DC Wave Questions

How come? Do you object to the term "DC" - is monophasic acceptable to you?

See also:

http://64.233.161.104/search?q=cache:SMA_gSlzQ18J:global.daikin.com/global/our_product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_en

Impedance varies with frequency if there are reactive components, L's and C's. Since you haven't told us whether this is a series or parallel circuit of L's, R's and C's, We don't know what the impedance is at DC, zero frequency or any other frequency for that matter. If it's a parallel circuit the DC impedance is zero unless there is resistance in series with the L as is the usual case. In that case, the impedance is R at DC. If it is a series circuit, the DC impedance is infinite. SO, you have three choices, Zero ohms, Infinite ohms or R ohms depending on the connection.

A peak detector will have to work on the range of voltages expected on it's input. I can't get to the URL, sorry. Bob

O.K. here's the combinatrics:

Combo 1: DC Sine Wave + (R+L in series with C parallel)

Combo 2: DC Sine Wave + (R+C in series with L parallel)

Combo 3: DC Sine Wave + (L+C in series with R parallel)

Combo 4: DC Sine Wave + (R, L, and C all in parallel with each other)

Combo 5: DC Sine Wave + (R, L and C all in series)

O.K., so can I correctly infer from your response that a negative peak detector will yield a value of +5V for a sine wave which varies from

offset.

Not that it's that important, but I don't see why a "DC sine wave" is an impossible concept, considering the definition of DC as a current which flows in one direction:

A "DC Sine wave" doesn't say that current reverses direction, only that the current flow wanes and waxes.....like a river is still a river even though its flow varies with rainfall...

circuit will be

applied

O.K. - now we're getting somewhere......you're saying the current and voltage (and the implied impedance Z = V/I) of the "DC sine wave" is the sum of the respective current and voltage of a +10V DC signal and a

-5V/+5V AC signal going into the same load.

Example: DC +10V into load produces 1 Amp, therefore implied resistance = 10 ohm. and AC -5V/+5V (and given frequency) into load produces 0.5 amps, therefore implied impedance = 20 ohms,

then what would the superposition prinicple predict as the resulting combined current and impednace?

read the original post - talking about a sine wave bouncing between +5V and +15V - no where near negative

Your posts have all the characteristics that indicate you are a troll. If you aren't I suggest you quit being combative and learn from what the posters are saying.

And re the link; that refers to an inverter that uses a DC input and outputs a sinewave. You must be troll.

So the 10V p-p sinewave is riding on 10VDC. There is no requirement that a sinewave must have an absolute negative component.

The impedance of a set of passive devices is independent of the voltage across them. It only depends on R, L, C, and f. The fact that there is a DC component makes no difference.

An inductor will pass DC current as if it were a wire. Only differences in current cause a voltage across it. A capacitor will not pass DC, so the DC does not matter. Obviously, a resistor is a resistor, and cares nothing for ac vs dc.

This is only true for ideal components. In the real world, inductors, caps and resistors have voltage limitatations. They are usually well beyond 15V, though.

Your link has crap on the end. Here it is without the crap:

With this circuit, the input at V+ will always be outside the power rails. Thus, it will not work.

NOTE: I changed the followup-to field to sci.electronics.basics, because that is where this thread belongs. I hope you don't mind.

If you think that the term "fully DC Sine Wave" even means anything, then you have not understood the coursework. Either your teacher is incompetent, or you have been spending too much time partying and not enough time studying.

Good Luck! Rich

Bullshit. This kid is not a troll, by any means. He's just a student desperate to weasel answers to his final without having to learn the material he was supposed to have learned while partying and chasing tail.

A troll is a much more serious matter. This is just a child who needs to fail the course, have Mom and Dad scold him, and next semester, pay attention in class.

Cheers! Rich

Varying DC? i.e. DC varying in amplitude a manner similar to an AC sine wave. If it goes into plus and minus regions I guess we are getting pretty close to an AC waveform?

http://64.233.161.104/search?q=cache:SMA_gSlzQ18J:global.daikin.com/global/our

The person I was replying to was being unnecessarily difficult and counter-productive....he knew what I meant (or should have known) as many other posters have graciously corrected....see also this previous thread where someone else uses the same terminology ("DC sine wave")....

the replies were most considerate and productive and were not done in a childish and smug manner. I suggest the real trolls here are people who jump on the missue of conventional terminology (eventhough the message is otherwise clearly understood) to engage in mental masturbation with an "oh-so-witty"(not)8th grade, sophomoric "gotcha".

P.S. 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.....Isn't a sine wave that operates as all positive voltages always yielding currents that operate in only one direction (i.e. "direct current")? Surely you wouldn't call this AC, would you? Isn't "DC sine wave" a more concise and readily (albeit only slightly more so) concept that an "AC sine wave that has been fully DC offset"? Is it conceivable that conventional terminology and nomenclature could have evolved such that "DC sine wave" was acceptable? If not, why not? How is it fundamentally wrong? (as opposed to being at odds with convention)

Is that definition of "DC" written in stone (i.e. fundametnally true) or as defined by convention? How is a sine wave operating as all postive voltages not yielding a current (albeit variable) of a single polarity, single direction that does not alternate? Isn't saying it is an "alternating current with a dc offset" a rather queer way of saying things since there actually is no (net) alternating (i.e. bi-directional) current flow?

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.....if it is fundamentally wrong, then please show how.....however, if we're just talking about convention, 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).

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)

According to Fourier analysis, any repeating waveform can be decomposed into harmonically related and appropriately phase shifted sine waves and also a DC component. If all the components involved are linear, then they react to each of these components, independently, and the result is the linear sum of all those reactions. So the capacitors react to the DC component as open circuits, and the inductors as short circuits. At all frequencies, the resistances follow ohms law, and at each AC harmonic, the inductances and capacitances react in their normal frequency dependent ways.

Throw in one nonlinear component, like a diode, and you have to do a completely different kind of analysis.

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.....

Yes. DC by definition is zero frequency.

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."