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The monitor is a hardware device which physicallyconnects to the video card. The monitor allowsinformation and current status be visually outputtedsimilar to a TV.

Two widely used monitor types are : CRT

LCD

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The CRT monitor usesolder technology thathas the same workingprinciples as the

conventional CRT TV. It consists of one

electron gun(monochrome) or 3electron guns (color)

and a phosphorcoated screen.

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Within the CRT are three electron guns, Red, Green andBlue. Each of these guns streams a steady flow ofelectrons left to right for each line of your monitor.

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A CRT is an evacuated glass bottle, with a heatingelement on one end and a phosphor coated screen onthe other. When a current flows through this heatingelement, called a filament, the conductivity of the metalfilament is reduced due to the high temperature. Thiscause electrons to pile up on the filament, because theycan not move as fast as they would like to. Some ofthese electrons actually boil off of the filament.

These free electrons are attracted to a strong positivecharge from the outer surface of the focusing anodecylinder. However, the inside of the cylinder has a weakernegative charge.

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Thus when the electrons head toward the anode they areforced into a beam and accelerated by the repulsion of theinner cylinder walls. By the time the electrons get out they'regoing so fast that they fly past the cathode they were headingfor.

The next thing that the electrons run into are two sets ofweakly charged deflection plates. These plates have oppositecharges, one positive the other negative. While their charge isnot strong enough to capture the fast moving electrons theydo influence the path of the beam. The first set displaces thebeam up and down, and the second displaces the beam left

and right. The electrons are sent flying out of the neck of thebottle, called a yolk, until they smash into the phosphorcoating on the other end of the bottle.

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The impact of this collision on the out valence bands ofthe phosphor compounds knocks some of the electrons to

jump into the another band. This causes a few photons tobe generated, and results in our seeing a spot on theCRT's face.

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In order to generate image on the entire screen, theelectron gun must sweep across the screen one row at atime, from left to right and from top to the bottom. Whilesweeping across, the beam intensity is varied to createdifferent brightness (and color) for each position (pixel).

Once the phosphors on the CRT have been hit with anelectron they will only glow for a short period of time,because of this the CRT must be refreshed which means

the screen will be redrawn again and again.

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Refresh rate (scan rate) is the number of time the CRTscreen is redrawn in a second. It is measured in Hz.

Typical CRT monitor refresh rate range from 60 120Hz. Refresh rates below 75Hz can produce an often

imperceptible flicker that can cause eyestrain after longviewing.

Some video cards can support refresh rate higher than100Hz but it is recommended you run 85-90Hz, rates

beyond 90 Hz add an unnecessary processing burden tothe video card.

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If the video cards refresh rate is not set high enough youmay encounter a flicker or a noticeable steady linescrolling from the top to the bottom of your screen. If youare encountering this issue, try to increase the refreshrate of the video card.

But due to the limits in standard VGA connectorbandwidth, the rate at which the screen is redrawndecreases as the resolution increases. Bandwidth is the

rate at which the monitor receives data from the videocard.

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The standard for flicker free images has been set to85Hz. Nevertheless, most viewers won't detect flicker aslow as 72 Hz. The best test to detect flicker is to lookslightly above or to the side of the monitor.

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The dot pitch is the distance between two adjacentpixels, or phosphor dots, that make up an image.

The finer (smaller) the dot pitch, the better image qualityyou will have. It is usually measured in millimeters (mm).

Todays monitors have a typical dot pitch of 0.24 to0.28mm

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LCD are organic molecules that, in the absence ofexternal forces, tend to align themselves in crystallinestructures. But, when an external force is applied theywill rearrange themselves as if they were a liquid. Some

liquid crystals respond to heat, others respond toelectromagnetic forces. When LCDs are used as optical (light) modulators they

are actually changing polarization rather thantransparency. In their unexcited or crystalline state the

LCDs rotate the polarization of light by 90 degrees. In thepresence of an electric field, LCDs behave like a liquidand align the small electrostatic charges of the moleculeswith the impinging E field.

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The LCD's themselves have extremely low powerrequirements. A very small electric field is required to excitethe crystals into their liquid state. Most of the energy used byan LCD display system is due to the back lighting.

Response Time of an LCD monitor is the amount of time ittakes for a liquid crystal cell to go from active (black) toinactive (white) and back to active (black) again. It ismeasured in milliseconds (ms). Lower numbers mean fastertransitions and therefore less visible image artifacts.

Typical response time for LCD nowadays is 2-10ms. OlderLCD with long response times (>20ms) would create a smearor blur pattern around moving objects (ghosting effect),making them unacceptable for moving video.

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Defective pixels are pixels on a LCD not performing asexpected. Three different types of defective pixels: Hot Pixel always on (white) pixel Dead Pixel always off (dark) pixel Stuck Pixel one or two sub-pixel is always on or always off.

Dead Pixel

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Aspect ratio refers to the ratio of the display's width to thedisplay's height. Most traditional computer monitors and TVshave a 4:3 aspect ratio where the width is slightly larger thanthe height. With the emergence of technologies such as

HDTV, many of these type displays carry either a 16:9 or a16:10 aspect ratio. HDTV has a 16:9 aspect ratio, but forcomputer displays, a 16:10 aspect ratio is optimal forrectangular displays because it allows for two full pages of textto be shown side-by-side on one screen.

Contrast ratio is the measure of the difference of brightnesslevels between the brightest white and the darkest black.Larger contrast ratio generally is better. Typical LCD screennowadays has absolute contrast ratio of over 300:1.

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CRT LCD

Size Bulky Slim

Response Time Quicker Slower, 2-10ms

Contrast Ratio Very high High

Viewing Angle No limit 150-170

Power Consumption 17 70watt 17 30 watt

Life (Half life) 15,000 hours 50,000 hours

Price Cheaper for smallersize but expensive for

bigger size

Cheaper for largersize (>17)

Image Quality Rich and accurate

color

Bright and flicker

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Some newer LCD monitors use LED as back light. Thistype of LCD monitors has many advantages over theconventional LCD monitors which use fluorescent lamp(CCFL).

LED backlight is smaller in size and thus make it possible to buildslimmer and lighter LCD panel.

LED consume less power compare to CCFL and thus making theoverall power consumption of the LCD monitor lower.

Using multiple LEDs as backlight make it possible to turn offsome LEDs when displaying black/dark regions and thusproducing much better contrast ratio.

LED has longer lifespan compare to CCFL (about double). As thelifespan of LCD monitor normally is limited by the lifespan of thebacklight, using LED as backlight increase the lifespan of LCDmonitor.

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The monitor size is an important factor on deciding yourscreen resolution. When picking the resolution, try tobase on the following recommended setting (4:3 aspectratio). 15-inch 800 x 600

17-inch 1,024 x 768

19-inch 1,280 x 1,024

For LCD monitor, it is recommended to use the default

(native) resolution of the LCD (i.e. 19 1280 x 1024)

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A higher resolution display lets you see more on yourscreen at one time and is particularly useful for operatingsystems like Windows. The maximum resolution that amonitor can display is limited by the size of the monitor

and the characteristics of the CRT/LCD. While running the monitor at a higher resolution can be

useful, it's important to remember that this makes eachpixel on the screen appear smaller as well. Running a

high resolution display on a small monitor can be veryhard on the eyes.

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Here is where youset your resolution.

And here is to setthe color depth

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There are two common types of interface used to connectthe video card and monitor : 15-pin VGA connector which is analog only.

Digital Visual Interface (DVI) which can carry analog or digitalvideo signal.

Other types include : HDMI, S-Video

VGA Connector DVI Connector HDMI Connector

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Clean the monitor every few months to clean up oilysubstances and dust.

Place monitor at suitable place, not in the kitchen cause it willget dirty very fast.

Use a smooth cloth to wipe away finger prints on the monitor. The monitor should not be used near water or exposed to

excessive moisture to reduce the risk of electric shock or fire. Proper ventilation is very important so never block the

ventilation openings with cloth or other materials. Should not be placed in book shelf or inside cabinet.

The monitor should be cleaned only with soft, dry or slightlydamp cloth.

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Symptom : Monitor has a tint of one color. Monitor cable is defective

Temporarily disconnect the monitor from the back of thecomputer and verify that there are no bent, burnt or

broken pins. If the end of the cable appears to be fine reattach the

cable and ensure it is firmly connected to the back of thecomputer. If you continue to experience the same issue,

try to connect the monitor to another system unit to verifythat the video card is not causing the problem. If thesame problem persist, then

Monitor is bad

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Symptom : No display on monitor Cable not connected properly.

Ensure that you are connecting the monitor to theVGA/DVI output of the video card.

Ensure that the computer is turned on and that themonitor is getting power. You can do this by checkingwhether the status LED of the monitor is lit or not.

Monitor settings are not correct. Ensure that the brightness and contrast is turned up or

attempt to adjust the brightness and contrast (for analogcontrol monitor).

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Symptom : No display on monitor No Post.

Check whether the computer perform POST when it ispowered on and or does it appear that the computer has

activity. If the computer does not beep or beepsabnormally it is possible that the computer itself isexperiencing a hardware issue or is exhibiting a No Post.

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Symptom : No display on monitor Hardware issue.

Disconnect the monitor and attempt to connect it toanother computer; OR, borrow a computer monitor and

connect it to your computer. If your monitor works on another computer it is safe to

assume that the video card within the computer is bad. If another monitor works on your computer it is safe to

assume that your monitor is bad.

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