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I've got a schematic that originated in Brazil that generally uses European symbols rather then US. But some values for capacitors are confusing me.

There are several that are marked 100n and so forth, which I take as being 100 nF; but there are also a bunch of electrolytics marked with "mk", such as 1mk and 10mk. Is 'mk" the same as µF? Just want to make sure. Where does mk come from? I'm guessing the "m" probably stands for micro, but what about the "k"?

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The markings are not very consistent, as they use n by itself instead of nF; but smaller values are shown as pf.

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Some languages do not have the µ letter on the default keyboard and use mk as abbreviation for mikro. 1µF and 10µF are typical sizes for "big" blocking caps.

Using just n for nanofarad and pF for picofarad provides a stronger optical difference between these units. Most caps in a digital circuit are expected to be in n range (small blocking caps), you want the shortest form here with just one letter.

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    \$\begingroup\$ I find it interesting that they aren't labelled simply with u. Yes I know mu is an m not a u, but it looks similar so for a schematic it makes sense - e.g. these would be all the prefixes I'd use f p n u m k M G \$\endgroup\$ – Tom Carpenter Feb 7 '16 at 15:51
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About the M: According to UTE C90-510 specification:

a number of 3 digits maximum for the value a multiplying factor to obtain the capacitance in pF ( K = 103, M = 106, G = 109 )

Eg : 330M = 330⋅106pF = 330μF

About the K: Tolerance can be given in % or specified by a code letter:

  • M = ±20%;
  • K = ±10%;
  • J = ±5%.
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  • \$\begingroup\$ Does this make sense? The caps in the schematic are all blocking cabs. Why would you use a simple 100n for 100nF, and then this UTE spec for the second cabs? I'd say 'mk' is an odd form of 'u' or 'µ'. You'll often find exactly this 'mk' on russian devices as transliteration from Cyrillic characters. \$\endgroup\$ – sweber Feb 7 '16 at 12:22
  • \$\begingroup\$ Could you provide a working link to the UTE C90-510 specification? I Googled it and came up with only two links; one wanted 94 € and the other supposedly free link didn't work. \$\endgroup\$ – tcrosley Feb 7 '16 at 18:32
  • \$\begingroup\$ @tcrosley I believe it is a payed standards document, I couldn't find any working links either. \$\endgroup\$ – jippie Feb 7 '16 at 18:34

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