Metric notation

Thread Starter

Gulliveig

Joined May 29, 2013
2
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
 

Georacer

Joined Nov 25, 2009
5,182
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!
 
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tshuck

Joined Oct 18, 2012
3,534
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.
 

Georacer

Joined Nov 25, 2009
5,182
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.
 

WBahn

Joined Mar 31, 2012
26,398
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.
 

studiot

Joined Nov 9, 2007
4,998
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.
A very good example of Engineering Common Sense.
 

Dcrunkilton

Joined Jul 31, 2004
422
"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
 
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WBahn

Joined Mar 31, 2012
26,398
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.
 
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