In this article, the foundation fieldbus segment configuration is determined based on the information obtained during the basic design and detailed design. Note that the results of the detailed design decisions vary depending on the capacity of the selected Fieldbus device as well as the bus topology, which may affect the segment configuration.
What is segment in FOUNDATION fieldbus?
A fieldbus trunk or segment either FOUNDATION fieldbus H1 or PROFIBUS PA—is a single twisted pair wire carrying both a digital signal and DC power that connects up to 32 fieldbus devices (temperature, flow, level and pressure transmitters, smart valves, actuators, etc.) to a DCS or similar control system.
Foundation Fieldbus Segment Configuration & Design
The segment configuration depends on the application, and is determined by FOUNDATION fieldbus-specific constraints such as the number of devices that can be connected, the length of the Fieldbus transmission route, and the power consumption, as well as the number of communication data points and the communication cycle involved.
However, characteristics such as the type and number of fieldbus blocks, throughput capacity, and power consumption vary depending on the selected Fieldbus device. In addition, the segment configuration and the wiring design closely affect each other according to conditions such as the number of connection parameters and the communication performance. For this reason, it is necessary to design the device assignment and the device selection for a segment at the same time because they influence each other.
The design of the segment configuration is a repetitive task due to this mutual influence. Repeat the detailed design and segment configuration steps until the results of each of the detailed design items are satisfactory.
When examining the segment configuration, the following items should be taken into consideration in addition to the ALF111’s restrictions on mounting, number of assigned points, current consumption, and total cable length.
• IS (Intrinsic Safety)
• Communication performance
• Distributed processing
• Maintainability
Use the following procedure as a guide to determining the segment configuration.
- Determine the device sensing method based on P&ID and process data.
- Design the control loop based on P&ID, and clarify the control method. If the control is performed on the Fieldbus device side, it is also necessary to consider the countermeasure when a Fieldbus communication error occurs.
- Select the devices to be connected to the segment based on steps 1 and 2.
- Check the positions of the assigned devices on the device layout drawing and determine the bus topology.
- Check the data throughput capacity, communication performance, and total current consumption with respect to the details determined in step 4. If this check result is not satisfactory, the devices should be reassigned and the device models reselected for the segment. Repeat the task until the result becomes satisfactory.
- Bus topology selection.
- Fieldbus Devices based on Project.
- Fieldbus transmission length.
- Total Communication data points.
- Fieldbus power consumption.
- Communication cycles.
General Question asked during this topic.