[time-nuts] CW12-TIM

Sat Jul 12 16:44:13 EDT 2014

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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