John Fields wrote in message . ..
On 17 Jan 2004 02:06:26 -0800, (Svante)
wrote:

(Stewart Pinkerton) wrote in message ...
On 16 Jan 2004 14:40:26 -0800, (Svante)
wrote:

(Stewart Pinkerton) wrote in message ...
On 16 Jan 2004 06:40:38 -0800, (Svante)
wrote:

Harmonic distorsion is expressed as the ratio between the distorsion
components and the fundamental. What surprises me is that it is the
VOLTAGES that are compared (in the electrical case) not the POWERS. So
if we have a second harmonic 40 dB down, the second harmonic
distorsion is 1 %, not 0.01 %.
(In this case the voltage of the harmonic is 1% of the fundamental,
and its power is 0.01% of the fundamental)

What is the reason for this convention? I'd think that power would be
more logical.

Think what you like, voltage is the standard.

Yes I will think what I like, and I know voltage is the standard, that
should be clear from my post. But I asked about the REASON for the
standard.

Why does it matter? Why is the kilogram the standard for mass?

To annoy the americans? :-) You might not find it interesting, and
that is OK. I did find it interesting and posted the question to see
if anyone else had thought about it too. I bet you could find people
interested in why a kilogram is a kilogram too. Why isn't it a gram?
Hmm...

---
To obtain a standard of length a quadrant of the earth (one-fourth of a
circumference) was surveyed from Dunkirk to Barcelona along the meridian
that passes through Paris. The distance from the pole to the equator was
divided into ten million parts to constitute the meter (spelled metre in
some countries).

Further subdivisions in the length of the meter, by orders of magnitude,
into more convenient-to-use units for some applications led to the
naming of the decimeter (one-tenth of a meter), the centimeter (one
one-hundredth of a meter), the millimeter (one one-thousandth of a
meter) and so on. Note that by defining the unit of length the
definition of the unit of volume followed automatically.

Note also the curious coincidence(?) of units in the metric system being
divisible everywhere by ten and the fact that we have ten digits on our
hands.

Now, since water is/was ubiquitous on the surface of the earth and,
presumably, weighed the same everywhere, it was decided that a certain
volume of water (the 'cubic centimeter', a cube one centimeter on an
edge) would become the standard of weight and was called the 'gramme'.

The prefix 'kilo', indicating that a multiplication of the quantity
following it by 1000 is required, means "1000 grams" when appended with
'gram'. Hence, kilo+gram = kilogram = 1000 * 1 gram = 1000 grams.

Also, note the new binary prefixes:

From http://physics.nist.gov/cuu/Units/binary.html

Prefixes for binary multiples
--------------------------------------------------------------------------------

Factor Name Symbol Origin Derivation
2^10 kibi Ki kilobinary: (2^10)^1 kilo: (10^3)^1
2^20 mebi Mi megabinary: (2^10)^2 mega: (10^3)^2
2^30 gibi Gi gigabinary: (2^10)^3 giga: (10^3)^3
2^40 tebi Ti terabinary: (2^10)^4 tera: (10^3)^4
2^50 pebi Pi petabinary: (2^10)^5 peta: (10^3)^5
2^60 exbi Ei exabinary: (2^10)^6 exa: (10^3)^6


--------------------------------------------------------------------------------

Examples and comparisons with SI prefixes
one kibibit 1 Kibit = 210 bit = 1024 bit
one kilobit 1 kbit = 103 bit = 1000 bit
one mebibyte 1 MiB = 220 B = 1 048 576 B
one megabyte 1 MB = 106 B = 1 000 000 B
one gibibyte 1 GiB = 230 B = 1 073 741 824 B
one gigabyte 1 GB = 109 B = 1 000 000 000 B

--------------------------------------------------------------------------------

Now I think this thread is drifting off the original subject... :-)