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.
An ordinary digital clock powered from the AC line is more accurate than that.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
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| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
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I love to cook with wine. Sometimes I even put it in the food.
On the surface, shouldn't that be "as accurate as that"? In North America and other 60-Hz realms, at least.
I have heard horror stories about short-term inaccuracies in the power system 60 Hz timing, that it is only guaranteed to be accurate within 1 cycle per day, for instance.
And I found this tidbit googling around for accurate clocks: "GPS time was zero at 0h 6-Jan-1980 and since it is not perturbed by leap seconds GPS is now ahead of UTC by 13 seconds."
As I understand it, for grid-power-hopping to work, the accuracy is _much_ better than that.
I think that's nonsense.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
I
of
build
otherwise.
America
I recall working with a marketing guy a few years back who had a customer interested in a ruggedized PC that had timing accurate to 1 second/month, even when turned off. He thought the PC's real-time clock chip would be ok, because it has its own battery.
*** GASP!!!!!! ***
An error of one part in 5,184,000??!?!?!?!?!
How could anyone possibly tolerate that???!?!?!?!?!
;^)
Dan, Sadly enough, there have been a number of replies to your question, but none have attempted to answer it directly. But, you didn't state the intended use or desired method of operation of the timer. Assuming that you are looking for a handheld timer suitable for tasks such as cooking or sunbathing, almost any of the common timers available at outlets such as Radio Shack, Target, Walmart, etc. should fill your bill. They are all crystal controlled, and although their accuracy isn't usually stated in the specs, they should easily meet your requirements. If you're looking for an industrial timer that can control other devices, then you need to specify what kind of equipment or the power requirements of the equipment.
-- Dave M MasonDG44 at comcast dot net (Just subsitute the appropriate characters in the address) Never take a laxative and a sleeping pill at the same time!!
GPS recievers. I've seen some with an alarm function. However, 1/60th of a second in 6 hours isn't impossible to do otherwise.
[...]
Just checking the math: 1/(6*3600*60)=7.716E-7
You are right. That may be difficult without an oven.
Darren's spec may be a little tight. Normally, people who need to measure to that precision already know the methods and where to get the needed equipment.
The next question : what is he measuring that is that stable? I don't know of anything that is expressed in seconds with
Only when averaged over at least a day. The OP needs accuracy of about
0.5 ppm, while the short-term accuracy of the AC line is no better than 600 ppm (0.1 Hz), IIRC.A quick Google search shows 0.5 ppm as a spec available for many TCXOs, so this can be built (relatively) cheaply using a TCXO and a microcontroller.
-- Tim Hubberstey, P.Eng. . . . . . Hardware/Software Consulting Engineer Marmot Engineering . . . . . . . VHDL, ASICs, FPGAs, embedded systems Vancouver, BC, Canada . . . . . . . . . . . http://www.marmot-eng.com
6 hours would be 6 x 3600 x60 units = 1,296,000 or better than one part in 10^6.
That is heading into TCXO crystal oven country. Or possibly locking to a NIST radio source such as WWV or WWVB.
Or, at the very least, a calibration from a traceable source.
Loosen your spec.
-- Many thanks, Don Lancaster Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 voice: (928)428-4073 email: don@tinaja.com Please visit my GURU\'s LAIR web site at http://www.tinaja.com
You will certainly find what you need here, though whether it is within your budget may be another matter. They have units that are far better than 1ppm accurate.
Or, have you considered a simple PC application that syncs its time from NIST via the Internet using an NTP client? Virtually free and accurate to
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, are:Best Wishes
Hello Darren,
This lets me assume that you need some kind of electronic triggering.
1/60th of a second is to precise for a finger to push a button.
Check out the sports markets. The devices for swimming relay contests may not quite offer 6 hours but equipment for marathons or triathlons should. It has been a while since I did competition swimming but I vaguely remember that the stuff mostly came from the major watch companies, usually from Switzerland.
Regards, Joerg
I had thought that maintaining an accumulated deviation of no greater than 1/60 sec in 6 hours is about like 24 seconds/year or 2 seconds a month. This is
Once you have this precision, you need some way to reliably use it.
I always get a chuckle out of "Star Trek". They've got massive computers calculating precise timing, trajectories etc. but they always initiate it with an imprecise verbal command, "ENGAGE". mike
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I'm sitting here looking at my homebuilt digital clock that is counting
120 zero crosses of the AC line as its 1 second time base. Motorola processor. Do you need the absolute accuracy or would counting 2,592,000 AC zero crosses do the trick? GG
It's about one part in 13 million, so, yes, this is pretty difficult. You won't do this with a straight crystal oscillator, and I don't know if any of the GPS units actually give out a clock signal that's fast enough to measure 1/60 of a second.
HP makes a 10 MHz ovenized crystal oscillator which is much more stable than this, however. There is one on ebay now for about $85. That's about as cheap as you are likely to find for this level of precision.
Do you really need this much precision?
------------------------------------------------ Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA
-----------------------------------------------
In order to be sure of the accuracy that you are seeking, I presume the timer woul dhave to have a readout in the order of 1/100's of a second.
Since this sort of accuracy is common in timing many sporting events (eg swimming, motor racing, running etc) a chat with the local swimming club etc might give you some leads to sources
David
snipped-for-privacy@mail.c> Can I get recomendations for the most accurate electronic timer that I
You can pick up a Radio Shack Model 100 from $5 and up on eBay. There is free software that will give you 8 separate accurate lap timers on that, one for each function key. It runs off 4 AA cells.
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