wrote in message
oups.com...
Can I get recomendations for the most accurate electronic timer that I
can buy?

It must to be accurate to within 1/60th of a second over the course of
6 hours.

Is something like this commercially available, or will I have to build
it, or have someone build it?

Any advice would be appreciated.

Thanks a lot.

Darren Harris
Staten Island, New York.
You really need to say more about the enviroment.
Crystals, can relatively easily get to 1ppm. (you need just slightly
better than this), and with a crystal oven to control the temperature,
accuracies better that 0.1ppm, are relatively easy. Omega offer off the
shelf timing systems warranted to better than this.
Some radio transmitters in most countries have warranted accuracies
(usually on the long-wave), and a receiver, with a PLL locked onto this
can give superb accuracies (some warrant 0.01ppm, and some go even
further - in the UK, the 60KHz used for this, is maintained to better that
2 parts in 10^12). In the US, WWVB, broadcasts a similar signal.
These same transmitters are usually the ones carrying MSF time and date
information, and the master source is usually now an atomic clock. Some of
the receiver systems for these, have inputs for the distance to the
transmitter, and give 'real time', compensated for this to mSec or better
accuracies.
The master clock for the GPS system, provides similar accuracies. A
receiver, with local PLL, can be used again to get access to this clock.
Mains provides good 'long term' accuracy, but in the short term is poor,
and would not meet your requirements in this regard.
So, if you have access to radio reception, look at using a local
oscillator locked to the WWVB transmissions. Otherwise you will need to
consider a high accuracy crystal, in a suitable oven. If internet
connectivity is available, you could use a time server, and a local clock
slaved to this (units to do this are off the sheld items).
In the UK, one of th companies doing a range of products using these
technologies, a
http://www.steatite.co.uk/downloads/...q_linecard.pdf

Best Wishes