Campbell Scientific EC155 CO2 and H2O Closed-Path Gas Analyzer and EC100 Electronics with Optional CSAT3A 3D Sonic Anemometer - Manual (Page 34)

EC155 CO
2
and H
2
O Closed-Path Gas Analyzer
dataloggers, the SDM protocol uses SDM-dedicated ports SDM-C1, SDM-C2,
and SDM-C3.
Each SDM device on the SDM bus must have a unique address. The EC155
has a factory default SDM address of 1, but may be changed to any integer
value between 0 and 14 (see Section 7.2.1, SDM Address).
The sample rate for SDM output is determined by the inverse of the datalogger
scan interval, as set by the user in the datalogger program. Data are output from
the EC100 when a request is received from the logger, i.e. a prompted output
mode. The number of data values sent from the EC100 to the datalogger is
also set by the user in the datalogger program. CRBasic, the programming
language used by Campbell Scientific dataloggers, uses the EC100()
instruction to get data from an EC155. This instruction is explained in detail
under Section 10, Datalogger Programming with CRBasic of this manual.
8.2 USB or RS-485 Output
In contrast to the SDM output mode, which is prompted by a datalogger, data
can also be output from the EC100 via USB or RS485 in an unprompted mode.
In this case the EC100 sends out data without initiation from the receiving
device, at a rate determined by the EC100. Only one unprompted output type
(i.e., USB, RS-485) may be selected at a given time. RS-485 output is
recommended over SDM if cable lengths exceed 100 meters. If a Campbell
Scientific datalogger is not being used to collect the data from the EC155,
either unprompted mode is recommended.
To use USB or RS-485 output, connect a USB or RS-485 cable from the
EC100 to the receiving device (see Section 6.3, Wiring and Connections), and
configure the settings (see Section 7, Settings).
The Unprompted Output parameter must be set to USB or RS-485.
If RS-485 is selected, the RS-485 Baud Rate must be set.
The Unprompted Output Rate must be set to the desired output rate.
All output data will be in ASCII format, with each data element separated by a
comma. Each record will terminate with a carriage return and line feed.
TABLE 8-1 below lists the elements in each output array, and FIGURE 8-1
shows an example USB data feed in terminal mode.
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