Re: [ARMini-support] Is it possible to get the correct time
- From: Andrew Pinder <Andrew.Pinder@xxxxxxxxxxxxx>
- To: armini-support@xxxxxxxxxxxxx
- Date: Sun, 29 Mar 2015 13:24:01 +0100
In message <54abe00083jcgl@xxxxxxxxxxxxxxx>
on 29 Mar 2015 Jim Lesurf <jcgl@xxxxxxxxxxxxxxx> wrote:
> In article <57d8d8ab54.Andrew-Pin@xxxxxxxxxxxx>, Andrew Pinder
> <Andrew.Pinder@xxxxxxxxxxxxx> wrote:
>>
>> Give the reported problems about smaller errors not being corrected,
>> I'm wondering what people have experienced with the switch to BST.
> FWIW the clock on my ARMiniX had drifted about 10 sec since I set it a few
> days ago. I set it OK with the program I wrote and it wasn't concerned
> about BST. (It deals with the underlaying UTC and the RO setup applies the
> zone correction.) Seemed consistent with my machine's clock being off
> by one or two seconds a day. (i.e. 10 - 20 ppm.)
>> After syncing at boot, my clock is currently 0.616643 seconds slow,
>> timer latch 129911 (+684ppm).
> Erm, I doubt people will be getting results via net adjustments of the type
> the OS does where you can state 'accuracy' to the nearest microsecond! To
> do that you'd probably have to put in some work calibrating the time delays
> in sending and getting times over the net. I suspect people would be better
> keeping values to about a centisecond. That's if you have reasons to be
> concerned at that level.
> And as I've suggested before, if people want to do this they'd also need to
> give detailed histories of when the machine was on/off, when any time
> nudges were made, etc. Otherwise it will be almost impossible to compare
> results and make any sense of how they may vary.
> If you want serious accuracy you'd be better looking for a radio time
> standard I suspect.
> Also...
> If my quick calculation is correct the rate offset you quote would
> nominally remove the error in about 15 mins. If you have the OS time
> system set to re-correct at a set interval, note that if that time is
> too long the error will 'saw' back and forth between fast and slow.
> Again, to know more you'd need to measure again just before you shut
> down the machine (having noted how long it was on and when any auto
> corrections were done). Then note how long it was off when repeating the
> process when you start it up again. If you don't do this the values
> you get may just seem random.
*nettime_status
Current time: Sunday, 29 March 2015 08:38:15.14
Status: Sleeping
Last adjustment: 5 minutes 23 seconds ago
Last delta: 0.616643 seconds slow
Last server: ntppub.le.ac.uk
Last protocol: SNTP
Poll interval: 15 minutes
Timer latch: 129911 (+684ppm)
*nettime_status
Current time: Sunday, 29 March 2015 08:41:41.80
Status: Sleeping
Last adjustment: 8 minutes 49 seconds ago
Last delta: 0.616643 seconds slow
Last server: ntppub.le.ac.uk
Last protocol: SNTP
Poll interval: 15 minutes
Timer latch: 129911 (+684ppm)
*nettime_status
Current time: Sunday, 29 March 2015 08:51:29.16
Status: Sleeping
Last adjustment: 3 minutes 36 seconds ago
Last delta: 0.099646 seconds slow
Last server: electra.pinklemon.net
Last protocol: SNTP
Poll interval: 15 minutes
Timer latch: 129971 (+223ppm)
*nettime_status
Current time: Sunday, 29 March 2015 09:30:44.62
Status: Sleeping
Last adjustment: 12 minutes 49 seconds ago
Last delta: 0.001416 seconds slow
Last server: time.videxio.net
Last protocol: SNTP
Poll interval: 15 minutes
Timer latch: 130000
*nettime_status
So within 45 minutes it was close enough to stop adjusting the clock.
This was just before I shut down. I restarted just after 1 PM ago and
got:
*nettime_status
Current time: Sunday, 29 March 2015 13:16:42.38
Status: Sleeping
Last adjustment: 13 minutes 14 seconds ago
Last delta: 0.379843 seconds slow
Last server: time.rdg.uk.as44574.net
Last protocol: SNTP
Poll interval: 15 minutes
Timer latch: 129945 (+423ppm)
Current time: Sunday, 29 March 2015 13:22:36.19
Status: Sleeping
Last adjustment: 4 minutes 7 seconds ago
Last delta: 0.104400 seconds slow
Last server: resntp-a-vip.lon.bitfolk.com
Last protocol: SNTP
Poll interval: 15 minutes
Timer latch: 129970 (+230ppm)
It looks like it can correct time pretty quickly on a poll interval of
15 minutes.
Regards
Andrew
--
Andrew Pinder
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