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DC Wave Questions
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 he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. |
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wrote in message ups.com... 2 questions about a fully DC Sine Wave One answer. Sine waves aren't DC. N |
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How come? Do you object to the term "DC" - is monophasic acceptable to
you? See also: http://64.233.161.104/search?q=cache...n&lr=lang_ en |
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wrote in message oups.com... How come? Do you object to the term "DC" - is monophasic acceptable to you? 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? |
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read the original post - talking about a sine wave bouncing between +5V
and +15V - no where near negative |
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wrote in message oups.com... read the original post - talking about a sine wave bouncing between +5V and +15V - no where near negative That's an AC wave with a DC offset. N |
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On Fri, 10 Jun 2005 16:51:10 -0700, Don Bowey wrote:
On 6/10/05 3:13 PM, in article , " wrote: How come? Do you object to the term "DC" - is monophasic acceptable to you? See also: http://64.233.161.104/search?q=cache...com/global/our _product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_ en Your posts have all the characteristics that indicate you are a troll. Bull****. 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 |
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"Don Bowey" wrote in message ... On 6/10/05 3:13 PM, in article , " wrote: How come? Do you object to the term "DC" - is monophasic acceptable to you? See also: http://64.233.161.104/search?q=cache...com/global/our _product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_ en 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. He's obviously not a troll, just not super knowledgeable about the subject at hand. If he were a troll he'd have crossposted to something like alt.vampires or alt.masturbation and alt.catholosism. |
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Don Bowey wrote:
How come? Do you object to the term "DC" - is monophasic acceptable to you? See also: http://64.233.161.104/search?q=cache...com/global/our _product/sp_Inverter/3_techno.html+%2B%22dc+sine+wave%22&hl=en&lr=lang_ en 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. 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").... http://groups-beta.google.com/group/...a075188ea87d6b 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) |
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On Fri, 10 Jun 2005 20:28:09 -0700, jackbruce9999 wrote:
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."" |
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NSM wrote:
wrote in message ups.com... 2 questions about a fully DC Sine Wave One answer. Sine waves aren't DC. N I like Jack's terminology. The wave itself isn't DC, but I think "fully DC" is an acceptable way of describing its location. AC generators and transformers are usually designed to produce sine waves with no DC, but sine waves were known long before those inventions. A wave is a succession of curves. A sine wave is a wave whose displacement follows the form of a sine. A pure acoustic tone is a sine wave regardless of ambient pressure. A ripple on a pond is a sine wave regardless of the water level. As not all voltage variations are curves, our generic term was "waveforms". If the plate voltage of an amplifier tube varied from 998 to 1000 volts in the form of a sawtooth, we'd call that two-volt variation a sawtooth waveform. If it was sinusoidal we'd call it a sine wave. To call a waveform an AC sine wave implies that there is no DC, but this thread is the first time I've read the claim that all sine waves are AC sine waves. |
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"Choreboy" wrote in message ... To call a waveform an AC sine wave implies that there is no DC, but this thread is the first time I've read the claim that all sine waves are AC sine waves. FWIW, most waveforms can be created as the sum of sine waves. I wrote an interesting computer demo once that showed how a sine and it's harmonics could be added graphically to form a better and better approximation of a square wave, running through what looked like Butterworth etc. responses. N |
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NSM wrote:
"Choreboy" wrote in message ... To call a waveform an AC sine wave implies that there is no DC, but this thread is the first time I've read the claim that all sine waves are AC sine waves. FWIW, most waveforms can be created as the sum of sine waves. I wrote an interesting computer demo once that showed how a sine and it's harmonics could be added graphically to form a better and better approximation of a square wave, running through what looked like Butterworth etc. responses. N With high frequency and amplitude, a sine wave could be very steep at 0 and 180 degrees. It could also turn sharply at 90 and 270, like the corner of a square wave. You would need low frequency and amplitude for a sine wave to approximate the flat peaks of a square wave. That part is simple enough for me, but I don't understand harmonics. If you overdrive an amplifier with a sine wave, the output will resemble a square wave. I know the output can be broken down into the input frequency and its odd multiples. I'll have to accept it on faith. |
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Choreboy wrote:
With high frequency and amplitude, a sine wave could be very steep at 0 and 180 degrees. It could also turn sharply at 90 and 270, like the corner of a square wave. You would need low frequency and amplitude for a sine wave to approximate the flat peaks of a square wave. That part is simple enough for me, but I don't understand harmonics. If you overdrive an amplifier with a sine wave, the output will resemble a square wave. I know the output can be broken down into the input frequency and its odd multiples. I'll have to accept it on faith. You might want to look into the basis of Fourier analysis. It all falls out of a very simple mathematical property of the sine wave. If you take any periodic waveform, and multiply its value at every point in time with the value of any frequency of sine wave at the same points in time, over all time and add up (integrate) all the products and divide by the total time (an infinite amount of time), only sine waves that fit an integral number of cycles within the period of the waveform will produce nonzero results (infinite integral divided by infinite time). In fact, it can be shown that you get the same quotient for harmonics if you use any integral number of periods of the waveform, including one period. Testing an infinite number of waves is only necessary to show that non harmonics always produce a zero contribution. For instance, if you test a sine wave that fits 1.000001 cycles into a cycle of the waveform, you don't reach the first zero result till you include a million periods of the waveform (and you get more zeros at every integer multiple of a million cycles, with a smaller and smaller cycle of results between those millions as the number of cycles increases because you are dividing by larger and larger times). Harmonics (sine waves that fit an integral number of cycles within the waveform) will produce a finite result representing that frequencies contribution to the waveform. (Actually you have to test both the sine and cosine against the waveform to cover all possible phase shifted versions of the sine. Any phase shifted sine can be broken sown into sine and cosine components. Another nice property of sine waves.) Since only harmonics contribute to the total wave shape, you can skip all the other frequencies, and just evaluate the part each harmonic contributes to making the total waveform. That is Fourier analysis. The rest is about making the math more efficient. |
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wrote in message ups.com... 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 he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. 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 |
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Bob Eldred wrote:
Impedance varies with frequency if there are reactive components, L's and C's. That is not always true. Take 1) A resistor of resistance R in series with a capacitor of capacitance C. 2) Another identical resistor of resistance R, but in series with an inductor L. Make R=sqrt(L/C) and put 1 and 2 in parallel and measure the impedance across that combination. The impedance is always R, and is independent of frequency. A useless fact I would admit!! |
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"Dave" wrote in message ... Bob Eldred wrote: Impedance varies with frequency if there are reactive components, L's and C's. That is not always true. Take 1) A resistor of resistance R in series with a capacitor of capacitance C. 2) Another identical resistor of resistance R, but in series with an inductor L. Make R=sqrt(L/C) and put 1 and 2 in parallel and measure the impedance across that combination. The impedance is always R, and is independent of frequency. A useless fact I would admit!! Not exactly useless, you just described a Zobel network. It is used as crossover to feed two loudspeaker on HI range and LOW range presenting a constant resistive load to the Amp. It is used to compensate a shunt at higher freq. The transfer function is perfectly flat even with two reactances in the circuit. It is used to terminate a DC distribution line R+L with a R+C to avoid resonances, the line is perfectly damped, when the load current steps there are no oscillatory transients. MG MG |
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Since you haven't told us whether this is a series or parallel circuit
of L's, R's and C's, 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) A peak detector will have to work on the range of voltages expected on it's input. 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 +5V to +15V? |
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wrote:
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..... There is no such thing as a "DC sine wave." I suspect you mean what would more correctly be described as a 10 volt peak-to-peak sine wave with a +10 volt DC offset. 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)? The principle of superposition applies: the currents and voltages in the circuit will be the sum of those that would result if the DC voltage and the AC sine wave were applied to it seperately. Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...20DETECTOR.htm work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? That circuit (I've fixed the link) exploits the fact that the LM139 comparator has an open-collector output. It runs off a negative rail, and cannot produce a positive output voltage. |
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There is no such thing as a "DC sine wave." I suspect you mean what would more
correctly be described as a 10 volt peak- to-peak sine wave with a +10 volt DC 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: http://www.answers.com/topic/direct-current 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... The principle of superposition applies: the currents and voltages in the circuit will be the sum of those that would result if the DC voltage and the AC sine wave were applied to it seperately. 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? |
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wrote in message oups.com... There is no such thing as a "DC sine wave." I suspect you mean what would more correctly be described as a 10 volt peak- to-peak sine wave with a +10 volt DC 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: Maybe you shouldn't believe everything you read. DC has: 1. Constant amplitude (that's not to say you can't change it. 2. Frequency of 0 Hz. Also, a non 0 frequency does not imply polarity changes. Tam |
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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? |
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#30
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wrote:
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 he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. Question 1: A capacitor "capacitates" whether it sees AC or DC. An inductor "inducts" whether it sees AC or DC. A resistor resists whether it sees AC or DC. You might find it beneficial to think of what happens to each component on a component level rather than thinking of total impedance. Understand what each component does, and circuit impedance will make more sense. Question 2: 404 file not found error That said, you can peak detect on a varying DC sine. As someone else said, its AC with a DC offset. Ed |
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wrote:
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)? 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. Question #2: Would a "regular" negative peak detector ciruit, like shown he http://www.elektroda.net/cir/index/D...CTOR.htmgative work for the DC Wave described? Will it output +5V or do negative peak detectors only work for AC signals? Thank you. Your link has crap on the end. Here it is without the crap: http://www.elektroda.net/cir/index/D...20DETECTOR.htm 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. --- Regards, Bob Monsen |
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On Fri, 10 Jun 2005 14:55:02 -0700, jackbruce9999 wrote:
2 questions about a fully DC Sine Wave.. 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 |
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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). If you think that the term "fully DC Sine Wave" even means anything, then you have not understood the coursework. |
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wrote in message oups.com... Again, is the term "DC Sine Wave" problematic because it is fundametnally wrong Yes. DC by definition is zero frequency. N |
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On Sat, 11 Jun 2005 04:12:52 GMT, "NSM" wrote:
wrote in message roups.com... Again, is the term "DC Sine Wave" problematic because it is fundametnally wrong 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." |
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On Fri, 10 Jun 2005 21:33:11 -0700, Bob Penoyer wrote:
On Sat, 11 Jun 2005 04:12:52 GMT, "NSM" wrote: wrote in message groups.com... Again, is the term "DC Sine Wave" problematic because it is fundametnally wrong 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." No, it is NOT DC. Sometimes when speaking casually people call it DC, but more often it will be called rectified AC. 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. I'm setting followups to sci.electronics.design. --Mac |
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"Bob Penoyer" wrote in message ... On Sat, 11 Jun 2005 04:12:52 GMT, "NSM" wrote: wrote in message groups.com... Again, is the term "DC Sine Wave" problematic because it is fundametnally wrong 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." The output of a rectifier contains both AC and DC. You put a filter on it to get close to pure DC. |
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Again, is the term "DC Sine Wave" problematic because it is
fundametnally wrong Yes. DC by definition is zero frequency Nice parse-job.....here's my original entire comment in context: 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 You conveinently left out the "OR...." part. You actually proved my point that DC is DEFINED (i.e. by convention) as "zero frequency". Is it that weird to posit that the superior concept with respect to considering any signal as AC or DC, be the actual NET current flow? I could see your point if signals were classified as either "ZF" ("zero frequency") or "NZF" (non-zero frequency") but we are dealing with "DC" or "AC" |
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wrote in news:1118461679.394136.299150
@g14g2000cwa.googlegroups.com: 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..... Look jackass, AC means it is alternating in time. If it is DC it is constant. A sine wave alternates in time, thus is AC. Now shut up. ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
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