Campbell CS650, Instruction Manual

Page: 28 / 59

CS650 and CS655 Water Content Reflectometers
17
This section briefly describes using SDI-12 commands.
Additional SDI-12 information is available at Appendix D ,
SDI-
12 Sensor Support
(p. D-1)
, www.sdi-12.org , or
www.youtube.com/user/CampbellScientific .
TABLE 8-3. CS650 SDI-12 Commands
SDI-12 command
(“a” is the sensor
address) Values Returned Units
aM!
1) Volumetric Water Content,
θ
2) Electrical Conductivity,
σ
3) Temperature
m 3 /m 3
dS/m
°C
aM1!
1) Permittivity, ε
2) Electrical Conductivity,
σ
3) Temperature
dS/m
°C
aM2!
1) Period, τ
2) Voltage Ratio, α
3) Temperature
µ s
°C
aM3!
1) Volumetric Water Content,
θ
2) Electrical Conductivity, σ
3) Temperature
4) Permittivity,
ε
5) Period, τ
6) Voltage Ratio,
α
m 3 /m 3
dS/m
°C
µ
s
aM4!
1) Volumetric Water Content,
θ
2) Electrical Conductivity, σ
3) Temperature
4) Permittivity,
ε
5) Period, τ
6) Voltage Ratio, α
m 3 /m 3
dS/m
°C
µ
s
aM5! .. aM9! No Values Returned
?! Returns the SDI-12 Address
aI!
CampbellSci, Operating System
Version, Product Serial Number
Campbell Scientific recommends using separate terminals when possible.
However, multiple CS650 sensors can connect to the same datalogger control
or U terminal. Each must have a unique SDI-12 address. Valid addresses are 0
through 9, A through Z, and a through z. The CS650 ships with a default
SDI-12 address of 0 unless otherwise specified at the time of ordering. Change
the SDI-12 address through Device Configuration Utility (see Section 8.1 ,
A200 and Device Configuration Utility
(p. 11)
) or with a terminal emulator in
SDI-12 transparent mode (see Appendix D ,
SDI-12 Sensor Support
(p. D-1)
).
8.2.1 M3! and M4! Commands
Typically, the M4! command is used to report volumetric water content,
electrical conductivity, temperature, permittivity, period, and voltage ratio. The
NOTE