Why do Americans not use nanofarads?

[Martin.M]

I have found the following hier in germany:

1000pF
1nF
102
0,001/voltage
brown-black-red- following colors for tolerance and voltage (compare to american Micas and bumble bees)

and vintage: 1000cm

greetings
Martin

[Pentium100]

In a lot of USSR circuit diagrams the units "pF" or "uF" are not specified as such, if the value is without a decimal point (200) then it is picofarads (or ohms), if it is specified with a decimal point (1,0) then it is microfarads (or megaohms). Kiloohms are marked with a letter "k" though.

[c4757p]

That's common in older American schematics too.

[jh15]

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

Regards,
Janne
[/quote]
Shouldn't it be YKMV in Finland?

[IanB]

Shouldn't it be YKMV in Finland?

Ah, but in metric countries fuel consumption is measured in litres per km. So it would be "literage" 

[amspire]

I know back in the 70's and 80's, some of the companies I had contact with had a strict policy to avoid nanoFarads and milliFarads to avoid confusion, particularly at a time when there was far more manual assembly. Even though parts often came on reels, the leads would be cut and formed in stores ready for hand placement, and the assemblers would pick parts out of bins.

A 100nF polyester cap could be the same size as a silver-mica 100pF cap. Since caps rarely used colour-code to represent values and some caps had no "p", "n" or "u", it was really easy to make mistakes. Is a ceramic cap with just "33" on it 33pF or 33nF? If you only buy capacitors that use 33 or 33p for 33pF and 0.033 or 0.033u for 33nF, it was hard to make a mistake.

In the surface mount era, it is not as big an issue. If you are dependent upon someones eyesight to check the correct valued resistors and capacitors are in place, you are in big trouble.

I have no idea if any companies still avoid nF as a strict policy. I think today, if you can get a part labelled 10nF cheaper then an equivalent part labelled 0.01uF, it is a no-brainer - you get the cheaper part.

[Sweeper]

I know back in the 70's and 80's, some of the companies I had contact with had a strict policy to avoid nanoFarads and milliFarads to avoid confusion, particularly at a time when there was far more manual assembly.
[...]

It sounds reasonable that it was in order to avoid some kind of confusion that companies banned the use of nF. Still, the "solution" requires more characters (0.033 as opposed to 33n or 10000 as opposed to 10n e.g.) than the alternative to use the prefix nano, so if the problem was the limited space to print characters on components, the solution seems somewhat backwards. Maybe I am expecting too much rationality here...

I wonder if IEEE had some policy or recommendation regarding the (non-) use of nF.

Per

[thmjpr]

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

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

Sure this explains the initial variations, but does not explain why they would not fix them. Updating a database where value = 1w, 1 watt, 1000mw and renaming to 1 Watt should be trivial.

Reminds me of a checkout bug on Newark. If I didn't fill out the billing address correctly (some unimportant line needed to be filled) it would display a generic message "system error has occurred". Leaving the buyer clueless, possibly in search of another distributor.

[jahonen]

Shouldn't it be YKMV in Finland?

Ah, but in metric countries fuel consumption is measured in litres per km. So it would be "literage" 

Actually, litres per 100 km is much more commonly used "unit" here to get numeric values usually between 1 and 10.

Regards,
Janne

[PA4TIM]

One of the leading companys in the USA in the field of measuring capacitance was General Radio. On my GR-1608 the range switch gives pF, nF, uF and mF ( desingned in 1962 and I have a very early version according to Henry Hall who designed them because my oscillator/detector was all germanium) I do not think they would use nF if it was allmost never used.

So nF was known in the USA, at least the last 50 years ;-)

[Martin.M]

the friends in the states use all,

on our scopes you see graticules of a cm, not half inches 

greetings
Martin

[beaker353]

I use nF all the time. In my EE classes the instructors are very strict about staying in standard SI units/prefixes/suffixes. The numeric part of an answer must be less than 1,000 and equal to/more than 1. Outside that range your answer in considered wrong, period.

-EM

[rsjsouza]

Updating a database where value = 1w, 1 watt, 1000mw and renaming to 1 Watt should be trivial.

Conceptually and practically it seems a trivial task, but you would be surprised to see how difficult it is to merge such databases in a foolproof manner and to cover all occurrences in all the relevant data fields, especially when they come from different manufacturers with different file formats. Imagine every manufacturer specifying their 10000pF/10nF/10kpF and so on?
 
In my experience the distributors do not manually input that data, as it is expensive, error prone and unreliable. They have to trust the suppliers to provide this database, and not many may be as cooperative to change their own internal standards to ease the distributor's life. 

[c4757p]

It really should not be hard to write a script that understands engineering units and prefixes. Even the horrid bastardization "10kpF" should be an easy one. Actually, I regularly use a calculator I wrote myself that would understand all of these just fine. I get the idea that DigiKey does this, actually - their component values seem to be relatively normalized.

[FenderBender]

Why do Americans not use nanofarads?

Because we want everyone in the world to hate us... even more. 

In all seriousness, I really haven't ever been under the impression that American engineers are against nF in any way. Some of the older naming conventions might still be in place, but I don't think too many people are going to say "I need a 0.001uF capacitor"..I don't think.

[BravoV]

on our scopes you see graticules of a cm, not half inches 

Really, is there such scope with imperial graticule ? 

[NiHaoMike]

I use millifarads and nanofarads as I need to. Since I do a lot of work on power electronics, it turns out I end up using them a lot. I have also been using the unit as a decimal for a few years now, the reasoning is that if the text gets smudged (easy to do on a rough draft), the decimal point is very easy to miss and the error might not be obvious on some designs.

[Sweeper]

Based on the comments here from Americans it seems like the "situation" is better than I expected in that lots of Americans apparently use nF happily.

Still, the big distributors avoid it and Wikipedia says "North American usage also avoids nanofarads [...]", so I still believe there is something to it, although the nF-phobia (if it ever existed) might hopefully be going away.

Per

[helloworld922]

Must be related to the huge push for "nano-technology"

My local uni's clean room was renamed from the microfab to the nanofab because of this.

[eliocor]

To me 10000pF and 10nF are not the same:
10000pF means the precision of the capacitor is very high (<= 1%)
10nF = precision is 5-10% or less.

[Tepe]

Ah, but in metric countries fuel consumption is measured in litres per km. So it would be "literage" 

Actually, litres per 100 km is much more commonly used "unit" here to get numeric values usually between 1 and 10.

Around here we use km/l so I guess it must be "kilometerage" 

[madires]

To me 10000pF and 10nF are not the same:
10000pF means the precision of the capacitor is very high (<= 1%)
10nF = precision is 5-10% or less.

Very true! I also would expect a high accuracy for a 10000pF cap. It's amazing how the different systems are impacting the view.

PS: I happily admit that I'm using m, µ, n, p and f since I learned about them in school :-)

[Zeta]

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.

Most EE use nF nowadays but distributors might be using pF out of conveniencesince because most Ceramic disk capacitor markings have been in pF.

for example, a capacitor marked 101 means 100pF while a capacitor marked 104 means 100nF (100000pF). I actually find it more convenient to have a part marked as 222 rather than 2n2.

[_Sin]

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

(off topic, but if you want to type greek letters on an i-device, you turn on the greek keyboard...)

[AlfBaz]

Speaking of off-topic, what's the go with the pronunciation of Farad as Feh-raad by some Americans?