SDI-12
SDI-12 (Serial Data Interface at 1200 Baud) is a serial data communication standard for interfacing multiple sensors with a single data recorder. The MRL-6.1 complies with SDI-12 Version 1.3.
The MRL-6.1 is equipped with two SDI-12 ports. The port on terminal Masters to Sensors operates as an SDI-12 master, and the port on terminal Slave to COM as an SDI-12 slave.
The functions in the parameter menu SDI-12 Master offers some helpful functions to query SDI-12 sensor addresses, to test communication and to handle extended SDI-12 commands..
Principles
The example below illustrates how the MRL-6.1 triggers the measurements and requests the results from three SDI-12 sensors.
The commands and the received responses are as follows:
- 0M! Response: 00013<CR><LF> 3 values are available in 1 second
- 0D0! Response: 0+1.1+2.2+3.3><CR><LF> 3 values:
1.1,2.2,3.3 - 1M! Response: 10022<CR><LF> 2 values are available in 2 seconds
- 1D0! Response: 1+4.4+5.5<CR><LF> 2 values:
4.4,5.5 - 2M! Response: 20031<CR><LF> 1 value is available in 3 seconds
- 2D0! Response: 2+6.6<CR><LF> 1 value:
6.6
At the beginning of each measurement interval the MRL-6.1 sends an M! command to the first sensor. The sensor answers by returning the number of available measurements and the measurement duration. After the required measurement time the MRL-6.1 sends a D! command to request the measurement results. This sequence is repeated for the other two sensors before the next measurement interval starts.
The MRL-6.1 supports all standard SDI-12 commands. See S-ADD in Measurement table for a full list of these commands. For a detailed description on SDI-12 communication please refer to www.sdi-12.org.
TIP If you need to know more about how to program multiple M! and D! commands please see the example in Send multiple SDI-12 requests.