SDI-12 commands

SDI-12 measurement and extended commands shows the measurement and extended SDI-12 commands for the RangeVue-series. The RangeVue-series responds to the M!, C!, CC!, R0!, and R0C! SDI-12 measurement commands. When using an M! command, the data logger waits for the time specified by the sensor, sends the D! command, pauses its operation, and waits until either it receives the data from the sensor or the sensor timeout expires. If the data logger receives no response, it will send the command a total of three times, with three retries for each attempt, or until a response is received.

The C! command follows the same pattern as the M! command with the exception that it does not require the data logger to pause its operation until the values are ready. Rather, the data logger retrieves the data with the D! command on the next pass through the program. Another measurement request is then sent so that data are ready on the next scan.

The R0! command directly reads the sensor measurements and outputs all of its values.

The MC!, CC!, and R0C! commands are the same as the previous commands, but where the C at the end of the command forces a validation for the data received from the sensor using a checksum. If the checksum is invalid, the data logger will re-request the data up to three times. The checksum validation increases the measurement time by about 40 milliseconds if there are no errors. Retries will increase the measurement time in proportion to the number of retries. The checksum option is necessary only for long cable lengths or when electronic noise may impact measurement transmission to the data logger.

Information about using the extended commands are provided in Configuring sensor via extended SDI-12 commands and terminal emulator.

NOTE:

Additional SDI-12 information is available at www.sdi-12.org .

SDI-12 measurement and extended commands
SDI-12 command	Values returned or function
a`M!`, a`C!`, a`CC!`, a`R0!`,a`RC0!`	Stage Distance Electronics temperature Signal-to-noise (SNR) ratio² Device status (Device-status codes)
a`XRPOM!`	Read power operation mode
a`XWPOM+`p`!` Where, p =power operation mode code	Write power operation mode. It returns: a`XWPOM+`p`+`nnn`!` Where, p is the power operation mode code: 0=low power mode 1=normal power mode nnn is the operational-status code (Operational-status codes)
a`XRDU!`	Read distance units Where: 0=m 1=ft 2=mm 3=inch
a`XWDU+`d`!` Where, d =distance unit code	Write distance unit code. It returns: a`XWDU+`d`+`nnn`!` Where, d is the distance unit code 0=m 1=ft 2=mm 3=inch nnn is the operational-status code (Operational-status codes)
a`XWTU+`t`!` Where, t =temperature unit code	Write temperature units. It returns: a`XWTU+`t`+`nnn`!` Where, t is the temperature unit code 0=°C 1=°F 2=K nnn = operational-status code (Operational-status codes)
a`XRS!`	Read stage reference
a`XSS+`ssssssss`!` Where, ssssssss =stage reference	Set stage reference. It returns: a`XSS+`ssssssss`+`nnn`!` Where, ssssssss is the stage reference. The format depends on units: ssss.sss for meter sssss.ss for feet sssssss for millimeter sssssss for inch nnn is the operational-status code (Operational-status codes)
a`V!`	Operating system (OS) version Device status (Device-status codes)
`?!`	SDI-12 address
¹a is the sensor address. In the `SDI12Recorder()` CRBasic instruction, the command parameter does not include the SDI-12 address because the address is a separate parameter. ²A higher signal-to-noise ratio (SNR) signifies a stronger and clearer radar signal relative to the noise. A good SNR can vary based on several factors including the specific sensor design, operating environment, and application requirements. As a general guideline, above 10 dB is the minimum threshold to reliably distinguish the signal from noise and interference. A SNR above 20 dB is a very good SNR, indicating a strong and clear signal with minimal interference, which can lead to highly accurate measurements.