Rs-485; Modbus - WIKA GD-20 Series Operating Instructions Manual

5. Commissioning, operation
Differential mode
T-connector
EN
Sensor
Gas tank
Interferences in the differential mode can be compensated by a network of decoupling
capacitors that are located in front of the read-out unit.

5.2.4 RS-485

The physical layer for the Modbus protocol is the serial RS-485 interface per EIA/
®
TIA-485. The differential signal between pins 4 and 5 (A and B) is evaluated with a
2-wire system (half-duplex).

5.3 Modbus

®
The Modbus communication protocol is based on a master/slave architecture. The
®
protocol implemented in the model GD-20 gas density sensor is Modbus -RTU with
®
serial transmission via a 2-wire RS-485 interface.
16 WIKA operating instructions gas density sensor, model GD-20