Cap values

Its easy to find cap value tables online:

0.1uF is 100 nF 0.01uF is 10nF or 10,000pF 0.001uF is 1nF or 1000pF -and so on-

And yes, the default units are microfarards.

Bob M.

It's in uF. Units of pF or nF wouldn't make sense and if it was in mF then (I assume) they'd just annotate it as "1.0". Could be unadorned farads but that's unusual enough that one would expect it to be so indicated.

A quick Spice run (too lazy to breadboard it ;-) indicates that .001 uF would behave in a sane manner...

--
Rich Webb     Norfolk, VA

The problem is that there are units on some of the caps, no units on others. My question relates to what the default units for a cap on a schematic generally are if there are no units specified.

I can most likely manage conversions :) Slide dat decimal place...

-- Les Cargill

That is what I figured...

-- Les Cargill

I sincerely hope so! Even a Spice run would be way too much work...

Thank you.

-- Les Cargill

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.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

The markings on capacitors are often ambiguous - you get used to it.

Many small capacitors (MLCs) use a three digit system based on pF, so =

102 is=20 1000 pF. It can be confusing for a 10 pF capacitor which would be = labeled=20 100, 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=20 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,=20 which is helpful on some copies of schematics where the decimal point = may be=20 very faint or disappear (as may happen in scanned copies and JPGs and = the=20 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=20 with 300mil lead spacing

I use a similar system for resistors, inductors, and other common=20 components. For ICs, transistors, and special components I use the part=20 number:

U_74HC139_SO16 Q_2N3904_TO92

I use these part numbers primarily for PCB design, so they are in the = PADS=20 libraries. Someday I may also cross-reference them to a database where I = can=20 keep track of cost, vendors, and quantities on hand.

Paul=20

As others have said, the default units are almost always microfarads. If it's something else it will be noted somewhere on the schematic.