Interpretation of anti-interference technology approach/action mode/source of computer control system

Because the working environment of industrial sites is often very harsh, computer control systems are inevitably subject to various interferences. These disturbances may affect the accuracy of the measurement and control system, reduce the performance of the system, reduce the reliability of the system, and even lead to chaotic or malfunctioning of the system, resulting in production accidents.

Because the working environment of industrial sites is often very harsh, computer control systems are inevitably subject to various interferences. These disturbances may affect the accuracy of the measurement and control system, reduce the performance of the system, reduce the reliability of the system, and even lead to chaotic or malfunctioning of the system, resulting in production accidents. Interference may come from the outside or from the inside; it acts on the control system through different ways, and its degree of action and its consequences are related to the nature of the interference and the intensity of the interference. Interference is an objective existence. Studying anti-jamming technology is to distinguish the source of interference and explore measures to suppress or eliminate interference to improve the reliability and stability of computer control systems.

Interference causes noise other than the useful signal or a destructive factor that prevents the computer device from functioning properly. The cause of the interference signal is called the interference source. A device or system in which an interference source is affected by a propagation path is called an interference object. Interference sources, propagation paths, and interference objects constitute three factors that interfere with the system. Anti-jamming technology is achieved by taking measures against one or more of these three elements. In order to effectively suppress and eliminate interference, it is first necessary to distinguish the source of the interference, the route of transmission, and the mode of action of the interference.

The sources of interference in computer control systems are multifaceted and sometimes even complex. In general, according to the source, interference can be divided into internal interference and external interference. External interference is related to the environment and conditions of use of the system and is independent of the internal structure of the system. Internal interference is introduced by system structure layout, manufacturing process, and the like.

External interference: Independent of the system structure, is determined by the conditions of use and the external environment. External interference mainly includes: interference from daylight, such as interference caused by lightning or atmospheric ionization; celestial interference, such as electromagnetic waves radiated by the sun or other planets; electromagnetic interference from surrounding electrical equipment; power frequency interference of power supply; Interference, such as humidity, temperature, etc.; geomagnetic field interference; electromagnetic waves generated by spark discharge, arc discharge, glow discharge, etc.

Internal interference: caused by the system's structural layout, circuit design, component properties and drift, etc., mainly include: coupling induction caused by capacitance and distributed inductance; electromagnetic field radiation induction; wave reflection of long-line transmission; multi-point grounding Interference caused by the potential difference; interference caused by parasitic oscillations and thermal noise, flicker noise, spike noise, etc.

In the field of computer control systems, there are often many strong electrical equipment, which will generate interference electromagnetic fields during start-up and production, as well as electromagnetic waves and lightning interference from space propagation, and the influence of alternating magnetic fields around high-voltage transmission lines. The main modes of interference propagation are: electric field coupling, magnetic field coupling, and common impedance coupling.

Electric field coupling: Also known as electrostatic coupling, it is capacitively coupled into other circuits. The distributed capacitance is formed between the two wires, and distributed capacitance is formed between the printed wires on the printed circuit board, between the transformer turns, and between the windings. The presence of these distributed capacitors can provide an interference reactance channel for the interfering signal, and the electric field interference can be broken into the system by the channel to form interference.

Magnetic field coupling: A magnetic field is generated around any current-carrying conductor. When the current changes, an alternating magnetic field is generated. This magnetic field will inevitably cause an induced potential in the closed loop around it. It is coupled through the mutual inductance between the conductors. Inside the device, the leakage of the coil or transformer can also cause interference; outside the device, the two wires placed in parallel will also cause interference. Electromagnetic radiation causes magnetic field coupling interference. When a high-frequency current flows through a conductor, electromagnetic waves propagating to the space are generated around the conductor. These disturbances are easily coupled to the computer via power lines and long signal lines. In addition, long-line interference has an antenna effect, that is, it can radiate interference waves and receive interference waves.

Common impedance coupling: Because the current flows through the common impedance between the loops, the voltage drop caused by the current of one loop affects the other loop. In computer control systems, common coupling impedances are common, such as power leads, ground and common power lines on printed circuit boards, bus bars, and the like. These bus bars all have a certain impedance, and for multiple circuits, they are common coupling impedances. When a large digital signal current flows, it acts like an antenna, introducing interference into each loop. At the same time, there is a capacitance between the reflow bars, and digital pulses can be coupled through this capacitor. The ground on the printed board is essentially a common return line. Since it still has a certain resistance, the signals are coupled between the circuits.

According to the different modes of interference, interference can be divided into: differential mode interference, common mode interference and long-line transmission interference.

Differential mode interference: Also known as series mode interference, it is the interference in the series and signal source loops. It is connected in series in the signal source loop, added to the measured signal and input into the system. The main factors that cause differential mode interference are electrostatic coupling of distributed capacitance, magnetic field coupling of space, mutual inductance of long-line transmission, power frequency interference of 50 Hz, and parameter variation of components in the signal loop.

Common mode interference: the ground of the computer used for process control, the ground of the signal amplifier and the ground of the field signal source are usually separated by a distance of tens of meters or even hundreds of meters, often between the two grounding points. A potential difference, the interference of this potential difference to the amplifier, called common mode interference, also known as common-mode interference or longitudinal interference. This interference can be either DC or AC interference, and its amplitude can be a few volts or more, depending on the environmental conditions in which the interference occurs in the field and the grounding of equipment such as computers.

Long-line transmission interference: In computer control systems, the field signal to the control computer and the control computer to the field actuator require a long line for signal transmission, ie long-distance transmission. For high-speed signal transmission lines, that is, in high-frequency signal circuits, how long the wire can be used as a long line depends on the frequency of the circuit signal. In some cases, a line of about 1 m should be considered as a long line.

Signal transmission in the long line will encounter three problems: one is the wave reflection phenomenon when the high-speed change signal is transmitted in the long line, the second is the signal delay, and the third is the long-distance transmission will encounter external interference.

USB Countdown Timer

Function description

The socket is ordinary converter,with two output 5V2A power USB power supply at the same time,can be very convenient in use electrical appliances and recharge the equipment at the same time,such as digital products like Iphone Ipad,MP3,MP4 etc.The charge apply to full range of international AC output,no-load power consumption less than 0.3W,with short circuit,overload,over-voltage protection,can be convenient for your life and save more energy

Timer Control Time Adgustment

1.Press the power switch 1 time,the 1HOUR LED will light on.The Timer into ON mode,USB and control socket output ON .

2.Continuously press the power switch the LED light on,the Countdown mode and LED light on will cycle change from 1HR,2HR,4HR,6HR,8HR,10HR.

3.Choose you need countdown time mode,the mode LED will lighto on,start countdown until countdown time finish,the control output and USB change to OFF

4.Then the countdown is start,The Time indicate LED will from high to low auto change until Countdown finish off.

Failure analysis:

1.check whether the power supply connection is good

2.check whether the USB cable is loosen

Warning Note:

1.Use indoor and dry location ONLY

2.The load max does not exceed 15A 3600W

3.This product does not convert voltage please do not miss use DO NOT exceed the maximum loading of 3600 Watts 15A

4.Always have earth connection for safety reason

5.If in doubt please consult with a qualified electrician

USB countdown timer, USB countdown timer socket, USB timer, USB charger timer, USB timer socket

NINGBO COWELL ELECTRONICS & TECHNOLOGY CO., LTD , https://www.cowellsocket.com