Resistive Touch Screens
The Resistive Touch Screen is the preferred solution for low-cost applications. It consists of a conductive bottom layer of either glass or film and a conductive top film layer, separated by transparent spacer dots. A voltage is applied to the conductive surface. When pressure is applied to the top layer, it is deflected and makes contact with the bottom layer resulting in a voltage change. This change is detected by the controller.
This technology is functional and economical for industries and applications such as food service, industrial controls, point-of-sale (POS), and handheld devices.
Resistive Touch Screen Features:
§ Activation by finger, glove, or stylus
§ High touch point resolution
§ Low power requirements
§ Value solution
§ Reduced optical clarity
Capacitive Touch Screens
Capacitive touch screens have an all-glass construction with greater than 9H surface hardness. A transparent conductive indium tin oxide (ITO) coating is distributed over both sides of the glass substrate. An electrode pattern is printed around the perimeter of the glass to generate an alternating current over the top conductive layer. The touch of a conductive probe draws the current to the specific point of contact. The controller then calculates the location of the touch.
Capacitive technology provides durability, reliability, and enhanced optical clarity. However, it is restricted to touch sensitivity by conductive materials such as a bare finger or capacitive stylus. Popular industry applications include casino gaming machines, industrial equipment, ATM machines and point-of-sale (POS) kiosks.
The unique ability of this technology, is that it allows for multiple zones of touch to occur simultaneously. This can be accomplished due to an invisible grid of sensors on the back of the substrate that map the location of all fingers that come in contact with the screen. The grid pattern detects location of touch by determining relative levels of current within the matrix.
Capacitive Touch Screen Features:
§ Activation requires either bare finger or capacitive stylus
§ Extremely durable
§ Excellent optical clarity
§ Good resolution
§ Very accurate
Surface Acoustic Wave
This technology is best suited for kiosks and Point of Purchase displays. It relies on piezoelectric transmitters and receivers arrayed along the edges of the touch screen. They transmit and receive signals at once, by converting the signal into ultrasonic waves. When you touch the screen, the waves fan out, are absorbed by the array of traces around the perimeter of the screen, and a touch event is directed to the point.
Surface Acoustic Wave Touch Screen Features:
§ Most widely used touch technology
§ Activation by finger, soft conductive stylus or some gloves
§ Low Cost and wide range of sizes
Touch Screen Technologies:
§ Projected Capacitive
§ Surface Acoustic Wave (SAW)
Touch Screen Design Considerations
When considering a touch screen application, use the following questions to help determine the right technology for you:
§ Interface – What type of touch interface do you need, finger, gloved finger, both, or stylus?
§ Options – Do you need touch buttons, drag and drop, or signature capture?
§ Display Clarity – Is optical clarity a high consideration?
§ Environmental - Will the touch screen be exposed to chemicals, liquids, or extreme weather conditions?
§ Cost - What are your cost considerations?
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