[time-nuts] Industrial control systems and IEEE 1588v2 time sync

Azelio Boriani azelio.boriani at screen.it
Thu Aug 1 18:06:00 EDT 2013


Cesium-based grandmasters can cost a lot of money but I think that
GPSDO-based ones are a lot cheaper.

On Thu, Aug 1, 2013 at 11:48 PM, Daniel Mendes <dmendesf at gmail.com> wrote:
>
> This is true, but what´s needed to generate the sync packets? I think they
> call them "Grand Masters", and cost a lot of money... Is there any cheap
> approach for this end of the problem?
>
> Daniel
>
> Em 31/07/2013 08:03, Bob Camp escreveu:
>>
>> Hi
>>
>> A number of the chip guys will sell you micro's that have one or more 1588
>> ethernet ports on them. Some of them are in the sub $10 range. With a bit of
>> Time Nut attention, they seem to be capable of well under 1 us performance.
>> If you have a daisy chain network they will do what you need without any
>> switches.
>>
>> As mentioned above, if your network has modern (gigabit rather than 10
>> megabit) switches on it, you can likely get to 1 us without any fancy time
>> stamping switches. There are a few other minor details you would want to pay
>> attention to, but they are manageable for a shop floor network.
>>
>> Bob
>>
>> On Jul 31, 2013, at 12:19 AM, Bill Hawkins <bill at iaxs.net> wrote:
>>
>>> Group,
>>>
>>> Has anyone used IEEE 1588 to synchronize clocks on an Ethernet network?
>>>
>>> I was involved in the design of time sync for Foundation Fieldbus circa
>>> 2000.
>>> We needed one millisecond accuracy, so we went with SNTP on local
>>> networks.
>>> I've just seen an ad for a switch that can do 1588, and looked up what
>>> it does.
>>>
>>> Microsecond accuracy is impressive, but what does it cost?
>>>
>>> Industrial sensors are generally sampled at about 10 millisecond
>>> intervals out
>>> to several seconds. SNTP would appear to be very adequate for time
>>> stamps as
>>> there is uncertainty introduced by when the computer gets around to
>>> sampling
>>> the sensor in its sampling and control cycle.
>>>
>>> Any thoughts appreciated.
>>>
>>> Bill Hawkins
>>>
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>
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