Exercise 7.1 Smart screen interface case study

There are a number of types of touchscreen technology.

Resistive touchscreen

A resistive touchscreen panel is composed of several layers, the most important of which are two thin, metallic, electrically conductive layers separated by a narrow gap. When an object, such as a finger, presses down on a point on the panel's outer surface the two metallic layers become connected at that point: the panel then behaves as a pair of voltage dividers with connected outputs. This causes a change in the electrical current which is registered as a touch event and sent to the controller for processing. Resistive touchscreens can also support Multitouch.

Surface acoustic wave

Surface acoustic wave (SAW) technology uses ultrasonic waves that pass over the touchscreen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touchscreen panels can be damaged by outside elements. Contaminants on the surface can also interfere with the functionality of the touchscreen.

Capacitive

Capacitive sensing

A capacitive touchscreen panel consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (ITO). As the human body is also a conductor, touching the surface of the screen results in a distortion of the local electrostatic field, measurable as a change in capacitance. Different technologies may be used to determine the location of the touch. The location can be passed to a computer running a software application which will calculate how the user's touch relates to the computer software.

http://en.wikipedia.org/wiki/Touchscreen

The example I use is electronic banking. You can either interact with your account using the internet or an Automatic Teller Machine (ATM). While the internet account means you can manage your account from any web connect computer including your home or an internet cafe anywhere in the world, you cannot get cash from the internet account. ATMs are well distributed across major world cities and can provide cash very conveniently. However, their dedicated functionality means managing account details (other than getting balances) is very clumsy and not user friendly.