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  1. #11
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    Re: Definition of beat error

    Quote Originally Posted by contrate_wheel View Post
    . . . . Pithy was right in his guess that I am writing my own timing software. . . . .
    Not real hard to deduct.

    Obfuscation is par for the F6 course.

    Virtually all the engineers that loaf here have one or more horological software projects.

    And counting/sampling isn't the most interesting of them.

    None of the systems utilizing an onboard transducer are effective enough to be of any commercial benefit.

    Most of the code - be it ported for whatever form factor - is only marginally productive even with a common external pickup.

    On the other hand, when I couple a huge old crystal to the sound card or specially shielded, preamp driven USB mic - the gain jumps and or sharpness of the attack is accentuated and the wave markers can be be unmistakeably discerned.

    Optimize the gain and filter the noise - then you'll have something - oherwise its more wheels.

  2. #12
    Member pithy's Avatar
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    Re: Definition of beat error

    Quote Originally Posted by Roland Ranfft View Post
    . . . . Do it better and display the error in degrees. . . . .
    You'd love the led strobe trigger.

  3. #13
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    Re: Definition of beat error

    Quote Originally Posted by Roland Ranfft View Post
    Hi there,


    Authority? based on what? The price?

    I'm pretty sure that Chinese manufacturers sell much more than Witschi. And standard should be what the majority uses, and not the one with the most overpriced equipment.

    However, if you create an own software, do it better than all: Displaying the error in milliseconds is pretty useless, disregarding wheter you display the time difference, half of it, or 37,58% of it. Do it better and display the error in degrees. This would help immediately to turn the spring collet to the right position with the first attempt.

    Regards, Roland Ranfft

    Thank you for your opinion Ronald. Let me make an apology first for my
    attribution of authority, as I, for once, don't have the authority to
    discuss that. Please everyone understand that it is not my intention to be
    contentious.

    Your suggestion of using angles is quite sensible from the watchmaking
    point of view: I trust you on this. Unfortunately from the signal
    processing point of view is a bad idea, for the following reason. I have
    designed my algorithm to work with crappy audio, this is my top priority
    in this project. So, the beat of a movement is the easiest and most stable
    number to get. Then comes the beat error (in time units), almost on par.
    You can get this numbers, up to a reasonable tolerance, even if you can
    not resolve the three sounds of each beat. The amplitude, by contrast, is
    far less reliable. Now, if we do the math, in order to get the angle
    corresponding to a given beat error, we basically need the amplitude and
    the beat error measured in time. In general, making the more reliable
    result depend on the less reliable is not good. It would be great if I
    were designing a program for clean signals, but I am doing the opposite.

    Still I can produce both results, or a translation table. I will
    definitely think to this, so thanks again!

    A funny thing that I noticed is that on a bad movement the tic and the toc
    waveform may differ in length by more than the beat error of the movement
    (say 1ms difference with 0.something beat error). So if you take as
    reference point for the computation, say, the first sound or the third
    sound you get entirely different results. This is why I say that the beat
    error has slightly larger uncertainty than the rate.

    Ok, enough boring stuff, and someone will complain again that I am asking
    for help, which I am not. I am sharing some precious bit of ignorance, so
    rare on the internet.

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  5. #14
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    Re: Definition of beat error

    Quote Originally Posted by pithy View Post
    Not real hard to deduct.

    Obfuscation is par for the F6 course.

    Virtually all the engineers that loaf here have one or more horological software projects.

    And counting/sampling isn't the most interesting of them.

    None of the systems utilizing an onboard transducer are effective enough to be of any commercial benefit.

    Most of the code - be it ported for whatever form factor - is only marginally productive even with a common external pickup.

    On the other hand, when I couple a huge old crystal to the sound card or specially shielded, preamp driven USB mic - the gain jumps and or sharpness of the attack is accentuated and the wave markers can be be unmistakeably discerned.

    Optimize the gain and filter the noise - then you'll have something - oherwise its more wheels.
    Thanks a lot, sorry for missing your answer. I am not an enigineer, in
    fact I have got my PhD in mathematics. But I guess it's almost the same.

    No, I am not trying to write anything commercial, as I said, I will
    release the source code as soon as it is presentable.

    For the filtering part, I decided to do away with the tigger based
    algorithms altogether, so I am not looking for edges. This is the
    technique that everyone uses, and it works fine if you have a very clean
    signal, but badly otherwise. What I do is to detect the whole waveform,
    more or less along the lines of what they do with adapted filters in
    radars. As it is now, the thingy can trigger happily on a decently loud
    watch held on my wrist at five centimeters from my laptop internal
    microphone, in a quiet environment. And I am quite pleased with it. Still
    it would be no match for a proper setup: if you can have a sharp waveform,
    just triggering on the edges is the way to go. The whole thing is designed
    to be much more amateurish.

  6. #15
    Member pithy's Avatar
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    Re: Definition of beat error

    Quote Originally Posted by contrate_wheel View Post
    Thanks a lot, sorry for missing your answer. I am not an enigineer, in fact I have got my PhD in mathematics. But I guess it's almost the same. No, I am not trying to write anything commercial, as I said, I will release the source code as soon as it is presentable. For the filtering part, I decided to do away with the tigger based algorithms altogether, so I am not looking for edges. This is the technique that everyone uses, and it works fine if you have a very clean signal, but badly otherwise. What I do is to detect the whole waveform, more or less along the lines of what they do with adapted filters in
    radars. As it is now, the thingy can trigger happily on a decently loud watch held on my wrist at five centimeters from my laptop internal microphone, in a quiet environment. And I am quite pleased with it. Still it would be no match for a proper setup: if you can have a sharp waveform, just triggering on the edges is the way to go. The whole thing is designed to be much more amateurish.
    There's been a bit of work been done on digital waveform recognition as an automated diagnostic tool.

    This will be incorporated into the next gen of professional timers.

  7. #16
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    Re: Definition of beat error

    Hi there,

    Quote Originally Posted by contrate_wheel View Post
    Your suggestion of using angles is quite sensible from the watchmaking
    point of view: I trust you on this. Unfortunately from the signal
    processing point of view is a bad idea....

    ....
    I have got my PhD in mathematics.
    Fine, from your math studies you'll know that the angle speed is nearly constant near the zero transition. So a linear approximation for the beat error angle would be more than sufficient for the needs of a watchmaker. You need just the frequency, the time difference, and a constant factor - peanuts compared with capturing the trigger points.

    Regards, Roland Ranfft
    Last edited by Roland Ranfft; September 22nd, 2015 at 04:03.

  8. #17
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    Re: Definition of beat error

    Quote Originally Posted by Roland Ranfft View Post
    Hi there,


    Fine, from your math studies you'll know that the angle speed is nearly constant near the zero transition. So a linear approximation for the beat error angle would be more than sufficient for the needs of a watchmaker. You need just the frequency, the time difference, and a constant factor - peanuts compared with capturing the trigger points.

    Regards, Roland Ranfft
    Sorry, no. The angular velocity at the center of the oscillation is
    directly proportional to the amplitude. So it has the same relative error
    (50% error in the amplitude immediately translates to 50% error in the
    angular velocity). Yet I could go for a default of, say, 250 degrees of
    amplitude, assuming that the watch is between 200 and 300 this gives me a
    +-20% error in the angle. Not totally wrong, but it doesn't feel right
    anyway, does it? Why to introduce a new source of uncertainty?

    On the other hand, you convinced me that showing both results is possibly
    a good idea. I will maybe display something like "x ms (~y deg)", to make
    it clear that the angle is just a guess, and then use a default amplitude
    for the computation. Do you think that 250 degrees is a reasonable choice?

  9. #18
    Member pithy's Avatar
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    Re: Definition of beat error

    Quote Originally Posted by Roland Ranfft View Post
    . . . . near the zero transition. . . . . .
    Quote Originally Posted by contrate_wheel View Post
    . . . . at the center of the oscillation . . . .
    hmmm

  10. #19
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    Re: Definition of beat error

    Hi there,

    Quote Originally Posted by contrate_wheel View Post
    The angular velocity at the center of the oscillation is
    directly proportional to the amplitude.
    And this is your problem??

    Math guys tend to make things complicated, while engineers are simple minds. So I thought you wanted to calculate the angle after the exact waveform of the balance motion, and therefore I mentioned that the velocity near zero transition is fairly constant.

    A modern timing software needs entering the lift angle to calculate the amplitude from measuring the lift angle by capturing the according noises. So you have the ratio between time (measured) and angle (entered). This actually is the angular velocity near zero transition, and you can use it to calculate the angular error from the (half) time difference.

    Here the simple formula (with ea = error angle, et = error time, la = lift angle, lt = lift time):

    ea = (et/2) * (la/lt)

    No callenge for an Apple II from 1980, peanuts for a phone processor. Of course it is an approximation, but it is better than a watchmaker will ever need to adjust the hairspring collet (by ea), and it is even sufficient if he takes a default 50 for the lift angle. And if this watchmaker hasn't lost his marbles, he'll not even consider a beat error unless the amplitude is reasonably bigger than the lift angle (after visual judgement).

    Regards, Roland Ranfft

  11. #20
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    Re: Definition of beat error

    Hi pithy,

    I have also another imagination from a center, but 1st I don't put every word on a scale, and 2nd I also should have defined zero as rest position of the balance to make the term zero transiton precise, and I should have given a precise deviation from linearity to define "near". But I believe too exact definitions prevent people from reading posts.

    Regards, Roland Ranfft

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