One of the things I like to do is to validate the quality of my work occasionally. I recently did a long term timing accuracy test of one of my 30cm WordClocks.
The test started on 20 May 2015, and ran through to 2 August 2015 – a total of 75 days (6,480,000 seconds) – I set the clock to the correct time (against a GPS standard), and I measured the time change every couple of days. I am pleased to announce that in those 75 days, the clock maintained the correct time to within 96 seconds (one minute and 36 seconds). That is a wonderful effort from a simple quartz oscillator.
Hang on – Am I saying that not keeping time is a good thing – Isn’t that really a bad thing???
Actually, no – In the clock business accuracy is very important, but that has to be measured against some realistic goals. Time is relative (I have been waiting ages to say that!) There are some beautiful timepieces that maintain accuracy, such as;
- Citizen Chronomaster with the A660 module which is specified at about 5 seconds p/y accuracy
- ETA thermoline – 10 seconds per year
- Seiko 8J/9F – 10 seconds per year
- Citizen E510 – 10 seconds per year
These are all beautiful timepieces that are worthy of mention – and they also cost significantly more than my clocks do.
Yes, there are clocks that have GPS receivers installed in them and that allows them to maintain time in the order of 10 seconds per 500 years, but these have to have external antennas and modules to allow the GPS signal to be received.
So… My clocks use a quartz crystal, which is specified at 20 parts per million in accuracy, so 96 seconds over 75 days works out to about 1.28 seconds per day, which I consider to be insignificant. It certainty is not noticeable when the display is updated every 5 minutes 🙂 We have to stay sane when it comes to super accurate timekeeping.
I also know in Europe and the USA, that there are low frequency time standard sources that can be used to automatically set clocks, such as;
- RTZ in Irkutsk/Russia
- MSF in Britain
- WWVB in the USA
- RBU in Moscow/Russia
- HBG in Prangins/Switzerland
- DCF77 in Mainflingen/Germany
Each of these services is able to be received by a $5 module that allows a clock to be automatically set – What an awesome idea!!! Here in Australia we used to have our own time standard station (VNG) located in Victoria, but sadly our sheep farming, coal mining, non technologically focused federal government decided to close that station down, removing the ability to cheaply synchronise clocks within Australia. So all we can use use is GPS technologies to synchronize clocks. – Oh well…
Now – I am not discounting GPS based clocks, I think they are neat. One of the things I would like to do is to look at the feasibility of adding a GPS receiver option to my 30 cm and above wall clocks. It will add a small optional cost to the clocks for the GPS receiver and antenna, but would be a very interesting thought.
Let me know what you think in the comments below.