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예식일 : Master The Art Of What Is Rs485 Cable With These Seven Tips
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In areas with a lot of signal interference, the software may need to perform multiple inquiries to get a valid response. OK, let's get cunning about this and just look at the specifications of an actual RS-485 interface. Please get it straight. 2. It is not allowed to use a network cable with a wire diameter that is too thin, which will reduce the transmission distance and reduce the equipment that can be connected. That is to say, the maximum transmission distance of RS485 can reach 9.6 kilometers in theory. This can be either by a wire between the two units or a wire on each unit to the read ground ( Earth ). The use of shielded twisted-pair cables helps to reduce and eliminate the distributed capacitance between the two 485 communication lines and the common mode interference generated around the communication lines. Differential mode interference is transmitted between two signal lines and belongs to symmetrical interference. 1. Ordinary network cables have no shielding layer and cannot prevent common mode interference. RS-485 is used as the physical layer underlying many standard and proprietary automation protocols used to implement industrial control systems, including the most common versions of Modbus and Profibus.

Control and monitoring systems: A single pair of rs485 signal cable can connect up to 32 devices, with a signal transmission distance of up to 1200m. Therefore, using rs485 cables is an ideal choice for industrial control and monitoring systems, especially those with large-scale and high dispersion. Most engineering companies are accustomed to using Category 5 network cables or over Category 5 network cables as 485 communication lines, which is wrong. Care must be taken that an SC connection, especially over long cable runs, does not result in an attempt to connect disparate grounds together - it is wise to add some current limiting to the SC connection. The most common cable type is Cat 5e-UTP (unshielded twisted pair) which may work over shorter distances in less demanding applications with low EMI noise levels. 6) What is common mode interference and differential mode interference? RS-485 adopts half-duplex working mode and supports multi-point data communication.

The RS-485 bus network topology generally adopts a bus-type structure with terminal matching. Up to 32 nodes can be connected on the same bus. Ordinary twisted-pair cables can be used in general occasions, and shielded coaxial cables can be used in environments with relatively high requirements. The communication line should be as far away as possible from interference sources such as high-voltage wires, fluorescent lamps, etc. When the communication line cannot be avoided from interference sources such as power lines, the communication line should be perpendicular to the power line, not parallel, and cannot be bundled together, and use high-quality twisted-pair cables. The longer the communication distance, the higher the baud rate, the thinner the wire diameter, the worse the wire quality, the worse the quality of the converter, and the insufficient power supply of the converter (passive Converter), the stronger the lightning protection, these will reduce the real load quantity. EIA-485 says that using the ground can be a advantage for longer lines, but its not nessecary. It should be judged according to the model of the chip in the 485 converter and the model of the 485 device chip, and the load capacity can only be determined according to the chip with a lower index.

When using the RS485 interface, for a specific transmission line, the maximum cable length allowed for data signal transmission from the RS485 interface to the load is inversely proportional to the baud rate of the signal transmission. In theory, the longest transmission distance of RS485 can reach 1200 meters, but the transmission distance in practical applications is shorter than 1200 meters. The condition is that the communication wire is high-quality and meets the standard, the baud rate is 9600, and only one 485 device is loaded, so that the communication distance can reach 1200 meters, so the actual and stable communication distance of the 485 bus is usually less than 1200 meters. According to the 485 bus structure theory, under the premise of an ideal environment, the 485 bus transmission distance can reach 1200 meters. 4) Why should the 485 bus adopt the hand-in-hand structure instead of the star structure? The star structure will produce reflected signals, which will affect the 485 communication. Common-mode interference will increase the above-mentioned common-mode voltage. Well, either you know that your grounds are at the same voltage due to other connections, or you provide a ground connection for a reference along with the data wires.

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