Research On Capacitive Pressure Sensor Based On Havar Alloy Thin Film

Capacitive pressure sensor has widely used in industrial automation testing and monitoring fields because of its high sensitivity,low temperature resistance and stability in work.With the increasing in complexity and deterioration of industry environments,the traditional pressure sensor shows more and more limitations.Therefore,a pressure sensor using Havar alloy as the center diaphragm is proposed.It has superior strength,toughness,corrosion resistance and anti-magnetic compared with traditional stainless steel.The detective function on small measure range can be implemented,through the capacitor values' changes caused by Havar diaphragm's moving from external pressure.Furthermore,this paper is around the theoretical basis of differential pressure capacitive sensor for in-depth study and implementation on production process and testing.Central diaphragm is the core of capacitive pressure sensor,which directly affects on the sensitivity and resolution of the pressure sensor.In this paper,software ANSYS WORKBENCH was used to analyze the working characteristics of the diaphragm,then the graph of 2-D distribution shall be as a result from stress changed process.Based on the spacing between the two fixed plates and the maximum detection pressure,we can calculate the minimum allowable of the diaphragm.The diaphragm sensitivity was obtained by constructing the characteristic curve of the diaphragm center point deformation and the input pressure value.Finally,the alloy film's thickness is 50?m,and a diameter is 26 mm.In this paper,the circuit design for capacitive pressure sensor detection is based on sensitivity and other key technical indicators,which use the oscillator,limiter,frequency discriminator and amplifier circuits.The core is the C / F conversion and F / V conversion,it's means the sensor's weak capacitance signal is converted to voltage signal.The output of voltage signal from simulated tests can meet requirements.Furthermore,the circuit is also optimized to improve the detection performance and anti-EMC capability.Finally,the test cases with related conditions for capacitive-pressure sensor are determined,and the engineering prototype is tested to get the calibration data of this sensor.Through the data analysis,we can see that the actual results are close to the simulation.Therefore,the accuracy of the pressure model based on the Havar alloy diaphragm is verified.