Campbell CS650, User Manual

Page: 51 / 56

D-1
Appendix D. SDI-12 Sensor Support
D.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 <CR><LF> (carriage return – line feed).
SDI-12 commands supported by the CS650 are listed in Table D-1 . Continuous
and concurrent measurements are not supported.
Table D-1. CS650 SDI-12 Command and Response Set
Name Command Response
Acknowledge
Active a! a<CR><LF>
Send Identification aI! allccccccccmmmmmmvvvxxx...xx<CR>
<LF>
Change Address aAb! b<CR><LF>
Address Query ?! a<CR><LF>
Start Measurement aM! atttn<CR><LF>
Send Data aD0!
aD1! a<values><CR><LF>
a<values><CR><LF>
Additional
Measurements aM1!
aM2!
aM3! atttn<CR><LF>
atttn<CR><LF>
atttn<CR><LF>
Address Query Command (?!)
Command ?! requests the address of the connected sensor. The sensor replies to
the query with the address, a .
Change Address Command (aAb!)
Sensor address is changed with command aAb! , where a is the current address and
b is the new address. For example, to change an address from 0 to 2 , the
command is 0A2! . The sensor responds with the new address b , which in this case
is 2.