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LOOKING INTO A MONITOR

photo, two people looking into monitorMonitors are integral to every computer system. They are our visual link to all applications and have become a vital component in determining the overall quality and comfort of our computer system. The more you understand about monitors, the better informed decisions you can make when purchasing one. Although the average computer user may be confused by the dizzying array of terminology and specsmanship surrounding computer equipment, monitors are relatively simple if examined step by step. Let's begin with something everyone can relate to - a TV. Many people assume a monitor is similar to a TV, but they actually differ considerably because we normally view a monitor up close, while we watch TV from a distance. TV images move and change continuously and are viewed as a whole. Not so with a monitor, we tend to read small text and concentrate intensely on specific images or portions of an image. These circumstances require monitors to display stable and accurate images. A monitor uses a Cathode Ray Tube (CRT) and a "mask" is used to direct electron beams to phosphor colors which illuminate to produce the image. The two most common types of "masks" used are shadow mask and aperture grille mask (also called a stripe mask). Both types of monitors produce excellent image quality but there are differences. An aperture grille mask displays brighter images with richer and more saturated colors. Popular aperture grille technologies include SonicTron from ViewSonic, DiamondTron from Mitsubishi and Trinitron from Sony. On the other hand, a shadow mask creates images with more precision when displaying text and fine lines. Better shadow masks are made of INVAR, a type of alloy metal that has high heat resistance to withstand prolonged usage without distortion.

photo, man reading newspaper with monitor in background It's a simple matter of user preference when selecting between shadow mask and aperture grille monitors. For color graphics applications such as electronic desktop publishing, the aperture grille technology is often preferred for its ability to display color more vividly. However, engineers doing CAD/CAM and other technical illustrators may prefer shadow mask technology for precision drawings. Another very important specification to understand when evaluating your monitor is "resolution." Resolution refers to the density of the screen image. Like a huge crossword puzzle, resolution is expressed as the number of dots or picture elements (pixels) across one line, multiplied by the number of horizontal lines. A 640x480 VGA screen has 640 pixels or dots across a line and 480 lines down. The higher the resolution the more information can be displayed on the screen. Presently, the maximum supported resolution is 1800x1440, greatly improved from the color TV resolution of 320x525. A typical 15" (various viewables) monitor will run best at a resolution of 800x600, a 17" (various viewables) will run best at 800x600 or 1024x768 and a 21" (various viewables) will run best at 1024x768 or 1280x1024, or higher. Another spec that needs defining is "refresh rate". Refresh rate refers to the speed at which a screen is repainted or refreshed. The horizontal scan rate, expressed in kilohertz (kHz), is the speed a line can be painted horizontally in one second. A higher horizontal scan rate allows a monitor to run at higher resolutions with acceptable refresh rates. While the vertical scan rate, expressed in Hertz (Hz), tells us how many times the screen is repainted from the top most line to the bottom line, per second. The higher the vertical refresh rate is, the less flicker you will notice, therefore less eye strain. The horizontal and vertical scan rates combine to provide the ability to produce high resolution, flicker-free images. Flicker is caused by untimely fading of phosphor due to a slow vertical refresh. When the phosphor begins to fade prior to being refreshed, the display appears to be "flashing." And, even if your eyes don't pick up the flashing, your brain may, causing headaches, eye strain and fatigue. To guard against "flicker," find out the refresh rate of the monitor in various resolutions, especially in the resolutions you plan to use. The standard refresh rate for a flicker-free display is a vertical scan rate of 75Hz or higher. Dot pitch relates directly to the image quality of a monitor. It's the measurement of the diagonal distance between two phosphors of the same color. For example, the diagonal distance from a red phosphor dot to the next red phosphor dot. It is normally expressed in millimeters (mm). Aperture grille tubes use stripe pitch or aperture grille pitch to measure the horizontal distance between its phosphor stripes. A general rule is the smaller the dot or stripe pitch, the better the display. Images look finer and crisper when the dot pitch is smaller. Edges and lines appear smooth and refined. If you're considering a high resolution display, a finer dot pitch is important so images will be crisp. A dot pitch of 0.25 - 0.27 is recommended. Controlling the image on your screen requires using the controls on the front of the monitor. There are three types of monitor controls to consider: Analog, digital and digital on-screen. Analog controls are the conventional rotating dials or knobs offered on most economy models. Digital controls are microprocessor-based so they're more precise and easier to use. Many digital controls offer an on-screen menu that appears every time controls are activated. With digital controls, adjustments or settings are stored in a microprocessor chip so, unlike analog-controlled monitors, the settings won't change even if you turn the power off.

Monitors, like most electrical appliances, are subject to rigid safety and regulatory standards. Most of these standards are country-specific and are established to protect consumers from environmental or usage hazards that can be prevented. In the USA, monitors are required to comply with UL and FCC standards. These standards were established to certify that the electronic equipment is safe and free from communications interference. Many foreign standards are more comprehensive and have become so popular that they are now the de facto US standards. Two of these standards for monitors are MPR-II and TCO '92. Established by the Swedish labor boards in 1990, MPR-II regulates electromagnetic, magnetic and electric field emissions. These standards led to the development of low emission monitors. TCO was later established in 1992 to provide the most stringent standards presently available in regulating electromagnetic field emissions as well as ergonomics, power and energy conservation standards. Over 10 million users decided to purchase their first or upgraded to a larger and/or superior monitor last year. Users purchase monitors and upgrade for various reasons. Some upgrade for larger screen size. Others do so for better image quality. There are many reasons to invest in a better monitor, but regardless of what they are, upgrading to a better monitor is a long-term investment, so plan your purchase accordingly. Make your best possible choice based on your current applications and future plans.

by Kelli Baker,

 

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