A LINEAR ELECTROMAGNETIC ACCELEROMETER

A linear electromagnetic accelerometer has been designed and fabricated from Si (100) wafers using silicon micromachining techniques. The amplified output voltage of the fabricated device for accelerations ranging from 0 to 50g is measured and the results are in good agreement with computer simulations. The actual size of the device is 4.2 mm X 4.2 mm, its amplified output voltage varies linearly from 0 to 9 V at a rate of 0.175 V/g and the power consumption is less than 2.5 mW, The device structure consists of two planar coils of 12 turns each and a seismic mass supported by two cantilever beams. The principle of operation is based on the variation of mutual inductance between the coils, caused by acceleration forces. This dual-beam structured accelerometer responds linearly to the acceleration force normal to the plane of the mass and the supporting beams; lateral accelerations have almost no effect on the output voltage. Due to the simple structure, batch processing with on-chip signal-conditioning circuitry is possible. The electronic circuitry required is much simpler compared to that for capacitive accelerometers.