# Difference between 330 (33pF) and 331 (330pF) capacitor markings

#### StephenDJ

Joined May 31, 2008
58

This may look confusing, but the one on the right is marked 330 as if the zero should not be included in the value of the cap, right? If the zero means 33 x (10 to the power of zero), then there should not be 330 pF, but 33pF, correct?

#### jpanhalt

Joined Jan 18, 2008
10,097

#### MikeML

Joined Oct 2, 2009
5,444
I have a lot of capacitors around here that are marked 330 that are actually 330pF. That is why I own one of these:

#### jpanhalt

Joined Jan 18, 2008
10,097
I agree. When it will make a difference, check -- not unlike confirming the fuel in your airplane. Standards change, and you can never be absolutely certain whether something is labeled according to the most current standard.

John

#### atferrari

Joined Jan 6, 2004
4,069
Right. Note, for low values, e.g., 33pF, the "zero" may be omitted. So, 33 pF could be labeled 33 or 330.

http://www.elecraft.com/Apps/caps.htm

John
That I recall, I've been lucky. I never run across the "330" type but always "33". But, good to keep in mind.

#### StephenDJ

Joined May 31, 2008
58
I have a lot of capacitors around here that are marked 330 that are actually 330pF. That is why I own one of these:
Thanks everyone. I was sorting my parts bin, and came across these. So are you telling me what I have in my bin may actually be 330pF? I have no way to check them. Just wanted to make sure they wind up in the right cabinet drawer.

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#### WBahn

Joined Mar 31, 2012
26,073
You have lots of ways to check them, depending on what you have available. Do you have an oscilloscope? If so, then make a little RC circuit using 1MΩ resistors and measure the time constant. If you have some basic digital parts then you can make any number of oscillator circuits that go into a frequency divider with enough stages to blink an LED as a slow enough rate for you to visually tell the difference between 1Hz and 10Hz, for example.

#### WBahn

Joined Mar 31, 2012
26,073
I agree. When it will make a difference, check -- not unlike confirming the fuel in your airplane. Standards change, and you can never be absolutely certain whether something is labeled according to the most current standard.

John
There's a current standard for capacitor marking?

#### StephenDJ

Joined May 31, 2008
58
You have lots of ways to check them, depending on what you have available. Do you have an oscilloscope? If so, then make a little RC circuit using 1MΩ resistors and measure the time constant. If you have some basic digital parts then you can make any number of oscillator circuits that go into a frequency divider with enough stages to blink an LED as a slow enough rate for you to visually tell the difference between 1Hz and 10Hz, for example.
Good idea. Yes, I have a 20Mhz oscilloscope. Since I'm just now getting started back on electronics and getting my workbence in order, I may check this later. But I think I could use t=RC at which V=70% of peek to confirm this value. Or I could do it by reactance measurements using X=1/(2piFC).

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#### RichardO

Joined May 4, 2013
2,271
It seems that if the value has a tolerance then the value is in picofarads (no multiplier digit). If not then the value is digit,digit,multiplier (also in picofarads).

Rant: I hate cap markings.