[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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