单片机控制的电子秤

电子机电论文编号:JD132 论文字数:24379,页数:61 有原理图

  目   录
摘 要 I
Abstract II

第1章 绪 论 1
1.1 称重技术和衡器的发展 1
1.2 电子秤的发展现状 2
1.3 本文的主要工作 2
1.4 本文的创新 2
第2章 电子秤的测量原理 4
2.1 称重传感器 4
2.1.1 应变式称重传感器 4
2.1.2 应变式称重传感器原理 5
2.1.3 传感器工作原理与分析 5
2.1.4 材料设计 7
2.1.5 应变式传感器的几何尺寸设计 7
2.2 A/D转换电路设计 10
2.3 放大电路及滤波电路设计 11
第3章 电子秤电路设计 14
3.1 电子秤的构成 14
3.2 电源电路 14
3 .2 .1 电源7805 15
3.3 单片机系统设计 16
3 .3 .1 MCS-51（8051）单片机 18
3.4 LED显示 21
第4章 仪器软件设计 24
4.1 仪器主程序 24
4.2 校正模块 26
4.3 键盘管理模块 27
4.4 数据处理模块 28
4.5 计价模块 30
第5章 仪器的误差及误差分配 32
5.1 仪器的误差来源 32
5.1.1 称重传感器的误差 32
5.1.2 电子设备的误差 32
5.1.3 机械承重系统的误差 33
5.1.4 仪器的误差分配 34
5.2 仪器误差的计算方法 34
第6章 仪器工程设计 37
6.1 仪器可靠性设计 37
6.2 可靠性设计方法 38
6.3 开关/键盘的使用 38
6.4 元器件的选用 38

结 论 39
致 谢 40
参考文献 41
附录1 42
附录2 47
附录3 54

摘 要
 现代社会的发展对其称重技术提出了更高的要求。目前，台式电了秤在商业贸易中的使用已相当普遍，但存在较大的局限性：体积大、成本高、需要工频交流电源供应、携带不便、应用场所受到制约。但是在工业测量中还没有让人们期待的电子秤出现。多年来，人们一直期待测量准确、价格低廉的在工业发展中起到巨大作用的电子秤投放市场。
 本文设计了一种电子秤，论述了仪器的工作原理，介绍了仪器的误差来源与误差分配，给出了仪器电路设计与软件流程，探讨了仪器的工程设计技术。针对应变式称重传感器非线性影响大的问题，提出并建立了应变式称重传感器的非线性影响模型与校正模型，为电子秤的低成本准确称量奠定了理论基础。
 电子秤是主要由电源、称重传感器、单片机、键盘/开关、LED显示器等部分构成。主要技术指标为：称量范围300kg—500kg；分度值0.01kg;精度等级m级;电源5v。仪器的技术指标参考了目前国内市场上使用最多、国内外产量最大的电子衡器的技术指标，其合理性无疑加大了产品投放市场后的竞争能力。仪器主要功能有自检、计价、累计、单价设定、过载报警等。
 目前国际化的趋势是电子秤向小型化，模块化，集成化，智能化，其技术性能趋向于速率高，准确度高，稳定性该，可靠性高等，其功能趋向是称重计量的控制信息和非控制信息并重的智能化电子秤。
 
关键词 单片机；应变式电阻器；放大器；滤波器
  
 
Abstract
 The development of the modern society has put forward higher request on weighing technology. The desk-top electronic scales have been great application in commercial trade, but they have many shortcomings such as large volume, high cost, AC supply power and not cove nince to carry, so they are restricted to use. The usual portable scales are lever scales which are mostly used by residents, and spring balance which measure through compression or drawing of spring. They are being rejected for their big measuring errors. People have been expecting cheap portable electronic scales which can measure accurately and be carried conveniently for many years.
 This thesis designs new-type portable electronic scales. It discusses the instrumental working principle, and introduces its error sources and how to distribute the error.  And, the instrumental circuit, software-flow-chart and engineering designing technology are presented. Because capacitance weighing sensor is of bad non-linearity, the author put forward and set up a math model to revise non-linearity, which establishes the theory basis for the instrument to measure accurately and be low-cost.
 The portable electronic scales consist of power, weighing sensor, microchip, keyboard/switch LED and etc. Its technical indictors include10kg maximal measuring range,10g division value, III precision, 1.5V work voltage. Its technical indictors refer to the indictors of the electri conic measuring tools of most popularity in the markets and of large output at home and board, so the instrument is strengthened the competitive power after putting on markets. It possesses many intelligent functions, such as shelling, lack-of-power display, overload alarm, unit price enactment, accumulation computation, self-calibrating and etc. It can "sleep" automatically in five minutes if it is not measuring.
 New-type portable electronic scales can measure mass rapidly and accurately and communicate value. Furthermore, it is small, simply structured, easy to operate and convenient to carry. The instrument is able to meet the needs of commercial trade and residents, so its application has a bright future.
Key Words Portable Electronic Scales; Capacitance Weighing Sensor; Non-linearity Revision; Microcontroller; Error distribution; Engineering Design.