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

Discussion in 'Homework Help' started by StephenDJ, May 12, 2015.

1. ### StephenDJ Thread Starter Active Member

May 31, 2008
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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?

Jan 18, 2008
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3. ### MikeML AAC Fanatic!

Oct 2, 2009
5,450
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I have a lot of capacitors around here that are marked 330 that are actually 330pF. That is why I own one of these:

4. ### jpanhalt AAC Fanatic!

Jan 18, 2008
5,699
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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

5. ### atferrari AAC Fanatic!

Jan 6, 2004
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That I recall, I've been lucky. I never run across the "330" type but always "33". But, good to keep in mind.

6. ### StephenDJ Thread Starter Active Member

May 31, 2008
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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.

Last edited: May 12, 2015
7. ### WBahn Moderator

Mar 31, 2012
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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.

8. ### WBahn Moderator

Mar 31, 2012
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There's a current standard for capacitor marking?

9. ### StephenDJ Thread Starter Active Member

May 31, 2008
58
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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).

Last edited: May 13, 2015
10. ### RichardO Well-Known Member

May 4, 2013
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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.