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| 摘要: |
| 在传统的概念中，为降低弱电回路的干扰，宜采用带屏蔽层的信号线，且屏蔽层应两端接地，以削弱电磁耦合的影响。但从干扰的来源、作用方式及对干扰的抑制上分析，屏蔽层应单端接地。干扰的作用方式主要有串模干扰和共模干扰。串模干扰可以通过合理的选择信号线及正确敷设电缆，以减弱或抵消干扰感应电势；或根据干扰信号频率与被测信号频率的分布特性，决定选用具有低通、高通、带通等传递特性的滤波器来抑制。共模干扰的抑制策略只有一个：使共模电压不成回路，或者说将不同的“地”隔离开来。屏蔽层的两端接地，在削弱串模干扰的同时也引入了共模干扰，因为现场的接地网并非实际的等电位面，且接地点必须根据接地方式正确选择。 |
| 关键词: 抗干扰 屏蔽层 接地方式 接地点 电缆敷设 弱电回路 信号线 |
| DOI： |
| 分类号:TM757 |
| 基金项目: |
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| Earthing Mode for Shielded Signal Wire of LV Circuit |
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YU Ai min WANG Lan hua SONG Yan
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| Abstract: |
| According to the traditional concept, the shielded signal wire should be applied in low voltage circuit to lower the interference and its screen connected to earth at both ends to weaken the electromagnetic coupling effect.But considering with the interference source,interfering mode and suppression means,only one end should be connected to earth.There are chain mode interference and common mode interference.The chain mode interference can be suppressed or offset by reasonably choosing signal wires and correctly laying cables,or by properly selecting low pass,high pass or band pass filter with different passing performances according to the frequency distribution features of interference signal and working signal.There is only one way to control common mode interference:cut off the circuit of common mode voltage,i.e.,isolate the earth points of different electric systems.Because the field earth net is not a real equipotential net,earthing at both ends weakens chain mode interference but strengthens common mode interference.Further more,the earthing end should be properly selected according to earthing mode. |
| Key words: interference immunity,shield layer,earthing mode,earthing point, |
