Campbell Scientific CR800 and CR850 Measurement and Control Systems - Manual (Page 175)

Section 7. Installation
175
7.8.3.1.1 SDI-12 Transparent Mode Commands
Commands have three components:
Sensor address (a) – a single character, and is the first character of the
command. Sensors are usually assigned a default address of zero by the
manufacturer. Wildcard address (?) is used in Address Query command.
Some manufacturers may allow it to be used in other commands.
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 and responses are defined by the SDI-12 Support Group
(www.sdi-12.org) and are summarized in the table Standard SDI-12 Command &
Response Set
(p. 175).
Sensor manufacturers determine which commands to
support. The most common commands are detailed below.
Table 25. Standard SDI-12 Command and Response Set
Command Name Command Syntax
1
Response
2
Break
Continuous
spacing for at least
12 milliseconds
None
Acknowledge Active a! a
Send Identification aI!
allccccccccmmmmmmvvvxxx...xx. For example,
013CampbellCS1234003STD.03.01 means address = 0, SDI-12 protocol
version number = 1.3, manufacturer is Campbell Scientific, CS1234 is the
sensor model number (fictitious in this example), 003 is the sensor version
number, STD.03.01 indicates the sensor revision number is .01.
Change Address aAb!
b (support for this command is required only
if the sensor supports software changeable addresses)
Address Query ?! a
Start Measurement
3
aM! atttn
Start Measurement and Request CRC 3 aMC! atttn
Send Data
aD0!
.
.
.
aD9!
a or a
a or a
a or a
a or a
a or a
Additional Measurements 3
aM1!
.
.
.
aM9!
atttn
atttn
atttn
atttn
atttn
Additional Measurements and
Request CRC
3
aMC1! ... aMC9! atttn
Start Verification
3
aV! atttn