Touch screens have become quite familiar things, especially with their existence in our daily life such as in smartphones, computers, ATMs, or grocery store checkouts. Moreover, businesses like restaurants have integrated touch displays for easy ordering and payment at the table itself. While individuals are constantly tapping and swiping screens, only a few know how these touch screen devices actually work.
Here are the facts to discover the technology behind interactive screens and how these touch screen technologies work.
Capacitive vs. Resistive Touch Screens
Since its introduction in the market, touch screen technology has gained tremendous advancements. As a result, today there are many different types of touch screens, but the most common ones with which the market is well-versed are capacitive and resistive touch screens.
Check out here how these technologies work for today’s demanding devices.
- Capacitive Touch Screens
Capacitive touch screen technology is the most common one and is used in smartphones, laptops and tablet displays. A capacitive touch screen is designed with multiple layers comprising two transparent conductive layers both having opposing traces or channels making up a gride pattern. The controller electronics sends an RF signal to each channel consecutively in the X or Y plane called the “excite” plane and listens for a return signal in the opposite plane called the “sense” plane. When the sensor is touched with a finger, it will “capacitively couple” one of the Y channels with an X channel. The X-Y touch position is determined by which channel is actively “excited” at the time and which channel in the opposite plane is “sensing” the RF through the finger touch position.
Capacitive touch screens offer brighter and clear displays and are significantly more responsive in comparison to resistive touch screens. Capacitive touch screens are popularly used in smartphones and tablets. In fact, they let the users experience life-like high-quality images. They also offer up to 10 simultaneous touches for multi-touch operations.
- Resistive Touch Screens
As the name suggests, resistive touch screens work with the resistance to touch. A resistive touch screen sensor uses pressure-activated analogue switch technology. It is designed with two conductive coated layers, usually, Indium Tin Oxide (ITO), facing each other and separated by a layer of tiny dielectric spacer dots. In 4-wire versions both layers have a conductive bus bar placed along two opposite edges. While one layer has bus bars located on top and bottom, bus bars on the other layer, are located on the left and right edges. The controller applies a DC voltage across one of the layers with the positive connection to one bar and the negative connected to the other, creating a voltage gradient through the conductive coating of that layer.
When a touch event occurs, the opposite layer comes in contact with the voltage layer, and the controller uses the opposite layer as a voltage probe to read the voltage at the touch point. The controller then determines whether the touch point is in plane X or Y.
To get to the other plane, the controller flips the functions of the layers so that the same happens but in X rather than Y or vice versa. This flipping of layer functions happens, typically more than 100 times per second, so the X and Y coordinate readings have no lag in reporting.
In 5-wire versions, the operation is similar, however, the voltage layer is always on the bottom with the top layer solely used as the voltage probe. There are no opposing buss bars on top and bottom layer but rather a linearity pattern on the bottom layer which allows the voltage to be applied in either the X or Y plane alternately.
Thanks to the hard PET layers, resistive touch screens are much more durable and economical to use than capacitive touch screens. However, resistive touch screens are not as transmissive as capacitive touch screens. Resistive touch screens are, typically used in ATM machines, ad displays, and POS (point of sale) terminals.
Final Thoughts
Every touch screen has distinctive strengths and weaknesses, making it a better selection for certain applications. However, when it comes to flexibility in functionality, capacitive touch screens are preferred over standard resistive touch screens as they lack the ability to register multiple touch points.
When you try to apply multiple touches on resistive touch screens, multiple touch points are very difficult to detect as their technology is based on recognizing pressure at a single specific location. But as we said earlier, touch screen technology has evolved with time, and that becomes more evident with A D Metro’s patented two-touch resistive touch screen controller.
A D Metro’s two-touch resistive touch screen controller with standard 5-wire resistive sensors becomes an ideal solution for Graphical User Interfaces (GUI) in applications that need to operate in environments that only resistive touch sensors can sustain but demand multi-touch capability. With 100 touch points per second for single touch and 70 touch points per second for multi-touch, this solution easily facilitates fast and smooth touch operations.
