In often be being operated actually, the biggest to systematic loss is low frequency in all modular interference, electric machinery of for example high-power, breaker or switch, short circuit, induction of be struck by lightning, these types are ab extra mostly in all modular signal, its arteries and veins is wide arrive in hundreds Us between S, cycle is the longest also be several seconds, such pulse causes the tall voltage wave motion to the ground continuously, injure a system thereby. But to high frequency in all modular interference, from interference the source begins, major energy transmits a way as energy with radiant means, and such in all modular interference is born at systematic itself prolifically.

 

product of ground of 1. butt joint, conduct on hope wire cable of course come over in all modular interference, control parts of an apparatus through capacitance or transient state, oriented earth or housing, prevent its to disturb sensitive circuit (like CPU) .

 

2. but to float ground product character, basically carry ring of series connection magnetism (or increase in all modular impedance) , prevent in all modular voltage translate into needs modular voltage, ; of road of interference quick electrification next, want to notice the wiring of PCB, make each circuit of PCB board referenced to its not only the ground (digital ground GND, the housing ground PG) of product of ground connection of and rather than holds 0 potential, and in I/O, RST, CS(piece anthology) the filter wave circuit that waits for crucial signal is placed. Such, again abominable in all modular interference also won’t generate interference to digital circuit.

 

 

3. the first kind of method is discharge (but the requirement has good ground connection or metallic housing) , the 2nd kind of method is to block up (avoid in all the model annoys translate into to need modular interference, affect circuit) . Before one kind of method, basically use at the ground facilities with good ground connection (be like) of communication radical station, the 2nd kind of method, basically use at the car to carry, equipment of airborne, carrier-borne.

 

4. of course, everybody can say the 2nd kind of method (float ground) , because PCB board and earth also are put in parasitism capacitance, likely to high frequency interference invalidation. But to spot of control of railroad, electric power, industry, main interference is electric machinery of transducer, high-power, breaker or switch, the interference that its generate basically is centered in 10MHZ above. In addition, ground wire is disturbed (strong report short circuit, be struck by lightning strikes back, ) of harmonic, leakage current, also be very serious with what do not stabilize (be as high as 0.8V) possibly at ordinary times, the working voltage 1.2V of crucial to the part CPU, it is a devil simply!

 

5. is high frequency in all modular electromagnetism interference, energy is general very won’t big. Radio frequency of for example mobile phone, high-power identifies (of my experience most high-power ability 3W) , because be high frequency, ferrite magnetism annulus or magnetism bead can absorb, metallic box (or the) of layer of spray electric conduction inside plastic box, can reflex its completely or absorb. The radiate that railroad asks to do 800~1000M, 1.4G~2.1G now fights —— faze checks (intensity is as high as 20V/M) , and the radiate of 2.1G~2.5G fights faze to check (intensity is as high as 5V/M) , equipment can appear scarcely problem. Of course, equipment should pass the test such as CS, ESD, EFT.