Research And Design Of CPLD/CCD-based Electronic Scale With High-Precision And Small-Scale

Weighing measurement is an indispensable part of human living.With the great development of modern economy and technology,people have higher and higher requirement on the accuracy of weighing measurement.Since electronic scale has the advantages of high accuracy,sensitive response,steady performance,simple construction and strong adaptability to environment,it is widely applied in the fields of business,light industry and food industry,medicine industry and so on.Meanwhile, it is very important to strictly limit the weight of some valuable metal,harmful substances and medication because of their expensive price or special property. Therefore,research on high accuracy and small scale electronic scale becomes the key to solve this problem.This high precision and small scale electronic scale is based upon Charge Coupled Device image sensor,it changes the object's weight into electrical signal through CCD,and then processes this analog signal so that it can find the weight.At the hardware aspect,this thesis uses Complex Programmable Logic Device to drive CCD,and optical system reflects the object's micro-displacement on scale pan to CCD.Then output signal of CCD is pretreated and converted into digital signal by special CCD signal processor.Finally,Digital Signal Processor is used to deal with the data and display it through Liquid Crystal Display in order to weigh the object.At the software aspect,according to hardware unit it is divided into three parts: CPLD,DSP and LCD display.The paper analyzes the function design method of CPLD and DSP,CPLD drives CCD and its signal processor by means of VHDL Language and Quartusâ…¡;DSP is developed by Code Composer Studio.It also designs a brief soft flow chart of this system.At the aspect of signal processing arithmetic,since lamp-house covers several area of CCD,it is necessary to fix on CCD image spots position exactly.The article introduces common algorithms for CCD image spots position,and compares these ways,then designs an appropriate one.Finally,experimental result is analyzed.