SHIVAM SINGHPROJECT ENGINEER

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Overview- Fieldbus is a generic term that describes a new digital

communications network that is being used in industry to replace the existing 4-20 mA analog signal standard.

The network is a digital, bi-directional, multi-drop, serial-bus communication network used to link isolated field devices, such as controllers, transducers, actuators and sensors.

Bi-directional means it is a duplex port; the data can be transmitted in two directions at the same time.

Multi-drop is also referred to as multi-access and it can be interpreted as a single bus with many nodes connected to it.

Serial-bus means the data is transmitted serially according to RS232 or RS485 protocol. Profibus uses RS485 protocol.

Fieldbus works on network structures such as daisy-chain, star, ring, branch, and tree network topologies.

Overview……

“Foundation Fieldbus Architecture”

Overview……

FOUNDATION fieldbus is an open, integrated total architecture for information integration. FOUNDATION fieldbus is an all-digital, serial, two-way communication system.

H1 (31.25 Kbit/s) interconnects “field” equipment such as sensors, actuators and I/O.

HSE (100 Mbit/s) (High Speed Ethernet) provides integration of high speed controllers (such as PLCs), H1 subsystems (via a linking device), data servers and workstations.

FOUNDATION fieldbus is the only protocol with the built-in capability to distribute the control application across the network .

Integrated Architecture-• Management Information Systems (MIS),• Enterprise Resource Planning (ERP), and• Human Machine Interface (HMI) access the

H1.• Fieldbus information via the Data Servers

H1 Basic Review-More Data for Better Decision Making-• Fieldbus allows “multiple variables” from each device to

be brought into the control system for archiving, trend analysis, process optimization, and reporting, predictive maintenance and for asset management.

• Fieldbus distortion-free characteristics digital communication enables improved control capability which can improve product yields.

H1 Basic Review……

Expanded View of Process & Instrument- Self-Diagnostics and communication capabilities of

microprocessor based fieldbus devices helps reduce downtime and improve plant safety.

Plant operation and Maintenance personnel can be notified and corrective actions taken quickly and safely

Wiring saving- The H1 fieldbus allows many devices to be connected

to a single wire pair. This results in less wire, fewer intrinsic safety

barriers and fewer marshaling cabinets.

H1 Basic Review……Reduction in System Hardware- Standard Function Blocks is used to implement the

Control Strategy. Many control system functions such as AI, PID and AO

can be performed by the field device through the use of these Standard Function Blocks.

Distribution of control into field devices can reduce the amount of hardware and cabinet footprint needed.

H1 Network Review-

Multi-Drop wire pair with Power and Signal on same cable.

Support Intrinsic Safety. Fault Tolerant, can have

multiple Link Masters. Function Blocks built into

Field Devices. Control on the Wire –single

loop integrity. Distance up to 1900 meters Add Repeaters to extend >

1900 meters Max. Of 4 repeaters can be

used to a maximum distance of 9500 meters

DD and CFF Files- Field Devices will consist of: Actual Physical Device,

Device Description (DD), & Common File Format (CFF). DDs and CFFs will be provided by the Device Supplier or

Host Supplier. Standard parameters present in devices. Option to

include specific manufacturer parameters. Parameters and Capabilities are defined in device files –

DD and CFF. Device files are key to off-line configuration. Device Descriptor (DD) File allows operation of devices

from different suppliers on the same fieldbus with single host system.

Common File Format (CFF) is a file which describes the functions and capabilities of a field device. The CFF file is used in conjunction with the Device Descriptor file to enable a host system to configure the system off-line.

H1 Fieldbus Model-

HSE –Subsystem Integration-

High Performance Control Backbone.

Standard Ethernet Equipment and Wiring.

Standard Function Blocks PLUS.

Flexible Function Blocks for Discrete/Batch/PLC.

Redundant HSE Interfaces and Devices.

Linking Devices (LD) Integrate H1.

HSE Provides the Open Interface for Data Servers.

4-20mA versus Fieldbus-A H1 fieldbus retains and optimizes the desired features of the 4-20mA analog system: Single Loop integrity. A standardized physical interface to the wire. A bus-powered device on a single wire pair. Intrinsic safety options.

In addition, FOUNDATION Fieldbus enables: 25 x faster communication speed compared to HART Increased capabilities (due to full digital

communication). Reduced wiring and terminations (multiple devices on

one wire). Increased selection of suppliers (due to

interoperability) Reduced control room loading (control on wire) Connection to HSE backbone

4-20mA versus Fieldbus……

Communications over a fieldbus require a fieldbus interface device in all of the

devices.

Advantages of Fieldbus-

A major advantage of fieldbus is the capital expenditure (CAPEX) savings associated with cable elimination; multiple devices share wire-pairs in order to communicate over the bus network and savings are also available through speedier commissioning.

Ongoing maintenance and process control system performance are significantly enhanced through fieldbus systems, which results in operations expense savings (OPEX).

Disadvantages of Fieldbus-

Disadvantages of fieldbus compared to the 4-20 mA analog signal standard: Fieldbus systems are complex, so more

training needed The price of fieldbus components is higher Fieldbus test devices are more complex Device manufacturers have to offer different

versions of devices due to different fieldbus standards. This can add to the cost of the devices and increases the difficultly of device selection.

Standards may predominate or become obsolete, increasing the investment risk.