EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: dusan on October 10, 2022, 12:36:04 pm
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I've noticed in older schematics that they avoided using nanofarads like a plague, using 0.1u 0.01u or even 0.001u or 0.0022mf instead of simply 100n 10n 1n 2n2. Was there a reason for it or was it just some convention? I can imagine someone requested print service to use expensive µ typesetting glyph and then angry redactor pointing finger and saying "You bought it you gonna use it" but besides that I really don't know. The cherry on top is using 0.1 without any unit and people were supposed to guess if it is micro, nano or pico.
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Old schematics also used \$\mu\mu\$ for the pico- prefix.
According to this page:
https://www.nist.gov/pml/owm/metric-si-prefixes (https://www.nist.gov/pml/owm/metric-si-prefixes)
micro, nano and pico didn't become official SI units until 1960:
1960 – Two prefixes were made obsolete (myria and myrio) and 6 were added, including 3 for forming multiples (mega, giga, tera) and 3 for forming submultiples (micro, nano, pico). Total Prefixes: 12.
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Depending on how far back you go it could simply be that nano as prefix was not common or not even invented yet. If you go far enough you also find cases of people using 'cycles' instead of 'Hz', and avoiding giga- and tera- and instead saying 'kilomegacycles' or 'megamegacycles'.
I also seem to remember it being convention for every capacitor to be in pF unless otherwise specified, and you would even get cases of people specifying capacitors in 'kpF' etc.
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some international standard
some auto-electrician tried to find +/- in wall outlet (almost, close)
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I can't say where the practice started, but many of us who began electronics in the 50s and 60s just copied what we saw. And after a decade or more of usage it became habit, with no really compelling reason to change so the practice continued long after the newer standards were published.
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There was an old standard for capacitors in schematic drawings:
Values below 1 were in microfarads for non-polarized capacitors;
Values above 1 were in picofarads for non-polarized capacitors;
Polarized capacitors were in microfarads;
Unless otherwise indicated.
This was before nanofarads were added to the language in 1960.
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The nano prefix may have been added to our technical lexicon in 1960, but it was not in common use then. Throughout the 60's and early 70's, mµ was used in spectroscopy. It was often written "mu" because of typewriter limitations, namely the IBM Selectric in the US and probably elsewhere too (https://en.wikipedia.org/wiki/IBM_Selectric_typewriter ).
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The nano prefix may have been added to our technical lexicon in 1960, but it was not in common use then. Throughout the 60's and early 70's, mµ was used in spectroscopy. It was often written "mu" because of typewriter limitations, namely the IBM Selectric in the US and probably elsewhere too (https://en.wikipedia.org/wiki/IBM_Selectric_typewriter ).
I believe a Greek character ball was available for the Selectric, but almost no one would take the time to change balls to type one character. No conventional typewriter (except those for native Greek text) had any capability for this symbol. The ability to routinely use symbols like these didn't come along until microcomputer type setting came along in the early 1980s.
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I remember being told the avoidance was keeping capacitor values intuitive using many decades i.e. between RF, audio, mains filters. pF and µF prevailed, nF is not really useful being a middle. Marking codes were simpler as well.
I don't use nF much but scream when I see this kind of junk from MLCC capacitor manufacturers and Digi-Key etc. also stuck in millions of pF land.
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In my youth, before nanofarads, we would use "mmf" up to about 1000, then switch to 0.001 "mf".
Of course, here "m" was parsed as "micro", not "milli".
"mmf" was pronounced "micky-mike".
One reason for the unwieldy example in DigiKey is to simplify lookup in Excel and similar packages.
I find some vendor searches difficult when they organize values by alphanumeric lookup, so 1.2 megohms comes before 22 ohms.
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I think the main reason was "blueprints", menaning schematics on paper. After being copied I don't know how many times, they got blurrier and blurrier, and the destinction between "u" and "n" became difficult, whereas "p" with it's tail stayed readable.
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I hate that. While ledtester showed us why it was the case before 1960, and we can understand that it lingered on for years, still seeing that notation on current schematics (which is still extremely frequent on schematics from the US apparently) is very annoying. It is all the more that using decimal dots on schematics itself is a bad idea for readability reasons.
So while it may have had a good reason over 50 years ago, doing that nowadays doesn't make any sense. Please stop doing that. :)
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Because, just like 'flammable', 'non-flammable', 'inflammable' the stupid term 'non-inflammable' wasn't needed. When someone said '100 puff' or 100 picofarads we knew exactly which drawer they were in. If someone needed 1000 picofarads we just knew instinctively to look in the .001uf drawer. It seems that at 1000pf and above we just went to .001uf or .0012uf etc. And, that is how the capacitors were marked. Even today in the engineering lab when a greenhorn wants a "one nan" I have a W.T.F. moment, Oh he wants 1000pf or .001, yes I know where those are kept. Schematics marked with .1 were simply assumed to be .1uf A.K.A. .1mf since .1pf wouldn't make sense anywhere except microwave frequencies and that wouldn't even be a solderable part, it would be an extra little hickey on the p.c.b. trace. Us old dogs are warming up to 'nanofarads' but really never felt a need for the term. I guess us old slide-rule jockeys faced with the 'horrible shortcomings' of having only two terms picofarad and microfarad could do the dauntingly difficult math in our heads realizing from countless thousands of hours of design work that .001uf and 1000pf were in the same drawer. Now I find that same drawer has disk ceramics marked '102', but I have never seen a 1N in that drawer!! (I think those hide away in the diode drawer) Respectfully, YMMV....
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I noticed in corporate environment the finance/accounting people use "M" notation for thousands and "MM" for millions. Now, THAT is bizarre. Caused me confusions. :wtf:
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I hate that. While ledtester showed us why it was the case before 1960, and we can understand that it lingered on for years, still seeing that notation on current schematics (which is still extremely frequent on schematics from the US apparently) is very annoying. It is all the more that using decimal dots on schematics itself is a bad idea for readability reasons.
So while it may have had a good reason over 50 years ago, doing that nowadays doesn't make any sense. Please stop doing that. :)
You are free to ignore any schematics which don't meet your marking standards. Presumably, since you don't value the dinosaur way of doing things you won't miss much.
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Bud is very accurate on the confusion of 'M' meaning a 'quantity of physical objects' based on 'one thousand'. That really messes up a young engineer or even an 'old dog' who has learned 'K' describes an electrical or electronic value based on 'one thousand' and 'M' indicates a value based on 'one million'. I had a hard time getting used to the weird symbol the Germans used in schematics for '7'. Like in Studer/Revox machines. It looks like a messed up arrow pointing up. I don't mind '7' or 'Z' with a flag through it as it seems normal to me. You've got to love Iceland and other European countries where '.' and ',' have reversed meanings from the English standard. Oh, then there is they joy of industrial electrical wiring color codes around the world!!! Having spent so much time knowing the 'black wire' was usually a chassis referenced return or possibly a negative D.C. voltage imagine my surprise to find 'black' being hot in home and industrial wiring!!
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My favorite obsolete wiring code is using "red" for ground/PE.
When we installed some x-ray equipment in an old building in Sweden, we were warned that the building was old enough that we might encounter that color code.
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Hi,
My recollection of the starting to use nanofarads is that it was more a decision on avoiding using the decimal point. I was educated UK.
4K7 or 4700 replaced 4.7K
0u1 or 100n replaced 0.1uF
The concern was that a spec of dirt on a photocopier or an original drawing, no CAD drawings, would be interpreted as a decimal point. In those days we used dyeline machines for copying drawings. It was a contact print using ammonia.
I am not old enough to remember mmF ;)
Jay_Diddy_B
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Using notation like 4K7 instead of 4.7k makes good sense, if you ever view schematics on screen or on paper using middle aged eyeballs.
As for not using the nano- prefix, I always thought it was a convention peculiar to the USA. I've always used nF and find it very strange seeing caps listed as 100000pF (quick! count the zeros!) or 0.001uF.
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Having spent so much time knowing the 'black wire' was usually a chassis referenced return or possibly a negative D.C. voltage imagine my surprise to find 'black' being hot in home and industrial wiring!!
That goes to the electrical concept of the 'identified conductor' which is the neutral. We don't care what the phase colors are although black-red-blue is common for 208V and purple-orange-brown is common for 480V. As long as both systems are in different enclosures, both may use white for neutral. If they are both in the same enclosure white is used for 120/208V and gray is used for 277/480V. In either case, it is the 'identified conductor' we keep track of.
Perhaps little known fact: On two wire zip cord (lamp cord) there will be two small ridges along one lead (or a flat edge). That is the 'identified conductor' and should connect to the shell of a lamp socket. Note that I didn't say anything about the hot conductor (which goes to the center of the socket), it's all about the 'identified conductor'.
Ground is green in all cases.
Phase color tape can be used to mark larger conductors where a colored jacket is not available. The wires need to be taped in every enclosure.
And, yes, I was around long before this silly nF stuff came up. I still prefer to think about 0.1 ufd rather than 100 nF. I also remember megacycles and especially cycles per second which seems a lot more descriptive than Hertz. One thing about the new units, they manifestly display the difference between change and improvement.
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I once asked a licensed electrician (US) why black was the "hot" or line wire.
He replied "black means death", which I assume was the mnemonic he learned as an apprentice.
When installing equipment in the UK, they were surprised that white denoted "neutral" in American wiring.
At least we were all able to compromise with the yellow-green ground/PE wire.
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really old schematics use centimeters unit for capacitance, it was at about beginning of 20 century :)
1 cm = 1.11 pF
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I had a hard time getting used to the weird symbol the Germans used in schematics for '7'. Like in Studer/Revox machines. It looks like a messed up arrow pointing up.
That's not a "7", it's a "1".
Studer/Revox is Swiss, BTW.
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Benta, you are correct '1' not '7'. Sorry, it has been a long time since I have looked at schematics using that symbol!!
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Nothing wrong with using decimal points, as long as they are preceded by a digit, especially if it is a number less than one, (use zero before your decimal). :horse: :popcorn:
)
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Oh, then there is they joy of industrial electrical wiring color codes around the world!!!
No need to travel the world,just come to the uk and i can show you at least 3 different colour codes,4 if you count the change from green to green/yellow for earth.The worst thought out was changing L3 from blue to black and neutral from black to blue,that led to 1 or 2 expensive mistakes.
(https://electrical.theiet.org/media/2620/table-1-colour-identification-history_v2.jpg)
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Man. Blueprints. Dyeline printers.
Ammonia fumes made my cigarettes taste bad. I gave smoking becasue of it!
Jeez I'm glad thats all over -or is it. Any users still out there?
Tabacco or blueprints that is.
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Nothing wrong with using decimal points, as long as they are preceded by a digit, especially if it is a number less than one, (use zero before your decimal). :horse: :popcorn:
)
I always say "zero-point-two-seven" when speaking the number 0.27.
My professor in grad school, who was educated in Europe, had the unfortunate habit of stating such a number as "zero-two-seven".
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My professor in grad school, who was educated in Europe, had the unfortunate habit of stating such a number as "zero-two-seven".
For continental Europe, I don't believe that. But perhaps the UK.
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My professor in grad school, who was educated in Europe, had the unfortunate habit of stating such a number as "zero-two-seven".
For continental Europe, I don't believe that. But perhaps the UK.
He was educated in Italy, and spoke perfect English.
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I had a university professor who referred to a metal cased instrument with a grounding point as having an "earthy output terminal".
It was a quirk peculiar to him personally, not a geographical thing.
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The nano prefix may have been added to our technical lexicon in 1960, but it was not in common use then. Throughout the 60's and early 70's, mµ was used in spectroscopy. It was often written "mu" because of typewriter limitations, namely the IBM Selectric in the US and probably elsewhere too (https://en.wikipedia.org/wiki/IBM_Selectric_typewriter ).
Why single out the Selectric? No standard typewriter outside of Greece would have had the μ or any other Greek character.
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The nano prefix may have been added to our technical lexicon in 1960, but it was not in common use then. Throughout the 60's and early 70's, mµ was used in spectroscopy. It was often written "mu" because of typewriter limitations, namely the IBM Selectric in the US and probably elsewhere too (https://en.wikipedia.org/wiki/IBM_Selectric_typewriter ).
Why single out the Selectric? No standard typewriter outside of Greece would have had the μ or any other Greek character.
The nm or mu (millimicron) was used in spectroscopy to be politically correct and to avoid the strange diacritic in Ao (not how it's written correctly) for Angstrom units (10-10m).
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Ok. But that wasn’t my question. ;)
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Digikey only started using nF a few years ago
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Ah-- dyeline printers-- choking on ammonia fumes--thank god that's a thing of the past.
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[The nm or mu (millimicron) was used in spectroscopy to be politically correct and to avoid the strange diacritic in Ao (not how it's written correctly) for Angstrom units (10-10m).
Å, and the name is Ångström - the advantages of a Swedish keyboard!
But the unit (not part of SI, though) is angstrom (or ångström), lowercase, as all units derived by personal names (volt, ohm, ampere etc.).
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The angstrom unit can be spelled without diacritics, but since 2019 it seems to be no longer politically correct as an addition to SI.
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Pounds and Farenheit seem to have been left out too. Plainly anti American!
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Not merely anti-American: Daniel Gabriel Fahrenheit was a Dutch citizen, of German ancestry, born in Danzig (Gdańsk), now in Poland.
Meanwhile, Anders Celsius, the great Swedish scientist, invented a temperature scale with 0 at boiling and 100 at freezing, which was later inverted by another great Swedish scientist, Carl Linnaeus (both names were latinized from Swedish originals). Both men have impressive monuments in Uppsala Cathedral.
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... I guess us old slide-rule jockeys faced with the 'horrible shortcomings' of having only two terms picofarad and microfarad could do the dauntingly difficult math in our heads realizing from countless thousands of hours of design work that .001uf and 1000pf were in the same drawer. Now I find that same drawer has disk ceramics marked '102', but I have never seen a 1N in that drawer!! (I think those hide away in the diode drawer) Respectfully, YMMV....
I can fix that. Not in a drawer but on a board, these are marked "1n0" for 1 nF. I can live with that, but the ones marked "n47" are too weird.
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"... routinely use symbols like these". That's an interesting take on it. I have written many, many capacitor values over many years, yes, even going back to the days of mmf and I have not until this day taken the trouble to find a way to use the "μ" character which is called the lower case, Greek Mu.
https://en.wikipedia.org/wiki/Mu_(letter)
For those of you who have the IBM style PCs, running a fairly up to date version of Windows, you can access this character via the Character Map which is, in turn, available in the Taskbar. In many of the fonts listed there you can search for character number 03BC to find it. Then Copy and Paste. If you can not remember that character number, then do four page downs and look about half way down on (near) the left. It is not in every font, but I found it in about a half dozen of them.
Dare I say that most authors in the field of electronics do not bother to use the correct character. They just substitute a lower case u which is a lot easier to find.
The nano prefix may have been added to our technical lexicon in 1960, but it was not in common use then. Throughout the 60's and early 70's, mµ was used in spectroscopy. It was often written "mu" because of typewriter limitations, namely the IBM Selectric in the US and probably elsewhere too (https://en.wikipedia.org/wiki/IBM_Selectric_typewriter ).
I believe a Greek character ball was available for the Selectric, but almost no one would take the time to change balls to type one character. No conventional typewriter (except those for native Greek text) had any capability for this symbol. The ability to routinely use symbols like these didn't come along until microcomputer type setting came along in the early 1980s.
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I think that comes from Roman numerals. M = 1000
I noticed in corporate environment the finance/accounting people use "M" notation for thousands and "MM" for millions. Now, THAT is bizarre. Caused me confusions. :wtf:
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Å
Sorry to burst your bubble, but no sweat in south Texas.
I love the Windows Character Map!
[The nm or mu (millimicron) was used in spectroscopy to be politically correct and to avoid the strange diacritic in Ao (not how it's written correctly) for Angstrom units (10-10m).
Å, and the name is Ångström - the advantages of a Swedish keyboard!
But the unit (not part of SI, though) is angstrom (or ångström), lowercase, as all units derived by personal names (volt, ohm, ampere etc.).
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Or on an Apple device, press and hold the “A” key until the menu pops up, then select Å. (On a Mac, there are additional ways to enter it on a keyboard or character map.)
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I too am lazy enough to occasionally still use a u instead of mu. But as I recall the Character Map has been around since W3.11 and it was a response to similar functionality on Apple systems. Character Map stores recently selected characters so unless you are really jumping around the various symbols it is very quick to use. Much, much simpler than changing a typeball so it really takes a superior kind of laziness to not use it, but I am guilty.
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On a Mac keyboard (with US keyboard layout, possibly others too) μ is simply Option-m. (On iOS, I’m not aware of any trivial way to enter it, but I use it frequently enough that I simply created a text shortcut to replace “mu” with μ.
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Why single out the Selectric? No standard typewriter outside of Greece would have had the μ or any other Greek character.
Simple: I was then and continue to be too busy doing what I enjoy instead of keeping up on typewriters around the world. I did add, "and probably elsewhere too," to satisfy typewriter enthusiasts who keep track of such things. ;)
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That’s like saying “Ford motor cars in North America almost always have the steering wheel on the left side”. It’s not technically untrue, but it’s certainly very odd to say it since it’s true of practically every car sold there.
Anyway, the core of my gripe wasn’t that you didn’t enumerate every country except for Greece, but that you singled out the Selectric, which was in no way unique, even just within USA, in not having Greek characters.
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I hadn't really thought about the different usage - 6800pF or 6.8nF - until I visited Dave's lab once when David was there and they asked me which way I went on the subject. It was only then I realised that my earlier involvement with electronics (the learning zone) had embraced a period where, while starting out with only pF, both were used - so I was comfortable either way (even though I had to figure it out for myself). This was on the presumption that the units were specified.
The "assumed" or "convention" approach without explicit units was not something I had encountered ... and I would not have liked it.
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really old schematics use centimeters unit for capacitance, it was at about beginning of 20 century :)
1 cm = 1.11 pF
It was the capacitance of an 1cm diameter metal ball in vacuum..
Provided you need a 100nF capacitor you put 89847 balls in a glass jar and that is it..
:D