Re: [foxboro] OPC again...

Re: Doing control with anything that requires Windows and DCOM makes me
nervous, but if it's supervisory (like APC), you can at least implement
a secondary mechanism.

Don't use DCOM.

Use AIM*OPC DA Server and load it in the PC where the APC software is
running. This will allow you to use COM and avoid the issues with DCOM.


Regards,

Alex Johnson
Invensys Systems, Inc.
10900 Equity Drive
Houston, TX 77041
713.329.8472 (voice)
713.329.1700 (fax)
713.329.1600 (switchboard)
alex.johnson@xxxxxxxxxxxxxxxx


-----Original Message-----
From: foxboro-bounce@xxxxxxxxxxxxx [mailto:foxboro-bounce@xxxxxxxxxxxxx]
On Behalf Of Corey R Clingo
Sent: Monday, April 30, 2007 1:58 PM
To: foxboro@xxxxxxxxxxxxx
Subject: Re: [foxboro] OPC again...

Personally, I would only use it in the manner Alex described: using a =

watchdog in the CP with fallback logic and control.  Doing control with =

anything that requires Windows and DCOM makes me nervous, but if it's =

supervisory (like APC), you can at least implement a secondary
mechanism. =


Most of the installation guides I've seen recommend opening things up
wide =

to ease getting DCOM working properly, which of course is derimental to =

security.  I have always taken that advice to heart, or avoided DCOM =

entirely by putting client and server on the same box.


And I've always heard a persistent rumor that writing to the I/A via OPC

(not sure of the mechanism, maybe AIM*OPC?) was not a very high
bandwidth =

proposition, but again, this may either not be true, or not an issue =

depending on the size of the APC.


Corey Clingo
BASF Corporation






"Joseph M. Riccardi" <Joe@xxxxxxxxxxxxx> =

Sent by: foxboro-bounce@xxxxxxxxxxxxx
04/30/2007 09:43 AM
Please respond to
foxboro@xxxxxxxxxxxxx


To
<foxboro@xxxxxxxxxxxxx>
cc

Subject
[foxboro] OPC again...






Folks,
I have always wondered if OPC was not just intended to collect data, or
is
it also considered a viable communication link for control?  I now have
a
vendor that wants to perform advanced process control from their
PC-based
software to specific control loops on the Foxboro System via OPC?  Read
measurement values, execute advanced control algorithms, write control
outputs, etc.
Is OPC considered secure, reliable, repeatable, etc. enough for control?

Your thoughts/recommendations?


Joseph M. Riccardi, Inc.
DCS Services - Industrial Process Control

North-Central Office (OH, PA, MI, IN, WV Area)
South-East Office (FL, GA, AL, SC, NC Area)

Joe@xxxxxxxxxxxxx

"To give real service you must add something that cannot be bought or
measured with money; and that is sincerity and integrity." - Donald A. =

Adams




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