monitor is an output device that is part of your computer's
display system. A cable connects the monitor to a video
adapter (video card) that is installed in an expansion
slot on your computers motherboard. This system converts
signals into text and pictures and displays them on a TV-like
screen (the monitor).
The computer sends a signal to the video
adapter, telling it what character, image or graphic to display.
The video adapter converts that signal to a set of instructions
that tell the display device (monitor) how to draw the image
on the screen.
Cathode Ray Tube (CRT)
The CRT, or Cathode Ray Tube, is the "picture tube"
of your monitor. Although it is a large vacuum tube, it's shaped
more like a bottle. The tube tapers near the back where there's
a negatively charged cathode, or "electron gun". The
electron gun shoots electrons at the back of the positvely charged
screen, which is coated with a phosphorous chemical. This excites
the phosphors causing them to glow as individual dots called
pixels (picture elements). The image you see on the monitor's
screen is made up of thousands of tiny dots (pixels). If you've
ever seen a child's LiteBrite toy, then you have a good idea
of the concept. The distance between the pixels has a lot to
do with the quality of the image. If the distance between pixels
on a monitor screen is too great, the picture will appear "fuzzy",
or grainy. The closer together the pixels are, the sharper the
image on screen. The distance between pixels on a computer monitor
screen is called its dot pitch and is measured in millimeters.
(see sidebar). You should try to get a monitor with a dot pitch
of .28 mm or less.
Note: From an environmental
point of view, the monitor is the most difficult computer peripheral
to dispose of because of the lead it contains.
are a couple of electromagnets (yokes) around the collar of
the tube that actually bend the beam of electrons. The beam
scans (is bent) across the monitor from left to right and top
to bottom to create, or draw the image, line by line. The number
of times in one second that the electron gun redraws the entire
image is called the refresh rate and is measured
in Hertz (Hz).
If the scanning beam hits each and every line of pixels, in
succession, on each pass, then the monitor is known as a non-interlaced
monitor. A non-interlaced monitor is preferred over an interlaced
monitor. The electron beam on an interlaced
monitor scans the odd numbered lines on one pass, then scans
the even lines on the second pass. This results in an almost
imperceivable flicker that can cause eye-strain.
This type of eye-strain can result
in blurred vision, sore eyes, headaches and even nausea. Don't
buy an interlaced monitor, they can be a real pain in the ...
ask your optometrist.
Interlaced computer monitors are
getting harder to find (good!), but they are still out there,
so keep that in mind when purchasing a monitor and watch out
for that "steal of a deal".