What is a touchscreen?
A touchscreen is any monitor,
based either on LCD (Liquid Crystal Display) or CRT (Cathode
Ray Tube) technology, that accepts direct onscreen input.
The ability for direct onscreen input is facilitated by
an external (light pen) or an internal device (touch overlay
and controller) that relays the X,Y coordinates to the computer.
Resistive Touchscreen Technology
Resistive LCD touchscreen monitors
rely ona touch overlay, which is composed of a flexible
top layer and a rigid bottom layer separated by insulating
dots, attached to a touchscreen controller. The inside surface
of each of the two layers is coated with a transparent metal
oxide coating (ITO) that facilitates a gradient across each
layer when voltage is applied. Pressing the flexible top
sheet creates electrical contact between the resistive layers,
producing a switch closing in the circuit. The control electronics
alternate voltage between the layers and pass the resulting
X and Y touch coordinates to the touchscreen controller.
The touchscreen controller data is then passed on to the
computer operating system for processing.
How Resistive Touchscreens Work
Polyester Film
Upper Resistive Circuit Layer
Conductive ITO (Transparent Metal Coating)
Lower Resistive Circuit Layer
Insulating Dots
Glass/Acrylic Substrate
Touching the overlay surface causes the (2) Upper Resistive
Circuit Layer to contact the (4) Lower Resistive Circuit
Layer, producing a circuit switch from the activated area.
The touchscreen controller gets the alternating voltages
between the (7) two circuit layers and converts them into
the digital X and Y coordinates of the activated area.
Because of its versatility and cost-effectiveness,
resistive touchscreen technology is the touch technology
of choice for many markets and applications. Resistive touchscreens
are used in food service, retail point-of-sale (POS), medical
monitoring devices, industrial process control and instrumentation,
portable and handheld products.
Resistive touchscreen technology
possesses many advantages over other alternative touchscreen
technologies (acoustic wave, capacitive, Near Field Imaging,
infrared). Highly durable, resistive touchscreens are less
susceptible to contaminants that easily infect acoustic
wave touchscreens. In addition, resistive touchscreens are
less senstive to the effects of severe scratches that would
incapacitate capacitive touchscreens. For industrial applications,
resistive touchscreens are a more cost-effective solutions
than Near Field Imaging touchscreens are.
8-Wire Resistive Technology
Resistive touchscreen technology
exists in 4-wire, 5-wire, or 8-wire forms. Chassis Plans
LCD touchscreens (Models CPFPV-218O-8A
and CPFPV-215O-8A) specifically
employ 8-wire resistive technology because of its benefits
over 4-wire and 5-wire touchscreens. Whereas 8-wire FastPoint
touchscreens are available in all sizes, 4-wire resistive
technology is restricted to small flatpanels (<10.4").
In contrast to 5-wire resistive touchscreens, 8-wire touchscreens
do not experience spacer dots and Newton rings. Neither
4-wire nor 5-wire resistive technologies can account for
the problems of high-level short-term varianecs and axis
linearity and drift that 8-wire resistive technology solves
