M command. The maximum number of characters returned in the <values> part
of the response is 75.
Each R command is an independent measurement. For example, aR5! need not
be preceded by aR0! through aR4!. If a sensor is unable to take a continuous
measurement, then it must return its address followed by <CR><LF> (carriage
return and line feed) in response to an R command. If a CRC was requested, then
the <CR><LF> must be preceded by the CRC.
aRv!
Request continuous data from the sensor.
Example Syntax:
aR5!
7.9.18.2 SDI-12 Recorder Mode
The CR1000 can be programmed to act as an SDI-12 recording device or as an
SDI-12 sensor.
For troubleshooting purposes, responses to SDI-12 commands can be captured in
programmed mode by placing a variable declared As String in the variable
parameter. Variables not declared As String will capture only numeric data.
Another troubleshooting tool is the terminal-mode snoop utility, which allows
monitoring of SDI-12 traffic. Enter terminal mode as described in SDI-12
Transparent Mode
(p. 267), issue CRLF (<Enter> key) until CR1000> prompt
appears. Type W and then <Enter>. Type 9 in answer to Select:, 100 in answer
to Enter timeout (secs):, Y to ASCII (Y)?. SDI-12 communications are then
opened for viewing.
The SDI12Recorder() instruction automates the issuance of commands and
interpretation of sensor responses. Commands entered into the SDIRecorder()
instruction differ slightly in function from similar commands entered in
transparent mode. In transparent mode, for example, the operator manually enters
aM! and aD0! to initiate a measurement and get data, with the operator providing
the proper time delay between the request for measurement and the request for
data. In programmed mode, the CR1000 provides command and timing services
within a single line of code. For example, when the SDI12Recorder() instruction
is programmed with the M! command (note that the SDI-12 address is a separate
instruction parameter), the CR1000 issues the aM! and aD0! commands with
proper elapsed time between the two. The CR1000 automatically issues retries
and performs other services that make the SDI-12 measurement work as trouble
free as possible. Table SDI-12Recorder() Commands
(p. 272) summarizes CR1000
actions triggered by some SDI12Recorder() commands.
If the SDI12Recorder() instruction is not successful, NAN will be loaded into the
first variable. See NAN and ±INF
(p. 482) for more information.
272
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