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What technology goes into a monitor and
how do I choose the monitor that suits my application?

Cathode Ray Tube (CRT) Technology

The main element in a CRT monitor is the Cathode Ray Tube(CRT). A CRT is a partially evacuated glass tube, which is filed with an inert gas at very low pleasure. The cathode (a negatively charged electrode, also called an ‘electron gun") beams a stream of electrons towards a positively charged electrode the screen. There are three separate electron beams, one each for red, green and blue. At the end of their flight, the electrons crash into the screen, which is coated with phosphor compounds. The kinetic energy of the electrons is converted into visible light and the coating glows to produce the picture.

Colour CRTs use thousands of triads-triangles painted across the inner surface of the tube to create a picture. A triad consists of three dots of the primary colours red, green and blue (RGB) arranged next to one another and makes up a ‘picture cell’ called a pixel.

To move the beam across the breadth of the tube face, powerful electromagnets are arranged around the tube, forming a yoke. They bend the electron beam in the course of its flight. The magnetic field set up by the yoke is carefully controlled and causes the beam to sweep each individual display line down the face of the tube. As opposed to colour tubes, monochrome CRTs have a single electron gun that continuously sweeps across the screen.

Shadow Mask v/s Aperture Grill

CRT monitors are based on two technologies:

Most of the CRT-based monitors use a commonly available technology called Shadow Mask. Some manufactures also refer to them as Flat Square Tube (FST). The shadow mask is a perforated sheet of metal, usually made of an alloy called Invar, placed just behind the glass of the monitor screen. This acts as a mask, ensuring that there is no spill over of the beam and that even if the beam is slightly mis aligned, a red phosphor dot will not receive the beam intended for an adjacent green one.

Advancement in this is the Trinitron screen technology; a proprietary technology by sony which is also used in their television sets. Introduced in 1968, the shadow mask in a Trinitron tube is replaced by what sony calls the ‘aperture grill’ and the inside of the screen is painted with phosphor stripes instead of dots. The advantage of a Trinitron screen is that they offer more saturated colour and better contrasts.

The new LCD monitors, because of their low space requirements, are fast replacing the CRTs. However, ‘short-neck’ CRTs have made an appearance. This condensed design used an electron gun with a wide 100-degree deflection area, thus shortening the distance that the electron has to travel in order to cover the screen.

What to look for while buying

The first decision that you need to make is whether to pursue a traditional CRT or be futuristic and go in for a flat screen monitor. LCDs are more expensive than traditional CRT’s, owing to the LCD technology, but though, the number of LCDs sold today is very less, these flat-screen devices are expected to grab around a half of the monitor market in the next five years.

Insight into the various features of a monitor:

Screen Size

Monitors are typically identified by the size of their display area. In CRTs, the edges of the screen are hidden behind the monitor cover. The portion of the screen which actually displays the visible picture is the ‘viewable image size’. The average 14-inch monitor, for example, has a viewable image size of between 12 and 13 inches (measured diagonally). If you are buying a CRT go in for the bigger size monitor-that is if it fits your budget.

Flat screen monitors are identified by their viewable area and not overall size only. Generally, a 14.1-inch flat screen monitor has a slightly larger viewable image size that a 15-inch CRT monitor. Similarly, 16.1-inch flat screen monitor will have a slightly larger viewable image than a 17-inch CRT monitor.

Dot Pitch/Stripe Pitch

Dot pitch is he distance (measured in millimeters) between adjacent phosphor dots of the same colour that make up your screen image on a conventional CRT. Stripe pitch is the distance between adjacent phosphor stripes of the same colour in aperture grill CRTs. In both cases, the smaller the measured distance, the sharper the picture.

Flat screen monitors are somewhat similar to aperture grill CRTs as they have vertical colour stripes, which are typically spaced in the range of 0.24mm to 0.3mm. One word of caution: One word of caution: although they are numerically similar, CRT and flat screen stripe pitch numbers should not be compared directly due to differences in the technologies.

Resolution: The higher, the better

Aim for a higher resolution while buying a monitor. The level of clarity you see on the monitor screen, as determined by the total number of pixels, is called addressability. For CRTs, a pixel is an addressable point of the screen encompassing multiple phosphor dots or stripes. The more the pixels shown on the screen, the tighter they are packed together and the better, the picture.

For flat screen monitors, a pixel is an addressable point of the screen composed of a single group of three colour filter stripes. Flat screen monitors offer the best results at their maximum addressability. Lower addressabilities are supported primarily for set-up and diagnostic purposes and display either a reduced picture size or spread the image to fill the entire screen.

Whether you’re shopping for CRTs or flat screens, make sure that you don’t buy a monitor based solely on its addressabilities. You will want to address other factors such as screen size, the physical size and weight of the monitor and the requirements of the applications you will be using.

Refresh Rate

While not always apparent to the naked eye, your monitor is constantly at work, rapidly redrawing (i.e., refreshing)images on the screen. Images on monitors are continuously being redrawn from left to right and top to bottom by an electron ‘gun’ or beam. The only time that you might notice this is when you experience ‘flicker’.

The ‘refresh rate’ is the number of times the monitor redraws the screen per second. Flicker occurs when your screen is not refreshed quickly enough, or when it uses an interlace refresh technique. When the image on the screen is refreshed by redrawing every other horizontal line and two passes are required to refresh the entire picture-it is termed ‘interlace’.

The refresh rate for a monitor is measured in hertz(Hz) and is also called the vertical frequency, vertical scan rate, frame rate or was 60Hz, but anew standard for monitor refresh rates ics Standard Association (VESA) has set the refresh rate at 75Hz for monitors displaying resolutions of 640*480 or greater. This means that the monitor redraws the display 75 times per second. The faster the refresh rate, the less the monitor flickers.

Images on LCD are continually being redrawn a line at a time from top to bottom. Due to differences in the base technology, these monitors are much less likely to display screen low refresh rates.

Ease of use: Go in for plug-and-play

No one wants equipment that is hard to set up, monitors included. Like Plug and Play technology for other computer components, a Plug and Play monitor should be able to connect your system and send key information to the computer for configuration with minimal work from the user. Take advantage of this technology and choose a monitor that supports Plug and Play.

A new feature called Universal Serial Bus (USB) capability represents a fast and easy way of connecting peripherals to your system. USB eliminates cable clutter and gives you added flexibility. Usb peripherals-mice, keyboards, joysticks, speakers, microphones, cameras-can be ‘hot swapped’, or changed without shutting down your system. It is important to note that the devices you plug into a USB hub must be also be USB capable.

Controls: Analog or Digital

There are two types of monitor controls: analog and digital. Analog(or wheel) controls were prevalent on early monitors and are still available. Digital controls provide push-button simplicity, a wide range of capabilities and memory functions. Some current monitors have analog-like controls for adjusting some features yet they actually make those adjustments digitally. Regardless of this, to take advantage of the latest technology you may want on-screen displays, which give you a pictorial indication of the current control settings.

The adjustments available will vary between CRT and flat screen monitor technologies. CRTs have a much wider range of adjustments as their image geometry can be varied while flat screen monitors have an image geometry that is fixed during the manufacturing process.

Consider your monitor size and the applications you will be using to determine the range of controls you wish to have. The larger the monitor and the more graphics-intensive your work, the greater the number of control settings you may require. Brightness, picture size and positioning may be the only controls you need for word processing and other basic functions. However, if you are planning to use a monitor for desk top publishing and graphics, you might want to choose a monitor with more detailed controls such as pincushion, barreling, colour convergence, trapezoid and image tilt correction.

In flat screen monitors a variation in controls has to do with the level of fine tuning the available to match the monitor to the incoming video signal.

Award-Winning Energy Efficiency

Energy Star compliance guidelines set by the Environmental Protection Agency require a monitor to idle down to 30 watts or less when not in use. Swedish NUTEK guidelines are more stringent, calling for 8 watts or less when not in use. Check for the Energy Star logo on the monitor before you pick up one for yourself.


The ‘footprint’ of a monitor is its width and depth, or the actual space it takes up when sitting on a desk or table. Large screen monitors have larger footprints. While buying a monitor keep in mind the available desk space and do not forget to take note of the height of the monitor.

Flat screen monitors have a distinct advantage with a significantly smaller footprint than the equivalent CRT monitor. In addition, the depth of a flat screen monitor does not increase in direct proportion to the screen size. Typically, flat screen models occupy only about one-sixth the depth and 85 percent the width and height of traditional CRT monitors.

Multimedia Monitors

Today, a number of vendors sell monitors with multimedia speakers attached to the sides of the monitor. Although these may save space on your desktop, these are not advisable as the magnet in the speakers may affect the convergence of the electrons inside the monitor.

The right monitor for you

Monitors with 15-inch CRTs ( 13.6 -inch viewable image size ) are the minimum standard for most systems today and are generally used for word processing, spreadsheets and games. Monitors with 17 - inch CRTs ( 15.7 - or 16.0 -inch viewable image size ) are suitable for people using multiple windows, graphics, desktop publishing and multimedia. Monitors with 19 -inch CRTs ( 17.8 - or 17.9 -inch viewable image size ) are suitable for mid-level desktop publishing and graphics work; they offer larger screen sizes than 17 -inch models without taking up any more space. Monitors with 21 -inch CRTs ( 19.8 -inch viewable image size ) are best for people performing high-end desktop publishing, CAD/CAE, and other graphics-intensive applications that require detail and clarity. After all, there is a monitor for everybody.


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