Correcting beat error using a PC

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  1. #1
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    Correcting beat error using a PC

    My watch has been out of beat for some time after a slip of the hand while attempting regulation. It has been keeping excellent time on my wrist regardless but I finally decided to attempt to get it in beat the other night for peace of mind. Everything seemed to go very smoothly so I'm interested to know if I've made any incorrect assumptions!

    I used a PC running Audacity (an audio sampler), a pre-amp, and a guitar pick-up mic. The movement is a Tudor ETA 2824-2.

    Firstly, I'm not trying to time the watch - I tend to regulate on the wrist over a period of a week and the signal through the contact mic is not clean enough to use timing software. Seeing the waveform in Audacity however, it is easy to manually identify the start of each beat. One key assumption I've made is that getting a watch in beat does not require calibration of my soundcard as I simply need to measure the percentage of each beat in relation to the total time for both (which, incidentally, Audacity seemed to get very close to the correct value of 250ms, i.e. 28,800bph). My aim was to use the ms value out of Audacity as a guide but really to concentrate on the percentage difference and get that as small as possible.



    I moved the stud carrier and re-recorded until I managed to get the percentage difference down to roughly 0.05% (approx 0.1ms difference) from a starting point of a 0.8% difference (around 2ms). As I never manually wind the watch, I performed these recordings after a full day of wear (assuming that is an average 'maximum' wind). I only tested dial-up. Also, I used just two beats (one tick, one tock) rather than analyzing over many beats. When I saw Audacity was coming back with a consistent 250ms for both beats each time I recorded, I felt that was okay.

    Before I start testing different positions, have I missed something here?
    Last edited by bonapardo; November 5th, 2010 at 18:41. Reason: Correction to bph

  2. #2
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    Re: Correcting beat error using a PC

    Quote Originally Posted by bonapardo View Post
    (...)Before I start testing different positions, have I missed something here?
    Yes. Screenshots for us.
    your "local" chemist

  3. #3
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    Re: Correcting beat error using a PC

    Quote Originally Posted by bonapardo View Post

    Firstly, I'm not trying to time the watch - I tend to regulate on the wrist over a period of a week and the signal through the contact mic is not clean enough to use timing software.
    You can clean up the signal a bit by passing it through the high pass filter 2 or 3 times and then normalize it. What timing software are you using?

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    Re: Correcting beat error using a PC

    Dbl, I'm a little reluctant to post pics as I know other problems can be identified from the waveform. That's a can of worms I'm not quite ready for! I'm trying to learn things step by step! What kinds of things do you think I've missed?

    Twi, I have managed to clean up the files in various ways, filters and noise reduction experiments but found that to measure beat only all that matters is that each beat in a pair is of equal length. Thought I'd save a bit of time! I've used three apps: wtm, escapement analyser demo, and a japanese one which i don't remember the name of.

    Thanks for the replies, I do love these forums!

  6. #5
    Member radger's Avatar
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    Re: Correcting beat error using a PC

    That is clever and innovative to use an audio sampler to analyse the waveform to put
    your watch into beat.
    A 0.1ms beat error is miniscule and I'll bet youl'll notice differences
    in beat error whilst testing positions with this degree of accuracy, let us know.

  7. #6
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    Re: Correcting beat error using a PC

    Quote Originally Posted by bonapardo View Post
    Dbl, I'm a little reluctant to post pics (...)
    And I don't insist.

    (...) and a japanese one which i don't remember the name of.
    (...)
    Biburo ?
    your "local" chemist

  8. #7
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    Re: Correcting beat error using a PC

    Biburo, that's it! With that software I was able to only monitor in real time. Results not great as unable to clean the signal on the fly or calibrate my soundcard. As I remember, the other two allowed me to use an audio file so I could clean it up a bit. The registered versions of them also allow auto-calibration I think.

    I'll test a full unwind at the weekend to see if isochronism has been improved. Previously there was a 5 sec variation during wind down compared to 1 sec on the wrist.

  9. #8
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    Re: Correcting beat error using a PC

    It's been a year since the above experiment, but I thought I'd give an update as I took the watch to a shop at the weekend.

    The contact mic method did not work for me. After my attempts at putting it back in beat, while I wore the watch, it was only losing about 5 secs a week, which was great. However, during wind down at night on my bedside table, the watch was gaining 20 secs in about eight hours. Even more out of beat. I suspect the fact I had got it SO wrong had something to do with the sample frequency/timing of my soundcard. I couldn't be bothered manually calibrating everything.

    So I simply wore the watch 24/7 for the last year, only taking it off near water as the 5 sec loss was absolutely fine.

    I was walking past a random watch repair shop on saturday and popped in to ask for a quote. The timing machine revealed that I'd pushed the watch well out of beat, as I thought. He fixed it while I waited for £18.

    I've been checking the watch regularly over the past few days and it is now running perfectly (literally +/-0 secs a day so far). Winding down on the bedside table, it now gains just 1 sec overnight. He was also able to show me there were no obvious problems with the second-hand Tudor 2824 revealed by the timing machine.

    For peace of mind, it was money very well spent.

  10. #9
    Member smpcollector's Avatar
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    Re: Correcting beat error using a PC

    Thanks for the update, i missed this thread when it was first posted but i think it was interesting to read about your try to correct the beat error and how it turned out.

  11. #10
    Member dacattoo's Avatar
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    Re: Correcting beat error using a PC

    You may be confused about beat error. Adjusting beat error may affect the rate but the rate is adjusted by changing the "effective" length of the hairspring. This is accomplished by moving the regulator pins if so equipped and the 2824 is so equipped. The beat error of .5 milliseconds is considered in beat. It (the beat error) may be adjusted by moving the pinning point at either end of the hairspring. Watches without a moveable outer pinning point are adjusted by rotating the collet on the balance wheel.

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