"Tim Wescott" wrote in message
The ARRL Handbook's old nomenclature was that fractional values
like your 0.001 would be in microfarad, and decimal values (i.e. 33
or 100) would be pF.
I would expect something similar. Particularly if the schematic
is over 10 or 20 years old, anything 1uF and above is almost
certainly going to be electrolytic, and will be marked with polarity.
_My_ nomenclature, heavily influenced by my college physics
courses, is to put the correct dimensions on everything -- so
that cap would be labeled "1nF" or (under duress) 0.001uF.
Many small capacitors (MLCs) use a three digit system based on pF, so 102 is
1000 pF. It can be confusing for a 10 pF capacitor which would be labeled
100, while a 100 pF would be 101. It's even more confusing, perhaps, for
values smaller than 10 pF, but they are relatively rare. And there are some
capacitors which use just one or two digits for actual values in pF.
There is also the nomenclature that uses the prefix for the decimal point,
which is helpful on some copies of schematics where the decimal point may be
very faint or disappear (as may happen in scanned copies and JPGs and the
like). I use a variation of that for my part numbering system, as in:
C_3N30_50V_5%_0805 which is 3.30 nF 50V 5% in a 0805 SMD package
C_25F0_2V7_D500_LS300 which is 25.0 Farads, 2.7V, in a 500mil diameter can
with 300mil lead spacing
I use a similar system for resistors, inductors, and other common
components. For ICs, transistors, and special components I use the part
number:
U_74HC139_SO16
Q_2N3904_TO92
I use these part numbers primarily for PCB design, so they are in the PADS
libraries. Someday I may also cross-reference them to a database where I can
keep track of cost, vendors, and quantities on hand.
Paul
Slide dat decimal place...
