Small Capacitance Detection System

Along with the rapid development of MEMS technique in recent years, the widely use of MEMS capacitive sensors and also the research of MEMS integrated circuits, the detecting study of tiny capacitance and its slight change is of great significance. Tiny capacitance detection theroies and methods are to be studied in this paper.This paper is for the tiny capactance detection beased on a chip AD7746 developed by AD company in March 2005. Following the on-site detection and controlling requirements against tiny capacitance for micro-mechanical devices and systems, MCU control and LED display are adopted to realize the accurate measurement and the error compensation of tiny capacitance. Starting from October, 2005, this program is the first research related with AD7746 at that time. This article makes some exploration on the internal principles and relative testing evalution board of AD7746 chip and finds out the A/D testing principles and D/A computing formula by ways of a in-depth analysis of evalution board, which helps forming the tiny capacitance detection methods on the basis of MCU and also determining the system's performance.The schematic design diagram, PCB design, printed board, assembly, software programing and also system debugging of tiny capacitance detection system including application test and data analysis of design system are all illustrated in this paper. Besides, some scalability design study are also given in the design process following the chip characteristics—multi-functional, such as accurate measurement of tiny vlotage, temperature measurement, etc. Moreover, to make it meet the needs more properly, this paper gives a systematic minilized design and research, which helps improve the system function.