Section 7. Software Reference
For test purposes, you can also choose Set Point for the Source, and enter a Set
Point voltage value; the DAC channel will then output that voltage continuously.
SDM Output
SDM addressing allows multiple SDM-compatible peripherals to be connected to a
single Campbell Scientific datalogger. Choose an address under the SDM tab
between 0 and 14.
The pin assignments of the SDM Interface Cable are given in LI-7550 Analyzer Inter-
face Unit on page1-6. Generally, the blue wire (SDM_DATA) will connect to C1 on
the datalogger, the white wire (SDM_CLK) to C2, the brown wire (SDM_EN) to
C3 and the black wire (ground) to ground.
SDM communications are enabled in Campbell Scientific®, Inc. dataloggers with
the LI7200 instruction. This instruction is only available in dataloggers pro-
grammed in CRBasic (e.g. CR5000). When using this instruction parameter three
(SDMAddress) should be set to match the SDM address of the LI-7200/RS. Para-
meter four (LI7200Cmd) is used to define what variables the datalogger collects
from the instrument. The LI7200 instruction supports a group trigger mode, and
so it can take on values from 0 to 7 (see Table 7-1 below) for what variables are
included in each option). Below is a programming example of the LI7200 instruc-
tion used to collect data from an LI-7200/RS at SDM address 0:
LI7200 (LI-7200/RS(),1,0,6)
Mode Items Sent
0 CO
2
dry (µmol/mol)
H
2
O dry (mmol/mol)
1 CO
2
(mmol/m
3
)
H
2
O (mmol/m
3
)
P
total
(kPa)
T
in
(°C)
T
out
(°C)
Table 7-1. Parameter 4 value definitions.
7-16 LI-7200RS Enclosed CO₂/H₂O Analyzer
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