The construction of a frequency-change-type single-crystal silicon two-axis acceleration sensor is proposed and is designed using the finite-element method. The sensor element is composed of two developed bending vibrators, a mass and support bars. The volume is about 4.0×4.2×0.5 mm3. The 1st out-of-plane vibration mode in the vibrator is used here, and the resonance frequency is about 80 kHz. The analyzed relationship between the applied acceleration and the resonance frequency change becomes linear in this sensor construction. A sensor sensitivity of about 468 ppm/G is realized. When acceleration is applied, the sensor mass moves in parallel along the x- and y-axes and does not rotate. Therefore, the linearity of sensor sensitivity with respect to the applied acceleration is consistently maintained.
The operation of the frequency-change-type two-axis acceleration sensor utilizing the phenomenon that the resonance frequency of a bending vibrator changes by the axial force is confirmed experimentally. The sensor is composed of two developed bending vibrators, a mass, support bars, and a frame for fixation. The experimental sample of the sensor is made of stainless steel and the volume is about 90.0 ×95.8 ×10.2 mm3. The first out-of-plane mode of the vibrator is used here and the resonance frequency is about 1,687.8 Hz. The vibrator is driven electrically by small piezoelectric ceramics. The relationship between the applied acceleration and the resonance frequency change was analyzed using the finite-element method, and then measured in the gravitational field. As a result, the analyzed characteristics of the sensor agreed with the experimental ones.
In this paper, the characteristics of the acceleration sensor utilizing the resonance frequency change in the flexural vibrator are examined experimentally. The sensor sample was produced using stainless steel. It was confirmed that the relationship between the applied acceleration and the resonance frequency change becomes linear and almost coincides with the theoretical value by the finite element analysis. The sensor sensitivities of approximately 2800 ppm/G and 2150 ppm/G are measured in the cases of using the 1st and 2nd modes, respectively. It was clarified experimentally that the spurious vibrations do not appear in the vicinity of the resonance frequency f
0. Moreover, it is shown that this sensor can also be used as an inclination angle sensor.
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