Development of clamped-clamped beam type piezoelectric sensor for vacuum pressure measurement

• Main Authors: Che-Yu Lin, 林哲宇
• Other Authors: Chia-Che Wu
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/45619720375140636940

碩士 === 國立中興大學 === 機械工程學系所 === 100 === 　　In this thesis, a clamped-clamped beam type piezoelectric vacuum pressure sensor was developed. The piezoelectric beam fixed at both ends consists of a PZT layer perfectly bonded to the copper substrate. The dimensions of the PZT layers and copper substrate are both 20mm × 5mm × 200μm. Two pairs of electrodes cover the surfaces of the PZT at the bottom and top layers near both ends. Input voltage was applied at one pair of electrodes to vibrate piezoelectric beam and output voltage was measured at the other pair of electrodes. 　　Experimental results showed that developed pressure sensor has a wide range from 6.5×10-6 to 760Torr. Output voltage generated by vibrations of beams which were varied by viscous gas damping forces acting on the beams in the vacuum. Damping forces can be calculated from damping ratio by half power method experimentally. Damping ratio of sensor includes the effect of strain rate damping and viscous gas damping. The strain rate damping is assumed to be proportional to the bonding stiffness of beam and gas damping is assumed to be changed by the pressure. Experimental results showed that output voltages of sensors were proportional to gas damping ratio. It indicated vacuum pressures can be estimated from output voltage. Vacuum pressures of nitrogen and argon are also compared. Experimental results showed that the gas damping ratio of argon is greater than the damping ratio of nitrogen. Piezoelectric outputs and damping ratios are in the same trend with the vacuum pressures.