Overview of SDI-12 commands

The Stevens HydraProbes use the SDI-12 protocol for configuration and transmitting data. Here we provide a basic overview of SDI-12 commands that you might use to configure the HydraProbes. You can connect and configure nearly any SDI-12 sensors. Refer to your sensor's documentation for details.

In order to configure SDI-12 sensors, you must connect to the DAqM via the SmartFlux System. The SDI-12 console only permits configuration commands. When you want to see measurements from the sensor, check live data in the gas analyzer desktop software.

Anatomy of a command

The first character in a command is sensor's address. It can be a number (1) or letter (a). In the examples in this section, we use 1 as the address.

Command Definition
The command 0A1 sets sensor 0's address (denoted by the A) to 1. 0 is the default address for probes.
The command 1XW_SOIL_G sets sensor 1's soil type to G for general. Soil type commands are G for general, O for organic, or R for rockwool.

Note: We recommend that you keep the HydraProbe in its default configuration for everything except the address and soil type.

HydraProbe firmware versions

The commands that you send to the probe, as well as the replies, may depend on the firmware version of the probe. Serial numbers are printed on probes.

HydraProbe Firmware Version Release Date Starting SN#
2.8 11/11/2008 187780
2.9 04/11/2018 256550
3.0 11/01/2018 260000
4.0 04/1/2020 268000

Identifying the probe firmware version

To send an inquiry to the HydraProbe, send the command 1I!. This command simply asks the probe named one (1) for information (I).

The probe will reply with something like: 512STEVENSW052126.200GSN00...

  • 512 the first digits are the address
  • StevensW is the probe type
  • 052012 is Stevens PN
  • 6 is for firmware version 6
  • .200 is the firmware sub version
  • G represents the soil type (G for general; O for organic; R for rockwool)
  • SN00... is the serial number for the probe.

Supported commands

The commands in Table A‑1 are used by Stevens HydraProbes (firmware version 4 and newer) and can be used to configure them.

Table A‑1. HydraProbe SDI-12 (firmware version 4 and newer) commands and definitions. Some commands may be supported by other sensors.
Command Sent Reply Description
0I (number zero followed by capital letter I) Probe information, including address, type, firmware version, serial number, soil configuration, and serial number See Identifying the probe firmware version
0A1 1 Sensor 0 address changed to 1
1XW_SOIL_<G/O/R> 1<G/O/R> Sets sensor 1's soil type to G for general. G for general, O for organic, or R for rockwool.
? Nothing or a sensor address The ? command is not supported. Click Query All to request the addresses of the sensors
1M Returns a single number

Parameter set and letter designators

Full documentation for HydraProbe SDI-12 is provided by at stevenswater.com/products/hydraprobe/.

Table A‑2. SDI-12 commands and definitions for firmware versions.
  Command Firmware Version
2.8 2.9/3.0 4.0 PRO and newer
Custom 1M 1XM<set> 1XM<set> NA
Factory calibration commands 1XM<set> 1XSO