Campbell IRGASON, Руководство по эксплуатации продукта

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8. EC100 outputs
The EC100 is the IRGASON electronics module that measures the sensors and controls the
system. It outputs data in one of four types: SDM, USB, RS-485, or analog. In general, Campbell
Scientific recommends that SDM be used if a Campbell Scientific data logger is responsible for
data collection. However, RS-485 output is recommended if cable lengths exceed 100 m (328 ft).
If a PC is being used as the collection vehicle, USB and RS-485 are suitable outputs. Analog
output may also be used; however, only CO
2
density and H
2
O density will be output. Information
regarding each output type is provided in the following sections.
8.1 SDM output
SDM (Synchronous Device for Measurement) is a Campbell Scientific communication protocol
that allows synchronized measurement and rapid communication between a Campbell Scientific
data logger and multiple devices including the IRGASON. Although nearly all of the Campbell
Scientific data loggers support SDM, only the CR6, CR1000, CR3000, and CR5000 data loggers
support the IRGASON.
To use SDM data output, connect an SDM cable from the EC100 (see Wiring and connections (p.
15)) to a CR6, CR1000, CR3000, or CR5000 data logger. On CR1000 data loggers, the SDM
protocol uses ports C1, C2, and C3. These are multipurpose control ports that are SDM-activated
when an SDM instruction is used in the data logger program. On CR3000 and CR5000 data
loggers, the SDM protocol uses SDM-dedicated ports SDM-C1, SDM-C2, and SDM-C3. On CR6
data loggers, the user must assign which set of three ports will be used for SDM. This is done in
the data logger program using the
SDMBeginPort() programming instruction. See the CR6
manual for more details.
Each SDM device on the SDM bus must have a unique address. The IRGASON has a factory
default SDM address of 1, but may be changed to any integer value between 0 and 14 (see
SDM
address (p. 21)).
The sample rate for SDM output is determined by the inverse of the data logger scan interval, as
set by the user in the data logger 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 data logger is also set by the user in the data logger program. CRBasic, the
programming language used by Campbell Scientific data loggers, uses the
EC100() instruction to
get data from an IRGASON. This instruction is explained in detail under EC100() instruction (p. 46)
of this manual.
IRGASON® Integrated CO
2
/H
2
O Open-Path Gas Analyzer and 3D Sonic Anemometer 27