Jump to content

How Does The Timegrapheror Vibrograph Measure Amplitude?

cdjswiss
 Share

Recommended Posts

cdjswiss WRT Addict

cdjswiss

Posted
Posted

My question is in the title: How does the Timegrapher or Vibrograph measure amplitude? Can anyone provide an answer?

 

The frequency of Simple Harmonic Motion does not depend on amplitude. So to first oder everything that can be measured by the Timegrapher is independant of amplitude. Does it use a second-order effect caused by the balance spring to extract the amplitude from the signal and, if so, to to what precision?

 

Or am I missing something simple?

Link to comment
Share on other sites
cdjswiss WRT Addict

cdjswiss

Posted
  • Author
Posted

Thanks Geo for the link. I shall PM Stefan - some time ago read his post.

 

It must be that the angular speed of the roller jewel is measured - this does depend on the amplitude. The speed can be calculated from the time difference between the sounds of roller jewel hitting the fork and the fork hitting the banking pin. But this will only be corrrect if the beat error is zero and the distance from the fork to the banking pin is known to the Timegrapher. Also there will be instrumental measurement errors.

 

I ask all of this because I strongly suspect inaccuracies in the measured values from my generic Timegrapher.

Link to comment
Share on other sites
Rob WRT Addict

Rob

Posted
Posted

Witschi has technical explanations of how the values are calculated. The amplitude is calculated from the noise of the escape-wheel tooth meeting the locking plane of the pallet-stone and the lever hitting the banking-pin.

 

"To calculate the amplitude, the time between the first pulse and the third pulse of the beat noise is measured.

 

Between these two pulses, the balance wheel rotates a certain angle. This so-called lift angle is determined by the construction of the movement and is entered as a parameter. The larger the amplitude of the balance wheel, the greater is the speed with which it goes through these lift angle and the shorter is the time it needs to traverse this angle.

 

The amplitude can therefore be calculated from the time between the first and the third pulses in the beat noise, taking into account the beat number and the lift angle."

 

  • Like 1
Link to comment
Share on other sites
cdjswiss WRT Addict

cdjswiss

Posted
  • Author
Posted

Thanks, Rob, for this link and technical information - it is exactly what I was looking for.

 

I conclude that my 'Timegrapher' is US. It always displays a beat error of 5.1ms irrespective of the separation of the two plots and the amplitude is another fiction. The timing information is reasonablly good but the rest is trash, presumably because of bad resolution of the individual pulses of the beat signal.

 

Perhaps the mike is faulty?  I shall look at the mike output on my 'scope to check that the three pulses are resolved. But almost certainly I shall be investing in a better instrument.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing


  • Recently Browsing

    • No registered users viewing this page.

  • Topics

  • Posts

    • aac58
      Rare Seiko 5actus Watch??!! With a lot🤪🤔😲

      By aac58 · Posted

      This is not rare at all, the dial code and case code don't usually match.
    • Kkramme
      Coil for old Seiko Credor -- 4002920

      By Kkramme · Posted

      Good question!! Anyone know of a substitute movement??!! 🤔🙏
    • Kkramme
      Rare Seiko 5actus Watch??!! With a lot🤪🤔😲

      By Kkramme · Posted

      Interesting issue that I just noticed: this Seiko 5actus Watch from 1977 has a calibre listing on the dial of 7019-8030R but on the case back it says 7019-8010!! Like a mis-printed coin, is this watch therefore worth a lot of money for its rarity?? 🤪😲🤔🤪
    • Mercurial
      Smit

      By Mercurial · Posted

      I wish that was the case. The Aegler movements used in the early days by Wilsdorf & Davis (for brands like Rolex and Rolco) came in several sizes and without designated calibre numbers that survive.  They become a bit easier to identify during the 1920s. Below is an Aegler-Rebberg, 25.74mm in diameter. It’s from a woman’s Rolex wristwatch. Stamped Rebberg and 500 on the dial plate (but it isn’t a Rebberg 500, it’s the wrong size).  I’d be interested if anyone can identify the movement.  It is based off the Aegler Nr.1, circa 1903, but they based many many calibres of different sizes on it. The closest I have to a positive ID is the  ‘Rolex Nr.50’ circa 1917, but no dial side images or movement sizes are available in the references. There are identical looking movements in many sizes.  The 25.74mm of this movement is a particularly strange size for the era, it equates to 11.41 lignes.      Best Regards, Mark
    • GuyMontag
      FHF70 balance jewels settings

      By GuyMontag · Posted

      It looks like this movement comes with a number of different shock settings. Emmywatch shows that it comes in versions with no shock settings, 'Incabloc', 'shock resist', and 'Supershock'. Perhaps the different settings position the impulse jewel/roller table in a non-ideal position relative to the pallet fork/guard pin. Are you able to check under high magnification if the pallet fork and roller table are able to operate without any interference? Just for fun I took a look and I have one FHF 70 in my collection, a West End Secundus with a non-shock protected FHF70. I had a note with the watch that said, "Movement is stamped 'FHF 70', but the FHF70 looks to have sub-seconds instead of center seconds movement (??)" but that a google search turned up both types for this movement. EDIT: I just took a look in my parts drawer and I have a few of these movements, both in center seconds and sweep seconds, but they all are non-shock protected.  
×
×
  • Create New...