Talking just about capacitive touchscreens, there are multiple ways to determine where you touched the screen.
- Surface Capacitive: This approach uses a screen that is made up of a conducting layer and an insulator on top (basically 2/3 of a capacitor). Voltage is applied and can be measured at each of the comers. When your finger (or another conductor) touches the screen, it acts as the final third of the capacitor and changes the voltage at each of the corners (1). How much the voltage changes at a given corner is related to how far away your touch was so the ratio of voltages can determine the location you touched (1). While this method is relatively simple, it is very touchy (is a bad way for a touchscreen – i.e. it may register so changes from you being close to other parts of the screen without even touching them), it isn’t touchy enough (it can only register one touch at a time which wouldn’t allow gestures that many touchscreens use), and it’s not very precise.
- Projected Capacitive: This approach works kind of like an LED array in reverse (assuming you know how that works). Like the surface capacitive touchscreen, a conducting layer is covered by an insulator to make 2/3 of a capacitor (2). However, the conducting layer only consists of gridlines instead of a full screen. A known frequency is applied to the grid. When your finger completes the capacitor, it changes the frequency of the grid. The x and y coordinates with the peak change in frequency correspond to the location that you pressed (2). Projected capacitive touchscreens allow multi-touch and are more precise that surface capacitive ones due to the gridlines (1). Both surface and projected capacitive touchscreens are durable and able to withstand relatively harsh environments because the insulating layer protects the conductive layer. Also, both can be made to be sensitive enough to process input from a finger that is close but not in contact with the screen (1). Two forms of projected capacitive touchscreens are mutual and self-capacitive.
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- Mutual Capacitive: These touchscreens involve two layers for the conducting grid: a driving and a sensing layer (3). Because the capacitor at each intersection of the grid is independent, two fingers can accurately be tracked as they move on the touchscreen (3).
- Self-Capacitance: These only involve one layer for the conducting grid (3). In order to accurately track two fingers using self-capacitance technology, two layers are needed (3).
Summary: your finger is a third of a capacitor (no, that doesn’t mean you can use three of your fingers together to make a full one). When you touch a touchscreen, it can tell that its two-third capacitors were completed and the flow of electricity is affected in a way that can be decoded.
I must have missed something - what kind of Christmas list is this!
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This blog is all about the capacitive touchscreen PCs. We can determine what touchscreen technologies being used in one device. It describes well on how to know what type of touchscreen technology it is. We can do two approaches for us to know what type of capacitive touchscreen PC. The surface capacitive approach use a conducting layer and an insulator on top. It normally uses a 2/3 of a capacitor that is applied a voltage to measure each of the comers of the screen layers. Based in the blog, this approach will not give you an accurate output to use. The projected capacitive touchscreen PC is coated with a layer by an insulator to make 2/3 of capacitor. But, its conducting layer only contains of gridlines instead of a full screen. A human finger can only manipulate the screen. Then, if the capacitor will be completed, it will change frequency of the grid. Projected capacitive touchscreen PCs are more accurate and allow multi-touch than surface capacitive. Many important information we need to know in this blog. Thanks for sharing this one.
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