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A+™ Essentials  Technologies

2.Display Adapters and Monitors

Monitor Connectors:

· If you are using a Monochrome / CGA/ EGA monitor, it is a digital monitor and will have a DB-9 Male connector that plugs into a digital adapter.
· If you are using a VGA/ SVGA monitor, it will have a male DB-15 connector that plugs into an analog adapter. You should never interchange an analog monitor to that of a digital adapter and vice versa, or severe damage may take place.

Video types

The table below compares various video types:

Video monitor

Max. Color depth

Max. Resolution

CGA

16 Colors

160X100

EGA

64 colors

640X350 (Graphics Mode)

VGA

256 colors

640X480 (Graphics Mode)

SVGA

16 Million Colors

1280X1024 or even more


When you are installing a different SVGA monitor, it is unlikely that the new monitor has the same capabilities as the old one. As a result, the image on the screen may not be readable. In such instances, change the video resolution to Standard VGA before installing the new monitor. You can change the resolution appropriately after the image on the screen is readable with the new monitor. It may also be necessary to load appropriate device driver, if you are installing a different display adapter.

LCD Monitors:

The ‘native resolution’ specification points out one of the big differences between LCD and CRT displays. If you run an LCD at any resolution other than its native resolution, the display will become blurry, especially with text. The reason this happens on LCDs is that they are made up of tiny cells in a matrix (called the native resolution). For instance, if the native resolution is listed as 1280×1024, then there are 1280 cells across and 1024 cells down the screen. If you only display at 1024×768, then a large number of the pixels are being ’stretched’ over multiple cells, which is what causes the image quality to degrade.

Various resolutions commonly used with LCD monitors are as given below:

1024 x 768 is XGA (eXtended Graphics Array)
1280x720 is WGA/WXGA (Wide eXtended Graphics Array)
1280 x 1024 is SXGA (Super eXtended Graphics Array)
1400x1050 is SXGA+ (Super eXtended Graphics Array Plus)
1680x1050 is WSXGA (Wide Super eXtended Graphics Array Plus)
1600x1200 is UXGA (Ultra eXtended Graphics Array)
1920x1200 is WUXGA (Wide Ultra eXtended Graphics Array)

Wide screen format aspect ratio is typically 16:10 for computer monitors and 16:9 for LCD televisions. Aspect ratio of 16:10 conforms with WUXGA standard. Further note that UXGA has a resolution of 1600X1200 and an aspect ratio of 4:3.

Products or instrumentation equipped with a touch screen normally require a calibration routine upon power up because it is difficult to perfectly align a touch screens coordinates with those of the display underneath it. Calibration is necessary when the coordinates of the area touched on the screen are not sufficiently close to the coordinates on the display. Without proper calibration, software may not respond correctly when a soft button or icon is pressed.It is recommended that you clean the LCD screen with clean water, using a soft cotton cloth. Do not spray water directly on the screen. First wet the cloth (no dripping of water), and wipe the LCD screen gently.

Monitors and static charge:

1. Monitors accumulate very high static charges and need to be handled very carefully. Before attempting any repair, it is important to discharge any accumulated charges on the monitor. You can use a jumper, one end of which is grounded, and touch the other end of the jumper wire to the anode of the monitor. While doing so, ensure that you are not in direct contact with the jumper wire or the anode. You can use a screwdriver, or a nose pliers with rubber handle for this purpose. A "POP" sound can be heard when the static charges accumulated on the anode lead getting grounded through the jumper wire. Static charges accumulated on monitors may lead to severe burn or even fatal, if come into direct contact. 

2. Never wear a wrist strap when working on monitors. Monitors contain very high voltages, sometimes fatal to human, even when the power is turned off. If you are wearing wrist strap, the human body works as a conduit to discharge the electric charge.

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