Who Is What Is Rs485 Cable? > 자유게시판

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Our range of IIoT products is wide, with different sensors and hubs for different scenarios and requirements. The configuration and specifications of RS485 make it faster and extend the range of data transmission. If long-distance transmission is really needed, optical fiber can be used as the propagation medium, and a photoelectric converter is added at both ends of the transceiver. 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. The WattNode® BACnet and Modbus® meters communicate using RS-485 (TIA/EIA-485-A) half-duplex, differential signaling at 9600, 19200, 38400, and 76,800 baud. No, if this induced signal is also picked up by the ground wire then the differential is still preserved. If there are many load 485 devices, the wire impedance is not up to the standard, the wire diameter is too thin, the converter quality is poor, the equipment lightning protection is complicated, and the baud rate is increased. ● The manufacturer will do a lot of testing work for its supporting 485 converter, and will require the 485 converter manufacturer to carry out production and quality testing according to its fixed performance parameters, so it has better compatibility with access control equipment.

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. 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. 3. Keep away from high-voltage wires when wiring, and do not bundle high-voltage power wires and signal wires together. Differential mode interference is transmitted between two signal lines and belongs to symmetrical interference. It transmits signals through the voltage difference between the two communication lines, so it is called differential voltage transmission. According to the 485 bus structure theory, under the premise of an ideal environment, the 485 bus transmission distance can reach 1200 meters. In theory, the longest transmission distance of RS485 can reach 1200 meters, but the transmission distance in practical applications is shorter than 1200 meters.

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. For these secondary devices you have to implement your periodic heart beat check in some device specific way. RS485 has no specific physical shape. 1. Ordinary twisted pair shielded cable STP-120Ω (for RS485 & CAN) one pair 20 AWG, the outer diameter of the cable is about 7.7mm. Suitable for indoor, pipeline and general industrial environment. 2. Ordinary twisted pair shielded cable STP-120Ω (for RS485 & CAN) one pair 18 AWG, the cable outer diameter is about 8.2mm. Suitable for indoor, pipeline and general industrial environment. 3. Armored twisted-pair shielded cable ASTP-120Ω (for RS485 & CAN) one pair 18 AWG, the outer diameter of the cable is about 12.3mm. It can be used in places with severe interference, frequent rodent damage, and lightning protection and explosion-proof requirements. The method to eliminate differential mode interference is to add a bias resistor (matching resistance in the dome camera) to the circuit, and use twisted-pair wires; common mode interference is transmitted between the signal line and the ground, which is asymmetrical interference.

The 485 communication line is composed of two twisted-pair lines. ● Use scientific and reserved solutions for 485 bus projects with long lines and heavy loads. This way, the lines will be biased to known voltages and nodes will not interpret the noise from undriven lines as actual data; without biasing resistors, the data lines float in such a way that electrical noise sensitivity is greatest when all device stations are silent or unpowered. The star structure will produce reflected signals, which will affect the 485 communication. The specifications of the shielded twisted pair used are related to the distance of the 485 communication line and the number of connected devices, as shown in the following table. If the branch line is not connected to the terminal, there will be reflected signals, which will cause strong interference to the communication. It is designed with RS485 built-in to be connected to the above data logger, where the data will wirelessly transmit to the cloud.

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