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

[Bob Camp]

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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