Embedded Accelerometers Provide 3-D Vibration Sensing

Embedded systems, already present in many medical devices, are becoming increasingly important in the development of new technologies. To keep up with growing demand, developers are creating more intelligent, more flexible, and more portable systems. Accelerometers, pressure sensors designed to receive and output motion and inertial data, are becoming prevalent in the medical device industry because of their ability to provide real-time information. Made by bulk micromachining then surface etching silicon wafers, accelerometers are smaller than mechanical sensors, have no moving parts, and are easily incorporated into circuitry.

Offered by Motorola Semiconductors (Phoenix), the MMA1220D low-acceleration sensor's applications include vibration monitoring and recording for use in physical therapy, rehabilitation, and safety equipment. According to marketing manager Raul Figueroa, the acceleration sensor is "signal conditioned and can be directly interfaced with a icrocontroller. The small surface-mount package lends itself to high-volume manufacturing and portable system design." The device consists of a capacitive sensing cell and a CMOS signal-conditioning, application-specific integrated circuit in a hermetically sealed package. Special features include an onboard four-pole switched capacitor filter, self-testing capabilities, ratiometric performance, and fault detection circuitry.

Katherine Sweeny