【 Weak current College 】 professional audio connections of noise and grounding problems

With electricity (signal), this is a pair of inseparable twins. Grounding, commonly referred to with conductor and the Earth. Available in electronic technology, probably had nothing to do with the Earth, it is just a circuit equipotential surface. Such as radio, TV set, it is only a receiver circuit in potential reference point. Grounded, in electricity and electronics, both simple and complex, but also essential. The role of the ground, can be divided into work grounding and protection earthing, overvoltage protection, earthing, anti-static grounding and shielding and grounding, signals etc. In radio technology, several grounding type above will encounter. Now with actual technical problems for some grounding for a description.
1. protective grounding
Protective earth is to prevent insulation damage equipment for the safety of live endanger personal settings of the protective device, it has grounded and zero. Press the power, where the use of three-phase four-wire power supply system, as a neutral grounding, so should be zero, but the device's metal casing by conductor received to zero line, not allowed for grounding device shell directly. The distribution of radio and TV system in the room of switching equipment, central air conditioners, transmitter, and other power switchgear and big power consumption is especially common in the device. In the planning and design, leads from the network to all devices, ground straps, then machine shell with conductor to ground straps. It is worth noting: Earth wire should be connected to a dedicated terminal equipment grounding, on the other end it is best to use welding.
Sometimes the device shell will Ma hands, this is due to AC leakage and device shell is not zero. Usually the power plug out of the swap out location then insert can be resolved. This move in some regular catalog device, due to the zero line often ignored, operators are likely to come into contact with both his hands and not zero zero equipment, it is possible to place the above phenomenon.
II. over-voltage protection earthing
This is the setting for the lightning and the grounding protection device. Lightning protection system most widely used is the lightning and surge arrester. Lightning Rod reinforced through Tower or building into the ground, through the dedicated ground lightning arrester into the ground. Arrester thunderstorm season each year shall be tested prior to prevent failure. If my desk hotline access for lightning, is because the words line SPD failure. In mine down lead, not to connect the ground wire of other equipment, lightning protection down lead directly into the ground alone, the lightning will pass down lead damage to other equipment. As a satellite TV receiver who has repeatedly been struck by lightning, its original trapped is a feeder and roof metal guardrail friction insulation damage, the metal retaining bar and lightning rod cited lower body welding together, as well as lightning cuanru and striking receiver.
III. shielding and
To prevent electromagnetic induction and Visual and audio cable shielded metal jacketing, electronic equipment, metal shell, shielding enclosures, buildings of metal shielding network (such as measuring sensitivity, selectivity and other indicators of shielding room) for the grounding of a protective measure. In all the Earth, the shield and the most complex, say, road unknown feeling. Because the screen itself can prevent outside interference, they may pass it on to outside interference, and the components in the device has to be between anti-electromagnetic interference, such as the familiar shell and tube in week shielding enclosures are examples.

Shielding, grounding incorrectly can cause interference, such interference:
1. the exchange of interference, this caused primarily by AC power. Protection against AC interference, usually on the power supply for filtering or in power transformer of the initial stage and shielding and grounding. In large stray electromagnetic field, electromagnetic interference shielding to prevent grounding necessary. For example, the city's new Asia new store opening ceremony, was spread equipment near the transformers, the electromagnetic fields that interfere with site PA. Spread through the recording after the equipment shield ground, a solution to this problem.
2. the high-frequency interference. This kind of interference from various wireless transmitter frequency or hyper-frequency signals, they are channeling into electronic device in the machine to get non-normal demodulation and audio interference forming.
The higher the signal frequency, buildings or equipment of metal mesh eyelet is smaller, the signal cable shielding braid it should more dense, shielding effect will be lost. To frequently swap signal cable, should prevent the shield in plug loose and falling off. Because sometimes instrument and equipment of the shield is shielded by the signal line into the ground (they join via plug socket) if shielded falls off, you can easily cause interference. As I stated in Shantou some electronics factory, testers, satellite TV receiver can sometimes have a buzzing for acoustic interference and affect image quality. Through observation, and the aircraft through the apparently chenghai airport radar signal cuanru and are caused by abnormal demodulation. The analysis finds that turned out to be the signal cable shielding layer in the outer shedding plug satellite TV receiver shielded no grounding.
IV. signal ground
A variety of electronic circuit, there is a benchmark potential points of this benchmark potential point, is the signal. Its role is to ensure that the circuit has a unified benchmark potential, not floating, signal errors.
Signal connections are: same device signal input-and output-end cannot join together and separately; the former level (equipment) to only output after the class (device) is connected to the input field. Otherwise, the signal may be formed through the ground, causing signal feedback. This equipment tests, signal connection with particular attention. For example, in an electronic company, quality inspection departments reflect the satellite receiver quality test results. Original, QC testing instrument, some shell grounding, have no grounding of shell (test signal transmitted by the signal Center to departments), the resulting signal through and feedback to make the measurement results are not consistent. After all the grounding of test instruments to not grounded, there is no such phenomenon. Specific situation in the actual operation.