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 <b...@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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