Miniature free-fall sensors

This paper describes an attempt to integrate the smart structure concept to the field of high-density data storage devices such as magnetic disk drives, optical disk drives, CDs compact disks), and DVDs (digital versatile disks), etc. With the rapid development of the data storage industry, methodologies that can be used to sense vibration, free-fall, and impact have been actively pursued throughout the last two decades. As data storage devices are now moving into portable applications, early detection of impact or free-fall has increasingly become more important. Based on this major issue, the concept of measuring the motion of the required free-fall is re-examined. In this article, it is shown that a fundamental characteristic of a free-fall motion, which is the acceleration from zero to one in gravity unit, will be introduced to provide the warning signal for data storage devices. The design concept and the experimental result of this miniature free-fall sensor will be detailed.