How SAW
Touchscreen Works
Surface-Wave touch technologies have a glass overlay with
transmitting and receiving piezoelectric transducers for both the X
and Y axes. The touchscreen controller sends a electrical signal to
the transmitting transducer, which converts the signal into
ultrasonic waves within the glass. These waves are directed across
the front surface of the touchscreen by an array of reflectors.
Reflectors on the opposite side gather and direct the waves to the
receiving transducer, which reconverts them into an electrical
signal—a digital map of the touchscreen surface.
When you touch the screen, you absorb a portion of the wave
traveling across it. The received signal is then compared to the
stored digital map, the change recognized, and a coordinate
calculated. This process happens independently for both the X and Y
axes. By measuring the amount of the signal that is absorbed, a
Z-axis is also determined. The digitized coordinates are transmitted
to the computer for processing.
Surface Acoustic wave (SAW)
Touchscreen Specifications
Mechanical
Construction:
Glass panel with transducers attached to the front surface of
the glass.
Positional
Accuracy:
Standard deviation of error is less than 0.080 in
(2.03 mm). Equates to less than ±1% error on most displays.
Touch
point Density:
More than 100,000 touchpoints/in² (15,500
touchpoints/cm²).
Touch
Activation Force:
Typically less than 3 ounces (85 grams).
Expected Life
Performance: No
known wear-out mechanism, as there are no layers, coatings, or
moving parts. SAW technology has been operationally tested to more
than 50 million touches in one location without failure, using a
stylus similar to a finger (Unlimited touch life).
Sealing:
Unit can be sealed to protect against splashed liquids, dirt,
and dust.
Surface Durability:
Surface durability is that of glass, Mohs' hardness
rating of 7.
Touch
Resolution:
4096x4096, size independent.
Optical
Light
Transmission:
up to 92%.
Environmental:
Operating: -20°C to 50°C;
Storage: -40°C to 71°C.
Operating Relative
Humidity: 90% RH at 40°C, no
condensing.
Chemical
Resistance:
The active area of the touch screen is resistant to
all chemicals that do not affect glass.
Altitude
Operating:
10,000 feet.
Storage/transport:
50,000 feet.
Electrostatic Protection:
Meets Level 4 (15 kV air/8 kV contact
discharges).
Fire
Retardation:
Meets the requirements of UL 94HB.
For
Tempered SAW only
1.
Construction: Pure 6mm-thickness heat strengthened glass with
transducers attached
to the beveled edge of the
glass.
2. Break Resistance
Meets
UL-1950 Steel Ball Drop Test
A 1-pound steel ball drops from
height of 130 cm onto the center of the
Glass without
breaking.
For
Protected SAW only
1.
Construction
Pure 6mm-thickness heat strengthened glass with
transducers attached
On the edge of the glass surface.
The
reflectors and transducers are sealed inside the ABS plastic
frame.
2. Break Resistance
Meets UL-1950
Steel Ball Drop Test
3. Dustproof
The
ABS plastic frame around the panel prevents dust and dirt
from
accumulating on the reflectors and
transducers.
4. Waterproof
Special glue
is applied to the gap between the ABS plastic frame and
glass
substrate to prevent water infiltration.
Test
Method: Set the touch screen horizontally, and pour water on
the
panel surface without overflow over the ABS plastic frame.
The panel
surface is soaked in water for 1 hour. The panel is in
normal condition
after water poured out and dried.
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