Geek Alert - what do you get when …
All non-geeks, ignore this post 
If you are still reading, you are either truly bored, a geek, or much too curious. In any of these cases, I will tell you what you get when you …
… combine an old microphone, digital oscilloscope, band-pass filter, signal trigger, and signal capture …
I used Visual Analyzer and an old PC microphone that was left over from a Compaq 386 (yes, that old). I set the microphone under the escapement of my small antique clock and then set the necessary filters and trigger. The image is of a 10 second capture. The arresting of the escapement at each end of the pendulum travel is represented by an impulse on the graph.
Addendum: I did a little thinking about using the digital oscilloscope for timing a clock and realized a bit of a problem. I planned to use this technique on a clock I hope to restore soon. However, the clock should have an accuracy of 1 second per week. At that rate, I would need to measure to one 500,000th of a second. Not likely since I am using an audio card which presumably is only good to about 20,000 hertz. I’ll resort to averaging over long periods of time.
April 3rd, 2007 at 17:46
Hey Glen, cool blog! And I managed to find the geekyest entry on it. I’d love to see a picture of what a similar tower clock looks like when not in pieces, just to get a general idea of what yours will become.
Also, just a thought about the audio analysis, since that’s my kind of thing. Presumably if your audio card is recording at 16 bits (CD resolution) then the most likely sampling rate is 44.1 kHz. So regardless of the fact that you can capture a maximum frequency of 20kHz, you would still be rendering 44,100 samples per second, right? My home studio interface does a maximum of 96,000 at 24 bit, I’m pretty sure. I know we’re still talking way less than the 500,000 that would make life easy, but maybe thinking about it in terms of sampling rate will help your calculations.
I suck at math, but I’m an audio geek to the core.
See you and Zen tomorrow!
-Doug
April 3rd, 2007 at 19:23
Hey Doug ! The clock doesn’t look like much when you really look at it. You can see it in my post on “disassembly” -> http://thesalmonfarm.org/blog/2007/03/24/before-and-after/
The full clock, once restored and running, will be a bit more interesting as it will be on a stand / craddle about 5′ tall to accomodate the 66″ pendulum. The clock, pendulum, and drive weight will tip the scales at about 500 lbs