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From Cesar Garcia <cesar.gar...@ceos.com.ve>
Subject Re: Best Practices / Experiences from the field (Subscription/Polling for Data)
Date Thu, 14 May 2020 19:17:30 GMT
Hello Wolfgang,

The answer will depend on the hardware you use for your machine, I can tell
you based on my experience with Siemens equipment.

*> If I am looking for gathering as detailed as possible Data from
Machines… what would be first choice ? Subcription for ChangedValues ?
Active Polling ? *

Do you want a (1) record historical data with that resolution in the time
signature or do you really want to (2) capture an event with that time
precision?

For the first case you can sample times by polling between 50 to 80 msec,
this for an S7-300 and between 17 to 20 msec for an S7-400. I do not have
an S7-1500 physically, but the performance should be close to that of an
S7-400, the same should happen with VIPA CPUs.

There are other sampling techniques for the S7-300 / 400 that guarantee a
stable subscription with multiples of 100 msec.

For the second case (events), you can use the data capture with the CPU
warning system with the SFC ALARM, NOTIFY, etc. which guarantee the capture
of data at ms, this is very well documented by Siemens. The important thing
is that the timestamp comes from the PLC not from the computer where you
are running PLC4X.

*> I know that these are also quite machine/protocol specific questions but
it would be interesting to learn what numbers could be achieved by using
PLC4x ? *

You are correct, the Modbus driver of PLC4X, I have captures of 10 msec,
but we are talking about Pears and Apples.

My grain of sand,
Best regards,









El jue., 14 may. 2020 a las 13:00, Wolfgang Huse (<wolfgang.huse@nutanix.com>)
escribió:

> Hi,
> maybe you could share some experiences from realworld-use-cases how to
> work with PLC4x ?
> If I am looking for gathering as detailed as possible Data from Machines…
> what would be first choice ? Subcription for ChangedValues ? Active Polling
> ?
>
> What is an interval which is usable in real world for polling ? 100ms,
> 10ms ?
>
> I know that these are also quite machine/protocol specific questions but
> it would be interesting to learn what numbers could be achieved by using
> PLC4x ?
>
> Mit freundlichen Grüßen – With kind regards
>
> Wolfgang Huse
>
>

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