The Design Of The Fiber-Capacitive Signal Processing Circuit In Liquid Drop Analyzer

The fiber-capacitive drop analyzer (FCDA) is based on a specially designed drop sensor by means of the fiber drop analyzing technology and the capacitive drop analyzing technology, and produces a volume-based fiber drop trace (VFDT), which shows the relation between the light intensity passing through the liquid drop and the instant drop volume. Using this principle, we are able to achieve the precise liquid measurement differentiations, as well as liquid detection for environmental protection, manufacture works, food and beverage regulations etc.The project is supported by the State Natural Sciences Fund (Project Number:60702004). This project aims to make the drop analysis experimental device become a practical instrumentation and to make some analysis of the experimental results of typical samples. It is the purpose of this project to introduce the systemic project of FCDA and the implementation technology of its components, to solve the problems in mechanical construction, data acquisition, signal processing and system control while merging fiber drop analysis (FDA) and capacitive drop analysis (CDA).The work of this thesis includes:(1)The processing circuit of fiber signal is introduced in detail, which includes light source modulation circuit, photoelectric conversion and preamplifier circuit, linear decrement circuit, opposite amplifying circuit and A/D conversion.(2) The processing circuit of frequency modulation capacitive signal is designed, which includes periodic circuit, frequency measurement circuit and interface circuit. Error analysis is taken into frequency measurement with pulse counting. The serial communication between the single-chip and the computer is introduced also.(3) Fiber-capacitive signal processing circuits are manufactured and debugged.(4) Some circuit experiments for system characteristics and stability are carried out. Software for data acquisition is programmed.(5)Experiments of typical samples are completed and qualitative comparison and analysis are presented.