Application of RS485 Bus in Intelligent Instrument Communication System

Abstract: The application information of RS485 bus in intelligent instrument communication system is provided by excellent flowmeter and flowmeter manufacturers. The 21st century RS485 serial communication technology is also widely used in the industrial control industry. Now the world instrument market is basically monopolized by smart instruments. The reason is the need for enterprise informatization. One of the necessary conditions for enterprises to select instruments is to have networking. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following is the application article details of RS485 bus in intelligent instrument communication system. The 21st century RS485 serial communication technology is also widely used in the industrial control industry. Now the world instrument market is basically monopolized by smart instruments. The reason is the need for enterprise informatization. One of the necessary conditions for enterprises to select instruments is to have a networked communication interface. The RS485 interface can realize point-to-point communication and networking, so RS485 has been maximized in the intelligent instrument communication system. The RS-485 interface communication link simply uses a pair of twisted pairs to connect the 'A' and 'B' ends of each interface. The connection of the signal ground is ignored. This connection method can work normally in many occasions, but it has buried a lot of hidden dangers. There are two reasons for this: (1) Common mode interference problem: RS-485 interface adopts The differential mode transmits the signal, and does not need to detect the signal relative to a certain reference point, the system only needs to detect the potential difference between the two lines. But people often ignore that the transceiver has a certain common-mode voltage range. The common-mode voltage range of the RS-485 transceiver is -7~+12V. Only when the above conditions are met, the entire network can work normally. When the common mode voltage of the network line exceeds this range, it will affect the stability and reliability of communication, and even damage the interface. (2) EMI problem: The common-mode part of the output signal of the transmitter driver needs a return path. If there is no low-impedance return path (signal ground), it will return to the source in the form of radiation, and the entire bus will be like a huge The antenna radiates electromagnetic waves outward. UT-2127 passive photoelectric isolation interface converter, compatible with RS-232C, RS-422, RS-485 standards, can convert single-ended RS-232 signals into balanced differential RS-422 or RS-485 signals, built-in Optical isolator, can provide isolation voltage up to 2500Vrms, with fast transient voltage suppression protector, this protector is designed to protect RS-422/RS-485 interface, using today's advanced TVS (TRANSIENT VOLTAGE SUPPRESSOR) Transient voltage suppressor, under normal circumstances, the TVS tube is in a high resistance state. When both ends of the TVS tube are subjected to an instantaneous high-energy shock, it can reduce the impedance at both ends of the TVS tube at a very high speed and absorb a large current. The voltage across it is clamped at a predetermined value to protect subsequent circuit components from being damaged by transient high voltage shocks. This protector can effectively suppress lightning (LIGHTNING) and ESD, provide 600W lightning surge protection power per line, as well as surge voltage and transient overvoltage generated on the line due to various reasons, and the extremely small inter-electrode capacitance guarantees High-speed transmission of RS-422/RS-485 interface. The RS-232 interface end is connected to a standard interface compatible with RS-232C through a DB9 female connector, and the RS-422 and RS-485 ends are output through six-position binding posts. The converter has zero-delay automatic transceiver conversion, the unique I/O circuit automatically controls the direction of the data flow, without any handshake signals (such as RTS, DTR, etc.), without jumper settings to achieve full duplex (RS- 422), half-duplex (RS-485) mode conversion, plug and play. Ensures compatibility with all existing communication software and interface hardware, without any software modifications to previous RS-232 based workings. Product features: ■ Interface features: The interface is compatible with EIA/TIA's RS-232C, RS-485/RS-422 standards ■ Electrical interface: RS-232 interface input DB9 female connector, RS-422/RS-485 interface six The bit binding post is the output end ■ Protection level: RS-232 interface +/-15KV ESD protection, RS-422, RS-485 interface 600W lightning surge protection per line. ■ Isolation: isolation voltage 2500Vrms 500DC continuous ■ Working mode: asynchronous half duplex or asynchronous full duplex ■ Transmission medium: twisted pair or shielded wire ■ Transmission rate: 115.2K BPS to 300M 38.4K BPS to 600M 9600 BPS to 1.2 KM Dimensions: 61mm×41mm×21mm ■ Use environment: -40°C to 85°C, relative humidity from 5% to 95% This is the entire content of this article. You are welcome to inquire about the flowmeter selection and quotation of our factory. 'Application of RS485 bus in intelligent instrument communication system'

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