HOW THEY WORK
How do the Different Types of Touch Systems Work
Projected capacitive touch sensors are made up of three major components: the sensor glass, cover glass, and flexible printed circuit including either an I²C or USB controller. The sensor glass is made up of a series of electrodes, composed of a transparent conductive coating, that are configured into rows and columns. Each electrode is routed back to a connected point where the circuit can be bonded. The cover glass buries the electrodes within a stack of lamination, and serves as a dielectric between your touch and the electrodes of the sensor glass. The cover glass also serves as a barrier layer- protecting the sensitive electrodes from environmental and human damage. By using complex algorithms to pull a small charge from the electrodes, the controller can determine the exact location of your touch. As a result, when your finger touches the surface of the cover glass, the controller can scan and monitor the electrodes it produces. Key benefits of projected capacitive touch are, up to 10 simultaneous touches, wear resistant cover glass, seem less mounting and an exceptional optical performance.
Often used: Mobile Phones, Computer Tablets, Data Capture Devices, Specialist Instrumentation.
4-Wire Resistive overlay technology consists of a glass overlay with a thin metallic coating, over which a transparent layer of polyester (coversheet) is placed. The polyester layer has a similar metallic coating on the interior surface. Tiny clear spacer dots of non-conductive polyester prevent the two surfaces from contacting each other. A final hardcoating is applied to the external surface of the polyester to reduce damage from sharp styli. A current is pulsed through the glass overlay along the x and y axis, when a finger or other stylus presses the two layers together, the current is shunted and the control electronics determine the co-ordinates of the touch location, which are then transmitted to the host computer.
Often used: Hand-Held Instruments, Electronic Point of Sale (EPOS) systems, restaurant systems and workplace applications.
5-Wire Resistive overlay technology is very similar in design and make up to the 4-Wire technology; it again consists of a glass overlay with a thick polyester coversheet separated by transparent insulating dots. A current is pulsed through the glass overlay along the X and Y axis which in the 5-Wire technology are on the glass substrate. When the two surfaces are pushed together the current is shunted and the touch controller determines the X and Y co-ordinates which are transmitted to the host computer. Due to the make up of the 5-Wire construction it is more rugged than its 4-Wire counter-part.
Often used: Electronic Point of Sale (EPOS) systems, restaurant systems and workplace applications.
Scanning Infrared (IR) technology relies on the interruption of an IR light grid in front of the display screen. The touch frame or opto-matrix frame contains a row of IR-light emitting diodes (LEDs) and photo transistors, each mounted on two opposite sides to create a grid of invisible infrared light. The frame assembly is comprised of printed circuit boards on which the opto-electronics are mounted and is concealed behind an IR-transparent bezel. The bezel shields the opto-electronics from the environment while allowing the IR beams to pass through. The integral IR controller sequentially pulses the LEDs to create a grid of IR light beams. When a stylus, such as a finger or pen, enters the grid, it obstructs the beams. One or more photo transistors detect the absence of light and transmit a signal that identifies the X and Y co-ordinates.Often used: Industrial Process Control, ATM’s, and Gaming/Casino Machines, Medical Instrumentation, Public Information Kiosks.
Surface Acoustic wave technology is based on transmitting acoustic waves across the surface of a glass overlay placed over the display surface. A transducer mounted on the edge of the glass emits the acoustic wave, which travels along the surface of the glass overlay and is reflected back across the overlay. Since the speed of the wave is known and the size of the glass overlay is fixed, the first reflector will send the first signal back first, then the second and so on. When a stylus such as a finger comes into contact with the wave, it attenuates the wave motion by absorbing part of the wave. This is detected by the control electronics and determines the touch location.Often used: Gaming Machines, Medical Instrumentation, Public Information Kiosks.
Capacitive overlay technology uses a glass overlay with a thin metallic coating over the surface of the display screen, a small amount of voltage is applied to all four corners of the overlay. The user must touch the overlay with a conductive stylus, such as a finger, to activate the system. Touching the overlay surface causes a capacitive coupling with the voltage field, drawing a minute amount of current to the point of contact. The current flow from each corner is proportional to the distance to the finger and the ratios of these flows are measured by the touch controller and used to locate the touch.Often used: Gaming/Casino machines, Electronic Point of Sale (EPOS) systems, restaurant systems, industrial applications, workplace applications and in public kiosks/shopping centres.
Ultra Touch Resistive overlays are revolutionary in their design, they are based on the same technology as 5-Wire Resistive however with the use of advanced materials engineering the front flexible polyester film usually associated with resistive touch technology has been replaced by a flexible glass/polymer laminate. This means that the Ultra remains a pressure sensitive technology but without the drawbacks of the polyester outer membrane which is susceptible to damage from sharp objects. For further information please see 5-Wire Resistive. Often used: extreme environments such as military, oil rig and marine applications as well as any public environments susceptible to vandalism.
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