單片機控制的電子秤

電子機電論文編號:JD132 論文字數:24379,頁數:61 有原理圖

  目   錄
摘 要 I
Abstract II

第1章 緒 論 1
1.1 稱重技術和衡器的發展 1
1.2 電子秤的發展現狀 2
1.3 本文的主要工作 2
1.4 本文的創新 2
第2章 電子秤的測量原理 4
2.1 稱重傳感器 4
2.1.1 應變式稱重傳感器 4
2.1.2 應變式稱重傳感器原理 5
2.1.3 傳感器工作原理與分析 5
2.1.4 材料設計 7
2.1.5 應變式傳感器的幾何尺寸設計 7
2.2 A/D轉換電路設計 10
2.3 放大電路及濾波電路設計 11
第3章 電子秤電路設計 14
3.1 電子秤的構成 14
3.2 電源電路 14
3 .2 .1 電源7805 15
3.3 單片機系統設計 16
3 .3 .1 MCS-51（8051）單片機 18
3.4 LED顯示 21
第4章 儀器軟件設計 24
4.1 儀器主程序 24
4.2 校正模塊 26
4.3 鍵盤管理模塊 27
4.4 數據處理模塊 28
4.5 計價模塊 30
第5章 儀器的誤差及誤差分配 32
5.1 儀器的誤差來源 32
5.1.1 稱重傳感器的誤差 32
5.1.2 電子設備的誤差 32
5.1.3 機械承重系統的誤差 33
5.1.4 儀器的誤差分配 34
5.2 儀器誤差的計算方法 34
第6章 儀器工程設計 37
6.1 儀器可靠性設計 37
6.2 可靠性設計方法 38
6.3 開關/鍵盤的使用 38
6.4 元器件的選用 38

結 論 39
致 謝 40
參考文獻 41
附錄1 42
附錄2 47
附錄3 54

摘 要
 現代社會的發展對其稱重技術提出了更高的要求。目前，臺式電了秤在商業貿易中的使用已相當普遍，但存在較大的局限性：體積大、成本高、需要工頻交流電源供應、攜帶不便、應用場所受到制約。但是在工業測量中還沒有讓人們期待的電子秤出現。多年來，人們一直期待測量準確、價格低廉的在工業發展中起到巨大作用的電子秤投放市場。
 本文設計了一種電子秤，論述了儀器的工作原理，介紹了儀器的誤差來源與誤差分配，給出了儀器電路設計與軟件流程，探討了儀器的工程設計技術。針對應變式稱重傳感器非線性影響大的問題，提出并建立了應變式稱重傳感器的非線性影響模型與校正模型，為電子秤的低成本準確稱量奠定了理論基礎。
 電子秤是主要由電源、稱重傳感器、單片機、鍵盤/開關、LED顯示器等部分構成。主要技術指標為：稱量范圍300kg—500kg；分度值0.01kg;精度等級m級;電源5v。儀器的技術指標參考了目前國內市場上使用最多、國內外產量最大的電子衡器的技術指標，其合理性無疑加大了產品投放市場后的競爭能力。儀器主要功能有自檢、計價、累計、單價設定、過載報警等。
 目前國際化的趨勢是電子秤向小型化，模塊化，集成化，智能化，其技術性能趨向于速率高，準確度高，穩定性該，可靠性高等，其功能趨向是稱重計量的控制信息和非控制信息并重的智能化電子秤。
 
關鍵詞 單片機；應變式電阻器；放大器；濾波器
  
 
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.