Common questions and answers for PLC engineer interviews

Detail

Basic electrical engineering knowledge is a necessary foundation for PLC engineers, including circuit principles, electrical safety and other aspects. The difference between servo motors and stepper motors is mainly reflected in control accuracy, response speed and applicable scenarios. Servo motors have higher control accuracy and faster response speed, and are suitable for occasions with high requirements for motion control; while stepper motors are relatively simple and low-cost, and are suitable for some occasions with low requirements for accuracy.

The basic principle of PLC is to control industrial equipment by receiving input signals, executing pre-written program logic, and then outputting control signals. Its role in automation cannot be ignored. It can improve production efficiency, reduce labor costs, and improve system reliability and stability.

In terms of project experience, job seekers need to give a detailed introduction to the projects they have participated in, including the scale, process, and equipment used. For the use of equipment, you need to be familiar with the characteristics and operation methods of different types of equipment. In terms of communication protocols, you need to understand common communication protocols such as Modbus, Profibus, etc. as well as their application scenarios and characteristics.

PLC scanning cycle is generally around 10MS - 15Ms, which consists of steps such as reading input data, executing programming logic and updating output data. There are many types of sensors, such as temperature sensors and pressure sensors. Temperature sensors are divided into thermocouples and thermal resistors. Thermocouples are suitable for high-temperature measurements, while thermal resistors have better performance in medium and low-temperature measurements. Pressure sensors can be used to measure the pressure of liquids or gases.

The main advantages of PLC include high reliability, strong anti-interference ability, simple programming, and easy maintenance. Its modular design makes system expansion and upgrading more convenient, and can adapt to industrial automation needs of different scales and complexities.

PLC (Programmable Logic Controller) is an electronic device specially used for industrial automation control. It can receive signals from various sensors and input devices, process these signals, and then control the machine or process through the output device. PLC is mainly composed of central processing unit (CPU), input module, output module, memory and other components. In automation, PLC plays a vital role. It can realize the precise control of industrial production process, improve production efficiency, reduce labor costs, and improve the reliability and stability of the system.

Different types of PLC mainly include integral type and modular type. Integral PLC integrates power supply, CPU, memory, I/O interface and other components in one chassis, with the characteristics of compact structure, small size and low price. Modular PLC makes each component into several separate modules, such as CPU module, I/O module, power module, etc. Various modules are installed on the rack or baseboard for easy expansion and maintenance.