# Ttally confused by AC capacitor narkings -- help please

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Could some electronics guru please help ? I am totally confused by markings on polystyrene AC capacitors. Unlike electrolytic capacitors which have their capacitance and voltage values very clearly printed, the ones on AC capacitors is very cryptic. For example, a 0.1 uF 100V AC capacitor has the marking: "28 104J" What does this mean ? Does the "J" indicate some multiplier -- as

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On Wed, 20 Jan 2016 21:57:00 -0800 (PST), snipped-for-privacy@gmail.com Gave us:

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He must not do much electronics... 104 on a cap screams 0.1uF to me. (without even thinking.) Older cap markings can confuse me sometimes.

George H.

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Well, we were all beginners once.

NT

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Most caps are marked in scientific notation to picoFarads. so 104 means 10. x 10^4 pF, or 100000 pF, which is 0.1 uF (or 100 nF). The J could mean anything, depending on the manufacturer's system. it could tell you the dielectric, the voltage, the capacitance tolerance, the temperature coefficient, or some combination of these. The 28 is probably a series number, again, without the manufacturer, no way to tell what it is.

Jon

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On Thu, 21 Jan 2016 13:03:47 -0600, Jon Elson Gave us:

Absolutely not.

The letter designation is for tolerance. PERIOD.

IF there is a two letter designator ABOVE the numeric value declaration, it is the voltage spec, and there is a standard for that as well, and NO, the makers do not get to simply willy nilly (or nelly elson) make up their own 'system'.

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On Thu, 21 Jan 2016 23:08:35 -0500, DecadentLinuxUserNumeroUno Gave us:

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I have this awful memory of trying to remember the code for the six colored dots on those rectangular brown mica "fixed" caps...

Mark L. Fergerson

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This a standard way to compactly code the value and its tolerance. Comes from a military standard, many years ago, I think.

0.1uF = "104" where the "10" is ten (10) and "4" is 10 raised to the 4th power (10^4, 10000). The base units are picofarads (pF). So 10x10^4 = 10^5 pF = 100 nF = 0.1 uF.

So do not get confused if you see "101". It is not

101 pF. It is 10x10^1 pF = 100 pF.

The "J" is assigned to a tolerance value of +/-5%. So "104J" would measure between 95 to 105 nF.

What about values under 100 pF? Leave off the third digit. A marking of "10K" is simply 10 pF (+/-10%).

And the "28"? Not part of the standard, AFAIK. Probably the manufacturer's chosen way to mark their model series type, or date code. Check their datasheet for marking info.

Regards, Rich S.

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1928? :)

NT

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On Sat, 23 Jan 2016 10:05:28 -0800 (PST), " snipped-for-privacy@bid.nes" Gave us:

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On Sat, 23 Jan 2016 12:43:31 -0800 (PST), Rich S Gave us:

Right

Wrong. The first two digit are called "significant digits"

The multiplier is "times ten to the fourth power".

That way a "474" would be 47 times ten to the 4th.

The result is ALWAYS in picofarads. It is up to the user to extrapolate other prefix monikers.

Yes..

Yes.

Wrong. It is always 3 digits.

No. 10pF is 100J or K etc.

Significant digits of 10 and zero multiplier yields 10pF.

It is likely an E or H, and represents the V max declaration.

Depends on where the marking is located.

Well hell.... with that he didn't need any of what you said and can go look at all of it for himself.

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