High Performance, Low Cost and Compact Accelerometers/Seismometer Based on Asymmetrically Gapped Cantilever

Accelerometers hold great potential in geophysics application such as seismometer. They are light in weight, built compactly and can save the power consumption of measuring instrument. Moreover, their small distortion in phase spectrum and linear response in low frequency band are greatly desired in ground motion measurements as well. In this paper, we developed an accelerometer based on asymmetrically gapped cantilever for seismometer application. The accelerometer is based on an asymmetrically gapped cantilever which is composed of a bottom mechanical layer and a top piezoelectric layer separated by a gap. Compared with conventional cantilever, the asymmetrically gapped cantilever helps to increase the sensitivity and enables the majority of mechanical energy to be effectively used to strain the piezoelectric layer. The overall energy conversion efficiency of air-spaced cantilever reaches over 90% while it is only 30-40% for conventional piezoelectric cantilever. The prototype of the piezoelectric accelerometer with a resonant frequency of 1100Hz is designed and characterized. The size of the prototype sensor is 30mm×18mm×5mm. A sensitivity of 86V/g and a resolution of 40ng/√Hz are obtained. The sensor shows superior results compared with commercial accelerometer. For accelerometers with the same structure, by lowering the resonant frequency to 10~100Hz, the estimated resolution will be further increased to above 4ng/√Hz.