Specifications
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driver will permit the touch screen and the computer to work together. The most
commonly used touch screen driver is the mouse-emulation type driver which
functions the same way as clicking the mouse at the same place on the screen.
The touch screen can coexist together with existing software and will permit new
technological applications to occur without the need for programming.
Another concept that a person needs to be aware of when trying to determine
what would be the best touch screen panel is to know what an NIT is. Candelas
per meter square is a measurement of light in the determining the brightness of a
touch screen display panel. Candelas per square meter is often referred to as an
NIT and this is equal to footlamberts * 3.43. Below are some formulas used to
figure out touch screen illumination, screen brightness, and total light outputted
from the screen:
A vital term that becomes important when considering touch screen displays is
the contrast ratio (CR). The contrast ratio is defined as being the proportion of
luminance to white and dark light that is formed on a touch screen display. This
takes place when figuring out the best picture quality between the various touch
screen displays: resistive touch screen, surface acoustic wave, and capacitive
touch screen. To have an enhanced sharp picture, a user must purchase a touch
screen with a high contrast ratio. The contrast ratio changes when measuring the
ambient illumination in a dark room compared to the touch screen being
calculated outside in the sunlight.
Last of all is the viewing angle terminology. A viewing angle for a touch screen
display is the angle at which the pixel resolution and image quality gets bad
enough and unacceptable for the user to view. In order for the viewing angle to
degrade on the touch screen it will go through three processes. The first course
goes through a drop in luminance or luminous flux. Next the contrast ratio will fall
at large angles and as a result the pixel or resolution colors on the touch screen
may start to deviate. Criteria based on viewing angles consist of the luminance
and contrast ratio.
2.6 Wireless Interfacing
One of the most important features for our HVAC design is to be able to
communicate wirelessly between the different components. The feedback and
control system will not use wires to connect the subsystems like the secondary
microcontroller and the main control unit. Wireless components are making
industries and systems like HVAC units easier to install, operate and fix as
wireless technology is becoming easier and more reliable to implement.