+++++++++++++++++++++
From: "Michael Harris" <mike.harris at horizon.co.fk>
To: <Elecraft at mailman.qth.net>
Date: Sat, 8 Jun 2002 13:45:16 -0400
Subject: [Elecraft] SI Units

Hi,

I wonder, does our credibility in a technical hobby falter a little when may
of us can't even get the common unit prefixes right.

For information:

The S I allows the sizes of units to be made bigger or smaller by the use of
appropriate prefixes. For example, the electrical unit of a watt is not a
big unit even in terms of ordinary household use, so it is generally used in
terms of 1000 watts at a time. The prefix for 1000 is kilo so we use
kilowatts[kW] as our unit of measurement. For makers of electricity, or
bigger users such as industry, it is common to use megawatts[MW] or even
gigawatts[GW]. The full range of prefixes with their [symbols or
abbreviations] and their multiplying factors which are also given in other
forms is

 yotta   [Y] 1 000 000 000 000 000 000 000 000 = 10^24
 zetta   [Z] 1 000 000 000 000 000 000 000 = 10^21
 exa     [E] 1 000 000 000 000 000 000  = 10^18
 peta    [P] 1 000 000 000 000 000  = 10^15
 tera     [T] 1 000 000 000 000       = 10^12
 giga     [G] 1 000 000 000    (a thousand millions = a billion)
 mega  [M] 1 000 000       (a million)
 kilo     [k] 1 000       (a thousand)
 hecto  [h] 100
 deca   [da]10
                  1
 deci    [d] 0.1
 centi   [c] 0.01
 milli    [m] 0.001       (a thousandth)
 micro [µ] 0.000 001       (a millionth)
 nano  [n] 0.000 000 001          (a thousand millionth)
 pico   [p] 0.000 000 000 001   = 10^-12
 femto [f] 0.000 000 000 000 001  = 10^-15
 atto    [a] 0.000 000 000 000 000 001  = 10^-18
 zepto [z] 0.000 000 000 000 000 000 001 = 10^-21
 yocto [y] 0.000 000 000 000 000 000 000 001 = 10^-24

[µ] the symbol used for micro is the Greek letter known as 'mu'

Nearly all of the S I prefixes are multiples or sub-multiples of 1000.
However, these are inconvenient for many purposes and so hecto, deca, deci,
and centi are also used.  deca also appears as deka [da] or [dk] in the USA
and Contintental Europe.

hertz [Hz]
The hertz is the SI unit of the frequency of a periodic phenomenon. One
hertz indicates that 1 cycle of the phenomenon occurs every second. For most
work much higher frequencies are needed such as the kilohertz [kHz] and
megahertz [MHz]. It is named after the German physicist Heinrich Rudolph
Hertz (1857-94).

Regards,

Mike VP8NO (IOTA SA-002)
GQRP 10148
K2 #1400

++++++++++++++++++++