The Research On The Capacitive Displacement Measurement System And The Embedded Application

Capacitive grating displacement sensor is the application of capacitive sensor in the field of wide range displacement measurement.Capacitive grating sensor realizes periodic coupling of capacitive and enlarges the measuring range of capacitive sensor by the design of stir grid and fixed grid's structure.Compared with other displacement sensors,the advantage of capacitive grating sensor is that it can be resetted at any position.So capacitive grating sensor can effectively overcome the drawbacks of the zero loss of mechanical measuring tools after long term use.In addition,capacitive grating sensor has the merits of small cubage,low quality and low power and it has been applied in the field of measurement and inspection,such as digital caliper,CNC machine tools and so on.This thesis aims at the carbonization depth measuring instrument by studying linear capacitive grating sensor.Firstly,it analyses the present situation at home and abroad in the research and development of capacitive sensor and uses the equivalent-circuit way to study the mathematical model of capacitive grate transducer To optimize the design of the sensor and to determine the most suitable design of capacitive grid sensor's stir grid and fixed grid by ansoft maxwell software.The realization scheme of analog circuit for amplifying and filtering the output signal of capacitive grating sensor is completed.Based on the depth analysis of the measuring mechansim,we chooses the MCU STM32F103 as the control core and programmable logic device CPLD chip EPM3032 as the core of digital phase discrimination.The schematic diagram and PCB design of hardware circuit are completed in Altium Designer.In addition,according to the actual functional requirements of carbonation depth measuring instrument,A complete software architecture of embedded system is presented,including screen display,key control,metric-inch interconversion,etc.Experiments show that the measurement scheme performs well in functional verification and the linear output characteristic is good by reasonably setting the parameters of the grid pole plate of the grid sensor.The error sources of the measurement system are briefly analyzed and corrected.Capacitive grating displacement sensor has great application prospects in the field of building detection instruments.Using the microcontroller STM32 and CPLD repeating the programmingcharacteristics,reduce the development cost,and leave room for the next step upgrading of the product.