Communication in SDI-12 mode
Snow depth sensor SHM 31, V2.1 43
10.4. Command overview
Details about the SDI-12 protocol can be found in the above-mentioned standard
document. Of the commands listed there, the following are available for the SHM 31-UMB:
In the examples in the following sections, logger queries are always shown in italics ( 0V! )
Address search (Wildcard request, one device only on bus!)
Request device identification
Address change to b ( 0 … 9, A …Z, a … z)
Restart is necessary to accept these changes on UMB or UMB ASCII Interface.
Measurement basic minimal data set
Measurement, basic minimal data set, transmit values with CRC
aMC2!
Measurement (assignment of values as for aMn! commands), transmit values with CRC
Concurrent measurement, full basic data set
aC2!
Concurrent measurement, assignment of values as for aMn! commands, partly extended data sets
Concurrent measurement, transmit values with CRC
Concurrent measurement, assignment of values as for aMn! commands, partly extended data sets,
transmit values with CRC
Data request from continuous measurement, data set 0
Data request from continuous measurement, data set 1
Data request from continuous measurement, data set 0 with CRC
Data request from continuous measurement, data set 1 with CRC
Command verification: Evaluate sensor status and heating temperatures, data request with aD0!,
aD1!
Change the unit system for SDI data
Firmware version v16 and newer (SDI-12 v1.4)
aIMC!
aIMn!
aIMCn!
aIC!
aICC!
aICCn!
aIVn!
Request the number of measurement values
aIMC_00m!
aIMn_00m!
aIMCn_00m!
aIC_00m!
aICC_00m!
aICCn_00m!
Request the measurement value parameters
Table 3: Command set for sensor with SDI-12 address ‘a’ (UMB ID 37 (0x25))
T
he scope of the minimal and the full basic data set is currently identical. The same applies to the
extended measuring commands (aM1!, aC1!, etc.).
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