+++++++++++++++++++++
From: "Michael Harris"
To:
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
++++++++++++++++++++