DCS Of Belt Weighing Devices With CAN Field Bus

Following the prominent standing out of the technologies of transducer,electronics and microcomputer, a rapid progress has been made on weighing technology. Weighing scales have much improvement in digitization and intelligence. The research and development of weighing scales are entering into a new stage. As a new kind of hightech industry, the weighing scales such as belt weighing devices are paid close attention to by many countries all over the world. Further applying new technologies to it, developing all kinds of automatic scales, improving the precise of dynamic weighing and consolidating the network function become the important points of development at present. The industry of weighing devices in our country has hitted on the larger scale, but the technology of superior quality weighing scales falls behind the average international level. Actively developing superior quality weighing scales possessing independent knowledge property right makes significant sense on the development of domestic industry of weighing scales. My subject just fringes with belt weighing devices.Cumulative displaying controllor is the core part of belt weighing device. And it is composed of the modules of A/D conversion, data processing, data display, data storage, data transmission, automatic control, and power supply and EMC design. The applied A/D converter is AD7730, the precise A/D converter of Analog Device Company,whose offset drift vs temperature can reach 5nV/℃. The data from A/D converter need microcontroller to process. And the microcontroller is P89C668, its high integration not only simplifies the design but also reduces cost. Data display employs LCM, which makes the device have a friendly man-machine interface. Data storage adopts PCF8583, which has the shorter access cycle and lower price, moreover it acts as clock/calendar at the same time. CAN field bus acts as data transmission, which has been extensively applied to industrial automatic control. CAN field bus has come into fasion because of its high reliability, the realtime ability, and flexibility in data transmission, long transmission distance and simple electronical connection, etc. The power supply is the TOPSwitch-II switching power supply substituted for the integrated regulated power supply, which not only saves energy but also constracts the volume of belt weighingdevice. Interference immunity test of belt weighing device and counterpart improving measures is an important part of the design, which is composed of interference immunity test of RF, ESD and EFT/B.When using CAN field bus as the carrier of the network of belt weighing devices, the DCS of belt weighing devices has a remote, high speed, reliable, flexible and low-cost communication interface. In fact, the TOPSwitch-II switching power supply is a kind of energy saving, simply designed and low-cost power supply system. After putting belt weighing device to some simplified interference immunity test, some defects in EMC had been found and some homologous solutions have been taken to improve its performance. Some presumable implementation methods to the generator of EFT/B have been brought out after research for it, and the research for it should be continuing and the sample should be made out.