Technical question on Amplitude

[owdeguy]

The Zigmeister,

Being that you're an engineer maybe you can explain how a timing machine is calculating the amplitude. I'm building my own timing unit and I'm not seeing anything detailing what exactly the amplitude is or is being calculated off of. I'd kill for one good diagram so that I could visualize it.

tia,

Pete

[RWG Technical]

I'll offer what I can.

My Vibrograph does not have a amplitude reader, I read the amplitude visually...

The amplitude is the degrees from neutral that the balance rotates after it passes by the pallet arm. From the point that the impulse jewel leaves the slot in the pallet fork, to the point that the balance stops moving (due to compression or expansion of the hairspring) is the amount of "Amplitude". Typically 270 - 310 degrees is normal, it varies of course with the position of the watch, being less in the crown down or up position.

My best guess is this, the timer records the tic or toc, which is the escape wheel hitting the entry or exit pallet stone. If you measure the time from the tic, until you hear the toc, you can calculate the rotation of the balance wheel in degrees. If memory serves me correctly, you need the lift angle of the particular movement your trying to measure to get an accurate amplitude reading. Lift is measured in degrees and is the amount of degrees that from the impulse jewel entering the pallet arm, until it leave it (not 100% sure on this part, I think this is what it is). All ETA data sheets show the angle of life for the balance which can vary from 44-52 degrees.

RG

[owdeguy]

Thanks The Zigmeister, You're understanding matches what I thought I understood about this subject. I figured it had to do with the tic vs toc, but I thought maybe there was something obvious I just wasn't thinking of so I wanted to bounce it off someone else. Now that I understand what you've explained about lift angle maybe I can start working on something. I wonder how the Chinese angles are done, maybe off their clone counterparts? Its a shame there isn't a really good graphical representation of this. Once I work it out maybe I'll build a flash animation of it.

Thanks again for being so helpful...