Touchpad: Difference between revisions

Revision as of 06:06, 22 January 2007

Revision as of 06:06, 22 January 2007

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A '''touchpad''' is an input device commonly used in [[laptop computer]]s. They are used to move the [[cursor (computers)|cursor]], using motions of the user's finger. They are a substitute for a [[computer mouse]]. Touchpads vary in size but are rarely made larger than 20 square [[centimeter]]s (about 3 square [[inches]]). They can also be found in PDAs.

'''Touchpads operate by sensing the [[capacitance]] of a finger''', or the capacitance between sensors. Capacitive sensors are laid out along the horizontal and vertical axes of the touchpad. The ___location of the finger is determined from the pattern of capacitance from these sensors. This is why they will not sense the tip of a pencil or other similar implement. Gloved fingers may be problematic (such as in a cleanroom environment) but can sometimes work. Moist, sweaty, or calloused fingers can be problematic for those touchpads that rely on measuring the capacitance between the sensors.

Touchpads are relative motion devices. That is, there is no [[isomorphism]] from the screen to the touchpad. Instead, relative motion of the user's fingers causes relative motion of the cursor. The buttons below or above the pad serve as standard [[mouse (computing)|mouse]] buttons. Depending on the model of touchpad and drivers behind it, you may also click by tapping your finger on the touchpad, and drag with a tap following by a continuous pointing motion (a ''click-and-a-half'').