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The Day The Symbol Changed

CDRIVE

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Somewhere over the past 60 years, ... possibly in between the Vodka's, Gin, Wine, Beer and wacky weed I seem to have missed the 'Symbol Change Memo' of what we used to call "Chassis Ground". The term "Chassis Ground" also morphed a bit with the advent of the PCB. This naturally gave birth to the term "Circuit Ground" because the metal chassis has become all but extinct.

Less I digress this post is about what used to be the standard electrical symbol for Earth Ground vs Circuit, Chassis, System, Signal or whatever Ground that is not actually Earth Ground. The Google image below indicates the accepted symbol for Earth Ground today but it used to be what's shown as "Chassis Ground"!

upload_2016-3-22_10-12-37.jpeg
Personally, what's NOW shown as "Chassis Ground" makes a hell of a lot more sense as it used to be... "Earth Ground", because it more aptly visualizes earthed ground rods. It's also the way I was taught and later taught my own students.

Just to confirm that I wasn't loosing my mind I dug out some schematics of my 1930's and 1940's vintage test equipment and radio stuff. Some included Mil Spec equipment which were sticklers for preciseness. They confirm that my mind is still present and safely nestled between my ears. It also seems to still be firing on all cylinders.

So, who the hell changed it? When did it change? Why did they change it?

Chris
 

Minder

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A pet peeve of mine.
See recent post.
https://www.electronicspoint.com/threads/difference-between-ground-and-ve-voltage.277846/
One of the biggest offenders is the well known 'Art Of Electronics' which use it throughout the book, so naturally all aspiring students think this is the way it is done.
The correct way is, and always has been as far as I am concerned is to use chassis or signal grounds unless the power common is to be connected to Earth ground.
One trouble is in N.A. the term Ground is used for chassis ground as well as earth ground, whereas UK for e.g. uses Earth for an actually grounded conductor.
See the Dr http://www.brucearch.com/videos.html#vid2

M.
 

shrtrnd

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I've talked to guys over the years about this and some of the other 'strange' symbols I've seen in schematics. I have no definitive explanation for it, but this is my 3rd person take.
Some group of guys at some electronics school in some part of the world decide that the symbol they create is stylish and representative of what they believe it should be.
So they teach it to their employees and/or students. Who in turn carry it over to their jobs, unwittingly dupes to their superiors. After all, nobody ever told them differently.
I understood the early 1960's guys who actually invented new components and circuits naming their stuff. Companies often patented the terms as a part of their product line.
I don't understand the pompous concept of some theoretical paper-pusher deciding his/her way is better than the here and now.
Sure, a lot of this stuff is making it's way into general population usage, some countries even officially adopting the new symbols as a matter of national pride since their guys did it.
The result of the mess is those international conferences where everybody 'agrees' to some new standard (like that new '4K7' means 4.7K Ohms).
Unfortunately, there are still a lot of us old *arts (present company excepted), who have difficulty changing our ways.
We know this because so many of us continue to turn-out schematics with the original symbols on them.
When us dinosaurs die-out, maybe those more stylish guys will win-out.
 

AnalogKid

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Raised on 60's Popular Electronics, Zenith TV, and Ampex and RCA broadcast equipment schematics, now do MIL electronics. What we use from post #1:

Chassis Ground symbol = both chassis and earth ground, since they are the same in MIL systems.
Earth Ground symbol = system ground, signal ground, power supply main DC output voltage return potential, etc. May be tied to Earth Ground or not, depending on the system.
Up and down arrow symbols = DC power rails, never a GND or return potential.

Note that in VME systems the relationship between earth and signal ground is not defined. In VXI land, they are defined as separate, but joinable as a user option.

ak
 

Minder

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Earth Ground symbol = system ground, signal ground, power supply main DC output voltage return potential, etc. May be tied to Earth Ground or not, depending on the system.

ak

To me that outlines the whole problem, you have an international symbol that indicates an Earth Ground connection, then everyone uses it regardless of whether the point is actually earth ground or not.
So that leaves the viewer of the circuit, unsure of whether an earth ground connection is intended or not.
Seems to make it pointless having International symbols!:rolleyes:
The way I was always taught was to use the right symbol in order for minimum confusion.
When you work in both Electrical supply and localized electronic circuitry you cannot afford to have any confusion.,
M..
 

CDRIVE

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When I want to indicate that circuit GND is connected to a earth ground I will insert this in my schematic. Yes, according to current conventions, it's backward but I don't care. I'm too damn old to change now. That's the way it was for my entire life and I have sh!t loads of old schematics to prove it.

Shrtrnd, rest assured I will not post 4K7 when all my life it's been 4.7K. Why the hell should the old bend for the young? Hell, they can at least wait until we're dead! Then they'll be the new old timer and get a taste of there own medicine. :p When I was 30 years younger I had a very old student in my class. He used to relish looking into the eyes of a young sprout and tell them.. "Life;...It's later than you think"!

My 22 year old grandson absolutely NEVER answers his cell phone when I call him. My Daughter explains that if I want to talk to him I have to trade in my flip phone for a smart phone and text him. Odd though, whenever Nicholas needs money he always knows how to dial Grandpa and inexplicably manages,.. struggle as he may, to actually use his vocal chords! :rolleyes:

Chrisupload_2016-3-22_18-8-17.jpeg
 
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Minder

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The history of industrial standards goes back to the JIC (Joint Industrial Standards) of 1919 in UK.
Later in N.A. from 1955 where the various symbols for electrical drawings was defined, later to become NFPA79.
Fortunately I still deal with companies that supply drawings based on these standards that are still valid today, and refreshing to know exactly what is intended, which I cannot say for the majority, unfortunately.
M..
 

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shrtrnd

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The worst mish-mash of circuit symbols I've seen are ones made in India. Half of their engineers were trained by the British, and the other half have been trying to comply with the Pacific Rim upstart companies versions of electronic symbols.
I don't worry too much about earth grounds CDRIVE, my engineers keep telling me everything that matters is a mobile device now anyway.
I got pretty pissed about the introduction of the 4K7 stuff when I looked around the rest of the first schematic I saw it on, and with all the other crap there, I couldn't even tell for sure I was actually looking at a resistor.
Maybe these new schematics are supposed to be scanned by computers, and not people?
Yeah, I know what you mean about not changing. I'm worried if I actually insert some of the new symbols into one of my drawings, somebody will ask me about it 3 years from now, and I'll forget what it was for myself.
(And by then some stylish people will have discarded that previous symbol for the newest stylish version somebody else came up with)
'Good' became 'neat', which became 'cool', which was discarded for 'groovy', which was transformed into 'phat', ...I'm not sure what the stylish people call 'good' right now.
Same with creativity in electronics I guess. The new guys might know what they're symbolizing to each other, but I won't have a problem understanding your schematics.
Maybe because we're still actually 'grounded', while the ungrounded wireless people have their heads in the 'Cloud'. (Or some other place where the sun don't shine).
 
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CDRIVE

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The history of industrial standards goes back to the JIC (Joint Industrial Standards) of 1919 in UK.
Later in N.A. from 1955 where the various symbols for electrical drawings was defined, later to become NFPA79.
Fortunately I still deal with companies that supply drawings based on these standards that are still valid today, and refreshing to know exactly what is intended, which I cannot say for the majority, unfortunately.
M..
I would also think that here in the U.S. schematic symbols are also cataloged by the National Bureau Of Standards (NBS).

Your image is essentially the same as the one I posted in post 1. Thus far in this conversation I'm still left with a big ? as to when and why the Earth GND symbol became Chassis GND and visa versa? If it was always as shown then the U.S. electronics industry & the military have had it backwards for damn long time! As I stated earlier, what they are now calling Chassis GND visually makes far more sense as Earth Ground. The diagonal rods alone make it far more logical depicting an earth connection.

An interesting aside is the fact that just about all Spice, CAD and schematic drawing editors use
images


for chassis & circuit GND, which conforms to what I've been using FOREVER! In fact the earth gnd symbol that I posted in post 6 was not included in my Tina Spice. I had to create it and add it to my symbol library, though I rarely use it because most projects on EP are not earthed.

Chris

PS: I see my ASCII art attempt failed so I removed it and replaced it with an image.. I hate ASCII art!
 
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Minder

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The oldest copy I have of the JIC Electrical Standards Va. (US) is 1960 and that still shows the symbols as in post #7. Right up to the current day NFPA79 2015.
All the CAD and Schematic capture programs I use have the same symbols, Kicad, Orcad etc.
They most likely came to be misrepresented due to prevalent misuse?
M.
 

CDRIVE

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1960? Hell, that was only yesterday! Here's a partial clip of my 1946 Hallicrafters SX42.
And as I've stated I have early 1930's mil manuals drawn the same way.
sx_42_18397.png


Come to think of it, my old RCA tube manual also used the same convention and so did my many printings of the ARRL Handbook. I also never had a student, some of which were employed by Motorola, Siemens and IBM call me and tell me that I gave them erroneous information regarding ground.

In the end it's a battle I won't win but I won't change either. :p
Chris
 

Minder

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It must be a N.A. thing.!;)

After looking up some of my old original academic reports from the U.K. and some manufacturers example product circuit manuals of the time showing valve and semi-conductor circuits, I can see why I feel comfortable with the present standard, they all conform to the present symbol standards for N.A. NEMA and Europe IEC 60417.!
M.
 

CDRIVE

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I'm thinking you're right. If it weren't for the world becoming much smaller and definitely more global with the advent of the internet I don't think we'd be having this discussion. I think there's a pun in there! :D

Anyway, I also did some digging and found a copy of the Amateur Radio Handbook that predates any printing I have in my library. I think my earliest copy is 1955. This one is from 1936..
http://www.tubebooks.org/books/arrl_1936.pdf
Not surprising the schematics follow the conventions I've always used.

For the fellow hams here give yourself a big treat and read through some of these 455+ pages. The nostalgia jumps off the pages and grabs you right by the heart.

I wonder how many hams also know that Hiram Percy Maxim, the founding father of the ARRL, was also credited with inventing and patenting the first practical silencer.

Chris

Edit: That would be 544 pages.
 
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Minder

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I notice the description of the symbol they use throughout is correct. .... Earth.

Unfortunately when various National & International standards are in place and the users of that particular discipline either ignore or use alternatives there is no longer a Standard and confusion reigns.:(
M.
 

n4nln

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As a gas-carrying old phart, I understand people's discomfort with nomenclature change. I've been on both ends of that particular stick more than a few times. The ISO/European influence on schematics has, for my money, been good. And it's not that I don't sometimetimes still do a doubletake. In particular, the notation of writing 2K7 for a 2700 ohm resistor instead of 2.7K kills two important birds with one stone.

First, how many times have you had a really small-print schematic in one hand and a charred resistor in the other and have had to figure out whether there as a decimal between those tiny digits?

Second, there is no uniform concensus about what character is used to separate the whole and fractional parts of a decimal number, nor is there any about separating groups of three digits to the left of the whole/fraction division. By using the multiplier as the separator, both of those problems are resolved and a character saved on top of it.

I personally think it was a brilliant hack. The results are schematics which are more likely to be understood correctly the first time all around the world. And that does matter a lot these days.

The rest of the changes you see in modern schematics all come from the same effort to globalize notation. And yes, nobody is complely happy, and you always habe to look around to see what is going on.

As for "ground" symbols, I *never* assume I know what's going on there without significant investigation. Different types of equipment have vastly different requirements which cannot be captured in a schematic even if the draftsman includes copious notes to assist the reader. Grounding architecture in Pro Audio, small signal RF, power RF, low power digital, high power digital/mixed-signal, circuit elements succeptible to B fields, and of course EMI radiation are all different, some more than others, but can easily make or break a product. So I identify what I can assume is "local power supply return" until further enlightnment is provided.

My personal "teachable moment" was being told about an expensive oscilloscope instrumentation amplifier being french-fried because a remote sense coil preamp rode on a 5KV common mode supply to an ionization chamber. Evidently Murphy was out for coffee because nobody was hurt but only because of dumb luck. That's when I learned that "ground", even "chassis ground" is a *local* concept.
 

Slick

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Somewhere over the past 60 years, ... possibly in between the Vodka's, Gin, Wine, Beer and wacky weed I seem to have missed the 'Symbol Change Memo' of what we used to call "Chassis Ground". The term "Chassis Ground" also morphed a bit with the advent of the PCB. This naturally gave birth to the term "Circuit Ground" because the metal chassis has become all but extinct.

Less I digress this post is about what used to be the standard electrical symbol for Earth Ground vs Circuit, Chassis, System, Signal or whatever Ground that is not actually Earth Ground. The Google image below indicates the accepted symbol for Earth Ground today but it used to be what's shown as "Chassis Ground"!

View attachment 25788
Personally, what's NOW shown as "Chassis Ground" makes a hell of a lot more sense as it used to be... "Earth Ground", because it more aptly visualizes earthed ground rods. It's also the way I was taught and later taught my own students.

Just to confirm that I wasn't loosing my mind I dug out some schematics of my 1930's and 1940's vintage test equipment and radio stuff. Some included Mil Spec equipment which were sticklers for preciseness. They confirm that my mind is still present and safely nestled between my ears. It also seems to still be firing on all cylinders.

So, who the hell changed it? When did it change? Why did they change it?

Chris
Slick says:
I have a little different aproach to the grounding issue. I look at both chasis ground and earth ground being the same.
Most electronic equipment and electrical equipment has a ground wire. If a system has a chasis ground then it is also connected to the earth ground. In the USA our NEC requires that the netural wire must be connected to the ground rod from your electrical service. Also, all receptacals must be grounded. When checking for a hot wire you only have to touch the metal cover or screw of the receptacle and one blade of it to get a reading. So either wire, white & green are connected to earth ground. Even though we say the white wire is a current carrying conductor and the green is a ground. So when checking for voltage we often go from ground to some other point. Even with 220 volt that has a stepdown transformer, usually one side is grounded. I'm looking at a pc board with a flat wire connector. The one post is marked "GD". could this be chasis ground or earth ground? Oh my! Just food for thought.
 

Rich Man

Jan 15, 2016
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1960? Hell, that was only yesterday! Here's a partial clip of my 1946 Hallicrafters SX42.
And as I've stated I have early 1930's mil manuals drawn the same way.
sx_42_18397.png


Come to think of it, my old RCA tube manual also used the same convention and so did my many printings of the ARRL Handbook. I also never had a student, some of which were employed by Motorola, Siemens and IBM call me and tell me that I gave them erroneous information regarding ground.

In the end it's a battle I won't win but I won't change either. :p
Chris
 

Rich Man

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Being an old DeVry man, circa '58/'59 , (when it was on Belmont Ave!) that Hallicrafters schematic looks strangely familiar to me. As for change, I'm still struggling with cps changing to Hertz!!
 

CDRIVE

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As a gas-carrying old phart, I understand people's discomfort with nomenclature change. I've been on both ends of that particular stick more than a few times. The ISO/European influence on schematics has, for my money, been good. And it's not that I don't sometimetimes still do a doubletake. In particular, the notation of writing 2K7 for a 2700 ohm resistor instead of 2.7K kills two important birds with one stone.

First, how many times have you had a really small-print schematic in one hand and a charred resistor in the other and have had to figure out whether there as a decimal between those tiny digits?
First let me welcome you to EP.

You make a very good point regarding seeing a decimal point in small or poor print. For that reason I will agree that 4K7 beats the hell out of 4.7K. Unfortunately my preferred schematic editor is Tina Spice which is a European company yet does not provide an option to enter values in that format. I won't be changing my GND symbols any time soon either for the same reason. Come to think of it neither does LT Spice.

In any case I will be 70 in June. It's waaaaaay too late to change now! :p

Chris
 

CDRIVE

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Being an old DeVry man, circa '58/'59 , (when it was on Belmont Ave!) that Hallicrafters schematic looks strangely familiar to me. As for change, I'm still struggling with cps changing to Hertz!!

It was 1967 or 1968 and I was working at my first post Vietnam service job as a Jr. Tech at a Mil service depot refurbishing ARC34 aircraft transceivers. My supervisor came by my work bench, gathered up all my data sheets and replaced them with new ones. Attached to the new data sheets was a government memo that proclaimed that from this date forward all frequency measurements shall be entered and specified in Hertz or Hz, KHz, MHz etc in honor of the late Heinrich Rudolf Hertz.

After a short adjustment period I was pleased to see that the ARC34 still performed the same way as it did when it's input and output frequencies were in Mcps.:D

On a side note if I'm speaking to a colleague and we're working in KHz I will invariably say "KC". Old habits die hard.

Chris
 
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