Hello everyone, welcome to the Xingyi class, in this issue, we will talk about how to wiring RS485 communication. The network topology generally adopts a terminal-matched bus structure. When building a network, you should pay attention to the following three points: (1) A twisted pair cable is used as the bus, and each node is connected in series, and the length of the lead line from the bus to each node should be as short as possible, so that the reflected signal in the lead line has the lowest impact on the bus signal. (2) Attention should be paid to the continuity of the impedance of the bus characteristics, and the reflection of the signal will occur when the impedance is discontinuous. In summary, a single continuous signal channel should be provided as a bus. (3) Pay attention to the problem of terminal load resistance, in the case of less equipment and short distance, the whole network can work well without terminal load resistance, but with the increase of distance, the performance will decrease. Generally, the termination resistor method is used for terminal matching, and RS-485 should be connected to the terminal resistor at both the beginning and end of the bus cable. The termination resistor is 120Ω in an RS-485 network. It is equivalent to the resistance of the characteristic impedance of the cable, because the characteristic impedance of most twisted pair cables is about 100~120Ω. This matching method is simple and effective, but there is a disadvantage, the matching resistor consumes a lot of power, which is not suitable for systems with strict power consumption restrictions. Another power-saving matching method is RC matching. Using a capacitor C to block the DC component can save most of the power. There is also a matching method using diode, although this scheme does not achieve real “matching”, but it can quickly weaken the reflected signal by using the clamping effect of the diode, so as to achieve the purpose of improving the signal quality, and the energy saving effect is remarkable. Star Meter Manufacturing Co., Ltd. is a high-tech enterprise integrating R&D, production and sales. Specializing in the production of pressure transmitters, liquid level transmitters, temperature transmitters, temperature and humidity transmitters, differential pressure transmitters, soil moisture transmitters, 3051 transmitters and related instrumentation accessories. A number of products under the Xingyi brand have obtained a number of patent certificates issued by the state, such as CE certification, IS9001 certification, SGS certification, TüV SüD certification, explosion-proof certification, etc. If you have any questions about product consultation, product customization, agency, technical inquiry, quotation, etc., please contact Xingyi: 400-600-4496!