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DC Wave Questions

D

Dr. Polemic

Jan 1, 1970
0
Thank you for your comment, but I respectfully disagree....I could
really care less if someone used the correct terminology in describing
something, as long as I could understand what they were talking
about....in fact, I run into this situation alot - I never, ever,
correct the use of improper terminology (until the person is
finished)

Ignorance, be not proud.

Nobody interrupted your first post; that's the one of the beauties of
usenet. You get to have your say without interruption. Nobody tried
to correct your improper use of terminology until you were well
finished with your first post.
....I find it to be stifling of the other person and the point
they are trying to make.....thousands of times per day, people (in
industry) with only high school diplomas (or less) in industry make
absolutely brilliant observations and suggestions, but well over 80% of
these are ignored, poo-pooed or brushed-aside, by people with advanced
college degrees....many times, in part, due to the unsophisticated way
in which the ideas are expressed

And is it characteristic of these people that when somebody freely
offers to help them learn to express their ideas better, they react as
you have here? Strongly resisting and refusing to learn?
.....it definitely is frustrating
trying to understand what someone is saying when they use unfamilar or
unconventional terminology, but it really can pay off big to suffer
through it......


How much more might it pay off if the person using the unfamiliar
terminology learns the conventions?

And, it certainly hasn't paid off big here. The majority of your
postings have been argument about terminology, rather than attempts to
get your questions answered.

You came to this newsgroup seeking instruction in electronics, an area
where you apparently lack extensive training. Your question # 1 is
ill-posed, and when you were offered instruction, you resisted with
vociferous arrogance. There is a considerable body of knowledge about
electricity, with a standard terminology. Why should we who would
instruct you use your sui generis terminology rather than you use the
standard language? Part of answering such an ill-posed question is
teaching the proper way to ask, which the qroup was willing to do, but
you want to bite the hand that feeds you.
 
C

cnctut

Jan 1, 1970
0
2 questions about a fully DC Sine Wave....let's suppose you have a DC
Sine wave which varies from +5V to +15V peak-to-peak going into a load
with R, L, and C components.....

Question #1:
Is the load's impedance a function of R, L, and C (and wave frequency)
or is it simply just R (i.e. Z=R)? In other words does non-resistive
impedance (L + C) really only matter with an AC signal OR anytime
voltage varies periodically (even if it is all DC)?


Question #2:
Would a "regular" negative peak detector ciruit, like shown here:

http://www.elektroda.net/cir/index/Detector Circuits/NEGATIVE PEAK DETECTOR.htmgative


work for the DC Wave described? Will it output +5V or do negative peak
detectors only work for AC signals?

Thank you.

jackbruce9--

Dis thing dat yu gots with da "DC Sine Wave" speak'n make no cents to
dis cat.

Tut
 
P

Pooh Bear

Jan 1, 1970
0
.see also this previous thread where someone else uses the same terminology ("DC sine wave")....

Just because someone else used the term doesn't make it right ! There's plenty of rubbish spouted on the net.

Graham
 
P

Pooh Bear

Jan 1, 1970
0
Don said:
Here's one last tip to help you with the homework assignment I gave you
earlier: You are wrong in assuming the current flows in only one direction.

Indeed - depending on the configuration of the R, L, C combination there may no
DC component *at all* and the current would be purely a.c.

Graham
 
R

R Adsett

Jan 1, 1970
0
If the low peak of the sine wave (and the rest of the the sine wave for
that matter) is "fully" above the "zero" reference point, then isn't it
true that the current DOES NOT alternate? That is to say, that current
only flows in one direction....i.e. "direct current"? Isn't it also
true that if the low peak of the sine wave is -0.00001V then the sine
wave results in current flowing in both direction (albeit for a
nanosecond)....i.e. "alternating current".....I'm not arguing that my
use of nomenclature is "pure" or conventional....but I don't see how it
is fundamentally wrong, without merit, or lacking a reasonable
basis.....

Try a simple experiment. Build a simple oscillator powered off of two 9V
batteries ie +/- 9V.

Now measure the output. with the scopes gnd probe on the point between
the two batteries, and again with the gnd probe at either exterme of the
batteries.

In the first case you will measure a signal that oscilates around 0, in
the other two cases it will be entirely above or below 0. The wave has
not changed. It would make absolutely no sense to describe it in one
case as AC and in the others as DC. As much to the point describing as
DC would make understanding it more difficult.

Just as there is no absolute inertial reference frame, there is no
absolute voltage reference.

Robert
 
T

Tam/WB2TT

Jan 1, 1970
0
Bob Penoyer said:
Um, no. DC is Direct Current, i.e., current that flows in one
direction. For example, the output from a rectifier is DC but it
certainly isn't "zero frequency."

The output of a rectifier contains both AC and DC. You put a filter on it to
get close to pure DC.
 
B

Bob Penoyer

Jan 1, 1970
0
No, it is NOT DC. Sometimes when speaking casually people call it DC, but
more often it will be called rectified AC.

Rectified AC _is_ DC. Now you might say, But it has a lot of AC stuff
riding on it and that makes it "rectified AC."

Okay, so let's hang a large capacitor across the rectifier's output.
Now, assuming there is some sort of load connected to the rectifier,
there will still be ripple on the load--so there is still some AC
present. Is this still rectified AC? Using your definition, when does
the signal change from rectified AC to DC?
I agree with you that DC stands for Direct Current. But what is the
logical meaning of that? Who knows. The bottom line is that when a
waveform varies with time, it is NOT DC in popular useage.

As long as there is a finite load on the rectifier that I've
described, anything less than infinite capacitance will permit some
ripple to be present. So, since you say "... When a waveform varies
with time, it is NOT DC in popular useage," then the signal will never
become DC.

The simple truth is that a current flowing in only one direction is,
by definition, direct current. It might have AC riding on it, but if
it's direction doesn't change, it's DC.
 
B

BFoelsch

Jan 1, 1970
0
Let me try this:

would you object to

"a sine wave which (net) results in a current that only flows in one
direction"

Yes, I would object. You can't predict that without knowing the whole
circuit. Connect your DC sine wave to a reactance and current (and energy)
will indeed flow in both directions.
 
C

cnctut

Jan 1, 1970
0
2 questions about a fully DC Sine Wave....let's suppose you have a DC
Sine wave which varies from +5V to +15V peak-to-peak going into a load
with R, L, and C components.....

Question #1:
Is the load's impedance a function of R, L, and C (and wave frequency)
or is it simply just R (i.e. Z=R)? In other words does non-resistive
impedance (L + C) really only matter with an AC signal OR anytime
voltage varies periodically (even if it is all DC)?

jackbruce9--

You're getting a variety of answers because your input source shape is
vague--because of the terminology--let me try to help, you pick whats
best for your "DC sine wave."

1.Nonsinusoidal, nonperiodic source + RCL circuit--difficult to
analyze--requires calculus, Fourier analysis, and Lapace transforms

2.Nonsinusoidal periodic source + RCL circuit--difficult to
analyze--requires calculus and Fourier series

3.Sinusoidal source + RCL-- fairly easy to analyze--requires some work
with complex numbers

4.DC source + RCL--not so easy to analyze--requires calculus and
differential equations to understand what's really going over time

5.DC source + resistor only circuit--easy to analyze with algebra and
ohms law, Kirkoff etc.

So there you have it.

Good luck

Tut
 
R

Rich The Newsgroup Wacko

Jan 1, 1970
0
I would challenge you to prove that the term "DC sine wave" is
objectionable because it is fundamentally wrong as opposed to being at
odds with conventional terminology and nomenclature...

This is clearly a sucker bet. Anyone with common sense knows that
"conventional terminology and nomenclature" are already "fundamentally
wrong."

Notwithstanding there's no such thing as a "DC Sine Wave."

It's like saying, "I'd like some red paint, but in blue."

It's an oxymoron. (which I'd always thought was pimple cream for
retarded people).

"Since the sky is green, I guess I'll plant some bluegrass, and
paint my house clear."
--
Cheers!
Rich
------
"The notorious Duchess of Peels
Saw a fisherman fishing for eels.
Said she, "Would you mind?
Shove one up my behind.
I am anxious to know how it feels.""
 
P

Pig Bladder

Jan 1, 1970
0
Right...but your reply actually doesn't address the NET effect......if
the wave had a DC-component of +2 V and an AC-component of 10Vpp, then
the wave would be NET AC (since its polarity changes
pos/neg/pos/etc.)......however if the DC-component was +10V instead,
then the wave would be NET DC (since its polarity never changes
polarity - i.e. always positive).....that is why I argue a "fully DC
sine wave" is a BETTER (albeit unconventional) and more concise way to
describe what I'm talking about (without using actual values) than the
conventional description you provided....your description is
ambiguos...could be NET "AC" (biphasic) or "DC" (monophasic)

Now, you're trolling.

**** off and read a fucking book.

Then, ask in sci.electronics.basics, _after_ you "get" some BASICS.

Sheesh!
Rich
 
P

Pig Bladder

Jan 1, 1970
0
I concede my terminology is anti-convention, and "wrong" (with respect
to convention) BUT I disagree with you here:


If you were given a sheet of paper a week ago, with only the phrase "a
fully DC sine wave" on it, and you were asked to come up with as many
realistic possible meanings, I have to believe that you could have only
come up with one (and rather quickly)

If that happened to me, I would snitch out the teacher to the principal,
or snitch out the professor to the dean, because the teacher/prof is
obviously incompetent, and has no business teaching wholesale bullshit
to impressionable students.

'nuff said?

Go read a _real_ book.

Sheesh!
Rich
 
M

Mac

Jan 1, 1970
0
I will absolutely buy what you said, but understand the import of what
you're saying....you're saying that the language of "AC" and "DC" has
essentially been somewhat bastardized from its original meanings to
also mean zero-frequency and non-zero-frequency signals. Therefore, to
describe a 10Vpp signal with a 10VDC offset as an "AC" signal is
actually contrary to the original connation of "alternating current"
since it (net) results in a signal which yields only a mono-directional
(i.e. direct) current flow (albeit time variant). So in a sense, you
could say I am holding "pure" to the original (circa 1890's) definition
of AC/DC while its use has been "officially" corrupted to cover the
concepts of "zero frequency" and "non-zero-freuency".

Agree?

I can't vouch for the historical facts, but as far as zero frequency and
non-zero-frequency goes, you are pretty much correct.

Another point to note is that many signals have both AC and DC. It is
not a dichotomy. The signal you mentioned at the start of this thread has
both AC and DC.

Historically, I think what happened is that the terms originally were used
to describe two competing power sources (the war between those who wanted
a DC power grid and those who wanted an AC power grid was surprisingly
fierce). Later, the terms started getting used to describe signals, and
that is probably when the shift to the ZF- and NZF-meaning happened.

Also, there may be people out there who still think of AC and DC in the
original sense (I'm not sure about this, but maybe people who work with
power stuff exclusively), but among electrical engineers, the signal
perspective prevails.

--Mac
 
M

Mac

Jan 1, 1970
0
Thank you for your comment, but I respectfully disagree....I could
really care less if someone used the correct terminology in describing
something, as long as I could understand what they were talking
about....in fact, I run into this situation alot - I never, ever,
correct the use of improper terminology (until the person is
finished)....I find it to be stifling of the other person and the point
they are trying to make.....thousands of times per day, people (in
industry) with only high school diplomas (or less) in industry make
absolutely brilliant observations and suggestions, but well over 80% of
these are ignored, poo-pooed or brushed-aside, by people with advanced
college degrees....many times, in part, due to the unsophisticated way
in which the ideas are expressed.....it definitely is frustrating
trying to understand what someone is saying when they use unfamilar or
unconventional terminology, but it really can pay off big to suffer
through it......

Well, look at it this way: almost all of us had to read your post twice
and think about it to make sure we understood the most likely meaning of
it.

If you worded it differently, the meaning would be crystal clear, and we
would only have to read it once. So in a sense, it is inconsiderate and a
waste of our time to post it in such a way that we can't immediately
understand. You can easily be forgiven for doing this once out of
ignorance.

Anyway, I agree that some people were rude to you. But you haven't exactly
showed yourself to be receptive to advice, either.

--Mac
 
N

NSM

Jan 1, 1970
0
Let me try this:

would you object to

"a sine wave which (net) results in a current that only flows in one
direction"

if you buy that, would you then accept it to be partially condensed
into:

"a sine wave which (net) results in a non-polarity-alternating current"

if you buy that, would you then accept this:

"a sine wave which (net) results in a direct current"

and then

"a (net) direct current sine wave"


I object to all of the above. Go read Scroggie's "Second thoughts on Radio
Theory".

N
 
N

NSM

Jan 1, 1970
0
Historically, I think what happened is that the terms originally were used
to describe two competing power sources (the war between those who wanted
a DC power grid and those who wanted an AC power grid was surprisingly
fierce). Later, the terms started getting used to describe signals, and
that is probably when the shift to the ZF- and NZF-meaning happened.

Pretty much. Even in other languages I believe that terminology is basic -
certainly German is the same (Gleichstrom. Wechselstrom.)

N
 
F

Fred Abse

Jan 1, 1970
0
Again, is the term "DC Sine Wave" problematic because it is fundametnally
wrong OR is it problematic because it is at odds with conventional
terminology and nomenclature.

It is fundamentally meaningless. A sine wave is a defined mathematical
function:

y = a sin(x)


I think what you are talking about is a sine wave with an added DC
component:

y = (a sin(x) + b)


which is not purely a sine wave, nor is it purely DC. It's "a sine wave
plus DC" if you like.

Referring to "a DC sine wave" is analogous to referring to "a curved
straight line".
....if it is fundamentally wrong, then please
show how.....however, if we're just talking about convention,

No, not just convention, this is engineering. The language we speak is
mathematics. I think I just showed you why.

then why
break balls? (Wait, I'm sorry, I don't mean literally "breaking balls",
that's just nomenclature).....if you were given a piece of paper a week
ago with just the words "A Fully DC Sine Wave" on it and you were asked to
come up with as many possible things it could realistically mean, how many
things could you come up with? If you were being truthful I think you
could only think of one thing (and think of it very quickly)

I could only think of only one thing: "This guy is not an engineer, or
scientist, or mathematician!"
 
F

Fred Abse

Jan 1, 1970
0
So only those with a very primitive view of frequency and are bothered by
describing a non alternating but time varying signal as a kind of
frequency (and informally called AC). The simple minded terms, AC and DC
are just not up to the job of describing many waveforms, unless you are
willing to be quite flexible in the usage.

In this case, the OP actually used the words "sine wave", which would
appear to preclude any such flexibility, anyway.

Where it matters, I prefer the use of "steady" or "varying"

"AC" and "DC" have overtones of Edison, Tesla, Ol' George Westinghouse,
and the unfortunate Mr. Kemmler.
 
J

John Fields

Jan 1, 1970
0
Thank you for your comment, but I respectfully disagree....I could
really care less if someone used the correct terminology in describing
something, as long as I could understand what they were talking
about....

---
That's because you want to excuse yourself for your faux pas by saying
that if someone else committed it you would ignore it as long as you
could understand what they were saying, so everyone should follow your
example. What you don't seem to understand is that unless they were
using the language properly, your take on what they meant to say might
be wrong. Your use of "DC sinewave" instead of "sinusoidally varying
DC" or "a sinusoidally varying unipolar voltage" is precisely that
sort of an occurrence and your use of "DC sinewave" was critcised
because there is no such thing as a DC sinewave. This is a technical
forum and, rather than argue with the people who have taken time out
of their lives to correct you, you should do as the Romans do and
adopt the language we use instead of trying to force us to try to
understand what you're trying to say on _your_ terms. Remember, it
was you who was looking for answers, not us.
---
in fact, I run into this situation alot

---
I'm sure you do.
---
- I never, ever,
correct the use of improper terminology (until the person is
finished)....I find it to be stifling of the other person and the point
they are trying to make.....

---
You may be relating to how you feel when you're corrected. I find
that many people accept correction graciously, and the sooner the
better in order to help them to keep from making fools of themselves
over and over again.
 
B

BFoelsch

Jan 1, 1970
0
If you learn the math the definition of AC and DC is totally irrelevant.
Your original Question #1 indicates that you don't know the math. That is
fine; it is something you can learn, but no amount of quibbling over
semantics is going to change the principles of circuits.

Forget the encyclopedia, learn differential equations instead. Encyclopedia
are for junior high school kids.
 
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