Abstract
本論文提出利用電磁力補償方式將重量轉換成電流值，換算得知載荷質量。此系統有許多優點，如準確度高、無機械損、無摩擦力、操作簡單、校正方便... 等。可應用於工業界或研究實驗室中作精密測重用的工具。此系統簡分為機械、控制與量測三個子系統。機械系統主要包含：載荷裝置、傳遞裝置與補償裝置。機械系統的轉換方程式於本文中有詳盡的推導。控制系統主要利用類比電路作定位控制，即在載荷改變時，需使舉重線圈回復原點，與天平秤重需使兩端平衡的原理相同。為求穩定性及精密定位，控制器採用內迴路和PI控制。量測系統主要利用數位電路作電流量測，並將量得之電流量轉成待測物實際質量值，並且針對系統之特性進行軟體補償。其中控制器與量測電路是利用新式電子元件重新設計製作。類比╱數位轉換器採HARRIS公司出品高精度的HI-7159A；微處理機8052除了量取電流、轉換數據和零點追蹤、控制人機介面外，更具有串列輸出入資料功能，易與其他電腦系統連線，使本系統之應用更具擴充性。至於系統軟體的寫作架構本文中亦有詳細說明。之後，再對製作完成的系統進行性能測試。本秤重系統之分度數為三萬點，最大秤量為三公斤，即分度值為零點一公克，符合國際法定計量組織所制定第 76號國際建議屬高準確度的Class II秤重衡器。秤量穩定讀值所需時間為三秒。讀值重複性、偏心載荷效應和遲滯作用等性能測試均能達到產品要求。In this thesis, the method of conversion from mass to currentby electromagnetic force compensation is investigated. Mainfeatures are high accuracy, no mechanical loss, no friction,and ease of operation and calibration. Such a system has wideindustrial application when precision mass measure ments arerequired. The entire weighing system consists of a mechanicalstructure and two electrical subsystems. In this work, thetransfer function of the mechanical structure is derived.Moreover, electrical subsystems including position controllerand measurement hardware have been redesigned and fabricated byusing up-to-date electronic components. The detailed algorithmof measurement software is also presented. Then the weighingsystem is tested in the laboratory to verify its performance.The certificate interval number of the weighing system studiedin this thesis is thirty thousand; the maximum capacity isthree kilograms. It belongs to Class II of the NationalSuggestion No.76 of OIML. It takes 3 seconds for a massreading. The performance of repeatability of reading, effect ofoff-center loading and hysteresis all meet the requirement ofcertificate specification.