FIELD BUSES ECE422-DATA COMMUNICATIONS & COMPUTER NETWORKS - - PowerPoint PPT Presentation

FIELD BUSES

ECE422-DATA COMMUNICATIONS & COMPUTER NETWORKS October 2020

WHAT IS A FIELDBUS?

• 1. Fieldbus is a digital communication bus line

connecting the field instruments with the control system components.

• 2. A field instrument is an instrument attached

to a process, e.g.: measurement devices, valves, motor starters and alarm switches .

• 3. A field instrument to be attached to a fieldbus

must be equipped with some intelligence for the bus communication.

• 4. Without fieldbus, each field instrument has to

be connected to the I/O of the control system, two wires for each instrument

BENEFITS OF USING FIELDBUS

The benefits of using fieldbuses are:

• Reduction of cables resulting in savings in cost and weight and a

tidier system without the mess that a multi-cabling system gives.

• fieldbus systems have less hardware components.
• Easier to maintain and configure.
• Interoperability: Fieldbus instruments from different vendors can

communicate directly on the same bus.

• A field instrument can easily be changed with another during run

time

FIELDBUS STANDARDS

1. In year 2000 International standardization organizations (ISO) developed the IECC 61158 standard, which includes 8 different fieldbuses in the same standard. 2. The 8 fieldbuses included in this Octobus standard are:

a) PROFIBUS b) ControlNet c) FF – H1 (Foundation Fieldbus) d) FF – HSE (Foundation Fieldbus) e) Interbus f) P-Net g) SwiftNet h) WorldFip

PROFIBUS

• PROFIBUS is a short form for PROcess FIeldBUS and is a vendor-

independent, open fieldbus standard.

• PROFIBUS is the world's most successful fieldbus with 70 million

devices installed by the end of 2019 with almost 10 million of these in the process industries.

• Utilizing a single, standardized, application-independent

communication protocol, PROFIBUS supports fieldbus solutions both in factory and process automation as well as in motion control and safety-related tasks.

HISTORY OF PROFIBUS

• 1. PROFIBUS was developed in 1990 in Germany as a

joint project between Siemens, Klöckner Möller (now Moeller Electric), and Bosch.

• 2. In 1991 it was taken in as a part of the German

standard (DIN 19245) and became later a European standard (EN 50170).

• 3. PROFIBUS is now part of the new ISO Octobus

standard IEC 61158.

PROFIBUS PROFILES

PROFIBUS has three types of profiles:

• 1. Station types: Application Profiles

(PA-devices, Encoders, Drivers, ..)

• 2. Protocols: Communication

Profiles ( DP, FMS, TCP/IP)

• 3. Signal transmission: Physical layer

signals (RS-485, IEC1158-2, O.F., Ethernet)

PROFIBUS ARCHITECTURE

PROFUBUS PHYSICAL MEDIUM-CABLE

The RS 485 transmission is the transmission technology most used on PROFIBUS. Its main characteristics are: 1. NRZ Asynchronous Transmission; 2. 9.6 kBit/s to 12 Mbit/s configurable baud rates; 3. Twisted pair shielded cable; 4. 32 stations per segment, 127 stations max; 5. Distance dependent on the transmission rate

12 MBit/s = 100 m; 1.5 MBit/s = 400m; < 187.5 kBit/s = 1000 m;

6. Expansible distance up to 10 Km with the use of repeaters; 7. 9 PIN, D-Sub connector.

TRANSMISSION OVER COPPER CABLE

CHARACTERISTICS PHYSICAL MEDIUM COMPLYING WITH IEC61158-2, H1 VARIANT Cable 31.25 kbits/s Topology Bus, tree, point to point. Power Supply Via bus or external medium Intrinsic Safety Possible Number of equipments (depends on current devices consumption) Maximum 32(non-Ex) Explosion Group IIC: 9 Explosion Group IIB: 23 Maximum Cabling 1900 m, expansible to 10 Km with 4 repeaters. Spur Maximum 120m/spur Communication Signal Codification, with voltage modulation

The transmission technology is synchronous with Manchester codification in 31.25 Kbits/s (voltage mode); it is defined according to the IEC 61158-2 and was elaborated aiming to satisfy the requisites by chemical and petrochemical industries: intrinsic safety and the possibility of power the field equipment through the bus.

TRANSMISSION OVER FIBRE OPTICLE CABLE