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Wiley Encyclopedia of Biomedical Engineering, 6-Volume Set is a living and evolving repository of the biomedical engineering (BME) knowledge base. To represent the vast diversity of the field and its multi-and cross-disciplinary nature and serve the BME community, the scope and content is comprehensive. As a peer reviewed primer, educational material, technical reference, research and development resource, the project encompasses the "best" in terms of its intellectual substance and rigor.
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comprised of a piezoelectric crystal supporting a small mass. Acceleration produces a force proportional to the mass, which causes a change in the electrical output of the piezoelectric crystal. Piezoresistive accelerometers measure the force produced by the acceleration of an internal mass by the change in resistance of the material (often silicon based) when a force is applied to it. Recently developed thermal accelerometers do not use a mass/spring configuration, but instead sense acceleration by changes in heat transfer between micromachined elements within a small, insulated space. ACCELEROMETERS LISA BENSON Clemson University Clemson, South Carolina 1. INTRODUCTION Acceleration is the rate of change of either the magnitude or the direction of the velocity of an object, and it is measured in units of length per time squared (i.e., m/s2) or units of gravity (g) (1 g ¼ 9.81 m/s2). Devices that measure acceleration, or accelerometers, are used in highperformance devices such as missile guidance systems, airbag deployment systems in automobiles, in handheld electronics, as well as in biomedical applications such as motion analysis or assessment of physical activity. In the most general terms, an accelerometer consists of a mass, spring, and damper. The acceleration of the mass is measured by the deformation of the spring, and oscillation of the spring is