【作者】 李乐；

【导师】 郑宾；

【作者基本信息】 中北大学 ， 测试计量技术及仪器， 2008， 硕士

【摘要】 随着称重技术的不断提高,称重设备从传统的模拟式逐渐向智能化、数字化的方向发展。本文结合称重领域的现状和发展趋势,研究了实现智能化、网络化以及高精度称重的相关技术,设计了一种与称重传感器分离的智能化称重模块,可以实现对传统模拟称重传感器的数字化改造,使其符合智能化称重传感器的特点。本论文所完成的工作如下:1)使用Silicon Laboratories公司的内部集成24位? ??型模数转换器的C8051F350单片机,采用通道交换测量、六线制和比率电压测量技术,并通过自校准和数字补偿处理,使称重模块对变化的环境参数具有自适应性。分析和实验表明,上述各项技术均提高了称重精度。2)对传统RS-485接口电路进行了功能的扩展,设计了可以实现总线监听和冲突检测/竞争的自定义通讯协议。这些工作使称重模块具备了数字变送功能,同时又可以接收主机的ASCⅡ码形式的控制命令,从而实现称重模块的网络化、智能化管理。3)为传统称重模块增加了新的内容:可以为称重传感器提供连续可调的激励源,使传感器不需单独设计激励源;实现了兼容六线制和四线制传感器的接口电路;具备JTAG编程接口,可实现在线调试和程序烧写,便于固件程序在线升级。这些工作使得传统称重模块的概念得到了扩展。更多还原

【Abstract】 With the improvement of weighing technique, intelligent and digital facilities are requiredto replace the analog ones used before. According to the present situation and development ofweighing technique, methods related in intelligent, network and precision weighing arestudied in this thesis, and an intelligent loadcell digitizing unit separated from the analogloadcell is designed to realize the digital alteration that makes an analog loadcell change to anintelligent one. The contributions of the thesis are presented as follows:1) Based on mixed-signal Micro-Control Unit (MCU) C8051F350 which integrates a24-bit ? ? ? Analog to Digital Converter (ADC) inside, channel switching, ratio voltagemeasurements and six-wire technique are studied, and a loadcell digitizing unit is designedwith self-calibration and digital compensation. The unit can work precisely at differentenvironments within the absolute maximum ratings. Experiments show that the mentionedtechniques meet the requirement of precise weighing.2) An expanding work is conducted to make the conventional RS-485 interface circuit meetthe requirements of bus snooping, multi-talker detecting and competition, and thecoresponding communication protocol is established. As a result, this loadcell digitizing unitpossesses of the functions of digital transmitter and is ready for instructions in terms of ASCⅡcode. The unit adapts to both network environment and intelligent management.3) Some novel functions are promoted and implimented, including: steplessly adjustibleexciting source supply for loadcell; interface accommodating six-wire and four-wire loadcell;JTAG interface for in-circuit debugging, flash programming, and on-line firmware upgrade.These functions expand the design concepts of conventional loadcell digitizing unit.更多还原