You're in denial Bill! If they are not units of measure what are they? Can you give me a definition for units of measure? What is the difference between BTU and flushes?
I am sorry to say but this thinking is a product of "everything goes" school. I am not trying to be sarcastic or arrogant. Please try to understand! You actually generated a false unit of measurement dot/cm. When in fact the correct rating would be the dimension of the pixel in mm, or submultiples. Do you see what I mean? Is there such unit as dot/cm in ISO or SI? Just the fact that it uses cm does not make it a valid unit of measurement! I was taught that when I build a tool I classify it by the strength of the material, or by the dimensional characteristics and not by how many holes it can drill per minute. And if I don't know how to characterize it I go and ask the specialists at the national institute for standards. Rating of a product should have to do with fundamental units of measure hence with fundamental physical properties. By generating a unit (or call it what you want) as "ppm" one does exactly what the cups per minute does or the gallons per flush. Creating a fictitious symbol in people's minds that has nothing with physical properties. The only true UofM in computers is MHz which truly represents the frequency of oscillation of the machine's "clock" which sets the speed for the chip. A. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Bill Potts Sent: Wednesday, 30 January, 2002 15:27 To: U.S. Metric Association Subject: [USMA:17772] Re: Democracy and metrication Adrian Jadic wrote: "The first and simplest example is the computer screen resolution. Although the pixel size can be easily expressed in mm (0.15..etc.) as it is in Europe the computer manufacturers have invented the dpi. Then they invented the bps (baud per second) then the mips, the flops, the ppm (pages per minute) and God knows how many are there that I don't know about." First, a pixel or a dot is an arbitrary element, not a unit of measure. In expressing resolution in dots per inch, the industry is not creating a new unit. Obviously, we would rather the measurement be dot/cm. In defining the resolution of a display, the significant measurement is dot pitch (i.e., the distance from the center of one pixel to the center of the adjacent pixel). That is specified only in millimeters (0.28 mm being a common value). Monitor advertisements specifying "dpi" are written by people who don't know what they're talking about, not by the manufacturers of the monitors. (Most ads do get it right, however, and say "dot pitch: 0.28 mm".) Again, the bit is an arbitrary element (the binary digit) and not a unit of measure. The term bps (bits per second -- a baud is already a rate, defined as one change of state per second) is atrocious, of course, but the standards bodies express it, correctly, as bit/s. Again, instructions (mips being "million instructions per second" and flops being "floating point operations per second") are not units of measure Still again, pages are arbitrary. If one is buying a laser printer, it's certainly necessary to know its performance in pages per minute. To reiterate, none of these terms introduces a new unit of measure. They simply use existing units of measure in conjunction with arbitrary, but necessary, elements or characteristics. Bill Potts, FBCS, CMS Roseville, CA http://metric1.org [SI Navigator]
