The Study Of Low Pressure Ceramic Capacitive Pressure Transducer

A novel low mechanical hysteretic ceramic capacitive pressure transducer has been made, by using of ceramic sealing technology; integrate circuit (IC) technology and thick film plane fixing circuit technology. This transducer is made of a deformable ceramic diaphragm and a ceramic base plate, between which has an air cavum. A coaxial gold electrode was fired onto the diaphragm and the base plate. So two capacitors were formed. The capacitance was changed due to deformation of the diaphragm by an external pressure, and then the capacitance was switch to a DC voltage signal by a hybrid circuitry.By mean of the CaO-MgO-Al2O3-SiO2 diagram,the chemicals of neon-size grade comprising CaO,MgO,Al2O3, SiO2, ZrO2 and Y2O3 were used as the starting materials. A high quality rein- toughed ceramic diaphragm was acquired. And the mechanism was discussed.The form of the gold electrode was designed so as the reference capacitor Cr can correct the non-linearity of the main variable capacitor Cp.The characterization on absorbability and erosive-proof to ceramic of gold conductive sol was studied.In order to obtain a high insulting film on the electrode of the base plate, the process and mechanism of sol -gel was emphasized. It was found that the thickness of the film can improved with adding some mucilage glue. A low temperature sinter can acquire a transparent SiO2 film on the gold electrode. And so on, the method of CVD and PVD were also discussed.Through the theoretical calculation and experimental results, the distance between the diaphragm and the base plate was optimize, which will touch in case of over loading. The damage of the transducer was avoided, so the ability of over -loading can be improved highly.In order to acquire a good hermetic seal between the diaphragm and the base plate, two sealing methods were used, namely, compound method and crystallite method. A hybrid circuitry was designed, so as the capacitancesignal can be transited to the DC signal directly, and considering the temperature compensation and linearity correction.In conclusion, the capacitive pressure transducer possesses many advantages, including: high precision, erosion-proof and the ability of over-loading. It is the most advanced pressure transducer, which will fill up the lacuna of our country.