which can be downloaded for free here). You can also use the WindCom or RCom2 software from Gill, here. Please refer to the R3 or HS manual for instructions to configure the output from the instrument. The anemometer can be connected using the following settings:
Baud rate 9600
Data: 8 bit
Stop: 1 bit
Flow control: none
Once the connection is established you can see numbers updating on the screen. Clicking on the screen (or clicking Edit, Paste<CR> in Tera Term) and typing “IM” enters interrogation mode, where the settings can be changed. The settings are changed by typing various commands. Simply typing in the commands by themselves gets you the current value of the instrument for that particular setting. Settings can be changed by adding appropriate parameters to the command, after a space. Some of the important commands are discussed below. For more details please refer to page 26 of the R3-50 manual or page 29 of the HS-50 manual.
AVERAGE sets the number of samples to be averaged, as an integer between 2 and 250. The anemometer sequentially samples every channel every 10 ms and if averaging is kept at 2, two records are averaged to produce a record at 20 ms, which comes to 50 Hz. An averaging period of 5 will produce a 20 Hz output and a 10 will produce an output interval of 10 Hz. If gas analyzer data is collected at 10 Hz, the anemometer should sample at a greater sample rate. The analog signals from the anemometer have to be output at a higher rate than the LI-7550 sampling rate to ensure that data is available from the sonic anemometer when the LI-7550 scans the analog inputs.
Example: AVERAGE 5 yields a 20 Hz output
AOPFSD changes the output voltage ranges for, U, V and W. The options are 10, 20, 30 and 60 m/s. Selecting any one of these options will scale the anemometer output voltage range (-2.5V to +2.5V) .
Example: AOPFSD 30 yields a -30 to +30 m/s range, corresponding to -2.5 to +2.5V
ALIGNUVW is used to configure how the U axis is aligned. This can be set as AXIS or SPAR. This setting is needed when data processing is done in software like EddyPro.
Example: ALIGNUVW AXIS when the transducer axis is aligned with north
WINDREP sets the format of the velocity outputs. The option UVW will output the wind velocities in U, V and W format—this is the most common format for eddy covariance.
Example: WINDREP UVW CAL sets the outputs in calibrated UVW format
The SOSREP command is used to control the output of the sonic temperature/speed of sounds/units of temperature. The options for this command are OFF; SPEED and SONICTEMP. Speed of sound is reported in m/s. The SONICTEMP option can have two options. The option C will produce the sonic temperature in °C—the voltage conversion is -40°C is -1.667V, 0°C is 0V, and 60°C is +2.5V. For more details please refer to page 31 of the R3-50 manual or page 35 of the HS-50 manual.
Example: SOSREP SONICTEMP C sets the fourth output to sonic temperature in °C
CTONE turns the audible beeping noise on or off. The Disable option turns it off always, unless an On command is sent. If the Off option is selected, the beep turns off until the anemometer is restarted.
Example: CTONE DISABLE turns off the beep
Again these are suggestions and the instruments should be configured according to the site and data requirements.
Configuring the LI-7550 Auxiliary Inputs
Please ensure that you have the latest version of the Windows operating software and the firmware for your instrument (LI-7500RS/LI-7200RS). The auxiliary inputs can be configured through the Site Setup tab on the Windows software for the analyzer.
Click on the Anemometer tab at the top. Select Gill, and the appropriate model. Enter the serial number and software version, for record-keeping purposes (these items are only critical for Gill Windmaster and Windmaster Pro sonic anemometers). Select the appropriate wind data format and north alignment. Enter the north offset and the height.
Click on Input Settings. Aux 1 is configured as the channel for U velocity, Aux 2 for V velocity, Aux 3 for W velocity and Aux 4 for the sonic temperature or speed of sound output based on the configuration.
If U, V and W are set to output in the 30 m/s full range, the slope m is 12 and the intercept b is 0. Entering the right type of measurement and the appropriate units will ensure that this data can be processed in data processing software like EddyPro.
If sonic temperature is output in degrees Celsius, the Aux 4 tab should have a slope m of 23.998 and an offset b of 0.0032.