How to avoid AC noise
Noise and grounding problems ground and electricity (signal), this is a pair of inseparable twins. Grounding, usually refers to the use of a conductor to connect to the earth. The ground in electronic technology may not be related to the earth, it is only an equipotential surface in the circuit. Such as the radio, the ground in the TV, it is just a potential reference point in the receiver line. Grounding, in power and electronics, is simple, complex, and essential. According to the role of grounding, it can be divided into working grounding, protective grounding, overvoltage protection grounding, anti-static grounding, shielding grounding, signal ground and so on. In the radio and television technology, the above grounding types will be encountered. Now, some grounding technical problems will be explained in combination with the actual situation.
one. Protective grounding
Protective grounding is a protection device designed to prevent the insulation from being damaged and causing personal safety. It has two ways: grounding and zeroing. According to the power regulations, for systems with three-phase four-wire power supply, since the neutral line is grounded, the zero connection method should be adopted, and the metal casing of the equipment should be connected to the neutral line through the conductor, and the equipment casing should not be directly grounded. This is especially common in switchgear, central air conditioners, transmitters and other power switchgear and power consuming equipment in power distribution rooms of radio and television systems. When planning and designing, the grounding busbar should be taken from the grounding grid to each equipment, and then the conductor of the machine casing should be connected to the grounding busbar. It is worth pointing out that the grounding wire should be connected to the grounding special terminal of the equipment, and the other end should be welded.
Sometimes the device case can be numb, which is caused by AC leakage and the device housing is not connected to zero. Generally, the power plug can be removed and replaced, and then inserted. In some frequently moving cataloging devices, the above phenomenon may occur because the zero line is often neglected, and some operators may touch the device with zero and no zero at the same time.
2. Overvoltage protection grounding
This is a grounding protection device for lightning protection. The most widely used lightning protection devices are lightning rods and lightning arresters. The lightning rod enters the ground through the iron tower or building reinforcement, and the arrester enters the ground through a dedicated ground wire. Arresters shall be inspected each year before the onset of the thunderstorm season to prevent failure. If the hotline telephone accessor of our station is struck by lightning, it is caused by the failure of the line lightning arrester. On the lightning protection lead line, never connect the ground wire of other equipment. The lightning protection down conductor can only enter the ground directly, otherwise the lightning will damage other equipment through the down conductor. For example, a satellite television receiver has been struck by lightning several times. The original trap is that the feeder is rubbed against the metal fence of the roof and the insulation is damaged. The metal guardrail and the lightning rod are welded together, so that the lightning strikes and the receiver is damaged.
3. Shielding ground
A protective measure for grounding the metal sheath of the optical cable, the metal casing of the electronic device, the shield, and the metal shielding net of the building (such as the shielding room for measuring sensitivity and selectivity) to prevent electromagnetic induction. . Among all the grounding, the shielding ground is the most complicated, and there is a kind of unclear and unclear feeling. Because the shielding itself can prevent external interference, and it may interfere with the outside world through it, and electromagnetic interference must also be prevented between the components in the equipment. For example, the well-known mid-circle outer casing and the electron tube shielding cover are examples.
Poor shielding and improper grounding can cause interference. These interferences mainly include:
1. AC interference, which is mainly caused by AC power. For protection against AC interference, the power supply is usually filtered or a shield is applied between the primary and secondary of the power transformer and grounded. In addition to large stray electromagnetic fields, it is necessary to shield the ground from electromagnetic interference. For example, at the opening ceremony of the new Asia New City Mall in our city, there was a transformer near the recording and expansion equipment, and its electromagnetic field interfered with the recording and amplification of the scene. This problem was solved by shielding the recording and expansion equipment from grounding.
2. High frequency interference. This kind of interference comes from the frequency conversion or over-conversion signals of various wireless transmitting stations. After they are broken into the electronic equipment, they are abnormally demodulated in the machine to form audio interference.
The higher the signal frequency, the smaller the metal mesh hole of the building or equipment should be, and the tighter the braiding of the signal line shielding layer, otherwise the shielding effect will be lost. For frequently removed signal lines, the shield should be prevented from loosening and falling off at the plug. Because sometimes the shielding of the instrument and equipment is shielded into the ground through the signal line (they are connected through the plug and socket), if the shielding is detached, it is easy to cause interference. When I was at an electronics factory in Shantou, the testers responded that there was sometimes a disturbance in the satellite TV receiver that affected the image quality. After tracking observation, it is related to the passage of the aircraft, which is obviously caused by the intrusion of the radar signal of Chenghai Airport and the abnormal demodulation. After analysis and searching, it turns out that the shielding layer of the signal line falls off outside the plug, so that the shielding of the satellite TV receiver is not grounded.
Signal ground
Various electronic circuits have a reference potential point, which is the signal ground. Its role is to ensure that the circuit has a uniform reference potential, which will not cause floating and cause signal errors.
The connection of the signal ground is: the signal input end of the same device cannot be connected with the signal output end, but should be separated; the output ground of the front stage (device) is only connected to the input ground of the latter stage (device). Otherwise, the signal may form feedback through the ground, causing the signal to float. In the test of the device, the connection of the signal ground is particularly noticeable. For example, when I was working in an electronics company, the quality inspection department reflected that the satellite receiver quality test results were different. Originally, the test equipment of the quality inspection department, some of the casing is grounded, and some of the casing is not grounded (the test signal is transmitted from the signal center to each department), so that the signal is fed back to make the measurement results inconsistent. After all the grounded test instruments are set to be ungrounded, this phenomenon is gone.
ZGAR bar 600 Puffs
ZGAR electronic cigarette uses high-tech R&D, food grade disposable pod device and high-quality raw material. All package designs are Original IP. Our designer team is from Hong Kong. We have very high requirements for product quality, flavors taste and packaging design. The E-liquid is imported, materials are food grade, and assembly plant is medical-grade dust-free workshops.
Our products include disposable e-cigarettes, rechargeable e-cigarettes, rechargreable disposable vape pen, and various of flavors of cigarette cartridges. From 600puffs to 5000puffs, ZGAR bar Disposable offer high-tech R&D, E-cigarette improves battery capacity, We offer various of flavors and support customization. And printing designs can be customized. We have our own professional team and competitive quotations for any OEM or ODM works.
We supply OEM rechargeable disposable vape pen,OEM disposable electronic cigarette,ODM disposable vape pen,ODM disposable electronic cigarette,OEM/ODM vape pen e-cigarette,OEM/ODM atomizer device.
Disposable Vape, bar 600puffs, ZGAR bar disposable, Disposable E-cigarette, OEM/ODM disposable vape pen atomizer Device E-cig
ZGAR INTERNATIONAL TRADING CO., LTD. , https://www.oemvape-pen.com