# How accurate will Sun clock be over 4 hours? - SUN

This is a discussion on How accurate will Sun clock be over 4 hours? - SUN ; On 2008-03-20, Dave wrote: > Huge wrote: >> On 2008-03-20, Dave wrote: >>> Rex Mottram wrote: >>> >>>> Put the indoor machine in the refrigerator. >>>> >>>> RM >>> Unfortunately, that is not practical given the particular constraints I have ...

# Thread: How accurate will Sun clock be over 4 hours?

1. ## Re: How accurate will Sun clock be over 4 hours?

On 2008-03-20, Dave wrote:
> Huge wrote:
>> On 2008-03-20, Dave wrote:
>>> Rex Mottram wrote:
>>>
>>>> Put the indoor machine in the refrigerator.
>>>>
>>>> RM
>>> Unfortunately, that is not practical given the particular constraints I have

>>
>> Are the machines close enough together to connect a cable between them?
>>
>>

>
> No - otherwise it would be easy with NTP over ethernet.

Quite.

So, how far apart are they?

--
"Be thankful that you have a life, and forsake your vain
and presumptuous desire for a second one."
[email me at huge {at} huge (dot) org uk]

2. ## Re: How accurate will Sun clock be over 4 hours?

Huge wrote:
> On 2008-03-20, Dave wrote:
>> Huge wrote:
>>> On 2008-03-20, Dave wrote:
>>>> Rex Mottram wrote:
>>>>
>>>>> Put the indoor machine in the refrigerator.
>>>>>
>>>>> RM
>>>> Unfortunately, that is not practical given the particular constraints I have
>>> Are the machines close enough together to connect a cable between them?
>>>
>>>

>> No - otherwise it would be easy with NTP over ethernet.

>
> Quite.
>
> So, how far apart are they?
>

The distance is not great - perhaps a few tens of metres, but it is
totally impossible to have any cables between the two locations.

3. ## Re: How accurate will Sun clock be over 4 hours?

In comp.unix.solaris Dave wrote:
> The distance is not great - perhaps a few tens of metres, but it is
> totally impossible to have any cables between the two locations.

Is that limitation a physical one, or one dictated by EMI (?)
concerns? If the latter, are there any empty slots in the systems
into which you can put a gigabit (or 100BT) fibre card?

rick jones
--
web2.0 n, the dot.com reunion tour...
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

4. ## Re: How accurate will Sun clock be over 4 hours?

Rick Jones wrote:
> In comp.unix.solaris Dave wrote:
>> The distance is not great - perhaps a few tens of metres, but it is
>> totally impossible to have any cables between the two locations.

>
> Is that limitation a physical one, or one dictated by EMI (?)

Both. Physically impossible, and even if it was, EMI would stop me doing
it.

5. ## Re: How accurate will Sun clock be over 4 hours?

On 2008-03-20 20:08:12 +0000, Dave said:

> Rick Jones wrote:
>> In comp.unix.solaris Dave wrote:
>>> The distance is not great - perhaps a few tens of metres, but it is
>>> totally impossible to have any cables between the two locations.

>>
>> Is that limitation a physical one, or one dictated by EMI (?)

>
> Both. Physically impossible, and even if it was, EMI would stop me doing it.

Would one of those Ethernet-over-power kits (eg Devolo) be any use? I
think both machines might have to be on the same circuit, but I'm not

Cheers,

Chris

6. ## Re: How accurate will Sun clock be over 4 hours?

Dave wrote:
> Huge wrote:
>> On 2008-03-20, Dave wrote:
>>> Huge wrote:
>>>> On 2008-03-20, Dave wrote:
>>>>> Rex Mottram wrote:
>>>>>
>>>>>> Put the indoor machine in the refrigerator.
>>>>>>
>>>>>> RM
>>>>> Unfortunately, that is not practical given the particular
>>>>> constraints I have
>>>> Are the machines close enough together to connect a cable between them?
>>>>
>>>>
>>> No - otherwise it would be easy with NTP over ethernet.

>>
>> Quite.
>>
>> So, how far apart are they?
>>

> The distance is not great - perhaps a few tens of metres, but it is
> totally impossible to have any cables between the two locations.

Wireless?

Or have I missed an earlier mention of it?

Cheers,
Gary B-)

--
__________________________________________________ ____________________________
Armful of chairs: Something some people would not know
whether you were up them with or not
- Barry Humphries

7. ## Re: How accurate will Sun clock be over 4 hours?

Chris Ridd wrote:

>> Both. Physically impossible, and even if it was, EMI would stop me
>> doing it.

>
> Would one of those Ethernet-over-power kits (eg Devolo) be any use? I
> think both machines might have to be on the same circuit, but I'm not
>
> Cheers,
>
> Chris
>

No, not possible. The two systems, will each be on separate petrol or
diesel generators.

I think the most relieable way is for me to generate my own 1 pulse per
second from a rubidium oscillator. That can first be synced to GPS, then
once the pulses are appearing at the right time, the GPS will no longer
be needed. The oscillator I have is said to be ok as a stratum one unit
for 72 hours.

8. ## Re: How accurate will Sun clock be over 4 hours?

Gary R. Schmidt wrote:

>>> So, how far apart are they?
>>>

>> The distance is not great - perhaps a few tens of metres, but it is
>> totally impossible to have any cables between the two locations.

> Wireless?
>
> Or have I missed an earlier mention of it?
>
> Cheers,
> Gary B-)
>

No, you did not miss an earlier mention, but it is by no means certain
they will be in radio range, given one is in a pretty well RF shielded
enclosure. Exactly how well shielded is the whole point of the
experiment, but it might be too well shielded for a WiFi connection.

9. ## Re: How accurate will Sun clock be over 4 hours?

Dave wrote:
[SNIP]
>
> No, you did not miss an earlier mention, but it is by no means certain
> they will be in radio range, given one is in a pretty well RF shielded
> enclosure. Exactly how well shielded is the whole point of the
> experiment, but it might be too well shielded for a WiFi connection.

And, of course, running an Ethernet cable *through* the RFI shielding
will no doubt bugger it all up...

What about a LASER or LED modem-thingie? They used to exist, I can
recall reading up on them back in the 1980's, but I can't recall a
recent mention of them (but then, I haven't read a BlackBox catalogue
for yonks!).

Or simple optical fibre through the shielding to a router or summat.
(Okay, there goes 90% of teh budget... :-))

Cheers,
Gary B-)

--
__________________________________________________ ____________________________
Armful of chairs: Something some people would not know
whether you were up them with or not
- Barry Humphries

10. ## Re: How accurate will Sun clock be over 4 hours?

On 2008-03-20, Dave wrote:
> Huge wrote:
>> On 2008-03-20, Dave wrote:
>>> Huge wrote:
>>>> On 2008-03-20, Dave wrote:
>>>>> Rex Mottram wrote:
>>>>>
>>>>>> Put the indoor machine in the refrigerator.
>>>>>>
>>>>>> RM
>>>>> Unfortunately, that is not practical given the particular constraints I have
>>>> Are the machines close enough together to connect a cable between them?
>>>>
>>>>
>>> No - otherwise it would be easy with NTP over ethernet.

>>
>> Quite.
>>
>> So, how far apart are they?
>>

> The distance is not great - perhaps a few tens of metres, but it is
> totally impossible to have any cables between the two locations.

Is this one of those interview questions which has no answer?

)

--
"Be thankful that you have a life, and forsake your vain
and presumptuous desire for a second one."
[email me at huge {at} huge (dot) org uk]

11. ## Re: How accurate will Sun clock be over 4 hours?

On 22 Mar 2008 12:46:21 GMT
Huge wrote:

> On 2008-03-20, Dave wrote:
> > Huge wrote:
> >> On 2008-03-20, Dave wrote:
> >>> Huge wrote:
> >>>> On 2008-03-20, Dave wrote:
> >>>>> Rex Mottram wrote:
> >>>>>
> >>>>>> Put the indoor machine in the refrigerator.
> >>>>>>
> >>>>>> RM
> >>>>> Unfortunately, that is not practical given the particular
> >>>>> constraints I have
> >>>> Are the machines close enough together to connect a cable
> >>>> between them?
> >>>>
> >>>>
> >>> No - otherwise it would be easy with NTP over ethernet.
> >>
> >> Quite.
> >>
> >> So, how far apart are they?
> >>

> > The distance is not great - perhaps a few tens of metres, but it is
> > totally impossible to have any cables between the two locations.

>
> Is this one of those interview questions which has no answer?
>
> )
>

Hi
What about a couple of linksys WET54G wireless bridges to connect them?

--
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SLED 10.0 SP1 x86_64 Kernel 2.6.16.54-0.2.5-smp
up 10 days 0:54, 1 user, load average: 0.24, 0.32, 0.35

12. ## Re: How accurate will Sun clock be over 4 hours?

Malcolm wrote:

>> Is this one of those interview questions which has no answer?
>>
>> )
>>

I think local generation of 1 pulse per second will be practical

> Hi
> What about a couple of linksys WET54G wireless bridges to connect them?

I dont know if there will be sufficient signal received. There might be,
but it depends on the RF screening, which I expect to be quite significant.

13. ## Re: How accurate will Sun clock be over 4 hours?

In comp.sys.sun.hardware Dave wrote:
> I think local generation of 1 pulse per second will be practical

Just a paranoid question - you will be able to make sure the two PPS
sources are in phase at the start right?

rick jones
--
portable adj, code that compiles under more than one compiler
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

14. ## Re: How accurate will Sun clock be over 4 hours?

[A complimentary Cc of this posting was sent to
Dave
], who wrote in article <47e06510@212.67.96.135>:
> I suspect if I sync them by NTP before the experiment starts, then they
> will not drift by more than 500 ms over a 4 hour period. Does that seem
> reasonable? Has anyone actually ever made medium term (few hours)
> stability measurements of the clocks in Suns?

Another (crazy?) idea: buy a digital clock which can beep every
minute, and syncronize via a mic.

Yours,
Ilya

15. ## Re: How accurate will Sun clock be over 4 hours?

Rick Jones wrote:
> In comp.sys.sun.hardware Dave wrote:
>> I think local generation of 1 pulse per second will be practical

>
> Just a paranoid question - you will be able to make sure the two PPS
> sources are in phase at the start right?
>
> rick jones

The unit I have

http://www.thinksrs.com/products/PRS10.htm

will sync its 1 pps output to a 1 pps input. Hence use GPS to generate 1
pps, then the rubidium generates 1pps in phase with that. Then, when the
GPS signal is lost, the rubidium will keep pretty accurate.

"When an external 1 pps signal is applied the PRS10 will verify the
integrity of that input and will then align its 1 pps output with the
external input. The processor will continue to track the 1 pps output to
the 1 pps input by controlling the frequency of the rubidium transition
with a small magnetic field adjustment inside the resonance cell."

I just need to get another of these.

16. ## Re: How accurate will Sun clock be over 4 hours?

In comp.sys.sun.hardware Dave wrote:
> That is a possibility. I have one of these

> http://www.thinksrs.com/products/PRS10.htm

> which is a rubidium oscillator. I could get another and sync them
> both to GPS. A bit more complexity than I wanted, but it might be
> necessary.

Nah, just get yourself one of these watches

http://www.leapsecond.com/pages/atomic-bill/

Then you can simply walk the time from one setup to the other.

rick jones
--
Process shall set you free from the need for rational thought.
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...

17. ## Re: How accurate will Sun clock be over 4 hours?

Rick Jones wrote:
> In comp.sys.sun.hardware Dave wrote:
>> That is a possibility. I have one of these

>
>
>> http://www.thinksrs.com/products/PRS10.htm

>
>> which is a rubidium oscillator. I could get another and sync them
>> both to GPS. A bit more complexity than I wanted, but it might be
>> necessary.

>
> Nah, just get yourself one of these watches
>
> http://www.leapsecond.com/pages/atomic-bill/

Yes, I was aware of that one. Tom has some other funny things on his web
site. Totally devoted to accurate time keeping. For anyone that has
never looked at Tom's site, especially if you have an engineering mind,
I suggest you do.

Another site I very much admire is this one. You only have to be male to
appreciate 50% of the site, and know about semiconductor physics to
appreciate the other 50%.

http://britneyspears.ac/lasers.htm

18. ## Re: How accurate will Sun clock be over 4 hours?

On Tue, 01 Apr 2008 22:40:58 +0100, Dave wrote:

> http://britneyspears.ac/lasers.htm

Ah, yes! It has been decades since I looked at Schroedinger's equation.

19. ## Re: How accurate will Sun clock be over 4 hours?

Dave Uhring wrote:
> On Tue, 01 Apr 2008 22:40:58 +0100, Dave wrote:
>
>> http://britneyspears.ac/lasers.htm

>
> Ah, yes! It has been decades since I looked at Schroedinger's equation.
>

I used to work for the now defunt Marconi Optical Components. Marconi
had some really strict rules about what web sites one could and could
not visit, but we never felt too bad about going to the Britney Spears
web site.