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| "Veritasium" (YT) - "The Big Misconception About Electricity" ? |
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| adx:
--- Quote from: hamster_nz on April 09, 2022, 06:24:05 am ---I'm sure you are aware of the Hilbert Transform. --- End quote --- Kind of. Spinning ballerina always turns clockwise when viewed from above - even my brain's brokenness is broken! --- Quote from: hamster_nz on April 09, 2022, 06:24:05 am ---You can use it to split the real-valued data into their positive and negative frequencies. These frequencies do exist, as seen in up-converted baseband signals. With the Hilbert Transform you can then throw one side of the spectrum away, allowing you to generate just upper side band or just lower side band signals. --- End quote --- Not really, not by my definition. If you look at the Matlab page: https://www.mathworks.com/help/signal/ug/analytic-signal-and-hilbert-transform.html ...first graph shows something like 20 negative peaks for the real signal, and 21 for the Hilbert transformed one (in the imaginary component). The "frequencies" are almost the same, whether viewed forwards or backwards. I couldn't get the signal package to properly install in Octave, so was unable to generate a simpler pathologically stupid example from scratch, but that one will definitely do. The facts are: The Hilbert transform doesn't "split the real-valued data into their positive and negative frequencies" (I know it's not what you're saying, but it sounds very much like what you mean - bear with me). The frequencies you speak of don't exist without the help of the transform I spoke of where the arbitrary signal is decomposed into frequency components, you just believe they do (think about the frequencies of a random noise signal). And that isn't done on real data, but complex (the analytic signal), so isn't even the same transform I spoke of (and you replied to). You may know full well what you are talking about, but in a discussion these words are supposed to mean something consistent: They don't. We are trained to fall victim to this fairy tale until it becomes second nature - and this isn't always helpful. Being a great example of my point. |
| adx:
--- Quote from: penfold on April 07, 2022, 11:05:48 pm --- --- Quote from: bsfeechannel on April 07, 2022, 07:18:53 pm ---But If you want to go down the rabbit hole of the meaning of numbers, whatever numbers, just start asking what is so two about two that makes it a two and not a three, or a four? That has nothing to do with engineering itself. And if you don't know how to answer those questions, you cannot possibly advocate for the eradication of the use of the number two from engineering. --- End quote --- So, hypothetically, just as an example, I could advocate for their eradication if I did know why two wasn't three? Yeah, the philosophy of numbers, before saying it has nothing to do with engineering... perhaps have a little think first, just in case there's one little application area you've not considered. --- End quote --- That's how I read it too :). |
| adx:
--- Quote from: bsfeechannel on April 07, 2022, 09:14:24 am --- --- Quote from: adx on April 07, 2022, 07:21:37 am ---He he. All that from saying "I don't believe". Religion and metaphysics eh? --- End quote --- Not believing in certain things is also part of any religion. --- End quote --- So science then? :) Tricky definition. Not believing, disbelieving, being a non-believer, athesim, being a skeptic etc, can all be interpreted various ways. I was hopefully clear enough to say I meant non-100% buy-in. --- Quote from: bsfeechannel on April 07, 2022, 09:14:24 am --- --- Quote ---I'll reply to a few points here and there, in a less 'aconventional' way --- End quote --- Yes, show us more how your belief in the power of ignorance can help engineering in the 21st century. We're interested. --- End quote --- Well, the most obvious and self-serving one, is the link posted by HuronKing here: --- Quote from: HuronKing on March 25, 2022, 07:20:57 pm ---See, you're still restricted by Descartes' idiotic naming convention. I can assign ALL of those same properties to the complex j numbers. In fact, I do, all the time. I can measure the impedance of a capacitor. Don't tell me it isn't physical... I can see it and its effects on my circuits! I can literally define the power consumption of a circuit as S = VI* = P + jQ volts-amps. Why is this so impossible or non-physical? I'm not citing waffle-y texts at you. I'm citing actual engineering practices. You can take them or leave them. https://www.electronics-tutorials.ws/accircuits/power-triangle.html ... --- End quote --- in response to me explaining my "issue with the 'physicality' of sqrt(-1)" - now forgetting about the details and my temerity for questioning sqrt(-1), the problem is clear. It confuses people. And it's optional! That link never mentioned sqrt(-1), with only trivial passing mention of j. Although it is slightly simplistic, it works, remember it was given to me as an example of "actual engineering practices" - a live example of "the power of ignorance can help engineering in the 21st century". But maybe I'm just being contrarian for the sake of it now. The true issue here is that engineering is a faith-based activity, if it is "applied science", and people believe it. Tifify too. |
| HuronKing:
I had planned to leave this thread alone but this is just not cool. --- Quote from: adx on April 09, 2022, 02:51:57 pm ---Well, the most obvious and self-serving one, is the link posted by HuronKing here: --- Quote from: HuronKing on March 25, 2022, 07:20:57 pm ---See, you're still restricted by Descartes' idiotic naming convention. I can assign ALL of those same properties to the complex j numbers. In fact, I do, all the time. I can measure the impedance of a capacitor. Don't tell me it isn't physical... I can see it and its effects on my circuits! I can literally define the power consumption of a circuit as S = VI* = P + jQ volts-amps. Why is this so impossible or non-physical? I'm not citing waffle-y texts at you. I'm citing actual engineering practices. You can take them or leave them. https://www.electronics-tutorials.ws/accircuits/power-triangle.html ... --- End quote --- in response to me explaining my "issue with the 'physicality' of sqrt(-1)" - now forgetting about the details and my temerity for questioning sqrt(-1), the problem is clear. It confuses people. And it's optional! That link never mentioned sqrt(-1), with only trivial passing mention of j. Although it is slightly simplistic, it works, remember it was given to me as an example of "actual engineering practices" - a live example of "the power of ignorance can help engineering in the 21st century". But maybe I'm just being contrarian for the sake of it now. The true issue here is that engineering is a faith-based activity, if it is "applied science", and people believe it. Tifify too. --- End quote --- You are now discussing in extremely bad-faith. Once again, you're ignoring every application manual from industrial manufacturers that I've posted for the sake of being 'contrarian.' You draw reference to the most introductory links I made and straight up excised the rest. THIS was my whole comment: My whole post was, --- Quote ---I'm not citing waffle-y texts at you. I'm citing actual engineering practices. You can take them or leave them. https://www.electronics-tutorials.ws/accircuits/power-triangle.html Go take issue with Keysight. Surely they have no idea about the lack of physicality of the j in their impedance analyzers >:D https://www.keysight.com/us/en/assets/7018-06840/application-notes/5950-3000.pdf Keysight Impedance Measurement Handbook: https://assets.testequity.com/te1/Documents/pdf/keysight/impedance-measurement-handbook.pdf --- End quote --- And BTW, this post was AFTER I had made many other references and I've made many references since then. Oh, I'm sorry 'appeals to authority. :palm: Ah yes, one link to an introductory level site for engineering n00bs, out of maybe a dozen I've posted now (and certainly not the only one I even posted IN THAT VERY POST), is obviously evidence of my belief in the power of engineering ignorance in the 21st century... I can't believe that advocacy for MORE knowledge of complex numbers is being construed as advocacy for ignorance. :scared: adx's world really is topsy-turvy land. Being contrarian for the sake of it is not evidence of there being any controversy about the meaning of this for people who use it. |
| TimFox:
--- Quote from: adx on April 09, 2022, 03:40:14 am --- --- Quote from: TimFox on April 08, 2022, 04:46:49 pm ---The simple complex algebra that I do on my I and Q values is easier than using trigonometry on the sine and cosine waveforms, which is also valid mathematics. What you see on an oscilloscope is a function of time. Often, as in frequency response or impedance calculations, what you want is a function of frequency, where complex algebra is useful. --- End quote --- Yes, tricky - "valid mathematics" I think being the sticking point (or question) for me. Time domain, everything is real-valued, and therefore "real" in my mind. Frequency domain is an abstraction which is much further removed from the direct analogue "this point 'has' this quantity of voltage right now" (itself a short abstraction away from potential difference of an electric field). Decomposing an arbitrary signal into frequency components is a transform which has no physical significance whatsoever (in the sense that inventing a fairy tale to describe some physical phenomenon is no more valid than some other description which works - a point made by penfold a while back). I like to keep this fact (it's a fairy tale) in mind where possible. Do I believe it? Yes - it takes one set of real quantities and converts it into another, isomorphically. The fairy tale gains physical meaning when we lose the arbitrariness of the signal and begin dealing with sinusoids - RF, sound, bandlimiting, synchronous demodulation... I am happy to think in terms of reactance and the give and take of energy - not a complex number in sight. But I still like to check myself when talking about "frequencies" so as not to get too carried away by the fairy tale. Complex numbers are where my belief in a fairy tale ends. Not because they don't work, but because the mathematical validity seems to be based on a leap of faith - a circular definition (no pun intended). Not entirely, but not 100% convincing. The fact that most 'proof' seems to consist of wildly gesticulating at my paragraph above saying "but but phasors" suggests that the proponents of the fairy tale have become so under its spell that they have lost the ability to reason. --- End quote --- The time domain is more appropriate for some measurements, and the frequency domain is more appropriate for others. Some clarification about I and Q measurements on my two-phase lock-in amplifier and (now more common) vector network analyzers: The two values I and Q are functions of frequency, and the front-panel outputs from the lock-in amplifier are not suitable for seeing on an oscilloscope. They are bipolar (positive or negative) non-sinusoidal voltages. They represent the amplitude of the in-phase and quadrature components that result from synchronous demodulation with respect to the reference input, one in-phase and the other in-phase-quadrature. On the lock-in amplifier, the averaging time to extract the amplitudes is switchable, and provides noise filtering at the expense of slowing the response to changes in the signal. (The low-pass filters are mandatory for synchronous demodulators, to extract the DC value for magnitude and reject the second harmonic of the reference frequency and other spurious outputs.) Thus, they are suitable for measuring behavior in the frequency domain, so long as that behavior is not varying too quickly. If you apply slightly different frequencies to the input and the reference, where the frequency difference is smaller than the low-pass filter cut-off, you will see the signal "rotate" between the I and Q outputs at the difference frequency. Of course, in a free country, you are not required to use mathematics with which you are uncomfortable, but I assure you that when dealing with the results from these analyzers, complex algebra is logically consistent, gives physically correct results, and is very convenient. What else is required to justify the use of a given mathematical method on a physical problem? |
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