Metric notation

Discussion in 'Feedback and Suggestions' started by Gulliveig, May 29, 2013.

  1. Gulliveig

    Thread Starter New Member

    May 29, 2013
    2
    0
    Vol. 1 Ch. 4 "Metric notation"

    "Because the major prefixes in the metric system refer to powers of 10 that are multiples of 3 (from "kilo" on up, and from "milli" on down), metric notation differs from regular scientific notation in that the significant digits can be anywhere between 1 and 1000, [...]"

    The highlighted number should read 999, as 1000 would be represented by 1 with the next higher metrix prefix, e.g. 1000 kA -> 1 MA.

    Regards,
    Herb Glarner
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    Yes, you are correct. Even though in real life we don't impose the 1-999 rule. We choose the prefix of the unit first and then adjust the mantissa, which may throw it out of limits.

    It's a valid correction though and will be documented.
    Thanks!
     
    Last edited: May 29, 2013
  3. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    I would argue that it is correct, well, at least partially.
    It says between 1 and 1000.

    Less than 1, and you would use the next smaller prefix. Saying that a number between the two is exclusive of the two bounds. The point could be made, I'd tend to agree, that the 1 should be included, but limiting the wording to say between 1 and 999 would mean that both 1 and 999, are to use another prefix.
     
  4. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
    In any case, the wording needs work.

    "Between 1 and 1000" and "from 1 to 1000" aren't easily distinguishable in human language.

    Unless it wrote c \in [1,1000) , then it's not clear enough.
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Well pretty well every capacitor manufacturer makes 1000μF caps (and above). and labels them as such.
     
  6. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    I'd also point out that the phrase "the significant digits can be anywhere between 1 and 1000" is confusing and wrong. The term "significant digits" refers to the digits that are significant. 42 is not a digit. Note that "digits" is, in general, plural. Each significant digit is between 0 and 9, inclusive. For example, given 42.03mA, all four digits are signficiant, but all four are between 0 and 9.

    The fix is easy, just say that the prefix is nominally chosen such that the mantissa falls in the range

    1.0 <= mantissa < 1000.0

    But note that this is not a hard requirement and values such as 4700uF and 0.1uF are quite commonly used. Also, in some instances is more clear to use a consistent prefix in order to make value comparisons more obvious. So it might be better to compare 800V and 7000V instead of comparing 800V and 7kV.
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    A very good example of Engineering Common Sense.
     
  8. Dcrunkilton

    E-book Co-ordinator

    Jul 31, 2004
    416
    11
    "Because the major prefixes in the metric system refer to powers of 10 that are multiples of 3 (from "kilo" on up, and from "milli" on down), metric notation differs from regular scientific notation in that the significant digits can be anywhere between 1 and 1000, [...]"

    "Because the major prefixes in the metric system refer to powers of 10 that are multiples of 3 (from "kilo" on up, and from "milli" on down), metric notation differs from regular scientific notation in that the mantissa can be anywhere between 1 and 999, [...]"

    credited to Gulliveig at ibiblio.org

    Thanks to all for your assistance,

    Dennis
     
    Last edited: Jan 28, 2014
  9. WBahn

    Moderator

    Mar 31, 2012
    17,715
    4,788
    As a bit of a nit, the proper term is "significand" and not "mantissa". The word mantissa has a precise meaning as being the fractional part of a logarithm and the word "significand" is the preferred term. Notice that I used "mantissa" in my post above. That's because I wasn't aware of this at the time. So my recommendation would be to have a sentence at the proper place that points out the distinction and the proper term and then uses the proper term from that point on.
     
Loading...