Product description: Communication Cable Type RS-485 usually uses twisted pair and differential transmission, it has strong anti-common mode interference capability, and the bus transceiver has high sensitivity and can de
Communication Cable Type RS-485 usually uses twisted pair and differential transmission, it has strong anti-common mode interference capability, and the bus transceiver has high sensitivity and can detect voltages as low as 200mv. Therefore, the transmission signal can be recovered beyond the kilometer. The maximum communication distance of rs-485 is about 1219m, and the maximum transmission rate is 10mb/s. The transmission rate is inversely proportional to the transmission distance. At the transmission rate of 100kb/s, the maximum communication distance can be achieved. Distance, need to add 485 repeater. Communication Cable Type RS-485 structure: 1) Conductor: Stranded tinned copper wire 2) Insulation: solid PE insulation 3) First shielding: aluminum foil shielding 4) Drainage line: stranded tinned copper wire 5) Second shielding: tin-plated woven mesh shielding, coverage rate is 80%, the braid layer requires smooth, burr-free, no-leakage, no oil and other obvious quality defects. 6) Sheath: black PVC Communication Cable Type RS-485 considerations 1，The RS485 cable must be grounded. In many technical documents, it is mentioned that the 485 bus must be grounded, but there is no detailed description of how to ground. Strictly speaking, the 485 bus must be reliably grounded at a single point. The single point is that there can only be one point grounding on the entire 485 bus, and it is not possible to ground more points because it is grounded because the voltage on the ground line (generally the shielded line is used as the ground line) is kept consistent to prevent common mode interference. If multiple points are grounded, it is counterproductive. When grounding reliably, the ground wire of the entire 485 line must have good contact, so as to ensure the voltage is consistent, because in actual construction, for the convenience of wiring, the wire is cut into multiple sections and then connected, but the shielded wire is not well connected. The ground wire is divided into multiple sections, and the voltage cannot be consistent, resulting in common mode interference. 2.485 signal line can not be wired with the strong power line. In the actual construction, since the traces are all taken through the pipeline, the construction party sometimes directly binds the 485 signal line and the power line for the convenience of the figure, because the strong electric power has a strong electromagnetic signal to interfere with the weak electricity, thereby The 485 signal is unstable, resulting in unstable communication. 3. Select a qualified cable Due to the rising prices of raw materials, the wire rods on the market are now mixed, and some bad businessmen use some kind of alloy to replace the copper wire to make the wire, and copper plating on the outside to mix customers. The specific difference method: look at the cross section of the cable, if it is copper, it is copper wire. If it is white, it is filled with alloy. Alloys are generally brittle, easy to break, and are far less conductive than copper wire, which can easily cause problems in engineering construction. It is generally recommended to select the standard 485 wire for the wire. It is a shielded twisted pair. The transmission wire is not a single strand of copper wire like a wire, but a plurality of strands of copper wire are twisted together to form a wire, so that even a small copper wire is broken. It will not affect the entire use. The 4.485 signal line can use a shielded line as a wiring, or an unshielded line can be used as a wiring. Since the 485 signal is transmitted using differential mode, the voltage difference between 485+ and 485- is used as the signal transmission. If there is an external interference source to interfere with it, when using twisted pair for 485 signal transmission, due to its twisted pair, the interference effect is the same for 485+, 485-, and the voltage difference is still unchanged. The interference to the 485 signal is reduced to a minimum. By the same token, if a shielded cable is used as a shielding function, the influence of external interference sources on it can be reduced as much as possible. 5.485 wiring can not be arranged into star wiring and tree wiring. The 485 wiring specification is a wiring that must be hand-held. Once it is not directly connected to a star connection and a tree connection by means of a 485 hub and a 485 repeater, it is easy to cause signal reflection to cause bus instability. Many construction parties use star wiring and tree wiring in the 485 wiring process. Sometimes the whole system is very stable, but sometimes there are always problems, and it is difficult to find the cause, generally due to irregular wiring. Caused by it. If a star connection or a tree connection is required due to site restrictions, a 485 hub must be configured to ensure stable system communication. Because Communication Cable Type RS-485 has good anti-noise interference, long transmission distance and multi-station capability, it has become the preferred serial interface. Because the half-duplex network consisting of RS485 interfaces generally only needs two connections, the RS485 interfaces are transmitted by shielded twisted pair.
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