PLC

1. Introduction In industrial electrical control systems, the concepts of self-locking, interlocking, and mutual locking are fundamental. Although similar in terminology, each has distinct logic, application, and purpose. This document provides a structured comparison of these three control methods, with definitions, working principles, typical applications, and schematic diagrams. 2. Self-Locking (Hold-On Circuit) 2.1 Definition Self-locking […]

In industrial process automation, the 4-20mA signal is one of the most widely used standards for transmitting analog data from sensors and transmitters to control systems. This signal range, where 4mA typically represents the zero or minimum of a process variable and 20mA represents the maximum, allows control systems to monitor and manage a wide

In industrial automation and safety-critical systems, ensuring the integrity of Safety Instrumented Systems (SIS) is crucial. The role of SIS in an industrial environment is to mitigate risks and initiate protective actions independently from regular operational control systems, specifically the Distributed Control System (DCS). A common question in this domain is whether a DCS can

Abstract RS485 is frequently misunderstood as a “communication protocol,” whereas in reality, it is a physical layer interface standard. This article explains the fundamentals of RS485, highlights common misconceptions, compares it with application protocols such as Modbus RTU, and provides practical engineering guidelines for installation, wiring, and troubleshooting. 1. What Exactly is RS485? RS485 is

In process industries, Distributed Control System (DCS) valves and Safety Instrumented System (SIS) valves play critical roles in process control and safety, respectively. When designing these systems, engineers must decide whether to install these valves in series or parallel. Each configuration has its advantages and challenges that impact the system’s overall safety, reliability, and maintainability.

In the field of electrical engineering, “strong current” and “weak current” are two fundamental concepts. These two types of electrical systems have distinct characteristics and serve different functions, with each playing an important role in modern technology. Let’s take a closer look at how they differ in terms of voltage, current, applications, safety considerations, and

Recently, during my service visit to a refining and chemical enterprise in Shandong, I had the opportunity to examine multiple systems where PID tuning had been previously conducted by various companies. It is evident that the industry has made significant advancements in PID tuning practices. However, there remains a considerable gap in the capability to

Safety Instrumented Systems (SIS) play a crucial role in ensuring the safety and reliability of industrial processes. These systems are designed to automatically detect and mitigate hazardous conditions, protecting people, equipment, and the environment. A typical SIS is composed of several key components, each with distinct functions that contribute to the overall safety of industrial

1. Traditional View of PID Tuning In the conventional approach, PID loop tuning is often treated as an isolated single-input, single-output (SISO) problem. The emphasis is placed solely on the controlled process itself. Once the process model is identified, suitable PID parameters can be directly calculated. From this perspective, testing and modeling the process are

1. Information Required for P&ID Design Before preparing a P&ID, a wide range of reference documents and data must be collected. These are essential for ensuring accuracy and consistency during the design phase: Process Flow Diagram (PFD) A P&ID is developed based on the approved and detailed PFD. The PFD must be reviewed and approved