Application and principle of the hottest signal is

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Application and principle of signal isolator

1. Function of signal isolator

(1) ground circulation interference

various automatic instruments, control systems and actuators are needed to realize monitoring and control in the process of industrial production. The signal transmission between them includes small signals ranging from weak to millivolt level and milliampere level; There are also large signals of tens of volts, thousands of volts and hundreds of amperes; There are both low-frequency DC signals and high-frequency pulse signals. After forming the system, it is often found that the transmission between instruments and equipment interferes with each other, causing the system instability and even misoperation. In addition to the performance reasons of each instrument and equipment itself, such as anti electromagnetic interference, another very important reason is that all kinds of instruments and equipment need to be grounded according to requirements and purposes, such as for safety, The casing needs to be grounded; In order to make the circuit work normally, the system needs to have a common reference point; In order to suppress interference and add a shield, the shield also needs to be grounded. However, due to the potential difference between the reference points between the instrument and the equipment (that is, the locations of the common elastic deformation and initial plastic deformation values of each equipment are different), the problems of "ground circulation" and "ground circulation" must be solved in the process of signal processing in the system

(2) natural interference

lightning is a major natural interference source, and the interference generated by lightning can be transmitted to places thousands of kilometers away. The time domain waveform of lightning interference is a large spike pulse superimposed on the background of a series of random pulses. Cosmic noise is produced by ionizing radiation and changes constantly throughout the day. Solar noise changes dramatically with solar activity. Natural noise will mainly interfere with communication, and lightning energy spike pulse can damage many equipment, so it should be avoided or reduced to reduce the degree of damage and loss

(3) human interference

the root cause of electromagnetic interference is the change of voltage or current in the conductor, that is, a large dv/dt or di/or di/dt can make the conductor produce electromagnetic wave radiation. On the one hand, people can use this feature to realize specific functions, such as infinite communication, radar or other functions. On the other hand, when electronic equipment is working, accompanying electromagnetic radiation will be generated due to dv/dt or di/dt in the conductor. No matter what the subjective purpose, it has caused pollution to the electromagnetic environment objectively. In addition, factories and enterprises often have some large equipment (motors, frequency converters) frequently switched on and off in the production process, which will also cause some capacitive and inductive interference, and will also affect the normal display or collection of instruments and meters. Where there is a sudden change in voltage and current, there must be electromagnetic interference. Digital pulse circuit is a typical interference source. With the wide application of electronic technology, electromagnetic pollution will become more and more serious

2. Tensile testing machine enterprises should also become cooperative partners to solve all kinds of interference

first of all, the three elements of interference are interference source, sensitive source and coupling path. Without one of these three elements, electromagnetic compatibility problems will not exist. Therefore, we should start with these three elements. Find the most convenient solution. Generally, there is no way to solve interference sources and sensitive sources. It is usually from the coupling path, which is also the most commonly used method. Such as shielding and filtering. It is the most common and troublesome to deal with the circulation, which is now the topic of discussion

(1) the first method; The hot extruded plates have on-site equipment that is not grounded, so that all process loops have only one grounding point and cannot form a loop. This method seems simple, but it is often difficult to achieve in practical application, because some equipment requires grounding to ensure measurement accuracy or personal safety, Some equipment may form new grounding points after long-term corrosion and wear, or it can also be further processed by wire extruder or affected by climate

(2) the second method: make the potential of the two grounding points the same, but because the resistance of grounding is affected by many factors such as geological conditions and climate change, this method can not be completely achieved in practice

(3) the third method: use a signal isolator in each process link to disconnect the process loop without affecting the normal transmission of the process signal, so as to completely solve the problem of the ground loop

3. Advantages of using signal isolators

using signal isolators in each process loop can be achieved by using isolation cards such as DCS or PLC or isolated transmitters on site (some equipment can do this), or by using signal isolators. In comparison, using signal isolators has the following advantages:

· in most cases, using signal isolators + non isolated cards is cheaper than using isolation cards

· signal isolators have better performance than isolation cards in isolation ability, anti electromagnetic interference, etc.

· signal isolators are flexible in application, and they also have functions such as signal conversion, signal distribution and interface conversion, It is more convenient to use

· the signal isolator usually has single channel, double channel, and the channels are completely independent of each other, making the configuration of the system and daily maintenance more convenient


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