Advanced Touch Screen Technology 
 
 
The working principle  
 
Touch screen technology has the potential to replace most functions of the mouse and keyboard. As the technology advances, people may be able to operate computers without mice and keyboards. Because of its convenience , touch screen technology solutions has been applied more and more to industries, applications, products and services, such as Kiosks, POS (Point-of-Sale), consumer electronics, tablet PC, moderate to harsh Machine Control, Process Control, System Control/Office Automation and Car PC, etc.
 
Nowadays there are four types of touch screen technologies applied in our life and industries.
 
 Capacitive 
 Resistive 
 Infrared
 Surface acoustic wave (SAW)
 
 
The capacitive technology is applied on glass sensor that is added conductive coatings. The electrical charge is set at the four corners of the glass along an X-Y axis, and spreads the stable voltage on the glass as a uniform field. When a user touches the screen, some of the charge is transferred to the user, and makes the potential difference on the screen. After the panel controller recognizes that, the controller will send the X-Y axis information to the PC port. The advantage is that capacitive technology transmits almost 90% percent of the light from the screen. The superior efficiency gives capacitive better than resistive technology.
 
The resistive technology is applied on two layers with overlaying a hard-coated ITO on a conductive clear glass. These two layers are held apart by spacers (dot). When the flexible layer is touched and contacts the other layer that is set on the stable glass, the voltage is detected and measured from same voltage applied as an electrical field. The controller uses voltage measured from along the X-Y axis to calculate the position of the touch. The advantage of resistive technology is referred to the cheap price, but the surface of resistive panel is not solid as capacitive panel, it cannot sustain strong punches and work in harsh environment. 
 
The infrared technology is applied on touch panels that place infrared receivers and CRT utilizing infrared Light Emitting Diodes (LED) along the horizontal and vertical X-Y axis. When a user touch the surface of screen, the infrared emitted from LED beam is broken and receiver transmits X-Y axis information to the PC port via touch controller.
 
The surface acoustic wave (SAW) technology is based on two transducers (transmitting and receiving) placed for the both of X and Y axis on the touch panel. The other important element of SAW is placed on the glass, called reflector. The controller sends electrical signal to the transmitting transducer, and transducer converts the signal into ultrasonic waves and emits to reflectors that are lined up along the edge of the panel. After reflectors refract waves to the receiving transducers, the receiving transducer converts the waves into an electrical signal and sends back to the controller. When the user touches the panel, the user absorbs a portion of the wave travelling across it. The controller compares and calculates the change of signal that transducers emits and receives. The calculation processes for both X and Y axis independently.