issue: July 2006 APPLIANCE Magazine Supplier Solutions: Switches and Switching Devices Sensor Selection 101: Types of Touch Panels	Share  Printable format  Email this Article  Search
by Jill Russell, Senior Associate Editor

As more appliances are designed with graphical LCDs, controlling the appliance directly from the LCD is now a valid option. By integrating controls that can be activated directly on the LCD, designers have the ability to decrease, if not eliminate entirely, mechanical controls such as buttons, switches, and knobs—thus creating a cleaner look. The two main touch panel technologies are analog resistive and capacitive.
Analog resistive touch panels are one of the most common type of touch panels. They have the advantages of being less costly than capacitive touch panels, and can be activated by anything that points, such as a finger or stylus. They also have near pixel level precision of their “hot spots,” allowing user interface designers to place “hot spots” anywhere on the LCD. However, they do have the disadvantages of possibly being damaged by sharp objects, and have an average of 80-percent clarity compared to regular glass. Additionally, calibration can drift over time, thus requiring customer calibration. Analog resistive touch panels are good choices when cost is important, if the user is expected to be wearing gloves, or if pixel level precision is required.
Capacitive touch panels have the advantages of a higher clarity than analog resistive touch panels and generally do not require user calibration. They are also resistant to, and not affected by, surface scratches on the panel. However, capacitive touch panels are typically more expensive, in part due to the necessity of a specialized capacitive touch panel decoder. They must be touched by a bare finger (without gloves or other pointing devices), and they usually only have a pre-defined grid of “hot spots” instead of allowing for pixel level precision. Capacitive touch panels are good choices if clarity and scratch resistance is paramount.
The above are only generalities. For instance, a new technology is coming out that is allowing pixel level precision on capacitive touch panels, thus removing that advantage of the analog resistive over the capacitive.

This information was provided by Jim Weber, senior firmware engineer, Amulet Technologies