One answer from the BWMA. Han ----- Original Message ----- From: "Joseph B. Fox" <[EMAIL PROTECTED]> To: "Han Maenen (by way of mail <[EMAIL PROTECTED]>)" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>; [EMAIL PROTECTED]>; <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]; [EMAIL PROTECTED]>; [EMAIL PROTECTED]>; <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Saturday, June 16, 2001 5:45 PM Subject: Re: Questions about measurement standards > TV screens and computer monitors are sized according to the dimension of their diagonals. A 17" screen, for example, measures seventeen inches from corner to corner. There are two good reasons for this. Firstly, the original cathode ray tubes were round - the rectangular image was projected onto them, with the corners just touching the outside of the circle. So the "diagonal" measure was also the diameter of the tube. Secondly, until the advent of widescreen TV, all the images were in the 3:4 format. Remember your Pythagorus: the diagonal of a 3:4 rectangle is... 5. So divide the diagonal measure of your screen by five and multiply by three for height and by four for width. > > But why inches? Because the technology was developed in non-metric America. ISO notwithstanding, computer components tend to be designed in imperial increments. The ISO may say that the connectors on a processor should be 2.54mm apart: we know that that really means one tenth of an inch. > > Similarly, you will find that with few exceptions, all the standards pertaining to magnetic recording tape are (were) imperial: quarter inch tape, fifteen inches per second, etc. Same reason - made in America. God, how refusing to adopt the metric system has held them back! ---------- From: "Han Maenen" <[EMAIL PROTECTED]> (by way of mail <[EMAIL PROTECTED]>) To: [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED] Subject: Questions about measurement standards Date: Jun 16, 2001, 07:41 Any replies? ss Dear Mr Delaney, I have some questions about standards. Could the BWMA answer these for me? 1.) The BWMA claims the floppy disk is imperial because it is called 3.5 inch. Which dimension does the 3.5 inch refers to? Is the BWMA aware of the ISO 9529-1 specification for floppy disks? This specification require the floppy disk to be 94 mm x 90 mm x 3.3 mm. The disk to be 86 mm in diameter and the mass to be 24 g. Why does BWMA's material state that a conversion of 3.5 inch would result in either an 88.9 mm name or an 89 mm name? Since the spec calls for one of the dimensions to be 90 mm, why not call it by this name? At least the name would match and actual dimensional part of the device. 2.) Why do computer monitors use inches for one dimension but don't follow through and use millimetres for dot pitch? Also, the manual for the Optiquest V73 calls it a 17 inch monitor, but gives the maximum viewing area as 325 mm x 244 mm and the default as 300 x 225 mm. It contains no information at all about what the 17 inch is supposed to refer to. The physical dimensions of the whole monitor are 405 mm x 405 mm x 425 mm, or 15.9" x 15.9" x 16.7". Is it a common practice to use inch numbers that don't refer to any part of the product? What is the purpose? 3.) How does the BWMA define the foot, inch, pound, the Imperial gallon etc.? Does the organization u accept the present "official" definition of the units as 0.3048 m, 0.0254 m, 0.4536... kg, etc.? If the BWMA doesn't accept the "official" definitions, how does it account for any errors that will exist between their definitions and the "official" versions? Yours faithfully, Han Maenen [EMAIL PROTECTED]
