Communications
Section
7
YSI Incorporated Drinking Water Monitoring Systems Operations Manual
7-
3
ttt
- Maximum time in seconds the Sonde will take to complete the measurement.
n
- Number of data that will be available when the measurement is completed. This number is the same as
the number of output parameters set in the Report menu, as described in
Section 2.9.6,
Report
. For ten or
more parameters, the sonde returns ":", ";", "<", "=", ">", "?", "@", "A", "B",…etc.
After finishing the measurement, the Sonde will usually send a service request "a[CR][LF]" to the bus
master. The bus master can then retrieve the measurement result by "D0" to "D9" commands (see below).
If the Sonde does not send a service request within the specified maximum time, the measurement is
canceled. The bus master can then restart with another "M" command.
Master:
aI!
Send identification.
Sonde:
allccccccccmmmmmmvvvxxx...xxx[CR][LF]
l
- 2 character SDI-12 level number.
c
- 8 character manufacturer identification. This field always contains "YSIIWQSG" (YSI Inc.,
Water Quality Systems Group).
m
- 6 character model number. This field always contains "EM600_" or "EM 6920"
(Environmental Monitoring System Sonde) depending on the sonde.
v
- 3 character version number. This field holds the sonde’s software version number ("100" for
version 1.00).
Master:
aD0! to aD9!
Retrieve measurement/verifying data
Sonde:
a<values>[CR][LF]
<
values
>-
33 characters or less. This field holds one or more values resulting from a measurement or
verifying sequence. A value contains between 1 to 7 digits with an optional radix mark (period '.' or
comma ','). Each value must be preceded by its sign (either '+' or '-' ) since the sign is also used to delimit
multiple values.
If the number of values returned by the "D0" command is less than the number specified in the previous
response to "M" commands, the rest of the data can be retrieved by using "D1" to "D9" commands. The
"D" commands are non-destructive. Thus if the same "D" command is issued multiple times before the
next "M" command, it will return the same data. If the response to the "D0" command is "a[CR][LF]" then
either no "M" command was received before the first "D" command or the "M" command was canceled.
Example:
Here is an example SDI-12 transaction. Here SDI-12 master will issue an Identify command
followed by a Measure command. The sonde is configured with a report output of Temperature, Specific
conductance, DO %, DO mg/L, pH (ISE1), ORP (ISE2), and Depth, a DO warm up time of 60 seconds, and
an SDI-12 address of 1.
Master: 1I!
Sonde: 110YSIIWQSGEM600_107[CR][LF]
The bus master asked for identification and the Sonde returned data showing the following.
SDI-12 level: 1.0
Manufacturer: YSIIWQSG
