On Fri, Mar 12, 1999 at 11:12:49PM -0500, Wagner Lipnharski wrote: > Hi Biswanath, > > I don't want to be a pest in your life, but by the fact > that you are learning, you would understand if I correct > you in few things, and I am sure some other people > around will learn it too. Sadly, there are competing "standards", which may not come from electronics per se but are a fact of life nonetheless. Many corrupting influences of course come from the vile world of computers, still somehow part of electronics, no? :-) > milli (m) 0.001 > micro (µ) 0.000,001 > nano (n) 0.000,000,001 > pico (p) 0.000,000,000,001 > deca (d) 10 > centi (c) 100 > kilo (k) 1,000 Yes, but kB always looks wrong, so in discussing memory capacity KB is not incorrect. In this context, of course, K is 2^10 instead of 10^3 anyway, so perhaps this is not a contradiction. Still, with this excuse, M meaning 2^20 and G meaning 2^30 result in a bit (NPI) of a conundrum. > Mega (M) 1,000,000 (upper case because the -m- milli) > Giga (G) 1,000,000,000 (upper case because -g- gram) > ...others > > For example, milli is just "m" it is not an abreviation > form, so it does not carry the dot "m." > Start using the right denomination as much as possible > and quickly you will do it without any effort. Of course, again in the context of computers, "b" is "bit" (0 or 1), while "B" is "byte" (eight bits). Thus we get "Kb" for 2^10 bits and "KB" for 2^13 bits, although one of course on occasion sees "kb" for 2^10 bits, as though the "K" needed to step down out of pity for the poor little bit. But surely "MB" is 2^23 bits, and "Mb" is 2^20 bits, and, my all-time favorite when it appears in print, "mb" is 0.001 bits. I'm still trying to figure that one out. > 10kOhms, or R10k, not 10K, someone can confuse it with > 10 Kelvin degrees. In this case, I will disagree. If 10kOhms can't be written "10K", then certainly 10 degrees Kelvin has no greater right to go around naked like that -- at least it needs to have the ¡, out of fairness if nothing else. But seriously, "K" by itself is not, AFAIK, assigned to *any* unit if measure; degrees Kelvin is ¡K, beginning and end of story; if you cannot write the ¡ symbol, use the word "degree". Horowitz and Hill argue vehemently that "10K" is unambiguously 10kOhms; the argument for this is that resistance is the only unit so fundamental to the study of electronics that it can be unambiguously stated without the use of the Omega or word Ohm. It is a judgement call whether or not to go along with this, but the potential for confusion with Kelvin isn't a valid argument against it, IMHO. The common usage of "5R1" for 5.1 Ohms and "5K1" for 5.1 kOhms is similarly contestable, but seems fairly well ingrained even in the labling of, say, 1% resistors. > 10uF, not 10mfd, someone can mixup it with milliFarads > or some bad name. > > Meter (m) doesn't make confusion with milli (m) since > milli alone doesn't exist. It is quantifying some other > unit, as Volts, grams, even meters (mV, mg, mm). > > "mts." for "meters", instead the simple "m", > "hrs." for "hours", "mints." for minutes, > "K" for "kilo", worse, KG for "kilogram", > looks like "a Kelvin degree in free falling > acceleration at G (gravity) 10m^2/s . As we drift out of symbols for units and into physical constants, "G" is the gravitational constant, approximately 6.6732x10^-11 N-m^2/kg^2, whereas "g", the acceleration due to gravity, is approximately 9.80621 m/s^2 at 45¡ latitude. (Note that, if a multiplicative prefix is used in a unit specification, (mA, or cm, for example), then a following exponant (e.g. cm^2) unambiguously applies to the entire combination, i.e. cm^2 is square centameters, not centasquaremeters.) Also, if units are combined, as in N-m for Newton-meters, a hyphen or a solidus should almost always be used, but no more than one solidus -- cm/s^2 is OK but cm/s/s is not. > Degrees use the "¡" symbol, as ¡F or ¡C, to type it > just press and hold ALT+SHIFT and type 0 1 7 6 at the > numeric keypad. > > The same for "µ" ALT+SHIFT+0181 (not 181) > "¸" ALT+SHIFT+0189 > "¹" ALT+SHIFT+0188 > "²" ALT+SHIFT+0190 This, I am afraid, depends greatly on one's choice of text editor and, perhaps, operating system. BTW, in preparing this response, I made extensive use of my trusty "Rubber Bible" -- the CRC Handbook of Chemistry and Physics, 55th edition, which is frighteningly dated 1974 (and purchased new by myself, I must add). I wish to report that Wagner's statement of the rules for SI multiplicative prefixes is exactly in agreement with that text, right down to "k" being lower case and "M" being upper. In good humor, --Bob -- ============================================================ Bob Drzyzgula It's not a problem bob@drzyzgula.org until something bad happens ============================================================