accurate portable time source
This request is different than the last one.
The most accurate TCXO watch is about 1 seconds/year, with regular
wear and lots of adjustment. For at least 1 order of magnitude in
accuracy, what can be made/bought given these initial requirements: it
has to run of its own power supply for ~18 hours a day, and recharge
fully at night. the device must be intrinsically accurate without be
disciplined by an external signal, although that could be done at
night. The size and wei8ght need to be pocketable such a a large cell
phone.I am open to all suggestions and more/altered requirements.
Ronald.
Ronald Held wrote:
This request is different than the last one.
The most accurate TCXO watch is about 1 seconds/year, with regular
wear and lots of adjustment. [...]
Really? What watch is good to 1s per year? Can you point me at one?
That's amazing for a watch.
jeff
This request is different than the last one.
The most accurate TCXO watch is about 1 seconds/year, with regular
wear and lots of adjustment. For at least 1 order of magnitude in
accuracy, what can be made/bought given these initial requirements: it
has to run of its own power supply for ~18 hours a day, and recharge
fully at night. the device must be intrinsically accurate without be
disciplined by an external signal, although that could be done at
night. The size and wei8ght need to be pocketable such a a large cell
phone.I am open to all suggestions and more/altered requirements.
Ronald.
Ronald,
Since a TCXO doesn't cut it, you could always try a miniature
OCXO. Take a look at Morion (http://www.morion.com.ru/) for
their tiny, low power, high stability, low drift quartz oscillators.
Do the math and see what the time error would be per month or
per year. Use lithium batteries; my guess is your 18 hour use
with 6 hour recharge requirement is easily met.
I don't quite get the "intrinsically accurate" requirement, though.
Time used to be something that you could have in isolation or
use in isolation but all the trends now are the other way.
No one predicted ten or twenty years ago that a billion people
today would have sub-second time (effectively, atomic clocks)
in their pockets or on their wrists. But that is exactly what radio
controlled watches, cell phones, internet enabled PDA's, and
personal navigation devices have done.
Send us a picture of your OCXO watch prototype when it's
ready! Combine that with one of these for extra credit:
Nixie Watch (David Forbes)
http://www.cathodecorner.com/nixiewatch/
The Nixie Tube Digital Wristwatch (Jeff Thomas)
http://www.amug.org/~jthomas/watch.html
Hi Ronald:
Here are a some of ideas for the heart beat for a LCD based clock like the ones
I've been developing.
Best) A Vectron EX-380 series Vacuum OCXO only draws 0.35 Watts and if the 5
volt version that's only 70 ma. So a single AA would have enough energy, three
AAA Ni-MH would be great. That was the good news. The bad news is that they
are made of unobtanium (i.e. very expensive or need to be bought in large lots).
Good) An alternative is the DS3231. This is an advanced version of the DS32khz
TCXO and is adjustable to 0.1 ppm using the digital serial interface.
Provision for a coin cell back up battery.
unknown) One of the DS3231 parts, in a thermal enclosure that has a time
constant in excess of 24 hours. I think it's about the size you request. A
temperature sensor changes the divisor based on calibration data. Sort of a
doubly compensated device TTCXO or T2XO. I like this one for a practical product.
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam
Ronald Held wrote:
This request is different than the last one.
The most accurate TCXO watch is about 1 seconds/year, with regular
wear and lots of adjustment. For at least 1 order of magnitude in
accuracy, what can be made/bought given these initial requirements: it
has to run of its own power supply for ~18 hours a day, and recharge
fully at night. the device must be intrinsically accurate without be
disciplined by an external signal, although that could be done at
night. The size and wei8ght need to be pocketable such a a large cell
phone.I am open to all suggestions and more/altered requirements.
Ronald.
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