Fieldbus Specific Technical Information
If you are new to the Fieldbus Industry, then this page is for you. Here, we will discuss what Fieldbuses are and why then are used. Also, other topics such has what constitutes are Fieldbus and what Fieldbuses are currently on the market will be discusses. If you have any questions, please don't hesitate to contact. We will always be available to answer any questions you may have.

What Are Fieldbuses

Fieldbuses are communication technologies and products used in automation and process control industries. We will distinguish between proprietary fieldbuses and open fieldbuses.

Proprietary Fieldbuses

Proprietary Fieldbuses are an intellectual property of a particular company or body. To use a Proprietary, a license is required, however this may only give you partial rights. Such licenses are usually only granted at the discretion of the owner or owners and are generally very expensive.

Open Fieldbuses

Open Fieldbuses however are the opposite. For a Fieldbus to be Open, it must satisfy the following criteria.

• The full Fieldbus Specification must be published and available at a reasonable price.
• Critical ASIC components must be available, also at a reasonable price.
• Well defined validation process, open to all of the Fieldbus users.

A Fieldbus may allow for the following.

• Interconnectivity

  Devices from different manufactures can be safely connected to the same Fieldbus.

• Interoperability

  The ability to connect successfully, elements from different suppliers.

• Interchangeability

  Devices from one manufacture can be replaced with functionally equivalent devices from another manufacture.

Interconnectivity is the minimum common denominator and does not offer any significant benefits by itself. If interoperability cannot be achieved, the Fieldbus installation exercise is worthless and the particular Fieldbus is useless. The ultimate goal is interchangeability. It can only be achieved if the Fieldbus specifications are complete and a proper system testing and validation process is employed.

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Why Use Fieldbuses

Fieldbuses, if correctly selected to suit the application offer the user many advantages both tangible and intangible. A list of these advantages follows.

Fieldbus Advantages

• Reduces the complexity of the control system in terms of hardware outlay. There is a reduction in the amount of PLC or DCS hardware requirements. This reduces the need for large control cabinets to house such equipment and associated connecting hardware. As cabling is reduced, the need for junction boxes, control panels and large cabling runs is eliminated. These advantages relate to a direct cost saving.

• As the hardware requirements are reduces so are the installation times and man power requirements. Commissioning of new installations is far more efficient as the diagnostic functions of Fieldbus systems identify any connection errors.

• Resulting in the reduced complexity of the control system, project design engineering is made simpler, more efficient and conversely less expensive. The need for designing complicated instrument loop drawing, cable schedules, termination schedules and wiring diagrams is to a degree eliminated.

• Future modifications, upgrades and refurbishment's are easily carried out at very little expense.

• By selecting a recognised and well established system, this will make the Fieldbus equipment in you plant or plants interchangeable between suppliers. The need to be concerned about connections, compatibility and other potential problems is eradicated.

• Downtime and production losses are reduced due to the superior diagnostic and fault finding procedure that fieldbuses are capable of.

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What Constitutes a Fieldbus

The specification of a Fieldbus should ideally cover all of the seven layers of the OSI model. An outline of how these layers should be covered follows.

Physical Layer [1]

What type of signals are present, levels, representation of 1's and 0's, what type of media, connects, etc.

Link Layer [2]

Techniques for establishing links between to communicating parties.

Network Layer [3]

Method of selecting the node of interest, method of routing data.

Transport Layer [4]

Ensuring the what was sent arrives at the receiver correcting any correctable problems.

Session Layer [5]

Not applicable to Fieldbuses.

Presentation Layer [6]

Not applicable to Fieldbuses.

Application Layer [7]

Meaning of data.

The best way of covering layer 7 is to define standard profiles for standard devices. For example, device parameters should be defined, the format of these parameters and the run time data to and from the device should also be defined.

If your Fieldbus and associated IO devices define a standard profile, the IO devices can be easily replaced with functionally equivalent devices from other manufactures. For example, take a variable speed motor driver, you can replace the motor driver you use with any compatible motor driver with minimal problems. If no standard profiles exist, your installation is specific and you will have no option of using alternative components.

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What Fieldbuses Are Currently On The Market

Below is a list of all the Fieldbuses Fieldbus Specialists are in contact with. A range of the listed Fieldbuses are fully defined Fieldbuses, whereas other are basic technologies (Fieldbus primitives). A number of Fieldbuses presented are proprietary, whereas the majority are open. Fieldbuses and similar technologies which are not industry specific have not been presented.

If you require any detailed information regarding any of the listed Fieldbus, please contact us directly. if you find any of the information inaccurate or incomplete and wish us to correct it, please send us an e-mail.

Technologics Fieldbuses are based on

RS-232

RS-485

CAN

ARCNET

IEC 1158-2

BITBUS (IEEE 1118)

 

Older Fieldbus Technologies

ModBus

HART

Conitel

DF1

Data Highway [+]

 

Established Fieldbus Systems

ModBus Plus	PROFIBUS DP	ISP SP-50	FIPIO	SINEC	Omron Sysmac Bus
DNP3	PROFIBUS FMS	CAN Open	P-NET	EIB	Allen-Bradley Remote IO
DeviceNet	PROFIBUS PA	CAN Kingdom	LonWorks	CEBus	FOUNDATION Fieldbus
WorldFIP	AS-i	FIP	IEC 870-5	IEEE-P1451.2	Smart Distributed Systems
SERCOS	InterBus	SERIPLEX

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