Specifications

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Section 4. Evaluating Touch Technologies
Each touch input technology has both
advantages and disadvantages. These
advantages and disadvantages consist of
physical factors associated with the
technology, and with each technology’s
ability to withstand the impact of factors
occurring in the application’s
environment.
Touch Technology Physical Factors
Factors to consider include:
resolution, transmissivity, response time,
stylus type, calibration, integration, and
reliability. Specifications covering each of
these factors are given in the Touch
System Comparison Charts (pages 22-23)
for each technology.
Resolution
Touch system resolution refers either
to the number of touch active points, or to
the physical spacing between the adjacent
touch coordinates. When considering the
resolution of the touch system, it is
important to keep in mind the touch
system’s intended application. For many
applications, such as control panels, public
access or computer-based training, fine
resolution is not required. In some
applications, such as signature
verification, a very high touch system
resolution is desired.
Transmissivity
Another variable to consider is image
clarity. The display image can be affected
by placement of any material between the
display image and the viewer’s eye. All
systems that require an overlay over the
display screen such as resistive,
capacitive, surface acoustic wave, near
field imaging, and guided acoustic wave
involve some visual obstruction between
the operator and the image on the screen.
Transmissivity is defined as the
percentage of light from a display
remaining after passing through a material.
Response Time
Response time is an important
consideration when evaluating touch
technologies. The faster a touch system
can respond to a user’s input, the better.
Response time is defined as the time
required for the touch system to locate the
touch and transmit the touch location to
the host system. However, several factors
contribute to the response time of the
complete touch application: touch system
response time, host processing speed,
access to the host electronics and
application software. Response times
specified in the Touch System
Comparison Charts relate to the response
time of the touch system only.