Campbell SR20-D2, Руководство по эксплуатации продукта

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6. RS-485 programming
The RS-485 output can be directly read by a MeteoPV, CR6-series, CR1000X-series, or Modbus
RTU RS-485 network. Other Campbell Scientific data loggers can use an MD485 multidrop
interface to read the RS-485 output (refer to the MD485 manual).
A CR6 or CR1000X data logger programmed as a Modbus Master can retrieve the values stored in
the Input Registers. To do this, the CRBasic program requires a
SerialOpen()
instruction
followed by the ModbusMaster() instruction.
The
SerialOpen
instruction has the following syntax:
SerialOpen (ComPort, Baud, Format, TXDelay, BufferSize, Mode)
The
Format
is typically set to logic 1 low; even parity, one stop bit, 8 data bits. The
Mode
parameter should configure the ComPort as RS-485 half-duplex, transparent. The
ModbusMaster() instruction has the following syntax:
ModbusMaster (Result, ComPort, Baud, Addr, Function, Variable, Start, Length,
Tries, TimeOut, [ModbusOption])
The
Addr
parameter must match the sensor Modbus address. To collect all of the values, the
Start
parameter needs to be 1 and the
Length
parameter needs to correspond with the
register count (see SR20-D2 register map (p. 4)). ModbusOption is an optional parameter
described in the CRBasic Editor Help. Refer to SR20-D2 example program (p. 5) for more
information.
7. SR20-D2 example program
Table 7-1: Wiring for example program
Wire color Function Data logger connection
Green RS-485A C5
White RS-485B C6
Red Power in (12 V) 12V
Black Power ground G
Clear Shield ⏚ (analog ground)
SR20-D2 ISO Spectrally Flat Class A (Secondary Standard) Pyranometer 5