A fieldbus is an industrial computer network for real-time distributed control of various devices. When Eltorque valve actuators are controlled by fieldbus, the functionality is extended in terms of positioning, commands, feedback and configuration. In addition to extended control possibilities, the major advantage of fieldbus is simplified cabling. The Eltorque Modbus interface uses RS-485 serial communication utilizing the Modbus RTU protocol. Modbus allows communication with max 30 actuators connected to the same “master-slave” network. The Eltorque CANopen interface uses the CAN (Controller Area Network) communications standard. CANopen allows communication between a maximum of 127 actuators connected to the same network. Compared to Modbus, CANopen offers a more reliable communication and extended functionality.
The Digital Interface allows simple Open & Close operation of valves, i.e. you can command the actuator to Close or Open the valve. The actuator provides feedback when the valve reach OPEN or CLOSED and any failure triggers the ALARM function. Actuators with Digital Interface can be controlled directly from a conventional panel with buttons/switches and indicator lamps. Alternatively, it can be controlled from a PLC with digital inputs and outputs.
The Analogue Interface allows regulating valves where positioning of the valve is needed. The actuator provides continuous feedback of its actual position, for comparison between desired and actual position. Both positioning and feedback signals are analogue 4-20 mA. The Analogue Interface also has a digital Alarm output, which is trigged by failures in both actuator and valve.