This manual focuses on the main issues of troubleshooting the industrial data communications network of today, enabling you to walk onto your plant or facility to troubleshoot and fix problems as quickly as possible. The focus is on the Modbus suite of protocols and their associated standards.
FOR MORE INFORMATION: http://www.idc-online.com/content/practical-troubleshooting-and-problem-solving-modbus-protocols-196
How to Implement Modbus TCP Protocol using VBA with ExcelACC Automation
We will use Visual Basic for Applications (VBA) to communicate to a PLC using Modbus TCP protocol. Reading ten registers in the PLC and displaying a bar graph in Excel.
The following steps will be done:
1.Explain Modbus TCP protocol
2.Install OstroSoft Winsock Component
– Winsock API Calls for communication on network
3.Develop the Excel and VBA application
(Microsoft Excel 2010)
4.Communicate to the PLC and sample code
(Do-More Simulator)
www.accautomation.ca
Data acquisition is the process of sampling real world physical information and the conversion of the samples into digital numeric values that computers and controllers can understand. Modbus based Data Acquisition devices include RTD, Thermistor, Thermocouple, Voltage, Current, Strain Gauge, Counter, Frequency, Relay, Digital Input, and Digital Ouptut and are widely used in industrial automation, remote monitoring, wastewater monitoring, process control, and building automation.
This training talks about Modbus RTU and Modbus TCP Protocols, Modbus Data Acquisition Technology, Modbus Data Logging, Stand Alone Modbus Systems, and how to configure PC Based Modbus Systems with SCADA Software.
More info: www.icpdas-usa.com?r=slideshare
In this session you will learn:
OSI reference model
OSI layers
Modbus communication protocol
Profibus communication protocol
Fieldbus communication protocol
For more information, visit: https://www.mindsmapped.com/courses/industrial-automation/complete-training-on-industrial-automation-for-beginners/
[Advantech] PAC SW Multiprog Tutorial step by step Ming-Hung Hseih
This is tutorial to give you basic concept and how to program PAC Software Multuprog.
•Level 1 : Create a new project and link test
•Level 2: IO configuration -IO slot
•Level 3 : IO configuration -Modbus client and
•Level 4 : IO configuration -Shared memory
•Level 5 : KW Program -R/W data and define user function
•Level 6 : KW Program -Modbus client and server expert
•Level 7 : KW Program -Do it !
Development of a Modbus RTU to Modbus TCP/IP compilerPratik Vyas
Detail description about How Modbus protocol works and Information about Modbus TCP/IP stack.
Description about how TCP/IP stack communicate between Server and Client from socket creation to socket close
[Advantech] WebOP designer Tutorial step by step Ming-Hung Hseih
This is tutorial to give you basic concept and how to program HMI Software WebOP Designer / WebAccess-HMI.
•Level 1 : Before Start
•Level 2 : Creating a Project
•Level 3 : Background and Screen Setting
•Level 4 : Data logger and History data display
•Level 5 : Alarm function
•Level 6 : Tag and Internal memory
•Level 7 : Macros
In this Office Security System project, image is captured by web camera, detected image is
compared with original data base for face recognition. If recognized image is known face then open the
door, otherwise sent the unknown image through LAN for displaying a new visitor, to all over the
network in various Departments. If the new visitor is to any one of the related person of staff member
then he will give the instruction to open door for the same visitor.
The Cortex M-3 system can measure all kind of electrical and thermal parameters RTD and so on. The
measured data can be displayed on the LCD/TFT of the system and at the same time can be transmitted
through RS – 485, or Ethernet N/W to remote DAS or DCS monitoring system by using mod bus / RTU
or mod bus / TCP control, The system has N/W with long distance communication function which can
ensure the disturbance rejection capabilities and reliability of the communication network. Hardware
platform use 32 bit embedded arm microprocessor and software platform use the microcontroller and
real time multitasking operating system which is open source. By using all these different port’s
functioning parameters of the Cortex M-3, Office Security System is developed
Practical Troubleshooting and Problem Solving of Ethernet NetworksLiving Online
While the basic structure of Ethernet has not changed much, the faster technologies such as Fast Ethernet and Gigabit Ethernet have increased the complexity and choices you have available in planning and designing these systems. As Ethernet has become more complex, a number of misconceptions have arisen as to how Ethernet functions and how the system should be optimally configured. This manual addresses these issues in a clear and practical manner, thus enabling you to apply the technology quickly and effectively in your next project. This manual commences with a brief outline of the Fundamentals of Ethernet and its operation.
The method of access is discussed in depth, and topics such as full duplex and auto negotiation are explained. The best methods of designing and installing the cabling systems are then explored with the discussion ranging from 10Base-T over twisted pair to Gigabit Ethernet cabling. Methods of optimising Ethernet to obtain best performance are then defined. Finally the all important topic of troubleshooting is examined with a summary of the typical problems you are likely to encounter from a two station network all the way up to a system comprising 30,000 PCs.
MORE INFORMATION: http://www.idc-online.com/content/practical-troubleshooting-problem-solving-ethernet-networks-26?id=48
How to Implement Modbus TCP Protocol using VBA with ExcelACC Automation
We will use Visual Basic for Applications (VBA) to communicate to a PLC using Modbus TCP protocol. Reading ten registers in the PLC and displaying a bar graph in Excel.
The following steps will be done:
1.Explain Modbus TCP protocol
2.Install OstroSoft Winsock Component
– Winsock API Calls for communication on network
3.Develop the Excel and VBA application
(Microsoft Excel 2010)
4.Communicate to the PLC and sample code
(Do-More Simulator)
www.accautomation.ca
Data acquisition is the process of sampling real world physical information and the conversion of the samples into digital numeric values that computers and controllers can understand. Modbus based Data Acquisition devices include RTD, Thermistor, Thermocouple, Voltage, Current, Strain Gauge, Counter, Frequency, Relay, Digital Input, and Digital Ouptut and are widely used in industrial automation, remote monitoring, wastewater monitoring, process control, and building automation.
This training talks about Modbus RTU and Modbus TCP Protocols, Modbus Data Acquisition Technology, Modbus Data Logging, Stand Alone Modbus Systems, and how to configure PC Based Modbus Systems with SCADA Software.
More info: www.icpdas-usa.com?r=slideshare
In this session you will learn:
OSI reference model
OSI layers
Modbus communication protocol
Profibus communication protocol
Fieldbus communication protocol
For more information, visit: https://www.mindsmapped.com/courses/industrial-automation/complete-training-on-industrial-automation-for-beginners/
[Advantech] PAC SW Multiprog Tutorial step by step Ming-Hung Hseih
This is tutorial to give you basic concept and how to program PAC Software Multuprog.
•Level 1 : Create a new project and link test
•Level 2: IO configuration -IO slot
•Level 3 : IO configuration -Modbus client and
•Level 4 : IO configuration -Shared memory
•Level 5 : KW Program -R/W data and define user function
•Level 6 : KW Program -Modbus client and server expert
•Level 7 : KW Program -Do it !
Development of a Modbus RTU to Modbus TCP/IP compilerPratik Vyas
Detail description about How Modbus protocol works and Information about Modbus TCP/IP stack.
Description about how TCP/IP stack communicate between Server and Client from socket creation to socket close
[Advantech] WebOP designer Tutorial step by step Ming-Hung Hseih
This is tutorial to give you basic concept and how to program HMI Software WebOP Designer / WebAccess-HMI.
•Level 1 : Before Start
•Level 2 : Creating a Project
•Level 3 : Background and Screen Setting
•Level 4 : Data logger and History data display
•Level 5 : Alarm function
•Level 6 : Tag and Internal memory
•Level 7 : Macros
In this Office Security System project, image is captured by web camera, detected image is
compared with original data base for face recognition. If recognized image is known face then open the
door, otherwise sent the unknown image through LAN for displaying a new visitor, to all over the
network in various Departments. If the new visitor is to any one of the related person of staff member
then he will give the instruction to open door for the same visitor.
The Cortex M-3 system can measure all kind of electrical and thermal parameters RTD and so on. The
measured data can be displayed on the LCD/TFT of the system and at the same time can be transmitted
through RS – 485, or Ethernet N/W to remote DAS or DCS monitoring system by using mod bus / RTU
or mod bus / TCP control, The system has N/W with long distance communication function which can
ensure the disturbance rejection capabilities and reliability of the communication network. Hardware
platform use 32 bit embedded arm microprocessor and software platform use the microcontroller and
real time multitasking operating system which is open source. By using all these different port’s
functioning parameters of the Cortex M-3, Office Security System is developed
Practical Troubleshooting and Problem Solving of Ethernet NetworksLiving Online
While the basic structure of Ethernet has not changed much, the faster technologies such as Fast Ethernet and Gigabit Ethernet have increased the complexity and choices you have available in planning and designing these systems. As Ethernet has become more complex, a number of misconceptions have arisen as to how Ethernet functions and how the system should be optimally configured. This manual addresses these issues in a clear and practical manner, thus enabling you to apply the technology quickly and effectively in your next project. This manual commences with a brief outline of the Fundamentals of Ethernet and its operation.
The method of access is discussed in depth, and topics such as full duplex and auto negotiation are explained. The best methods of designing and installing the cabling systems are then explored with the discussion ranging from 10Base-T over twisted pair to Gigabit Ethernet cabling. Methods of optimising Ethernet to obtain best performance are then defined. Finally the all important topic of troubleshooting is examined with a summary of the typical problems you are likely to encounter from a two station network all the way up to a system comprising 30,000 PCs.
MORE INFORMATION: http://www.idc-online.com/content/practical-troubleshooting-problem-solving-ethernet-networks-26?id=48
Highway Addressable Remote Terminal(HART), one of the most modern technology used in process industries for communication between field instruments and DCS.
OPC is the world’s most popular standards-based data-connectivity method. It is used to answer one of the automation industry’s biggest challenges: how to communicate between devices, controllers, and/or applications without getting caught up in the usual custom driver-based connectivity problems.
Practical DNP3 and Modern SCADA SystemsLiving Online
This manual covers the essentials of SCADA communication systems focusing on DNP3 and the other new developments in this area. The manual commences with a brief review of the fundamentals of SCADA systems hardware, software and the communications systems (such as RS-232 and RS-485 Ethernet and TCP/IP) that connect the SCADA operator stations together.
A solid review is then done on the DNP3 protocol where its features, message structure, practical benefits and applications are discussed. The manual is intended to be product independent but examples will be taken from existing products to ensure that all aspects of the DNP3 protocol are covered. The manual provides you with the tools to design your next SCADA system more effectively using DNP3 and draw on the latest technologies.
View Full Manual Here - www.idc-online.com/content/practical-dnp3-and-modern-scada-systems-20?id=33
Scada Industrial Control Systems Penetration Testing Yehia Mamdouh
Scada Industrial Control Systems Penetration Testing
Start from Types of Scada Networks, then Penetration testing, finally what Security should be follow
THE WORKSHOP:
This practical workshop covers all the essentials of process control and tools to optimise the operation of your plant and process, including the ability to perform effective loop tuning.
Practical process control is aimed at engineers and technicians who wish to have a clear, practical understanding of the essentials of process control and loop tuning, as well as how to optimise the operation of their particular plant or process. These persons would typically be primarily involved in the design, implementation and upgrading of industrial control systems. Mathematical theory has been kept to a minimum with the emphasis throughout on practical applications and useful information.
Inspection, Testing and Commissioning of Electrical Switchboards, Circuit Bre...Living Online
THE WORKSHOP:
Whether you are designing, specifying, installing, testing or commissioning electrical equipment from small to large commercial and industrial installations, you need to have a thorough understanding of switchboards, switchgear, circuit breakers and associated protective relays.
The overall focus of this workshop is on electrical inspection, testing and commissioning and will commence with a detailed examination of switchgear (and circuit breakers). Circuit breakers are critical components in electrical distribution systems and their operation significantly affects the overall operation of the system. Protection relays are then discussed. These are used in power systems to maximise continuity of supply and are found in both small and large power systems from generation, through transmission, distribution and utilisation of power in plant, industrial and commercial equipment.
We cover commissioning and periodic inspection of cables and their various failure modes and how to detect these faults. The often neglected topic of switchboards will be detailed next, followed by the interesting topic of interfacing to the control system (either PLC’s or other control devices).
Case studies and practical sessions are used throughout to illustrate key practical principles.
This workshop covers key elements in a practical and project focused way. Many people assume (wrongly) that inspecting, testing and commissioning is a fairly straightforward process and is simply a rubber stamp confirmation of a so-called outstanding design. Our experience in the field demonstrates quite the opposite; where the litany of problems ranges from design and installation errors to equipment manufacturing defects. It is best that these problems are identified and corrected before the inevitable downtime comes in an operational installation where many thousands of dollars are lost in correcting the faults. The situation today is made more challenging by the heightened safety requirements and interfacing to low powered electronic control and monitoring devices (such as PLC’s) using software that has to also be verified.
Hands on Data Communications, Networking & TCP/IP TroubleshootingLiving Online
THE WORKSHOP:
Data communication is given high priority in today’s industrial environment. This workshop is designed to be hands-on, providing the participants with essential knowledge and helping them to understand and troubleshoot systems.
This is a comprehensive two-day hands-on workshop that covers practical aspects of data communication such as serial communications, Ethernet networking, TCP/IP, Modbus, wireless communications and security.
This workshop is for enthusiastic engineers and technicians who wish to develop and enhance their practical knowledge in the field of data communications and networking. It will help them to understand the concepts behind data transmission, the various protocols involved, and the topologies that govern data exchange among various systems in industry. It will also equip them with the skills and tools to design and/or maintain these systems on an ongoing basis.
Fundamentals of Instrumentation, Process Control, PLCs and SCADA for Plant Op...Living Online
THE WORKSHOP:
This course represents a tremendous opportunity to gain expertise in all the key areas of the fast growing area of industrial automation in two days. Presented by an expert in the area but who is passionate with getting the key chunks of know-how and expertise across to you in a simple understandable manner which you can immediately apply to your job. This is most definitely not a boring lecture style presentation but an intensive learning experience where you will walk away with real skills as a result of the hands-on practical exercises, calculations, case studies and group sessions to ensure an understanding of the concepts and ideas discussed. You will undertake practical sessions at approximately 20 to 30 minute intervals to maximise the absorption rate.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
In this month's edition, along with this month's industry news to celebrate the 13 years since the group was created we have articles including
A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
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Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Saudi Arabia stands as a titan in the global energy landscape, renowned for its abundant oil and gas resources. It's the largest exporter of petroleum and holds some of the world's most significant reserves. Let's delve into the top 10 oil and gas projects shaping Saudi Arabia's energy future in 2024.
CFD Simulation of By-pass Flow in a HRSG module by R&R Consult.pptxR&R Consult
CFD analysis is incredibly effective at solving mysteries and improving the performance of complex systems!
Here's a great example: At a large natural gas-fired power plant, where they use waste heat to generate steam and energy, they were puzzled that their boiler wasn't producing as much steam as expected.
R&R and Tetra Engineering Group Inc. were asked to solve the issue with reduced steam production.
An inspection had shown that a significant amount of hot flue gas was bypassing the boiler tubes, where the heat was supposed to be transferred.
R&R Consult conducted a CFD analysis, which revealed that 6.3% of the flue gas was bypassing the boiler tubes without transferring heat. The analysis also showed that the flue gas was instead being directed along the sides of the boiler and between the modules that were supposed to capture the heat. This was the cause of the reduced performance.
Based on our results, Tetra Engineering installed covering plates to reduce the bypass flow. This improved the boiler's performance and increased electricity production.
It is always satisfying when we can help solve complex challenges like this. Do your systems also need a check-up or optimization? Give us a call!
Work done in cooperation with James Malloy and David Moelling from Tetra Engineering.
More examples of our work https://www.r-r-consult.dk/en/cases-en/
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
The family offers a choice of engines
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSE
Practical Troubleshooting and Problem Solving of Modbus Protocols
1. PRACTICAL
TROUBLESHOOTING AND
PROBLEM SOLVING OF
MODBUS
PROTOCOLS
Web Site: www.idc-online.com
E-mail: idc@idc-online.com
PRACTICALTROUBLESHOOTINGAND
PROBLEMSOLVINGOFMODBUSPROTOCOLS
REV
4.1
2. 1
Introduction
Objectives
When you have completed study of this chapter you will be able to:
• Describe the modern instrumentation and control system
• List the main industrial communications systems
• Describe the essential components of industrial communications systems
1.1 Introduction
Data communications involves the transfer of information from one point to another. In
this book, we are specifically concerned with digital data communication. In this context,
‘data’ refers to information that is represented by a sequence of zeros and ones, the same
sort of data handled by computers. Many communication systems handle analog data;
examples being telephone systems, radio and television. Modern instrumentation is
almost wholly concerned with the transfer of digital data.
Any communications system requires a transmitter to send information, a receiver to
accept it, and a link (the medium) between the two. Types of link include copper wire,
optical fiber, radio and microwave.
Some short–distance links use parallel connections, meaning that several wires are
required to carry a signal. This type of connection is confined to devices such as local
printers. Virtually all modern data communications systems use serial links in which the
data is transmitted in sequence over a single circuit.
Digital data is sometimes transferred using a system that is primarily designed for analog
communication. A modem, for example, works by using a digital data stream to
modulate an analog signal that is sent over a telephone line. Another modem demodulates
the signal to reproduce the original digital data at the receiving end. The word ‘modem’ is
derived from modulator and demodulator.
3. Troubleshooting and Problem Solving of Modbus Protocols2
There should be mutual agreement on how data is to be encoded, that is, the receiver must
be able to understand what the transmitter is sending. The rules governing the
communication are known as protocols.
In the past decade, many standards and protocols have been established, and this allows
data communications technology to be used more effectively in the industry. Designers
and users are beginning to realize the tremendous economic and productive gains possible
with the integration of systems that are already in operation.
Historically, developers of software and hardware platforms have developed protocols
that can only be used on their own products. In order to develop more integrated
instrumentation and control systems, standardization of these communication protocols
was required.
Standards may evolve from the widespread use of one manufacturer’s protocol (a de facto
standard) or may be specifically developed by bodies that represent certain industries.
Standards allow manufacturers to develop products that communicate with equipment
already in use. For the customer this simplifies the integration of products from different
sources.
The industrial communications market is characterized by a lack of standardization.
There are, however, a few dominant standards. Modbus has been a de facto standard for
many years and the tried-and-tested physical standards such as RS-232 and RS-485 have
been widely used. The area that has caused a considerable amount of angst (and dare we
say - irritation) amongst vendors and users is the choice of an acceptable fieldbus, which
would tie together instruments to PLCs and PCs. This effort has resulted in a few
dominant, but competing standards such as PROFIBUS, DeviceNet and FOUNDATION
Fieldbus being used in various areas of the industry.
The standard that has created an enormous amount of interest in the past few years is
Ethernet. Initially it was rejected as being non-deterministic, which means there is no
guarantee that a critical message is delivered within a defined time. This problem has
been solved with the latest standards in Ethernet and the use of switching technology. The
other protocol suite that fits onto Ethernet extremely well is TCP/IP. Being developed
specifically for the Internet, it is very popular and widely used.
1.2 Modern instrumentation and control systems
In an instrumentation and control system, data is acquired by measuring instruments and
transmitted to a controller, typically a computer. The controller then transmits data
(control signals) to the control devices, which act upon a given process.
The integration of systems in a plant allows data to be transferred quickly and effectively
between different systems along a data communications link. This eliminates the need for
expensive and unwieldy wiring looms and termination points.
Productivity and quality are the principal objectives in the good management of any
production activity. Management can be substantially improved by the availability of
accurate and timely data. From this, we can surmise that a good instrumentation and
control system can facilitate both quality and productivity.
The main purpose of an instrumentation and control system in an industrial environment
is to provide the following:
4. Introduction 3
• Control of the processes and alarms
Traditionally, analog controllers operating on standard 4-20 mA loops provide control
of parameters such as temperature and flow. The 4-20 mA standard is used by
equipment from a wide variety of suppliers, and it is common for equipment from
various sources to be mixed in the same control system. Stand-alone controllers and
instruments have largely been replaced by integrated systems such as Distributed
Control Systems (DCS), described below
• Control of sequencing, interlocking and alarms
Typically, this was provided by relays, timers and other components hardwired into
the control panels and motor control centers. The sequence control, interlocking and
alarm requirements have largely been replaced by PLCs.
• An operator interface for display and control
Traditionally, several operators are responsible for a portion of the overall process,
operating process and manufacturing plants from various local control panels. Modern
control systems tend to use a central control room to monitor the entire plant. The
control room is equipped with computer-based operator workstations that gather data
from the field instrumentation and use it for controlling the processes, monitoring
alarms, control sequencing and interlocking.
• Management information
Management information was traditionally provided by taking readings from meters,
chart recorders, counters and transducers and from samples taken from the production
process. This data is required to monitor the overall performance of a plant or process
and to provide the data necessary to manage the process. Data acquisition is now
integrated into the overall control system. This eliminates the gathering of information
and reduces the time required to correlate and use the information to remove
bottlenecks. Good management can achieve substantial productivity gains. The ability
of control equipments to fulfill these requirements has depended on major advances
that have taken place in the fields of integrated electronics, microprocessors and data
communications. The four devices that have made the most significant impact on how
plants are controlled are:
o Distributed Control Systems (DCSs)
o Programmable Logic Controllers (PLCs)
o SCADA (Supervisory Control And Data Acquisition) systems
o Smart Instruments
1.2.5 DCSs
A DCS is a hardware- and software-based (digital) process control and data acquisition
system. The DCS is based on a ‘data highway’ (bus) and has a modular, distributed, but
integrated architecture. Each module performs a specific dedicated task such as the
operator interface/analog or loop control/digital control. There is normally an interface
unit situated on the data highway allowing easy connection to other devices such as PLCs
and supervisory computer devices.
5. Troubleshooting and Problem Solving of Modbus Protocols4
1.2.6 PLCs
PLCs were developed in the late sixties to replace collections of electromagnetic relays,
particularly in the automobile manufacturing industry. They were primarily used for
sequence control and interlocking with racks of on/off inputs and outputs, called ‘digital
I/O’. They were controlled with a central processor using easily-written ‘ladder logic’
type programs. Modern PLCs now include analog and digital I/O modules as well as
sophisticated programming capabilities similar to a DCS, e.g. PID loop programming.
High-speed inter-PLC links are also available, such as 10/100 Mbps Ethernet. A diagram
of a typical PLC system is given in Figure 1.1.
Figure 1.1
A typical PLC system
1.2.7 SCADA
This refers to a system comprising a number of Remote Terminal Units (RTUs) collecting
field data and connected back to a master station via a communications system. Figure
1.2 below gives an example of this.
6. Introduction 5
Figure 1.2
Diagram of a typical SCADA system
1.2.8 Smart Instrumentation systems
During the 1960s, the 4-20 mA analog interface was established as the de facto standard
for instrumentation technology. As a result, the manufacturers of instrumentation
equipment had a standard communication interface on which to base their products. Users
had a choice of instruments and sensors from a wide range of suppliers, which could be
integrated into their control systems.
With the advent of microprocessors and the development of digital technology, the
situation has changed. Most users appreciate the many advantages of digital instruments.
These include more information being displayed on a single instrument, local and remote
display, reliability, economy, and self-tuning and diagnostic capability. There is a gradual
shift from analog to digital technology.
There are a number of intelligent digital sensors with digital communications capability
for most traditional applications. These include sensors for measuring temperature,
7. Troubleshooting and Problem Solving of Modbus Protocols6
pressure, levels, flow, mass (weight), density and power system parameters. These new
intelligent digital sensors are known as ‘Smart’ Instrumentation (see Figure 1.3).
The main features that define a Smart Instrument (SI) are:
• Intelligent, digital sensors
• Digital data communications capability
• Ability to be multi-dropped with other devices
There is also an emerging range of intelligent, communicating, digital devices that could
be called ‘smart’ actuators. Examples of these are devices such as variable speed drive,
soft starters, protection relays and switchgear control with digital communication
facilities.
Figure 1.3
Graphical representation of data communication
1.3 Open Systems Interconnection (OSI) model
The OSI model, developed by the International Organization for Standardization, has
gained widespread industry support. The OSI model reduces every design and
communication problem into a number of layers as shown in Figure 1.4. A physical
interface standard such as RS–232 would fit into Layer 1, while the other layers relate to
the protocol software.
8. Introduction 7
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application
Presentation
Session
Transport
Network
Data Link
Physical
Network
Data Link
Physical
Router
Server Client
Communications Medium
Figure 1.4
Representation of the OSI model
Messages or data are generally sent in packets, which are simply a sequence of bytes. The
protocol defines the length of the packet. Each packet requires a source address and a
destination address so that the system knows where to send it, and the receiver knows
where it came from. The user of the stack, e.g. the Client (residing on, say, a controller)
passes the message to the Application layer at the top of the stack. It then proceeds down
through the other protocol layers until it reaches the Physical layer. It is then sent over the
link. When traveling down the stack, the packet acquires additional header information at
each layer. This tells the corresponding layers at the next stack what to do with the
packet. At the receiving end, the packet travels up the stack with each piece of header
information being stripped off on the way. The receiver (e.g. the Server, residing on, say,
an RTU) only receives the data sent by the Client.
The arrows between layers indicate that each layer reads the packet as coming from, or
going to, the corresponding layer at the opposite end. This is known as peer-to-peer
communication, although the actual packet is transported via communications medium.
The middle stack in Figure 1.4 (representing a router) has only the three lower layers,
which is all that is required for the routing of a packet between the two devices in this
particular case.
The OSI model is useful in providing a universal framework for all communication
systems. However, it does not define the actual protocol to be used at each layer. It is
anticipated that groups of manufacturers in different areas of the industry will collaborate
to define software and hardware standards appropriate to their particular industry. Those
seeking an overall framework for their specific communications requirements have
enthusiastically embraced this OSI model and used it as a basis for their industry specific
standards.
9. Troubleshooting and Problem Solving of Modbus Protocols8
1.4 Protocols
As previously mentioned, the OSI model provides a framework within which a specific
protocol may be defined. A protocol, in turn, defines a frame format that might be
made up as follows. The first byte(s) can be a string of ones and zeros to synchronize
the receiver, or flags and to indicate the start of the frame (for use by the receiver). The
second byte could contain the destination address detailing where the message is going.
The third byte could contain the source address noting where the message originated. The
bytes in the middle of the message could be the actual data that has to be sent from the
transmitter to receiver. The final byte(s) are the end-of-frame indicators, which can be
error detection codes and/or ending flags (see Figure 1.5).
Figure 1.5
Basic structure of an information frame defined by a protocol
Protocols vary from the very simple (such as ASCII-based protocols) to the very
sophisticated (such as TCP/IP), which operate at high speeds transferring megabits of
data per second. There is no right or wrong protocol; the choice depends on a particular
application.
1.5 Standards
A brief discussion is given below on the most important approaches that are covered in
this book.
These are the following:
• RS-232
• RS-485
• Modbus
• Modbus Plus
• Ethernet, IEEE 802.3
• TCP/IP
• Wireless, IEEE 802.11 and IEEE 802.15
1.5.1 RS-232 interface standard
The RS-232C interface standard was issued by the EIA in 1969 to define the electrical
and mechanical details of the interface between Data Terminal Equipment (DTE) and
Data Communications Equipment (DCE), which employed serial binary data interchange.
In serial data communications, the communications system might consist of:
• The DTE, a data sending terminal such as a computer, which is the source
of the data (usually a series of characters coded into a suitable digital form)
• The DCE (e.g. a modem), which acts as a data converter to convert the
signal into a form suitable for the communications link, e.g. analog signals
for the telephone system
10. Introduction 9
• The communications link itself, for example, a telephone system
• A suitable receiver, such as a modem, also a DCE, which converts the
analog signal back to a form suitable for the receiving terminal
• A data receiving terminal, such as a printer, also a DTE, which receives the
digital pulses for decoding back into a series of characters.
Figure 1.6 illustrates the signal flows across such a simple serial data communications
link.
Figure 1.6
A typical serial data communications link
The original RS-232 interface standard describes the interface between a terminal (DTE)
and a modem (DCE) specifically for the transfer of serial binary digits. It left a lot of
flexibility to the designers of the hardware and software. With time, the standard has been
adapted for use with numerous other types of equipment such as PCs, printers,
programmable controllers, PLCs, instruments and so on. To recognize these additional
applications, a subsequent version of the standard, (TIA/EIA-232E) expanded the
meaning of the acronym DCE from ‘Data Communications Equipment’ to the more
general ‘Data Circuit-terminating Equipment.’ The latest version of the standard is TIA-
232F.
RS-232 has a number of inherent weaknesses that make it unsuitable for data
communications for instrumentation and control in an industrial environment.
Consequently, other TIA interface standards have been developed to overcome some of
these limitations. The most commonly used among them for instrumentation and control
systems are RS-423, RS-422 and RS-485.
1.5.2 RS-485
RS-485 is a balanced system with the same range as RS-422 but with increased data rates
and up to 32 ‘standard’ transmitters and receivers per line. It is very useful for
instrumentation and control systems, where several instruments or controllers may be
interconnected on the same multipoint network.
A simple diagram of a typical RS-485 system is shown in Figure 1.7.
11. Troubleshooting and Problem Solving of Modbus Protocols10
Figure 1.7
Typical two-wire multi-dropRS-485 network
1.5.4 Modbus
This protocol developed by Modicon (now part of Schneider Electric) is used for process
control systems. This standard only refers to the Data Link and Application layers so that
any Physical layer implementation can be used. It is a very popular standard, with some
estimates indicating that over 40% of industrial communications systems use Modbus.
Modbus Serial operates on a master-slave basis with up to 247 slaves (see Figure 1.9).
Figure 1.9
Format of Modbus Serial message frame
The Unit Identifier field refers to the number of the specific slave device being accessed.
The Function Code field indicates the operation that is being requested, for example, read
or write of an analog or digital point in the slave device. The Data field is an elaboration
on the requested Function Code (for a request from the master) or the actual data being
transferred from the slave device back to the master (a write operation). Finally, the Error
12. Introduction 11
Check field is to ensure that the receiver can confirm the integrity of the protocol; it could
almost be considered to be a unique fingerprint.
1.5.5 Modbus Plus
Unlike Modbus, this is an actual turnkey system based on Modbus, and includes hardware
as well. Unlike Modbus, which uses a master/slave Medium Access Control mechanism,
Modbus Plus uses Token Passing.
1.5.12 Ethernet
Ethernet (especially the Industrial versions thereof) is rapidly growing in importance after
initially being dismissed as not being reliable enough. One of the main reasons for its
success is its simplicity and low cost. Originally, Ethernet used only CSMA/CD (Carrier
Sense Multiple Access with Collision Detection) as its Media Access Control method.
This is a non-deterministic method, not ideal for process control applications. Although
all modern versions of Ethernet (100 Mbps and up) conform with CSMA/CD
requirements for the sake of adherence to the IEEE 802.3 standard, they also allow full-
duplex operation. Most modern Industrial Ethernet systems are 100 Mbps full-duplex
systems and The IEEE 802.1p standard allows switch ports to be prioritized, resulting in
very deterministic behavior.
1.5.13 TCP/IP
Since it forms the basis of the Internet, the Transmission Control Protocol/Internet
Protocol (TCP/IP) suite is also becoming popular for industrial applications, especially in
conjunction with Ethernet. The suite covers three layers:
• The Process/Application layer
(equivalent to upper three layers in the OSI model)
• The Services or Host-to-host layer
(equivalent to the Transport layer in the OSI Model)
• Internet layer
(equivalent to the Network layer of the OSI Model)
It is a very low-cost protocol with wide support due its use on the Internet. Arguably it is
an overkill for some industrial communications applications. However, its low cost and
wide support makes it very attractive.
1.5.14 Radio (or wireless) communications
The use of wireless in the industrial context commenced with the use of radio modems as
indicated in Figure 1.15 where, for example, Modbus could be used over the specific
radio modem as Physical layer. The use of the latest Wireless LAN standards such as
IEEE 802.11b/a/g and IEEE 802.15 ‘Bluetooth’ is making this a reliable and a low-cost
form of communication.