Campbell Scientific AVW200-series Vibrating Wire Interfaces - Manual (Page 52)

AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules
If a check summed command fails, a NAN will be returned and the command
will be retried.
Mult, Offset The Mult and Offset parameters are each a constant,
variable, array, or expression by which to scale the results of
the measurement.
6.2.2 Extended SDI-12 Commands
Extended SDI-12 commands can be used to change the beginning frequency,
ending frequency, and excitation voltage of the vibrating wire sensors attached
to the AVW200. However, these extended SDI-12 commands only work for
the next measurement command. By default, standard SDI-12 measurement
commands use the begin/end/excite voltage settings specified in the AVW200
settings using DevConfig (see Section 4, Connections). However, after issuing
an extended SDI-12 command, the next measurement will use the bbbb,eeee
and vvvv values specified in the extended command.
An example of an extended command is: 0XVW450,5000,1! This command
configures the next measurement with Begin Freq=450, End Freq = 5000 and
5Volt excitation. For example, an “aM!” command that immediately follows
an extended command will use the settings specified in the extended command.
The second and remaining measurements will revert back to the settings
specified via DevConfig.
The SDI-12 aI! command is used to obtain information about a specific sensor.
When executed against the AVW200-series device, the following information
is returned:
1. The SDI-12 address of the device (1 character)
2. The SDI-12 implementation version (2 characters, "13" is interpreted as 1.3)
3. The Vendor ID "Campbell" (8 Characters)
4. The Sensor Model "AVW2xx" (6 characters)
5. Sensor Version "000" (3 characters)
6. The Serial Number (up to 13 characters), which is the version of the
currently loaded firmware followed by an equals sign and the device's serial
number (“Std.04=875321")
6.2.3 Use with Multiplexers
The AVW200 interface module cannot control multiplexers in the SDI-12
communication mode. Hence, when communicating with the AVW200 via
SDI-12, multiplexers attached to the AVW200 must be controlled by the
datalogger. This is achieved by using PortSet instructions in the datalogger
program and by connecting the clock and reset lines of the multilplexers to
control ports on the datalogger. When using SDI-12 with the AVW200, the
clock and reset lines on the AVW200 are not used.
Read more! Example programs of SDI-12 are provided in Section 7.5.
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