Why do Americans not use nanofarads?

[Sweeper]

It is my experience that Americans shun the prefix nano, at least before farads and I wonder why. If you search for capacitors on Digikey, smaller values up to 10 nF are shown in pF (10000 pF) and above that it is 0.011µF etc. The Farad article on Wikipedia says this.

"North American usage also avoids nanofarads: a capacitance of 1×10^?9 F will frequently be indicated as 1000 pF; and a capacitance of 1×10^?7 F as 0.1 ?F."

The article on "nano" says something similar:

"In the United States, the use of the nano prefix for the farad unit of electrical capacitance is uncommon; capacitors of that size are more often expressed in terms of a small fraction of a microfarad or a large number of picofarads."

No reference or reason is however given in either of these articles. There are many other sites on the net that has the same or similar text (probably just copied from Wikipedia), but also without reference.

One speculation that I have heard is that the letters n and u or µ in handwriting might be easy to mistake for each other, but I have not seen any sources for this.

So, is there anyone here who knows why Americans avoid the nano prefix? I am mostly interested in references to trustworthy sources and not quite as interested in wild speculation.

[EEVblog]

IIRC this goes back a long way, like before the 1960's when I believe everyone in the world used either uF or pF, or sometimes mmf (mili-micro-farad!) was used to mean nF
I'm not sure of the reasons behind the lack of nF in the early days though, but the US were not alone in doing this in the old days. They just haven't been dragged into the modern age like we have 

Dave.

[Gall]

I've seen really old USSR-made capacitors marked "100000mmf" or even "1000000mmf".

[mark-r]

One possibility is that I've noticed that in old publications (mainly British but some American) from before about the 1950s, prefixes smaller than micro weren't used at all. Very small capacitances were labelled as uuF (micro-micro-Farad, i.e. millionths of millionths of a Farad which is equivalent to a picofarad). For values around the nanofarad values, it seemed to be a matter of preference or house style whether to label a capacitor (or should I say condenser!) say 1000uuF or 0.001uF. (I'm using u for the greek mu because I'm not sure how to get a mu symbol here, texts of the day would universally use mu).

Maybe when pF became more accepted, designers simply replaced uuF with pF, but were already used to there being no equivalent to nF so felt no compulsion to use it. In Europe where metrication and the SI units and prefixes were being adopted more rapidly than the US, perhaps we accepted nF more readily?

All speculation, but plausible maybe? I don't buy the n being confused with mu explanation - surely in scribbled handwriting, p is more easily confused with mu?

I expect the reason we associate this phenomenon with capacitors is that they are the only common component where pico- and nano- sized values are regularly used.

[Sweeper]

According to http://physics.nist.gov/cuu/Units/history.html, the prefix micro existed in 1874 while Wikipedia http://en.wikipedia.org/wiki/Metric_prefix claims that micro, nano and pico were introduced in 1960 (I doubt Wikipedia is correct that it is meaningful to say that micro was not introduced until 1960).

Clearly there was a period when micro existed, but not nano and pico, so I see the need for micromicrofarads etc (and I have seen that notation in old schematics as well). However, I doubt pico was introduced before nano and to me it seems more convenient to use both nano and pico and not just pico, so I am still confused why pico is so consistently preferred by US people.

[w2aew]

As an analog design engineer in the US for 25 years, I guess I never really noticed any lack of use of nF for values between 1nF and 1uF. In my experience, nF was fairly popular.  Specific example, I'd see 0.01uF about 60-70% of the time, 10nF used 30-40% of the time (and 10,000pF almost never).

[casinada]

Probably if you use nano Apple will sue you 

[robrenz]

(I'm using u for the greek mu because I'm not sure how to get a mu symbol here, texts of the day would universally use mu).

Hold down the Alt key and type +0181

[w2aew]

(I'm using u for the greek mu because I'm not sure how to get a mu symbol here, texts of the day would universally use mu).

Hold down the Alt key and type +0181

Doesn't work for my iPad 

[robrenz]

Being an Apple product it should have some "obviously insanely intuitive no manual needed way" to insert the "µ"

[jahonen]

(I'm using u for the greek mu because I'm not sure how to get a mu symbol here, texts of the day would universally use mu).

Hold down the Alt key and type +0181

At least on Windows, AltGr+m produces µ. I have finnish/swedish keyboard layout so YMMV.

Regards,
Janne

[IanB]

At least on Windows, AltGr+m produces µ. I have finnish/swedish keyboard layout so YMMV.

Regards,
Janne

I was going to say it's hard to enter µ because the forum software eats it, but apparently you have succeeded.

As a test, here is 10 microfarads written with the Greek letter mu and not the graphic character mu: 10 ?F
And here is 1000 ohms: 1000 ?

Let's see which of them survive.

(Apparently neither of them.)

[Sweeper]

As an analog design engineer in the US for 25 years, I guess I never really noticed any lack of use of nF for values between 1nF and 1uF. In my experience, nF was fairly popular.  Specific example, I'd see 0.01uF about 60-70% of the time, 10nF used 30-40% of the time (and 10,000pF almost never).

That's positive. But there has got to be a reason that Digikey, Mouser, Arrow and Farnell consistently do not use nF, but only pF and µF despite the inconvenient numbers that result, whereas Swedish distributors like Elfa (http://elfa.se), RS Components (http://se.rs-online.com/) and Bejoken (http://www.bejoken.se/) also uses nF when appropriate.

Per

[jahonen]

At least on Windows, AltGr+m produces µ. I have finnish/swedish keyboard layout so YMMV.

Regards,
Janne

I was going to say it's hard to enter µ because the forum software eats it, but apparently you have succeeded.

As a test, here is 10 microfarads written with the Greek letter mu and not the graphic character mu: 10 ?F
And here is 1000 ohms: 1000 ?

Let's see which of them survive.

(Apparently neither of them.)

I'm not sure if it is due to forum software but choice of character encoding in the database containing this forum. Perhaps it is set to some ISO-charset instead of UTF. Maybe Dave will tell us and could it be possibly changed?

Regards,
Janne

[IanB]

That's positive. But there has got to be a reason that Digikey, Mouser, Arrow and Farnell consistently do not use nF, but only pF and µF despite the inconvenient numbers that result, whereas Swedish distributors like Elfa (http://elfa.se), RS Components (http://se.rs-online.com/) and Bejoken (http://www.bejoken.se/) also uses nF when appropriate.

I'd suggest it's due to a lack of customary use of SI measurements and prefixes in the US engineering community as a whole. Outside of electricity, SI prefixes like micro-, nano- and pico- are not in common usage (neither are milli-, kilo- or mega-). Something unfamiliar is less likely to be found in common usage.

If we look back in British engineering practice before SI units became common, a 100 µF capacitor would have been marked 100 MFD.

If we look today in US engineering we find things like "mil" for 1000th inch, MMSCFD for "million standard cubic feet per day" and Mlb for "thousand pounds".

If the SI system of measurement is not common, then SI prefixes will feel somewhat foreign too.

[mzzj]

testing: µF and microfarad.

Not using nanofarads is not a big deal. Not using metric SI-system is a big deal. 

[DarkPrince]

I can say tha at my university we use the term nano when necessary. So at least my university isnt pushing that crazy notion. Wouldn't accept it anyway.

[Sweeper]

I'd suggest it's due to a lack of customary use of SI measurements and prefixes in the US engineering community as a whole. Outside of electricity, SI prefixes like micro-, nano- and pico- are not in common usage (neither are milli-, kilo- or mega-). Something unfamiliar is less likely to be found in common usage.

That might be the most plausible suggestion so far I think. But it does not explain why the habit does not change. It is a global world in electronics nowadays and I am pretty sure American EEs have no trouble understanding nF in e.g. European circuit diagrams, so why not take advantage of this knowledge and simplify how they express a range of capacitance values? American electrical engineers are in my experience pretty well versed in the SI system, so just because most Americans do not have a clear sense of how heavy a kg is or how tall a person who is 1.80 m is does not really explain a consistent avoidance of nF by EEs. I find it really odd and I am still curious about this.

Per

[c4757p]

This American uses "nano" all the time. 1000pF/10000pF/0.1uF is much clumsier than 1/10/100 nF!

[And Dave, I'm pretty sure MMF never meant "milli-microfarad"/nanofarad. I've done a lot of work with older (50s-60s) electronics from back when MMF was common, and it's always been "micro-microfarad"/picofarad.]

[helloworld922]

I've always written/used 100nF instead of 0.1uF (or 0u1F). I prefer 100nF or 0u1F because there's no decimal to lose, and 100nF doesn't have a "strange" notation where the metric scalar is used as a decimal holder. 100000pF is just too many digits to easily keep track of.

That's just me, though, and I'm relatively new to electronics

[c4757p]

I often switch multipliers to avoid writing a decimal point - 2200 pF instead of 2.2 nF, 4700 instead of 4.7 k, etc. I will also write "2n2", but not "2n2F" - that looks weird.

100000pF is just too many digits to easily keep track of.

Anyone who writes "100000pF" should never be allowed to write a zero ever again. Is "hanged, drawn and quartered" too much?

[Sweeper]

This American uses "nano" all the time. 1000pF/10000pF/0.1uF is much clumsier than 1/10/100 nF!

That's good. I totally agree with you regarding the clumsiness.

I just sent a question to Digikey to see if they can come up with a reason for avoiding nF. This seems to be harder to figure out than I expected.

Per

[c4757p]

While you're at it, write Mouser and ask them why they can't be bothered to normalize values at all. Why I have to select "1 watt", "1 Watt" and "1000 mW" to see 1W resistors is beyond me.

[SeanB]

That is because of mixing systems over the years...............

You will have had various entry operators who each used a different system.

[JoeyP]

This American routinely uses nanofarads, and has been doing so for decades. I find it odd every time I have to specify 10000pF to order 10nF caps from Digikey. I'd have no issue with 0.01uF but there seems no justification for 10000pF.