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Chapter 1

Chapter 1. INTRODUCTION. Topics. Introduction Modern Instrumentation and Control OSI Model Protocols Standards. Introduction. Transfer of Information From One Point to Another Transmitter/Receiver/Link Serial Links vs Parallel Links Digital Data vs Analog Mutual Agreement.

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Chapter 1

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  1. Chapter 1 INTRODUCTION

  2. Topics • Introduction • Modern Instrumentation and Control • OSI Model • Protocols • Standards

  3. Introduction • Transfer of Information From One Point to Another • Transmitter/Receiver/Link • Serial Links vs Parallel Links • Digital Data vs Analog • Mutual Agreement

  4. Historical Background • Telegraph System • Morse Code • Baudot Code

  5. Three Themes • Physical Standards • Open Systems Interconnection • Protocols

  6. Standards • EIA-232 Interface Standard • EIA-485 Interface Standard

  7. A Typical Serial Data Communications Link

  8. Modern Instrumentation • Distributed Control System (DCS) • All Electronic tightly integrated system • Programmable Logic Controller (PLC) • Came from Relay Equipment • SCADA System • RTU’s and Master Station - radio links • Smart Instrumentation • Intelligent Sensors on comms link • Fieldbuses and Devicenets ( and HART)

  9. Distributed Control System (DCS) • Based Around a Data Highway • Modular Distributed & Integrated • Each Module Performs Specific Dedicated Task • “Good” on Analog Control • Easy Connection to PLC’s / supervisory Computer Interfaces

  10. PLC • Programmable Logic Controller • Sequence Control and Interlocking • On/Off Inputs/outputs • Ladderlogic Type Programs

  11. A Typical PLC System

  12. SCADA • Supervisory Control and Data Acquisition System • RTU’s to Master Station • Radio Links /Landlines • Also term used for SCADA Software package eg Citect

  13. Smart Instrumentation • Microprocessor Based Instrument • Embedded Controllers • Data Communications Capability • RS- 232, RS 485 or Fiber Optic • Ability to Multi-drop With Other Instruments on Same Highway • Wave of the Future...Eg Fieldbus

  14. OSI Model • Developed by the ISO • Universal Framework for Building A Communications Systems • 7 Layer Model • 3 Layer Model Very Common for Industry • Missing the 8th Layer

  15. Representation of the OSI Model

  16. Standards Within A Communications System • Code - Morse - Hex - ASCII • Physical - 232 - 422 - 485 • Protocol - Modbus, Profibus, Hart, Foundation Fieldbus, Ethernet • Open Systems Interconnection Model

  17. Protocols • Rules for Transmission of Data (Packets) • Packet Can Include: • Sync Byte • Destination Address • Source Address • Data • Error Detection • Modbus - Profibus - Canbus - Ethernet - TCP/IP • HDLC - DH+ - HART - DNP3 - Interbus - FTP

  18. Basic Structure of an Information Frame Defined • SYNCHRONIZING BYTE Is Used To Synchronize The Receiver. • DESTINATION ADDRESS Is Where The Packet Is Going. • SOURCE ADDRESS Is Where The Packet Has Come From. • DATA Is The Information Contained In The Packet. • ERROR BYTE Is The Result Of The Error Correction Calculation.

  19. Voltage Standards • EIA/RS-232 Interface Standard • Half / Full Duplex - Point to Point • EIA/RS-485 Interface Standard • Half Duplex - Multidrop

  20. RS-232

  21. Two Wire Multidrop RS-485

  22. Fiber Optic Cable

  23. Modbus Protocol Structure

  24. Modbus Plus • Builds on Modbus • Token Passing and deterministic • High Speed - minimum of 1Mbit/s

  25. HART Protocol4 - 20 ma Communications

  26. ASI Bus • Idiot Proof • 167kbps and fast for digitals • 31 slaves and 124 I/O points with 5ms scan

  27. The DeviceNet Model

  28. ProfibusTypical Architecture of System

  29. Foundation Fieldbus • Newest Fieldbus • H1 standard - 31.25kbit/s • HSE - 100Mbit/s • Three layers plus excellent User Layer

  30. Ethernet 10BaseT MAC = Media Access Control

  31. TCP/IP • Internet Protocol (IP) • Transmission Control Protocol (TCP) • Application Layer • Three Layer Model • Derived from Internet

  32. Wireless Communications

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