Specifications

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The surface acoustic wave technology features two transducers so that when the
panel is touched it can find the coordinate accordingly. These transducers are
positioned on the x and y axes of the coordinate plane of the screen‟s insulated
plate. The controller calculates the time at which the height of the acoustic wave
falls to determine the x and y coordinates position on the x-y coordinate plane.
This technology can also figure out how much pressure is applied to by the
screen. The Z axis (is going into the screen) will determine this depth information.
Once the touch screen locates the finger touched on the panel it will relay
information to the microcontroller. The surface acoustic wave system has the
best image graphics on the screen because 100% light is transmitted. There are
no metallic layers on the screen to block light from going through it. Figure 12
pictured below undergoes the surface acoustic wave touch screen technology
process.
Figure 12 Surface Acoustic Wave touch screen (Reprinted with Permission
from 3M Touch)
The capacitive touch screen system stores an electrostatic charge while placing
your finger on the glass insulated panel. The electrostatic charge is displaced
when the user places their finger on the monitor. Therefore the capacitive layer is
reduced. An advantage of the capacitive touch screen system is that it sends
90% of light from the monitor to give the screen a crisper and clearer picture than
the resistive system. Figure 13 is a detailed overview as to what happens in a
capacitive touch screen display.
Sensor
Controller measures
wave amplitude changed
to determine touch
location
Touch absorbs some
acoustic energy form
sound waves
Sound wave
reflector
Transducers emit
sound waves
along sides