ABSTRACT
Sensors convert a physical signal into an electrical signal that may be manipulated symbolically on a computer. A wide variety of sensors have been developed for aerospace, automotive, and robotics applications (Fraden, 2003). Continual innovations in manufacturing and reductions in cost have allowed many sensing technologies to find application in consumer products. An interesting example is the development of the ubiquitous computer mouse. Douglas Engelbart’s original mouse, so named because its wire “tail” came out of its end, used two metal wheels and a pair of potentiometers to sense the wheels rolling over a desk surface. Soon, mice used a ball and a pair of optical encoders to convert the movement of the hand into digital signals indicating precise relative motion. Now, even the most inexpensive mice employ a specialized camera and image processing algorithms to sense motions at the scale of one onethousandth of an inch several thousand times per second. Accelerometers, devices that sense acceleration due to motion and the constant acceleration due to gravity, are another interesting example. Today’s tiny accelerometers were originally developed for application in automotive air-bag systems. Digital cameras now incorporate accelerometers to sense whether a picture is taken in landscape or portrait mode, and save the digital photo appropriately. Many laptops with built-in hard disks also include accelerometers to detect when the laptop has been dropped, and park the hard drive before impact. Meanwhile, mobile phone manufacturers are experimenting with phones that use accelerometers to sense motion for use in interaction, such as in-the-air dialing, scrolling, and detecting the user’s walking pattern.
