• 목록
• 답변
• 글쓰기
• 게시판 리스트 옵션
  • 수정
  • 삭제

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. We will concentrate on the RS485 interface here. It also defines three generator interface points (signal lines); A, B and C. The data is transmitted on A and B. C is a ground reference. The board with dual RJ11 jacks is the more popular since is can use commercial straight-through, non-reversing, 6-wire data cables with RJ11 connectors. Therefore RS485 will be in use for many years in the future. RS485 is used as the electrical layer for many well known interface standards, including Profibus and Modbus. This works well and prevents the existence of ground loops, a common source of communication problems. If I cannot find out the characteristic impedance of the cable from the supplier, would you put two 120ohm resistors in or could this potentially make the problems worse? Several volts difference in the ground level of the RS485 transmitter and receiver does not cause any problems. What is rs485 cable?

If the 8-core cable shipped with the device is used for RS485 communication, please trim the length and try to use a short wire to reduce noise interference. In this situation, bandwidth can be used for almost 100%. There are other implementations of RS485 networks where every node can start a data session on its own. Because there is a chance of data collosion with this implementation, theory tells us that in this case only 37% of the bandwidth will be effectively used. Those little price checkers that are kind of spread out throughout the store, you just bring your merchandise up there and just check the prices. They can easily update one PC, which will take care of all prices to the store. Therefore RS485 can overcome the practical communication speed limit of RS232. Sig- line. The RS485 receiver compares the voltage difference between both lines, instead of the absolute voltage level on a signal line. We also see that the maximum allowed voltage levels for all interfaces are in the same range, but that the signal level is lower for the faster interfaces. It’s important to note that all devices on the network need to use the same logic for interpreting voltage differences as bits (i.e., whether A being at a higher voltage than B represents a ‘1’ or a ‘0’).In a network with multiple devices, each device needs to have a unique address so that it knows when to listen and when to ignore the communications on the line.

RS485 is however most popularly used in programmable logic controllers and factory floors where there are lots of electrical noise. N nodes are connected in a multipoint RS485 network. For higher speeds and longer lines, the termination resistances are necessary on both ends of the line to eliminate reflections. The transmitter and receiver compare the voltages of the data- and handshake lines with one common zero line. The picture shows the magnetic field lines and the noise current in the RS485 data lines that is the result of that magnetic field. And now the most important question, how does RS485 function in practice? The fastest RS-485 transceivers out there right now are running about 50 megabits. Now check it again with the 192.168.0.7 address. This helps to minimize the impact of electromagnetic interference, causing the voltage between the two wires to deviate. The shielding may be braided (be formed by a mesh of thin conducting wires) or be a foil (consisting of a sheet of metal wound around the conductors): the two types are equivalent. Anti-inteference layer: Rs485 cables are designed with 2 anti-inteference layers to shield the internal conductors.

RS232, RS422, RS423 and RS485 are serial communication methods for computers and devices. Xwire protocol over RS485 will allow cable runs of up to 1km - with suitable cable and grounding precautions- and up to 32 devices. Because of this RS485 and the others can be used in situations with a severe ground level shift of several volts, where at the same time high bit rates are possible because the transition between logical 0 and logical 1 is only a few hundred millivolts. In the straight cable, all noise current is flowing in the same direction, practically generating a looping current just like in an ordinary transformer. Based on information from the Wikipedia page you posted, it looks like there are a limited number of communication standards transmitted over 485, with one being pointed out as the most frequently used. So remember, differential, any noise subjected to the cable is canceled out.