700-SDI-RADAR-300W-Man Rev 2 30 May 2022
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Part# 21370
A.3.2
Measurement command errors
When a measurement (aM!) command is issued, the SDI-12 adapter will try to communicate with the
radar instrument, regardless of the last saved radar status. If, for example, the radar was not
connected initially during the power up, the SDI-12 adapter will internally store the radar status as
ERROR; but when the measurement (aM!) command is issued, the SDI-12 adapter will try to power
up and communicate with the radar sensor.
After the measurement command is executed, the SDI-12 adapter will update its internal radar
status. If the measurement command has been successfully executed, the internal radar status will
be updated to OK. If the last measurement command has failed, the SDI-12 adapter will update the
radar status to ERROR.
If a subsequent verify (aV!) command is issued, the adapter will return the last known (updated)
radar status.
Additionally, if the SDI-12 adapter fails to communicate with the radar instrument after issuing a
measurement (aM!) command, the response to Read data command (aD0!) will be empty, even
though the measure command has informed the datalogger that 4 values will be ready.
The following command sequence illustrates getting measurements from the radar instrument
when the instrument is operational, and when the radar instrument is not properly connected to the
SDI-12 adapter:
1. If the radar instrument is fully operational:
Command : 1M!
Response : 10154<CR><LF>
…
Command : 1D0!
Response : 1+1.7+1.64+12+45<CR><LF>
2. If the SDI-12 adapter cannot communicate with the radar instrument:
Command: 1M!
Response: 10154<CR><LF>
Command: 1D0!
Response : 1<CR><LF>
