[time-nuts] CW12-TIM

Sat Jul 12 22:00:23 UTC 2014

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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