ICS Schneider Messtechnik GD-20 Manual página 48

5. Commissioning, operation
5.2.2 Pin assignment (model GD-20-D)
Circular connector M12 x 1 (5-pin)
1
2
EN
3
4
5
5.2.3 Requirements for shielding and grounding
■
Only use shielded cables and connect the shield on one side to the read-out unit.
■
The gas density sensor must be grounded via the process connection.
■
Ensure that no earth circuits can occur.
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).
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5.3 Modbus
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The Modbus communication protocol is based on a master/slave architecture. The protocol implemented in the model
GD-20 gas density sensor is Modbus
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The Modbus protocol is a single-master protocol. This master controls the entire data transfer and monitors any possible
timeouts (no reply from the addressed instrument). The connected instruments may only send telegrams after request by
means of the master.
RTU (RTU: Remote Terminal Unit) transmits the data in binary form, guaranteeing a good data throughput.
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Modbus
Detailed information on the protocol under www.Modbus.org
48
- -
U
Supply voltage
+
U
Mass
-
A Signal RS-485
B Signal RS-485
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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WIKA operating instructions gas density sensor, model GD-20