Ultrasonic of touch technology advantages and Character LCD Modules disadvantages of the

Ultrasound: the use of ultrasound emitters emit ultrasonic waves to a receiver to accept at least two groups after calculating position
The ultrasonic positioning is somewhat similar to radar, the difference is that the radar signals reflected from objects encountered by the receiving end launch receiver to calculate the distance, and ultrasonic handheld device (pen) above send out ultrasonic allowed to receive, to have two receivers main reasons can calculate the position by triangulation, the same as the optical image are using triangulation to calculate a position, the type of the ultrasonic wave is obtained by the distance between the transmitting end to the receiving end, and the optical image is calculated through angle, which currently class applications in tablet, whiteboard, some people do touch screen, most teaching purposes, because it still need a pen to match, its drawback is that accuracy is not high jitter (distance), slow response, and so on.240x64 lcd display
The decision is a positioning two long like a microphone receiver, and the products currently on the market because of its sonic frequency relationship, will hear the sound vibration like flies wings fly.
This technology is different because the application is made quite a lot of different types of products, technical principles are the same, but the receiver separately in the sensing face on both sides, or in the same corner but there is a certain distance, or in a on one side with a certain distance, as long as it is receiving two have a certain distance to the ultrasonic wave emitting source may be disposed a certain distance, in theory, the farther away the more precise calculation, but in fact, the acoustic wave is easily attenuated with disturbed, therefore, the distance is too far when the interference with attenuation problems will increase.16x2 oled