Elements for a monolithically integrated rotation imbalance detector

The main focus of this paper is a description of a set of analog circuits, which are the essential parts of an integrated microsystem to detect imbalance in rotating machines. The system comprises an instrumentation transconductance amplifier at the front end, whose role is to provide an appropriate conditioning for the signal produced by an accelerometer that senses the vibration caused by the rotation motion of the machine and a pair of triangular- to-sine converters operating with a constant phase difference of 90 degrees. By multiplying the vibration transducer signal by the generated sine and cosine, the system determines the Cartesian coordinates of the imbalance vector. Auxiliary circuits like a bandgap reference and a pair of low-pass filters are also part of the system. All these elements were implemented in 0.6 μm CMOS using multi-project wafer services and fully characterized. Experimental results are presented and discussed.