RS485 signal cable ,produce by AIXTON

RS485 is a standard defining the electrical characteristics of drivers and receivers in a balanced digital multipoint system, defined by the Telecommunications Industry Association and the Electronic Industries Alliance. Digital communication networks using this standard can transmit signals efficiently over long distances and in electronically noisy environments. RS-485 enables connection to local networks as well as configuration of multi-drop communication links. [s1]
RS485 has two kinds of wiring, two-wire system and four-wire system. The four-wire system can only realize point-to-point communication mode, which is rarely used now, and the two-wire system connection mode is mostly used. This wiring mode is a bus topology. Up to 32 nodes can be connected to the same bus.
In the RS485 communication network, the master-slave communication mode is generally adopted, that is, one master has multiple slaves. In many cases, when connecting the RS-485 communication link, simply connect the "A" and "B" ends of each interface with a pair of twisted pairs, and ignore the connection of the signal ground. This connection method is used in many The occasion can work normally, but it has buried a lot of hidden dangers. Reason 1 is common mode interference: the RS-485 interface uses a differential mode to transmit signals, and it does not need to detect signals relative to a certain reference point. It is enough to detect the potential difference between the two lines, but it is easy to overlook that the transceiver has a certain common-mode voltage range. The common-mode voltage range of the RS-485 transceiver is -7 to +12V. Only when the above conditions are met, the entire network It can work normally; when the common-mode voltage of the network line exceeds this range, it will affect the stability and reliability of the communication, and even damage the interface; the second reason is the problem of EMI: the common-mode part of the output signal of the sending driver needs a return path, if there is no one The low-impedance return channel (signal ground) will return to the source in the form of radiation, and the entire bus will radiate electromagnetic waves outward like a huge antenna.