Process control hardware fundamentals

In order to analyse a control system, the individual components that make up the system must be understood. Only with this understanding can the workings of a control system be fully comprehended. The rest of this book deals extensively with controller and process characteristics. Therefore, it is appropriate and necessary that hardware fundamentals for the primary elements and final control elements be studied first in this chapter. Discussion of controller hardware is delayed until Chapter 4, where the control equations governing the controllers are covered. Several of the concepts introduced in this chapter are discussed in further detail in later sections of this book. 

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Currently open system designs with global bus architecture and local area networks (LANs) are being used for computer control, as shown in Fig. A.l. Unlike earlier networks, which were normally isolated, the LANs are often connected to other networks via gateway devices. The traditional host computer functions are divided functionally and are implemented in separate autonomous computers, which share the same data bus. When more than one operator interface node is installed, the operator interface to the process can be maintained even when several operator stations fail. A DCS for process control is fundamentally the same as for other real-time distributed systems used in business data centers or server facilities (Herb, 1999 Lewis et al., 2006), although specialized hardware such as data acquisition equipment is required. 

This course will deal with fundamental and underlying principles of automatic process control and simulation. The course covers the theory associated with SISO loops and how these are configured into multi-loop schemes to control complex unit operations and entire plants. It will not discuss in detail the hardware or individual measurement teclmiques, such as flow, temperature, pressure, etc., except as the measurement affects the control loop. In the course, note that Chapter 2 provides a simplified summary of control loop hardware. 

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