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I have a cap labeled 470K. I would have thought for sure that it would be 47pf until I saw this link where it said if a capacitor has a 0 as the last digit, it is the whole thing in nano-farads. How can I figure out this without a capacitance meter. 470K 100V C is the whole label if that helps.

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  • \$\begingroup\$ You've misquoted the link: it means "whole thing in pico-farads". And it says MAY ... be a marking of the actual value ...[in picofarads]. \$\endgroup\$ – david May 9 '13 at 7:59
  • \$\begingroup\$ The limit for the best technology is about 350F/g, so if it weighs less that a kg it's not 470kF. But give it a few years, and we might see caps marked 470k and mean it. \$\endgroup\$ – Pete Kirkham May 9 '13 at 12:36
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If you have a 471 capacitor of the same type, then clearly a 470 capacitor is not 470pF. If you have a 47 capacitor of the same type, then clearly 470 capacitors are not 47pF. You can make the same judgements if you have capacitors of the same type marked xx1 or xx For example 331 (330pF) and 33 (33pF).

You can compare the physical size of the capacitor to a 472 and a 479 of the same type.

You can connect it to a resistor, and observe the decay curve with an oscilloscope.

You can download the spec sheet for the capacitor, or for the manufacturer, and read what the marking convention is.

You can connect it to a linear regulator that requires 470pF load, and see if it oscilates

You can buy a 47pF capacitor of the same type, and see what how it is labeled.

OR

You can assume that it is a 47pF capacitor. If it's a K labeled capacitor, the chances that anyone would label a 471 as 470 are small. 470 10% on a small can might be 470pF, but 470K is 47pF.

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According to this site, 470k would be 47pF...

And you can see in the image below:

Small ceramic capacitor

471 -> 47 x 10 = 470pF

In general, on those small, rounded, ceramic capacitor, you don't have too much space to write. The brown color doesn't help, too, to use colors like resistors. And in general this size of capacitor will have a low value.

So, to me, it makes sense to write the value using just 3 numbers, and also it's ok that those values are expressed in pF...

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    \$\begingroup\$ That's a dumb way to write 47, isn't it. \$\endgroup\$ – Kaz May 9 '13 at 2:14
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    \$\begingroup\$ @Kaz Not dumb, but too clever. By the same token, 472k is a clever way of writing 4700pF. \$\endgroup\$ – Nick Alexeev May 9 '13 at 2:22
  • \$\begingroup\$ I understand that; but \$10^0\$ is useless. If you don't have too much space to write why add a useless 0 which just means "this 47 multiplies by 1". \$\endgroup\$ – Kaz May 9 '13 at 3:21
  • \$\begingroup\$ @Kaz But what if somebody reads 47k as 40μF ? \$\endgroup\$ – Nick Alexeev May 9 '13 at 3:49
  • \$\begingroup\$ @NickAlexeev Then they failed to apply the simple rule that a two digit figure gives picofarads, or tune in to the idea that something in the ballpark of 40uF won't be expressed in picofarads. Not to mention that 40uF is not a common value. None of the E series have 40 or 400. \$\endgroup\$ – Kaz May 9 '13 at 4:01
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For a lot of small capacitors, the letter at the end of the value simply denotes a tolerance. Sometimes, it's a single letter, and sometimes it's a string. Generally, I'd take a 470k cap to be 47 pF. You can read more at this link.

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  • \$\begingroup\$ Beat me to it by 10 seconds. \$\endgroup\$ – Alfred Centauri May 9 '13 at 1:16
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I think it would mean 0.47uF or 470 micro. I have never come across 470K capacitor. Are you sure this is correct?

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  • \$\begingroup\$ -1. Incorrect. A 470 microfarad 100 Volt (see the question) capacitor would be pretty massive, and invariably have space enough to be labeled in full. A 0.47 microfarad capacitor would not be labeled 470. \$\endgroup\$ – Anindo Ghosh May 9 '13 at 5:04

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