Category: Cyclopedia of Industrial instrument

Pneumatic control valve uses compressed air as the power source, cylinder as the actuator, and drives the valve with the help of valve positioner, converters and other accessories to realize switching or proportional adjustment, and accepts the control signal of the industrial automation control system to regulate flow, pressure, temperature and other process parameters of the fluid in the pipeline. At present, pneumatic control valves are widely used in petrochemical, electric power, metallurgy and other process industries, and are an indispensable and important tache in the control system. Therefore, it is very important to ensure the stable and reliable operation of the pneumatic control valve. When the pneumatic control valve fails, it can be checked according to the common faults of the control valve, to find the reason of the fault in time.

In the field of industrial automatic control, whether the process can meet the requirements of various process control index, make the control process be stable, safe, efficient, and produce qualified products, the regulating valve is a key equipment, therefore, a high-quality control valve with good quality, excellent flow characteristics, small leakage, and reliable and smooth action is selected to make production run smoothly and reduce labor intensity.
The regulating valve is installed on the process pipeline, directly contact with the operating medium, and is affected by harsh working conditions such as high temperature, high pressure, corrosion and friction for a long time. Therefore, the quality of the regulating valve has a great influence on the system control. Therefore, the correct and reasonable choice is particularly important.

Industrial Ethernet, Fieldbus, and Industrial Wireless are the three mainstream technologies in the field of industrial communication. Blend Fieldbus, Ethernet, Embedded Technology and Wireless Communication Technology into Control Network, while ensuring the stability of the system, it also enhances the openness and interoperability of the system, thereby helping enterprises to speed up the development of new products, reduce production costs, and improve information services. Accompany with the increasing demand of human beings for communication, the network has become an indispensable means of transmission.
With the increase of network applications, there will be more and more disputes that who will become the main mode of industrial communication in the future. So which communication mode will be the mainstream in the future?

PLC wiring method of source type (NPN) and drain type (PNP)

Today’s closed-loop automatic control technologies are based on the concept of feedback to reduce uncertainty. The elements of feedback theory consist of three parts: measurement, comparison and execution. The key of measurement is the actual value of the controlled variable, compare with the expected value, use this difference to correct the system’s response, execute regulating control. In engineering practice, the control law of the most widely used regulator is proportion, integration and differentiation control, known as PID control.

What is the function of surge protector in the control system

Structure, principle and range selection of pressure gauge

Instrument zero inspection and adjustment is a skill that instrument operator must master. This article introduces the method of checking and adjusting zero point of pressure transmitter, differential pressure transmitter, thermocouple display instrument and thermal resistance display instrument, It is of great help to the instrument operators for improving their technical level. When the operator has doubts about the indicator value of the instrument, it is necessary to check the instrument, the most commonly used method is to check whether the zero point of the instrument is correct. For pressure transmitter and differential pressure transmitter, check zero point after stopping process. The zero point of the instrument refers to the lower limit of the instrument’s measuring range (that is, the minimum value that the instrument can measure under its specific precision).

The difference between signal safety barrier and signal isolator

RS485 and MODBUS are the concepts which are often used in the industrial control system, but they are different, the following is a brief introduction.