Modbus; Modbus ® Start-Up Kit - WIKA GD-20 Operating Instructions Manual

5. Commissioning, operation
5.2.4 RS-485
The physical layer for the Modbus
between pins 4 and 5 (A and B) is evaluated with a 2-wire system (half-duplex).

5.3 Modbus

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The Modbus communication protocol is based on a master/slave architecture. The protocol implemented in the model
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GD-20 gas density sensor is Modbus
The Modbus protocol is a single-master protocol. This master controls the entire data transfer and monitors any possible
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timeouts (no reply from the addressed instrument). The connected instruments may only send telegrams after request by
means of the master.
Modbus RTU (RTU: Remote Terminal Unit) transmits the data in binary form, guaranteeing a good data throughput.
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Detailed information on the protocol under www.Modbus.org
5.4 Modbus start-up kit
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The gas density sensor, with the optionally available start-up kit (order no. 14075896), can be configured for operation
at the measuring location.
A further function is an integrated data logger, showing measured data in a specific cycle or writing it in a file.
The start-up kit consists of:
Power supply unit
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Interface converter (RS-485 to USB)
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USB cable type A to type B
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Sensor cable with M12 x 1 connector
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Adapter cable for GDM-100-TI
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Modbus tool
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WIKA operating instructions gas density sensor, model GD-20
protocol is the serial RS-485 interface per EIA/TIA-485. The differential signal
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-RTU with serial transmission via a 2-wire RS-485 interface.
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EN
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