"This limits the compensations one can put into a pendulum clock" unless you actually build compensation for those effects too :)
I would think the timing of gravitational effects of the moon and the sun can be easily predicted. I am not sure the amplitude of these effects can be precisely modeled, but that would be an interesting part of the project. If you know the timing of a perturbation, you can measure the effect from the instrument itself (by checking it against a reference that is insensitive to that perturbation and applying the proper filtering algorithms) and determine the coefficients experimentally. That is what the Thunderbolt does while it is locked to GPS, so that when it loses the signal, it can keep its OCXO in check. Didier ------------------------ Sent from my BlackBerry Wireless thingy while I do other things... -----Original Message----- From: "Ian Sheffield" <[email protected]> Sender: [email protected] Date: Mon, 9 Aug 2010 18:34:40 To: 'Discussion of precise time and frequency measurement'<[email protected]> Reply-To: Discussion of precise time and frequency measurement <[email protected]> Subject: Re: [time-nuts] Regulating a pendulum clock Unfortunately Gravity is not constant. Pendulum clocks show cyclic errors due to the influences of the Moon's and Sun's Gravitational fields. I forget the amounts but it is in the region of parts in 10 to the 7, which is easily measurable. This limits the compensations one can put into a pendulum clock. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of mike cook Sent: 09 August 2010 18:21 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Regulating a pendulum clock Le 09/08/2010 18:46, Bob Holmstrom a écrit : > > Food for thought. > > I find it interesting that no one has suggested alternatives to > improving the performance of a pendulum clock other than controlling > it with a higher performance clock. If the goal is a better clock why > not attempt to understand the source of the errors and work on methods > to control or compensate for them? Teddy Hall has been taken to task > for using a quartz controlled oscillator to measure the amplitude of a > pendulum in the control loop of his Littlemore clock. > > Tom Van Baak has developed techniques for analyzing the performance > and hence potential error sources of pendulum clocks - perhaps he will > share some of his work here. > > Horological history is full of many attempts at solutions to the > problem, but it would seem that the creativity of this group might > generate some new ideas that are more in the spirit of better > timekeeping than attaching the pendulum to a better oscillator. > > How about a wireless controlled device attached to the pendulum that > changes its position based on error sensor readings, not time errors, > but instead, temperature, barometric pressure, gravity, etc. that > would maintain a more constant pendulum period? Yup. We have temperature and pressure ICs available , I think that gravity is pretty constant if the clock isn't being moved about. Humididty might also need logging aswell. So it should be easy enough to predict the pendulums response to changes given a reasonable time of observation. That said, clocks have always been adjusted against better references.. IIRC Harrison (and probably others) was using star transits to regulate his long case clocks. > > Bob Holmström > Editor > Horological Science Newsletter > www.hsn161.com >_______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
