Industrial Network and Communication Protocols Fundamentals

Industrial networking is important in industrial automation and process control. Industrial automation provides interconnection between devices (sensors, actuators, controllers, and PCs) and also enables communication between them. An industrial network differs from traditional communication, which allows communication between computers and their peripherals such as printers, scanners, and more. An industrial network is a powerful network that connects industrial automation and control devices (PLCs, HMIs, PCs, VFDs, transmitters, and more) and provides real-time monitoring, control, and data integrity in a harsh environment.

By reading this chapter, you should have a better understanding of industrial networks and the various topologies and communication media. You will learn about the basics of wireless networks and understand what 5G is. You will also learn about industrial network protocols, which are important for...

Understanding industrial networks

When two or more devices are connected for data exchange, it is referred to as a network. Each device in the network can be referred to as a node. Industrial networks consist of controllers (PLC, PAC, or DCS), field devices, PCs, and other industrial devices that are connected to share and exchange data. A node in an industrial network can be a controller (PLC, PAC, or DCS), field device (sensor/transmitter or actuator), HMI, server, or workstation. The nodes in an industrial network utilize a special protocol for communication and to automate processes in the industry.

Understanding network topology

Network topology is the bedrock of a network. It shows how the nodes are arranged and interconnected. It refers to the physical and logical arrangement of a network. Hence, network topology can be grouped into two areas:

• Logical topology: This refers to the pattern in which data is being transferred between the nodes in the network. It defines the path that data takes when it is being transmitted. It describes the way data travels in the network.
• Physical topology: This refers to the physical layout or arrangement of the nodes in the network. It shows how various nodes in the network are connected.

The following are some common physical topologies:

• Point-to-point topology: In a point-to-point topology, a connection is made between two devices with a single wire. There is a direct link between two devices in a point-to-point network, as shown in the following diagram. An example of a point-to-point topology in a home or office...

Network media – wired and wireless (Bluetooth, Wi-Fi, and cellular communication – 1G, 2G, 3G, 4G, and 5G)

Network media can be defined as the channel of communication used to interconnect nodes on a network. Examples of network media include copper twisted pair cables, copper coaxial cables, and fiber optic cables, which are used in wired networks, and radio waves (Bluetooth, Wi-Fi, cellular communication, and so on), which are used in wireless networks. Hence, a network can be wired or wireless, depending on the communication channel being used:

• Wired network: A wired network uses cables such as copper twisted pair cables, copper coaxial cables, and fiber optic cables as a communication channel.

The following figure shows a coaxial cable:

Figure 13.7 – Coaxial cable (RG59) (source: https://commons.wikimedia.org/wiki/File:Coaxial_cable_cut.jpg)

The following figure shows a PROFIBUS cable:

...

Network connectors and other network components

Let’s have a brief look at network connectors.

Network connectors allow wired network media (coaxial cable, twisted pair, fiber optic, and so on) to connect to a network such as hubs, switches, routers, controllers, PCs, and other devices in a network. They are used to terminate a segment of network cable.

The following are some examples:

• BNC Connector: BNC is an acronym for Bayone-Neill-Concelman. A BNC connector is used for coaxial cables:

Figure 13.11 – BNC connector (source: https://commons.wikimedia.org/wiki/File:BNC_connector_20050720_001.jpg)

• PROFIBUS connector: This is usually used with a PROFIBUS cable to establish communication between devices using the PROFIBUS protocol:

Figure 13.12 – PROFIBUS connector (source: https://commons.wikimedia.org/wiki/File:0x-pb-stecker-verschieden.jpg)

• RJ45 connector: This is one of...

Understanding network protocols

A network protocol can be referred to as a method of data communication between two or more devices on a network. It is a set of rules that should be adhered to for communication to occur between two or more connected devices. Industrial network protocols enable communication between industrial network devices such as PLCs, HMIs, VFDs, PCs, transmitters, actuators, and more. This protocol encompasses the network topology, network media, network connectors, and more.

Many protocols are used around the world for communication. We will focus on industrial network protocols in this book.

Common industrial network protocols can be grouped as wired and wireless networks.

Wired network protocols

Wired network protocols can be grouped into two areas, as follows:

• Fieldbus: Fieldbus is a group of industrial network protocols used for real-time distributed control, standardized as IEC 61158. One great advantage of the Fieldbus protocol is that...

Common industrial network protocol – Foundation Fieldbus

This protocol is developed by the International Society of Automation (ISA). Its application areas include petrochemicals, food and beverages, power, and other heavy-process applications. It is used to connect foundation Fieldbus-enabled devices such as sensors/transmitters to a control system with less wiring. It allows several Fieldbus devices to use a single cable.

Two types of foundation Fieldbus implementation are Foundation Fieldbus H1 and Foundation Fieldbus High-Speed Ethernet (HSE):

• Foundation Fieldbus H1: This version provides speeds of up to 31.25 Kbps. Twisted pair cables and fiber optic cables can be used as network media. It provides digital communication and DC power over the same twisted pair. It is implemented using a bus or star topology. Its network can have up to 32 nodes per segment. It is used for communication between several sensors/transmitters and actuators (field devices) and a PLC...

Common industrial network protocol – PROFIBUS

PROFIBUS is an acronym for Process Fieldbus. It is a standard protocol that can be used to connect sensors/transmitters, actuators, controllers, HMIs, VFDs, and more. Two-core twisted, shielded cables called PROFIBUS cables (Figure 13.8) are used for communication. A PROFIBUS connector (Figure 13.12) is used to connect to each device in the network. The PROFIBUS protocol comes in two forms, as follows:

• PROFIBUS DP (Decentralized Peripherals): PROFIBUS DP is among the most commonly used network protocols in the industry. It is an industrial network protocol that reduces the number of wires required to connect sensors and actuators by decentralizing the input and output (I/O) modules.

Before PROFIBUS DP, I/Os were centralized in the control room, as shown in the following diagram, leading to lots of cables being used to wire sensors and actuators (which could be far away from the control room) to the input and output...

Common industrial network protocol – Modbus

Modbus is an open protocol that can be used by any manufacturer or vendor without restriction. It was originally designed in the mid-1970s by Modicon as a way to connect intelligent devices with PLCs using a simple master/slave concept. It was initially designed for Modicon PLCs only (that is, a proprietary protocol) but it was later made available for use by any manufacturer without any restriction (that is, an open protocol).

Various vendors now manufacture their PLCs and other industrial devices to support the Modbus protocol. Hence, you will find the Modbus protocol available for use in industrial equipment from various manufacturers, such as Siemens, Allen Bradly, Mitsubishi, and Omron. The Modbus protocol solves the problem of communication between industrial equipment from different manufacturers. With the Modbus protocol, a Siemens PLC can communicate with an Omron PLC, Allen Bradley PLC, Omron VFD, or any other industrial...

Common industrial network protocol – HART

The Highway Addressable Remote Transducer (HART) protocol is the world standard protocol and provides data exchange between smart/intelligent field devices and a controller (PLC, DCS, and so on) or handheld communicator. You can control and monitor HART-enabled field devices (sensors, transmitters, and actuators) with the HART protocol. In HART communication, a digital signal is superimposed on the traditional 4-20mA analog signal, allowing the 4-20mA analog signal to co-exist with the digital signal on the same two-wire loop without distortion. Hence, two signals are transmitted simultaneously – that is, the 4-20mA signal and the digital signal. The 4-20mA analog signal represents the measured variable regarding the temperature, pressure, level, or flow while the digital signals carry other device details, such as the device’s health, status, diagnostics alerts, and more.

Each sensor/transmitter and actuator (transducer...

Common industrial network protocol – PROFINET

PROFINET is an industrial Ethernet protocol designed to exchange data between devices and controllers in industrial automation. It is the most well-adopted industrial Ethernet protocol. It can operate at a higher speed than PROFIBUS because it is Ethernet-based. The connector that’s used for PROFINET is a standard RJ45 connector (Figure 13.13) and the network cable can be a standard Ethernet cable such as those you find in offices, such as twisted pair CAT 6 cables (Figure 13.9). A standard Ethernet cable can be damaged easily due to the challenging environmental conditions in the industry. For that reason, an industrial Ethernet cable is suitable for use in PROFINET. It is characterized by shielding protection and ruggedized and proper jacketing. A standard Ethernet switch (Figure 13.14) can also be used because it uses the same physical connection standard as Ethernet. PROFINET is now becoming a popular protocol that’...

Summary

Congratulations! You have completed this chapter. You should now understand what is meant by an industrial network and be able to explain the basic physical topologies available (point-to-point, bus, star, and ring). You also learned about network media and should now understand wired and wireless network media. This chapter also explained various cellular communication generations (1G, 2G, 3G, 4G, and 5G). You should also have an understanding of common network connectors and other components used in industrial networks. Most importantly, we covered the network protocol and discussed some of the commonly used protocols in the industry (Foundation Fieldbus, PROFIBUS, Modbus, HART, and PROFINET).

In the next chapter, we will cover another important topic you cannot afford to miss, smart factories (Industry 4.0).

Questions

The following questions will help test your understanding of this chapter. Ensure you have read and understood the topics in this chapter before attempting these questions:

1. The term ____________ describes the connection between two or more industrial automation/control devices such as controllers, sensors/transmitters, actuators, PCs, and more to exchange data for real-time monitoring and process control purposes in harsh environments.
2. Each device in a network can be referred to as a _________________
3. __________________ refers to the physical and logical arrangement of a network.
4. ___________________ refers to the pattern in which data is being transferred between the nodes in the network.
5. In the ______________ topology, each node is connected to a central device, which can be a switch, router, or hub.
6. ________________ can be defined as the channel of communication that’s used to interconnect nodes on a network.
7. A ________________ network...