485 communications to earth? How will you grounded?

According to long-term comrades engaged in the work of the technology: (1) RS485 communication distance ( Within 800 m) The general ordinary twisted-pair cable (2) can be used without blocking interference can use when the heavier belt shield twisted-pair ( Shielding layer of air suspension and/or grounded at one end only - — With 'high voltage' especially 'inverter' apart) (3) signal to general air suspension ( No connection) , if ground is not good but can't normal communication. The majority of Internet users is above opinion. But there are also some netizens think: should be connected devices altogether; Otherwise, if the receiver has a high common-mode input, it may damage the receiver device. In most cases, the RS - connection 485 communication link simply with A pair of twisted pair to each interface respectively on the tip of the 'A', 'B' together, and air suspension will signal - — This kind of connection method is to work on many occasions, but should pay attention to the following two questions: ( 1) Common-mode interference problem: RS - 485 interface adopts differential method receives the input signal, does not need to be relative to a reference point to detect signals, by detecting the potential difference between the two input thread system. But people often ignores the receiver has certain common mode voltage range, the RS - To - 485 receiver common-mode voltage range 7 ~ + 12 v, only to meet the above conditions, the whole networks to work properly. When the communication lines common-mode voltage of the communist party of China is beyond the scope of the can affect communication is stable and reliable, even damage the interface. ( 2) Electromagnetic radiation problem: drive the output signal of common mode requires a return channel, without a return channel (low resistance Signal ground) , will return in the form of radiation source side, the whole bus would be like a giant antenna to the radiation electromagnetic waves.