[quote author=Jack Christensen link=topic=124085.msg933487#msg933487 date=1348497283]... but getting to these levels of accuracy raises the question of how to measure and observe the effect of adjustments without waiting A Long Time.
There's an interesting discussion on this subject in the watchuseek forum here - http://forums.watchuseek.com/f9/methods-determining-accuracy-watch-382752.html
I've seen great prices for TCXO, OCXO, and other high quality clock sources on E-bay, either new old stock or recently pulled from equipment.
OK I'm now hooked on the idea of using an ebay sourced OCXO. Am I right in thinking I could possibly use one like this? - http://www.ebay.co.uk/itm/310380778466?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
Looks to be a very nice one at an attractive price. What does the current consumption say from the datasheet?
I've run over the specs as presented in the listing, as well as the Micro Crystal datasheet linked to from there, and have come up with a 'conceptual design' on which I would very much appreciate any and all feedback.
The general idea I have in mind is to use the 10MHz output from the OXCO as the clock for a small micro controller, such as an ATtiny45, running a simple program which uses the timer to generate a suitable timing pulse, eg 1 pps, for use as an interrupt signal on an arduino controlling the RTC and clock display. Could this be made to work, or am I being too simplistic?
I don't see why not. Just make sure the ATtiny45 has clock fuses set for external clock signal input.
A second more specific question relates to the Frequency Adjustment referred to. Would I be correct in assuming this means that I can fine tune the output frequency by applying a fixed dc voltage in the range .5V to 5V, as provided by a simple voltage divider with a variable resistor in it, say? Or again, have I misunderstood the complexity involved?
No, you have it correctly, but keep in mind the adjustment range is small +/- 40hz. One might ask how you will determine that an adjustment is required, that is what standard will you use to suggest a change is required?