How Do Touch-Screen Monitor Know Where You're Touching?

Hello Readers !
Have any one here know or have an idea on how do touch-screen monitor know where exactly where you are touching? Anyone? If none,let me share with you guys.
Generally there are three basic system that are used to recognize a person's touch. There are known as resistive system, capacitive system and surface acoustic wave system. The resistive system consists of a normal glass panel that is covered with a conductive and a resistive metallic layer. These two layers are held apart by spacers, and a scratch-resistant layer is placed on top of the whole setup. An electrical current runs through the two layers while the monitor is operational. When a user touches the screen, the two layers make contact in that exact spot. The change in the electrical field is noted and the coordinates of the point of contact are calculated by the computer. Once the coordinates are known, a special driver translates the touch into something that the operating system can understand, much as a computer mouse driver translates a mouse's movements into a click or a drag.

In the capacitive system (most smart phones) , a layer that stores electrical charge is placed on the glass panel of the monitor. When a user touches the monitor with his or her finger, some of the charge is transferred to the user, so the charge on the capacitive layer decreases. This decrease is measured in circuits located at each corner of the monitor. The computer calculates, from the relative differences in charge at each corner, exactly where the touch event took place and then relays that information to the touch-screen driver software. One advantage that the capacitive system has over the resistive system is that it transmits almost 90 percent of the light from the monitor, whereas the resistive system only transmits about 75 percent. This gives the capacitive system a much clearer picture than the resistive system.

On the monitor of a surface acoustic wave system, two transducers which one receiving and one sending are placed along the x and y axes of the monitor's glass plate. Also placed on the glass are reflector, they reflect an electrical signal sent from one transducer to the other. The receiving transducer is able to tell if the wave has been disturbed by a touch event at any instant, and can locate it accordingly. The wave setup has no metallic layers on the screen, allowing for 100-percent light throughput and perfect image clarity. This makes the surface acoustic wave system best for displaying detailed graphics (both other systems have significant degradation in clarity).

Another area in which the systems differ is in which stimuli will register as a touch event. A resistive system registers a touch as long as the two layers make contact, which means that it doesn't matter if you touch it with your finger or a rubber ball. A capacitive system, on the other hand, must have a conductive input, usually your finger, in order to register a touch. The surface acoustic wave system works much like the resistive system, allowing a touch with almost any object except hard and small objects like a pen tip.

As far as price, the resistive system is the cheapest whereby its clarity is the lowest of the three, and its layers can be damaged by sharp objects meanwhile the surface acoustic wave setup is usually the most expensive.

So how it works?

There are three components used in touch screen technology:

• In general the sensors of these three types of system (resistive system, capacitive system and surface acoustic wave system) have an electrical current running through them and touching the screen causes a voltage change. The voltage change signals the location of the touching.
• The controller, is the hardware that converts the voltage changes on the sensor into signals the computer or other device can receive.
• Software tells the computer, smartphone, game device, others on what is happening on the sensor and the information coming from the controller. Who's touching what and where, then it allows the computer or smart phone to react accordingly.

Thank you !