The launch of Apple iPhone three years back made the touch screen popular in the mobile phones. Long back, before Apple, Nokia had flirted with touch screens but did not get the same success as Apple. Some people attribute the success of iPhone, apart from itunes, to its capacitive touch screen and its ability to support multi-touch. This article is an attempt to examine the difference between resistive and capacitive touchscreens.
Resistive Touch Screen
Resistive touch screens are composed of two flexible sheets coated with a resistive material and separated by an air gap or microdots. When pressure is applied to the screen, by a finger or other objects, the sheets are brought into electrical contact which causes a switch closure and a command is registered. The figure (source: Screen Tek) on the left shows how does a resistive screen works. Examples of resistive touch screen phones are Nokia 5800 Samsung Omnia, etc.
Cost effective and duarble
Can work in all climate conditions and in any environment like the restaurants, hospitals, etc.
Input can be made using a stylus or finger. However, stylus is better suited.
Less sensitive to scratches as compared to capacitive screens
Normally does not support multi-touch though Nokia has announced that on its handsets, multi-touch would be supported on both resistive and capacitive touch screens
Recalibration might be required over time as resistive touch screens are known to drift over time. However, this is a simple process and can be performed by users by a simple dot mapping.
While using fingers, slightly more pressure needs to be put on the screen
Provides only 75% optical transparency which means that its clarity is lower than capacitive touch screen
Capacitive Touch Screen
A capacitive touchscreen panel consists of an insulator such as glass, coated with a transparent conductor (mostly indium tin oxide). As the human body is also a conductor, touching the surface of the screen results in a distortion of the body’s electrostatic field, measurable as a change in capacitance. Unlike its resistive counterpart, capacitive touch screens must be touched by a human finger or some sort of conductive device being held by a human hand. The figure on the right from Electronic Design shows how does capacitive screens work. Examples of devices with capacitive touchscreens are the Apple iPhone and the T-Mobile G1. Advantages:
Higher clarity display (up to 90% optical transparency)
High touch resolution
Needs a human finger to register input. It is not possible to use this screen wearing gloves
Cannot be used in all weather scenarios
Which touch screen is better?
The type of touchscreen that a device needs depends on the circumstances in which the device would be used but for the mobile phones, it is now clear that the user experience is much superior on capacitive touchscreen (even my opinion on this has changed over the years). The penetration of touchscreens in the mobile phones would continue to increase but in the low end of the mobile phone, it would be constrained by higher cost of capacitive touchscreens. Consumers certainly do not want resistive touchscreens.
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Mohit is a telecom professional with rich experience over 15 years. His expertise is in the area of strategy and planning and his work experience includes stints with two of Big 5 consulting organizations, a telecom operator and a handset vendor. Mohit can be reached at firstname.lastname@example.org