Specifications

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Section 5. Comparison of the Touch Technologies
Having shared an overview of the
various touch technologies and the factors
that can affect their suitability for use in
various application environments, let us
compare each technology’s advantages
and disadvantages.
Capacitive Overlay Advantages
n Resolution - Capacitive overlay
systems can deliver a resolution of up to
4096 x 4096 touch points.
n Sealability - Capacitive overlay
system sensors can be sealed to the
display, preventing water and dirt from
penetrating the display’s inner electronics.
Capacitive overlay systems can be sealed
to meet NEMA 4 requirements.
n Flexibility - Capacitive overlay
sensors are adaptable to a wide range of
displays without expensive custom
designs.
Capacitive Overlay Disadvantages
n Transmissivity - Capacitive
overlay systems typically have a
transmissivity of 85% to 92%. This can
adversely affect image quality, particularly
for high resolution video modes.
n Stylus Requirements - Capacitive
overlay touch systems require a
conductive stylus to operate. Materials
that will not conduct a current, such as a
pencil, fingernail, or insulated glove, will
not activate the system. Although a
capacitive system’s sensitivity can be
adjusted to activate with a thin cotton or
surgically gloved hand, it cannot recognize
a gloved and an ungloved hand using the
same sensitivity setting.
n Sensor Drift/Calibration -
Capacitive overlay touch systems are
subject to drift, where the touch-active
zones move from the graphic targets
representing them. Periodic calibration is
required.
n Integration - Capacitive sensors
typically require an invasive installation to
maximize the display’s optical quality and
reduce the chance of breaking the glass
overlay. This invasive integration requires
disassembly of the display and
(optionally) permanent optical bonding of
the sensor to the display. Although flat
capacitive overlay sensors can be attached
to the exterior of the display, thereby
avoiding an invasive integration, optical
distortion and the possibility of breakage
are greatly increased. Mounting the flat
capacitive overlay sensor externally to
either a spherically or cylindrically curved
display will intensify parallax.
n Environmental Resistance -
Capacitive sensors are a type of
mechanical switch, even though there is a
hard coating applied over the sensor
surface. Through repeated, heavy use, the
hard coating and metallic coating can be
worn off or abraded over time. Also, the
glass overlay is susceptible to breakage.