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Sine wave frequency 2

Discussion in 'Electronic Design' started by thejim, Dec 13, 2005.

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  1. thejim

    thejim Guest

    I wasn't very clear in my first post regarding sine wave frequency.
    What i am trying to say is if can we have a sine wave of frequency 40
    or 50 or 60 Hz.
    Suppose we have a sine wave frequency. By decreasing or increasing
    the frequency from a limit and on the wave stops from being sine or is
    not?

    Thank you
     
  2. Paul Burke

    Paul Burke Guest

    It's not dreadfully clear what you are asking; though if I asked a
    question in wg=hatever is your native language (Greek?) I doubt if it
    would make any sense at all.

    This is an answer to what I think is your question.

    A sine wave is defined as a voltage/ frequency/ whatever which varies as
    a function of time such that the instantaneous value V = Vm sin wt. Vm
    is the peak absolute value, w is 2*pi*frequency, and t is time.

    Obviously, any deviation from that relationship makes it, strictly
    speaking, not a sinewave. The deviation could be noise, distortion,
    maximum amplitude variation, frequency variation etc. A Fourier analyser
    attached to the signal would show these up as the base level, harmonics
    etc. as well as the pure single fundamental of a sinewave.

    You are talking of a signal which can be expressed as V = Vm sin w(t) t,
    where w(t) is itself a function of time- in your case, I think, a ramp.
    You can plug that function into the Fourier calculation, do the sums and
    come up with the answer, for any function of time that you choose.

    But we are a bit lax, and basically if it LOOKS like a sinusoidy
    squiggle on the scope, we call it a sine wave. Most of the time,
    everybody understands, or don't care anyway.

    Now, why do you need to know?

    Paul Burke
     
  3. PeteS

    PeteS Guest

    I think what you are asking is:

    Start with some sine wave at arbitrary v = ASinw(1)t and vary the
    frequency to some new signal v = ASinw(2)t.

    Is that correct?

    You are then asking, if one does this, will the result still be a sine
    wave?

    Is that also correct?

    At all instantaneous points (time) during the transition, you will have
    a single sine wave, assuming you are simply changing the frequency of a
    single source.

    Cheers

    PeteS
     
  4. theJackal

    theJackal Guest

    I am guessing what you are trying to say. Possibly you want to vary
    the frequency of a Sine wave oscillator you have designed or have.
    Your question is by simply changing a component value or 2 do I still
    have a Sine Wave? If you are using an Analog oscillator I'd think
    No. Don't believe what the books say it won't work so easily . You
    have to redesign the whole thing.
    With a digital oscillator ... Yes very likely.

    If your question is about Sine wave purity ... Yes it can be
    compromised by changing the frequency. It all depends on the details
    on what you are using to generate the thing.

    "Go easy on the whisky"

    theJackal
     

  5. A sine wave may be any frequency you wish - from one cycle per week or
    more, up to Gigahertz.
     
  6. I think you might be asking about frequency modulation. If you are, the
    result is a group of sine and cosine functions (frequencies) that can be
    predicted with Bessel functions.
     
  7. Phil Allison

    Phil Allison Guest

    "theJackal"

    "theJackass"


    ** This laughing Jackass piece of *Eurotrash* is a pure vermin.

    Must be posting straight from an asylum for the criminally insane.





    ....... Phil
     
  8. Rich Grise

    Rich Grise Guest

    I understood well, I've just been reading your thread waiting for someone
    else to get it. :)

    A sine wave can be at any frequency, and still be a sine wave. The term
    "sine wave" just defines the _shape_ of the wave, but the wave can be
    at any frequency you wish. (well, within limits, of course).

    If you put a small pen sticking out the bottom of a pendulum bob, and
    drag a piece of paper under it at a constant speed, it will draw a
    sine wave.

    And someone else has already typed the trig expression, which boils
    down to y = sin x. :)

    Hope This Helps!
    Rich
     
  9. theJackal

    theJackal Guest

    LMAO Phil you are too repetitious.

    But better die than live mechanically a life that is a repetition of
    repetitions.
    D. H. Lawrence



    "Go easy on the whisky"

    theJackal
     
  10. Phil Allison

    Phil Allison Guest

    "theJackal"
    "theJackass"



    ** This laughing Jackass & psychopath is pure usenet vermin.

    Likely posting direct from an asylum for the criminally insane.

    His comments are all plagiarised from Google.

    Would almost be funny - if he was not so dangerous.





    ......... Phil
     
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