AoE x-Chapters - 1x.1 Wire-&-Connectors

The way to avoid ground loop errors is to keep signals differential.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

On a sunny day (Tue, 6 Aug 2019 11:31:10 -0400) it happened Phil Hobbs wrote in :

I just wished people would no longer use filenames like ThisSchematicIsTheLatestAndGreatest.PDF

3x.20_Precision-1.5kV-1us-Ramp_WH.pdf

Or even worse: This\ Schematic\ Is\ The\ Latest\ And\ Greatest.PDF Hurley\ in\ de\ Waterkampioen\ feb\ 2008.pdf

as the \ sucks in Linux

But use like this: this_schematic_is_the_latest_and_greatest.pdf

On a sunny day (Tue, 06 Aug 2019 09:31:58 -0700) it happened John Larkin wrote in :

Go optical.

Hmm, OK I guess that would help... In the end thinking is required. I think most of the time I have ground issues, I don't think about it enough ahead of time. Or maybe you just have to bump your head into a ground problem before you know enough to think about it. And then it's a circuit redesign or adding a crutch* to the instrument.

George H.

*I'm thinking of this piece of plastic I had to add to our diodle laser controller to isolate the DB9 connector shell from the back panel ground.

I'm not spotting anything, can you add an arrow to the "huge noisy inverter in the box"?

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
Website: https://www.seventransistorlabs.com/

My favorite is the,

Customer Project 12345_dingleBerryPOWERSUPPLY_REV_E.SCH

A true blend of DOS-style ALLCAPS (but still using LFNs?), caps-avoidance, underscores (when a space apparently isn't available?) AND spaces (oh..).

Working with other people has only reinforced my understanding that the

90-10 rule applies no matter how "educated" a group you're sampling...

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
Website: https://www.seventransistorlabs.com/

I most always bolt the connector shell to the box, and also solder it to the main PCB ground plane. You never know what nasty stuff might come in over the shield. Best to stop it soon.

VME is an exception. Dsub shells are bolted to the module front panel (rack ground) but not connected to the PCB/VME ground plane. Caps are OK.

Pretty much the entire upper-right quadrant. The prime power is 24 volts DC which we were required to isolate. It's huge and noisy by the standards of a 12-bit 250 MHz ADC. Not "reading trash."

The CW multiplier string is to make up to 75 volts for an EUV photodiode.

Or using a current not a voltage as signal.

Arie

I concur, the circular mil per square foot times ounce parlance is hardly compehensible to a person grown up in a SI-only environment.

Best regards, Piotr

It is usually in the form "universal ground _potential_ doesn't exist", all ground potentials are different. Absolute ground potential doesn't exist even in Sevre outside Paris, where they used to keep the standard kilogram prototype and the standard meter prototype :-).

While there has been a lot of discussion in this thread about grounding topologies inside the box, things get nasty when boxes are connected together with perhaps a large distances between boxes.

A good practice is to have three separate grounding networks on site, one for mains neutral N, one for the PE network and a separate Technical/functional earth TE/FE networks. Each of these networks have dedicated bars at the mains entry point of the building or complex. At exactly this single point only the three bars are joined together with jumpers as thick as your thumb. When the system is down, the jumpers can be removed and measurements can be made to check that the networks are truly separate.

The N network is polluted by mains return current of a single phase system or the current imbalance in a three phase system. Even in a balanced three phase system the third harmonics due to rectifier load will pollute the neutral.

Mains power supply filters are usually connected to the PE, so it is polluted by power supply noise.

Signal grounds are usually connected to the hopefully clean TE/FE network. This requires that no equipments which has a signal ground connected to the chassis and then to the PE are connected to TE/FE, since a single mains filters will pollute the whole TE/FE network.

For this reason N, PE and signal grounds (TE/FE) should ne kept separated and all three brought to the connection pins of a box, so that they can be connected to three separate ground networks.

I have noticed a problem with some installers in foreign countries that when they notice these three ground terminals they simply connect jumpers between these terminals outside the box and use a single wire for a connecting to mains neutral, now actually PEN :-(

l e

Found the formerly lost aphorism! It is indeed from Whitlock, part of his AES presentation. [1] The pertinent excerpt is shown below. Allow me to note that my mix-amp utilizes two "grounds" at different potentials. The mixer uses a virtual "ground" that's halfway between +6V and -6V. The single supply amp uses +12V and 0V on its power rails (AKA Vcc and Vdd) so the amp "ground" sits at -6V (Vdd) relative to the mixer "ground."

-------------------------------------------------------------------- What Does "Ground" Mean * Also known as "Earth" in the rest of the world * Utility Power: an actual electrical connection to SOIL * Electronics: a common return path for various circuits, whether or not actually connected to soil * A FANTASY invented by engineers to simplify their work * The "uni-potential" fantasy assumes all ground symbols in schematics are at exactly the same voltage * Truth: Real-world conductors have resistance, causing small voltage drops * Truth: Ground circuits most often serve, either intentionally or accidentally, more than one purpose * Meaning has become vague, ambiguous, and often quite fanciful

The use of ground symbols in schematic diagrams (actually just a convenience for avoiding more lines in the drawing) lulls us into thinking that they?re all at the same potential. That's the essence of the fantasy ... but far from the truth. Until room- temperature super-conductors become a common reality, "grounds" are connected by wires, PCB traces, or sheets of metal - all of which have both resistance and inductance. So much for the fantasy!

Misguided Strategies * Reduce unwanted ground voltage differences by "shorting them out" with massive wires or bus-bars * Reduce noise experimentally by finding a "better" or "quieter" ground * Skillfully route noise to an earth ground, where it disappears forever! * Is an earth ground for electronic systems really necessary? Think about aircraft electronics ...

Random experimentation with grounding connections is the worst possible way to solve the problems. Not only is little learned in the process, but the experiment can be lengthy ... usually ending only when someone says "I can live with that." The idea that "mother earth" will simply absorb noise is often called the "sump theory" of grounding. And when was the last time you saw an airplane dragging around a ground wire? --------------------------------------------------------------------

Note.

1. formatting link
   Thank you, 73,

--
Don Kuenz KB7RPU 
There was a young lady named Bright Whose speed was far faster than light; 
She set out one day In a relative way And returned on the previous night.

Really? I somehow hadn't realised this in all these years. ;)

Jokes aside, the footnote I mentioned specifically mentions/quotes a German noun, which needs to be capitalised. Lowercase-"litzendraht" wouldn't make sense in either language.

? David

That fancy approach works great until you find yourself working next to a big VF motor drive. :(

At that point, squeezing everything onto one board and keeping the loop areas tiny is a big help.

Cheers

Phil Hobbs

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

I use camel case e.g. because it helps a lot finding the right file from my archives, e.g.

2019-08-05-InvoiceABC05.pdf TLV431AshuntRefOnSemiUnstableHorribleAvoidAvoid.pdf ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

It's a matter of usage. For instance, in English there's such a thing as a cousin-german. (Not cousin-German.) I'd never write "litz wire" with a capital.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Oh, sure.

But said circled-capital-L footnote in the text is about referring to the German word rather than the English loanword. You'd still say that the word "litz wire" comes from "Litzendraht", not "litzendraht".

That's all I was trying to point out ? but as the editors will catch that anyway, back to electronics design, shall we? ;)

? David

AWG is some sort of inverted non-linear system. We avoid it!

NT

Camel case programmers should be removed from this earth.......