[time-nuts] CW12-TIM
SAIDJACK at aol.com
SAIDJACK at aol.com
Mon Jul 14 17:09:04 EDT 2014
Good point.
I am a sucker for great surplus equipment too, in fact I have two rooms
full of stuff most of which is used from time to time.. I envy Tom's
collection.
I think we need to have a "Time Nuts For Dummies" article written that
takes J. Vig's writing and puts it into much less of a technically rigorous 3
to 10 page article that makes timing accessible to the average product
manager or systems engineer, and adds a hole bunch of GPS Disciplining
explanation as well.
This should be non-academic (who cares about Leesson's formulas digested to
the N'th degree when simply looking for a lab reference) and should be fun
and easy to read, but still get all the important points across.
bye,
Said
In a message dated 7/12/2014 15:01:33 Pacific Daylight Time,
magnus at rubidium.dyndns.org writes:
Said,
... and deprive us from cheap surplus oscillators of good performance?
What where you thinking? :)
But I agree fully with your point, people don't understand how their
poorly speced requirements translate into cost and design-time.
Accurate time to the fs for no budget is what you can expect if they
push their wishlist, but they have seen the E-18 numbers in some fancy
article, so as is now possible. I think not (mixing time and frequency
numbers is just what you can expect among other things).
Also, ADEV numbers isn't everything, it can be a splendid answer to the
incomplete and incorrect asked question.
Cheers,
Magnus
On 07/12/2014 10:44 PM, SAIDJACK at aol.com wrote:
> Graham,
>
> I think that is the real challenge here: most folks don't know what
> "precise" means for them. Timing is such a novel technology that most
folks are
> amazed that we are trying to get parts per trillion (or better) accuracy
and
> stability!
>
> We get customers all the time that want very precise timing, very good
> phase noise, and overall very good performance but are only used to
TCXO's with
> maybe 10ppm frequency accuracy and cannot specify anything beyond that.
>
> The challenge is to explain the cost-benefit to them, like:
>
> 1ppm == $1
> 0.01ppm = $300
> 10ppt == $1500
> 0.1ppt == $$$ etc.
>
> Once dollars are mentioned, desired specifications usually are attained
at
> fairly quickly :)
>
> We recently had an inquiry that we forwarded to a major atomic oscillator
> vendor, and the estimated $10 Million design cost and 10 year design
time
> quickly shut that idea down..
>
> bye,
> Said
>
>
> In a message dated 7/12/2014 08:54:09 Pacific Daylight Time,
> gh78731 at gmail.com writes:
>
> Shane:
>
> The question I think that is being asked is ...
> What does "precise" mean to you?
> To the nearest order of magnitude, what kind of accuracy are you looking
> for
> on your three signals. This defines the kind of system you will need.
>
> This group normally aspires to the more accurate end of the scale.
>
> If you are doing simple time logging of some process, then you are
> probably at the other end of the possible accuracy scale, and can
> do things much more simply and cheaply.
>
> So ...
>
> 1 PPS: +/- 1 ns? 10 ns? 100 ns? 1 us? 10 us ?
> NTP: +/- 10 ms? 100 ms? 1 second?
> 10 MHz: +/- 10E-6? 10E-9? 10E-12? 10E-14?
>
> --- Graham
>
> ==
>
>
> On Sat, Jul 12, 2014 at 3:57 AM, Shane Morris <edgecomberts at gmail.com>
> wrote:
>
>> Hal,
>>
>> As much as I'd like to explain the "big picture" in list, it would make
> God
>> awful noise - if you wish to know any details, I encourage you to
respond
>> to me off list. Given the fact that the robotics is so totally off
topic,
>> I'm not willing to discuss them here. Thats only out of respect to the
>> topic of the list. The only real stipulations at this design part of
the
>> project is 10MHz out, 1PPS out, and NTP out. Please don't think I'm
being
>> narqy, I'm really not going to pollute the list with off topic
chatter. I
>> am more than happy to discuss off list, as and when.
>>
>> David,
>>
>> I was planning to use RaspberryPis in some part of the network, and of
>> course, I must be silly, they have ethernet, and can run Real Time
Linux
>> (the LinuxCNC distros that have been made for control of CNC
machines).
> By
>> the way, the whole network uses heterogeneous CPU types, I'm pretty
>> agnostic to CPU type, as long as it does the job I need it to. The
actual
>> ethernet interface won't be as deterministic as we'd like, being
chained
> to
>> the USB bus, but if one was not to put any other USB devices on, nor
> attach
>> anything that draws power, the USB performance would be good enough for
>> second accuracy NTP frames. This is without any real analysis of any
spec
>> sheets, although I have this link:
>>
>> http://www.synclab.org/?tag=raspberry%20pi
>>
>> Thats an interesting read in and of itself. An additional link is:
>>
>> http://www.geekroo.com/products/795
>>
>> Which is a Mini ITX motherboard for RaspberryPi, which can then go
nicely
>> into a 1RU case. Add LCDs and other bits and bobs as needed (I saw a
nice
>> little LCD with an ATMega driver taking TTY strings in the ODROID
> Magazine
>> earlier today - it was meant for an ODROID, but it will work with
> anything
>> that'll output VT100 codes). Once in an 1RU case, it looks neat, and
> would
>> work just as well as a $500 NTP ethernet time source second hand off
> eBay,
>> if not much more configurable and hackable.
>>
>> Many thanks for the thoughts!
>>
>> Shane.
>>
>>
>> On Sat, Jul 12, 2014 at 5:50 PM, Hal Murray <hmurray at megapathdsl.net>
>> wrote:
>>
>>>
>> > edgecomberts at gmail.com said:
>>>> I am needing a GPS source of precise time, in three flavours - 10MHz
>> (or
>>>> so), 1PPS, and ethernet NTP. In the beginning, the NTP will be most
>>> > important, and as time goes on, I'll need the 1PPS signal.
>>> ...
>>>> If a static CW12-TIM ethernet clock could be made, I would be willing
>> to
>>> try
>>>> my hand at mounting them to mobile robots, again, for synchronised
>>> timing of
>>>> events.
>>>
>>> I'm missing the big picture. Are the robots the end target? What
are
>> you
>>> going to do before that?
>>>
>>> Do the robots have a network connection? (maybe only WiFi to a local
> PC
>> > controlling them)
>>>
>>> How accurately do the robots have to be synchronized?
>>>
>>>
>>> --
>> > These are my opinions. I hate spam.
>>>
>> >
>>>
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