Campbell Scientific CS650 and CS655 Water Content Reflectometers - Manual (Page 47)

Appendix B. SDI-12 Sensor Support
B.1 SDI-12 Command Basics
SDI-12 commands have three components:
Sensor address (a) – a single character, and is the first character of the
command. CS650 sensors are usually assigned a default address of zero unless
option –VS is selected at the time of ordering. Sensors with the –VS option are
addressed with the last digit of the probe’s serial number. This allows for
multiple CS650’s to be connected to a single control port without requiring the
user to change the SDI-12 addresses from zero.
Command body (e.g., M1) – an upper case letter (the “command”) followed by
alphanumeric qualifiers.
Command termination (!) – an exclamation mark.
An active sensor responds to each command. Responses have several standard
forms and terminate with (carriage return – line feed).
SDI-12 commands supported by the CS650 are listed in TABLE B-1.
Continuous and concurrent measurements are not supported.
TABLE B-1. CS650 SDI-12 Command and Response Set
Name Command Response
Acknowledge
Active
a! a
Send Identification aI! allccccccccmmmmmmvvvxxx...xx
Change Address aAb! b
Address Query ?! a
Start Measurement aM! atttn
Send Data aD0!
aD1!
a
a
Additional
Measurements
aM1!
aM2!
aM3!
atttn
atttn
atttn
Address Query Command (?!)
Command ?! requests the address of the connected sensor. The sensor replies
to the query with the address, a.
B-1