HB Blog 112: Resistive VS Capacitive Touchscreen.

A touchscreen is an input device normally layered on the top of an electronic visual display of an information processing system. A user can give input or control the information processing system through simple or multi-touch gestures by touching the screen with a special stylus and/or one or more fingers.

There are a variety of touchscreen technologies with different methods of sensing touch.

1. Resistive
2. Surface acoustic wave
3. Capacitive
4. Infrared grid
5. Infrared acrylic projection
6. Optical imaging
7. Dispersive signal technology
8. Acoustic pulse recognition

Resistive Touchscreens: -

A resistive touchscreen panel comprises several layers, the most important of which are two thin, transparent electrically-resistive layers separated by a thin space. These layers face each other with a thin gap between. The top screen (the screen that is touched) has a coating on the underside surface of the screen. Just beneath it is a similar resistive layer on top of its substrate. One layer has conductive connections along its sides, the other along top and bottom. A voltage is applied to one layer, and sensed by the other. When an object, such as a fingertip or stylus tip, presses down onto the outer surface, the two layers touch to become connected at that point: The panel then behaves as a pair of voltage dividers, one axis at a time. By rapidly switching between each layer, the position of a pressure on the screen can be read.

Advantages of Resistive Touchscreen

1. Low production cost.
2. High resistance to dust and water.
3. Best used with a finger, gloved hand or stylus.
4. Best suited for handwriting recognition.

Disadvantages of Resistive Touchscreen

1. Not too sensitive, you have to press down harder.
2. Poor contrast because of having additional reflections from extra layer of material placed over the screen.
3. Does not support multi-touch.

Capacitive Touchscreens: -

A capacitive touchscreen panel consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (InSnO). As the human body is also an electrical conductor, touching the surface of the screen results in a distortion of the screen's electrostatic field, measurable as a change in capacitance. Different technologies may be used to determine the location of the touch. The location is then sent to the controller for processing.

Advantages of Capacitive Touchscreen

1. Because capacitive touchscreen has glass layer instead of plastic, it looks brighter and sharper.
2. Highly touch sensititive and doesn’t need a stylus.
3. Supports multi-touch.

Disadvantages of Capacitive Touchscreen

1. Because the technology is dependent on the conductive nature of human body, it doesn’t work if the user is wearing gloves.
2. Because of having a complex structure, these are quite expensive.
3. Glass is more prone to breaking.

To understand what is inside the mobile phone you can follow my blog Inside The Mobile Phone.