Touch screen monitors seem to be everywhere. The great thing about them is that they are extremely easy to use.
A touch screen is like an invisible keyboard, but it displays only as
much data and button choices as users need to complete a specific task,
or set of tasks. That explains their popularity in devices from cell
phones to kiosks and industrial machinery.
The most important
decision in selecting the best touch screen monitor for your application
will be the type of touch screen technology to use. There are several
types, each with its own advantages and disadvantages. We will cover
the three most common types:
Resistive Touch Screen Monitors
A
resistive touch screen monitor is composed of a glass panel covered
with thin conductive and resistive metallic layers, separated by a thin
space. When a user touches the screen, the 2 layers touch at that
point. The computer detects the change in the electrical field and calculates the touch point.
Resistive
touch screens are generally the most affordable, but they only offer
approximately 75-80% image clarity. The touch can be activated with
nearly any type of object (stylus, gloved finger, etc.), but the outer
surface can be damaged with sharp objects.
Capacitive Touch Screen Monitors
In
a capacitive touch screen monitor, a layer that stores a continuous
electrical current is placed on top of the monitor's glass panel. When
an exposed finger touches the monitor screen, some of the electrical
charge transfers to the user. This decrease in capacitance is detected
and located by circuits located at each corner. The computer then
determines the touch point.
Capacitive
touch screens are a durable technology that is often used in kiosks,
point-of-sale systems and industrial machinery. Capacitive touch
screens have a higher clarity than resistive-type (88-92%), and have
greater endurance (up to 225 million touches) than a Resistive-type.
However, capacitive screens can only be activated with an exposed finger
(no gloves, pointers, etc.), and are slightly more expensive.
SAW Touch Screen Monitors
SAW (Surface
Acoustic Wave) touch screen monitors utilize a series of transducers and
reflectors along the sides of the monitor's glass plate to create an
invisible grid of ultrasonic waves on the surface. When the panel is
touched, a portion of the wave is absorbed. The receiving transducer
locates the touch point, and sends this data to the controller.
SAW
touch screen panels have no layers on the screen, thus enabling over
90% image clarity, and can display high-detail graphics. They can be
activated by a finger, gloved hand or soft-tip stylus. However, SAW
panels are the most expensive of the three, and moving liquids or
condensation on the face can cause false-triggers; solid contaminants on
the screen can create non-touch areas, until they are removed.
Other Technologies
Infrared and optical imaging are gaining popularity for larger (22"+) displays.
Other Considerations
Other factors to consider in your selection process include:
Interface: Touch screen panels must
communicate with the computer. The most common interface types are
RS-232 and USB. New HID-compliant touch screen monitors eliminate the
need for drivers.
Mounting: Options include panel mount,
rack mount and free-standing. If free-standing, be sure that it uses a
heavy-duty stand designed for touch screens; standard table top bases
will topple over.
Environment: Touch screen monitors are
available in standard, stainless steel and waterproof
enclosures for a variety of environments.
Screen Size: Touch screen monitors are
available from 3.5" to 52" in size. The most common sizes are 15"-19",
and 32"-42" for large control rooms. The aspect ratio (4:3 or 16:9)
should also be considered.
The type of touch screen monitor you select will
be contingent upon many factors, including type of data to be displayed
(video, graphics, text), the intended users, the operating environment
and where/how it will be mounted. Chosen correctly, touch screen
monitors will be an excellent addition to your system.
