Xylem 6-Series Multiparameter - Manual (Page 288)

Communications Section 7
YSI Incorporated Environmental Monitoring Systems Operations Manual 7- 2
7.3 RS-232 INTERFACE
The sonde has an auto-baud feature that allows the instrument to automatically adjust to the terminal baud
rate. If the sonde is set to a baud rate of 4800 and a 9600 baud terminal is attached to it, after a few
carriage returns are entered, the sonde will recognize the communication mismatch and attempt to change
its own internal baud rate to match the terminals.
7.4 SDI-12 INTERFACE
SDI-12 is an industry-standard serial digital interface bus. The bus was designed to allow compatibility
between data collection devices and sensors of various manufacturers. The description below applies
specifically to the Sonde implementation of SDI-12 interface. For complete SDI-12 technical
specifications please contact:
Campbell Scientific, Inc.
P.O. Box 551
Logan, Utah 84321 USA
(801) 753-2342
SDI-12 is a single master multi-drop bus and command protocol. As many as 10 sensors can be connected
to the bus at a time. Each sensor is pre-assigned a unique address from 0 to 9. Each Sonde is factory-set to
address 0. The address can be changed in the System menu, see Section 2.9.5, System menu for details.
Running the sonde in SDI-12 mode requires it to be connected to a SDI-12 master device. An example of
such a device is the YSI 6200 or units from Campbell Scientific or Handar Instruments. These instruments
provide the commands necessary to communicate with the sonde in SDI-12 mode. In addition, the sonde
also supports the following commands which are entered from the command line at the # prompt
:
SDI12
This command activates SDI-12 mode. This is the only mode in which the Sonde will respond to any
SDI-12 command. To exit to command line, press any key from the terminal connected to the RS-232 port.
The Sonde implements the basic SDI-12 command set. Below are the descriptions of each command and
their responses.
The following notations are used:
a
Sonde SDI-12 address (ASCII '0' to '9')
[CR]
Carriage return (ASCII 13)
[LF]
Line feed (ASCII 10)
Master
Any SDI-12 compatible data collection device
Master: aM! Initiate a measurement.
Sonde:
atttn[CR][LF]