An integrated Surface micromachined capacitive lateral accelerometer with 2 uG/rt-Hz resolution

ABSTRACT A capacitive position measurement interface minimizes noise from parasitics in the electromechanical interface and uses correlated double sampling to achieve better than 10 -3 A/√Hzdisplacement resolution. This translates into 2µG/√Hzacceleration resolution when the device is operated in a vacuum. INTRODUCTION Surface micromachined accelerometers are finding widespread commercial use [ 1,2 ] in automotive and industrial applications. However, owing to the small proof-mass, the resolution of present devices is limited to 100µG/√Hz or more. Substantially better performance is achievable with bulk micromachined devices [ 3-6 ], albeit at the expense of a much larger proof-mass and more expensive fabrication technology. This paper analyzes the factors governing accelerometer resolution to design a surface micromachined device with a noise floor of 0.75µG/√Hz from electronic sources only. When operated in a vacuum to minimize Brownian noise, 2µG/√Hz acceleration resolution is achievable, which is comparable to the performance of bulk-micromachined parts.

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