Research On Adaptive Composite Multilayer Scanning Capacitive Sensor

With the widely application of inexpensive and simple-structured capacitive level sensor in various fields of level measurement,the capacitance-detection-based level value method is often affected by many unstable factors,such as the dielectric constant of measured liquid,the external environment and so on.These unstable factors lead capacitive level sensor to many defects.In order to improve the measurement accuracy of capacitance sensor in measuring liquid,this thesis designs a new type of capacitive level sensor with a multilayer structure.To add the extensibility of sensor with limited layers,the thesis designs a sensor with multilayer frame of reference.The top layer and the bottom layer of the new sensor adopt self-reference form to achieve capacitor self-calibration.The new sensor also adopt a double-evaluation system to ensure the accuracy of the limit level measurement results.The thesis describes the types and the working principles of common level measurement instruments and analyzes a variety of level measurement methods,which mainly discusses the structure and working principles of the capacitive level sensor.The thesis analyzes the defects of traditional capacitive level sensor in conducting level detection.Based on the design of traditional capacitive level sensor,our new sensor featured an optimized-structure and an improved level algorithm.The thesis designs a new type of coaxial cylinder structure of capacitive level sensor.A level calculation method,which is independent of dielectric constant of measured liquid,is proposed.The thesis uses a dual evaluation system to process the data,which can effectively improve the accuracy of the sensor.The proposal of the gain adaption has expanded the permittivity adaptation range of the sensor and makes the adaptive medium possible,and it can also increase the capacitance value measurement range.Matlab is used to build and analysis sensor model.Meanwhile this thesis adopts BP to correct the nonlinearity of sensor.The thesis makes a detailed discussion on production process of capacitive level sensor from both hardware and software respectively.In order to simulate different media,the thesis respectively uses water and diesel fuel for level measurement experiments.Experimental results show that the method achieves the level measurement with independent media and verifies the effectiveness of the research results.