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Many capacitance values occurring in electronic circuits can be conveniently expressed in nanofarads, e.g. "a 10nF decoupling capacitor" .

However, the use of the term "nanofarads" or its abbreviation "nF" is often avoided and instead the numerically equivalent terms "10000pF" or "0.01μF" are used. The first term is three characters respectively two syllables longer while the latter is two characters respectively five syllables longer. This seems inconvenient, so there should be a reason for that.

Nanofarads are avoided by

  • distributors, e.g. Digikey, Mouser, Farnell, but not by RS;
  • manufacturers, e.g. AVX, Kemet, Wima, but not by Vishay;
  • and engineers, e.g. Robert Kollman from Texas instruments.

As an example reference, here is a screenshot from Digikey:

Digikey screenshot

Interestingly, resistances and inductances are generally stated without avoiding a particular prefix.

realtime
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    I don't think Americans avoid it at all. I certainly talk about nanofarads. However, it is usually easier to talk in terms of one unit, if possible. If most of your caps are in the uF range, you keep uF in the conversation and say .1 uF instead of 100 nF. If my board had mostly nF values, I would keep the convo in nF. – scld Jan 08 '14 at 16:31
  • @scld Could this be something new? I remember reading some older American books (say 60s and 70s) about electronics and when talking about capacitors, they do actually skip nano prefix. I'll try to dig up some references for that. – AndrejaKo Jan 08 '14 at 16:45
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    Another example of similar behavior I see even today are millifarads. From what I see, it's a bit rare to find a 10 mF capacitor, but 10 000 microfarad is not rare at all. – AndrejaKo Jan 08 '14 at 16:47
  • @AndrejaKo Well, if it's from the 70s, I might not know about it! However, I would guess that much of the modern terminology still intermingles with the older stuff. Hell, some of the test equipment I use has "KMC" instead of "GHz". So, you'll see examples of both but it is more likely just preference. Even on digikey you can probably order the same cap value under 2 or 3 different designations. – scld Jan 08 '14 at 16:53
  • @realtime I understand your question a bit more now. This is just a digikey/mouser type of thing. When I purchase these values, I label them under nF. If you purchase from Vishay, they'll be under nF. And if you look at the datasheets of the SMT caps on digikey, they'll have nF. It could just be a database/sorting thing to help with selection? – scld Jan 08 '14 at 16:59
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    When I was in school and starting my career in electronics ( in the 80's and 90's) I never saw the term 'nanofarads' used. It has only been in the recent decade or so that I've started to notice it. I wonder if the growth of the internet has caused more globalization of the terminology. – jwygralak67 Jan 08 '14 at 17:29
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    @AndrejaKo: I dislike the use of milliFarad since when I started in this business, before the Greek alphabet was invented, "mF" was microFarad, and "mmF" was micromicroFarad (now picofarad). I think I'll still consider "mF" to be microfarad, unless there is very strong evidence otherwise. I do recall nF appearing, perhaps sometime in the 1980s (I'm in Canada). – Peter Bennett Jan 08 '14 at 17:46
  • We never used nF in the 60's 70's 80's in school or Silicon Valley. However we used plenty of "mikes" and "puffs". One hundred puff and point one mike were pretty common. Like much of the French Metric, Nano did not fit into the mono-syllable shorthand. There is klick for kilometer and mil for milliliter but I don't recall any more. The Imperial and U.S. systems are loaded with mono-sylables that do not even sound like each other, which avoids confusion in verbal communication. Maybe it is syllable chauvinism. – C. Towne Springer Jan 08 '14 at 18:48
  • @C. Towne Springer: Your "syllable chauvinism" theory could be correct. When one talks about resistances there's "ohms" "kays" and "megs", all having just one syllable. But on the other hand, it would be just as easy to coin a one-syllable term for "nanofarads", for example "nans". Somewhat surprisingly this didn't happen... – realtime Jan 08 '14 at 19:27
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    This question appears to be off-topic because it is about Semantics. – Passerby Jan 08 '14 at 19:35
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    @Passe: It's more about the history of electronics, which I think is acceptable enough. It would help a lot though if the title didn't appear to be American-bashing. – Olin Lathrop Jan 08 '14 at 19:56
  • I think in this case (filter menu on some vendor's website) its more to do with a choice made by some database programmer, either to optimize searchability or readability. I wouldn't put too much stock in it being the language of preference of American EE's – Scott Seidman Jan 08 '14 at 20:32
  • @Olin its history of literal semantics, on why Sociolingual group A prefers slight variation X instead of slight variation Y that Sociolingual group B prefers. It's a even less interesting version of farenheit vs celcius, since both groups agree on using the SI prefixes for the Farads unit. Completely off topic. This wouldn't even stay open in english.se. Hell, lets open questions on using Condenser vs Capacitor as well. – Passerby Jan 08 '14 at 21:13

2 Answers2

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They don't. I'm American and I use nano for Farads like any other prefix, which is when doing so would put 1-3 digits to the left of the point.

A long time ago, nF wasn't used much for whatever reason. This wasn't a American thing as much as a long time ago thing. I've even seen pF referred to as µµF. Even worse, that was sometimes abbreviated to "mF". Over time these ancient designations have been depricated, and now we routinely use mF, µF, nF, and pF.

Other places where high technology meant a metal plow behind your horse while we were using vacuum tubes didn't pass thru this phase. When they got around to learning to spell "EE", the common metric prefixes for powers of 1000 were already in common use. One disadvantage of being early leaders is that you can end up with some baggage when common conventions eventually emerge.

I have mentioned this exact issue to some distributors when seeing a dropdown list like you show. They say that there are still a few obstinate old farts out there that get upset or confused when you show them nF and mF, so they avoid those. Time will fix this, and largely already has.

Olin Lathrop
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  • µµF is a rather common sight in old text books (pre-1960 breed). – oakad Jan 09 '14 at 01:41
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    One of my favorite units of old is KMC, or kilo mega cycles. It's another example of how we didn't havea full SI range back in the day. – W5VO Jan 09 '14 at 05:14
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    Back in my day (mid 60s), µF and µµF were the units we used. In spoken shorthand they were "mikes" and "mickey mikes". At some point that changed to "mikes" and "puffs". – Pete Becker Jan 09 '14 at 13:56
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I think its just because it is a middle ground and so using just uF and pF, we can usually classify where a capacitor is being used just by that unit and then partially the value. If we were to use the nF more predominantly, it may become more difficult to discern where that is being used.

Just spit-ballin.

Funkyguy
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