### Practical Coilgun Design

It's popular to replace your aging CRT with a fancy new LCD widescreen monitor. But what size should you get? How do you convert CRT sizes into LCD specifications? Here's my advice.

In December 2009 I was shopping to replace my 21" CRT with a crisp modern LCD display. The current advertisements are always for widescreen format and online searches return very few non-wide displays. The price for widescreen devices are way down, but not so much for non-wide units.

## Widescreen = "Aspect Ratio"

In computer displays, the adjective "widescreen" sucks. It's a great-sounding description that is a fiendishly diabolical marketing ploy that misleads consumers into unsatisfactory choices.

Here's a common example. Suppose you have a nice 19" CRT monitor that you like. But now you want to upgrade to a space-saving lightweight and crystal-clear LCD monitor. Should you replace it with a "widescreen 19-inch LCD" monitor? NO! You will be very unhappy.

At first glance, a "19-inch widescreen monitor" sounds better than a plain "19-inch CRT monitor." But you will find it's actually much smaller and feels cramped. Why?

"Widescreen" is another name for aspect ratio. There are two common widescreen ratios of 16:9 and 16:10.

Computer monitor ratios are:

• 4:3    = 1.333
• 16:10 = 1.60
• 16:9   = 1.777

The higher the ratio, the worse the display because it becomes shorter from top-to-bottom. And neither one exactly matches theatrical releases in anamorphic display so you always get black bars playing movies anyway.

## Diagonal Measure

The measurement specified is the diagonal distance between two opposite corners. Let's do the math. Given a diagonal measurement and Pythagoras' Theorem (a2 + b2 = c2) we can calculate the viewable height.

Keep in mind the last fiasco foisted on the public by monitor manufacturers. The CRT diagonal measurement was the glass tube itself. But some of that was covered by the bezel. You must subtract one inch to find its viewable size. All CRTs advertised as "19 inch" only provided 18 inches of viewable size. Thankfully this is no longer true of LCDs where the measurement is exactly the viewable size.

The height of LCD displays and televisions for 19-inch monitors are:

• 4:3 height    = 12.0 inches
• 16:10 height = 11.1 inches
• 16:9 area     = 10.3 inches

You lose height if you simply swap any CRT monitor for the "same size" widescreen monitor. This is why you must always buy a bigger widescreen LCD than CRT.

## How much bigger should you buy?

Example 1: You have a 19" CRT and you want a new LCD with the same (or more) vertical height.

• 16:10 replacement LCD should be 21" widescreen (rounded up from 20.4")
• 16:9 replacement LCD shoule be 22" widescreen (rounded down from 22.04")

Example 2: You have a 21" CRT and you want an LCD with same (or more) viewable height.

• 16:10 replacement LCD should be 23" widescreen (rounded up from 22.6)
• 16:9 replacement LCD should be 25" widescreen (rounded up from 24.5)

Conclusion: Add three inches to CRT sizes to get the equivalent LCD size.

The Display and Monitor Industry is still a pack of misleading scumbags.

How about the advertisement I saw last week for a "10-inch widescreen movie player!". C'mon, get real, a 5x8 inch screen is NOT wide!

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