Re: [foxboro] OPC again...
- From: <tom.vandewater@xxxxxxxxxxxxxx>
- To: <foxboro@xxxxxxxxxxxxx>
- Date: Fri, 4 May 2007 08:34:22 -0400
Corey Clingo said:
"My gut tells me that something like Modbus/TCP or Ethernet/IP would
probably do the job in 99% of cases."
"I would think simple, open protocols (like Modbus/TCP and Ethernet/IP)
would eventually help lead to better security."
We agree on your points Corey. Modbus TCP or Ethernet IP are
good "single port" transport mechanisms to get/send most of the data
needed by the DCS control applications with minimal overhead. OPC, (OLE
for Process Control), seemed to be a solution for people running small
PC based SCADA applications that needed a way to pull data from, and
serve data to, other applications, all running in an MS environment.
Full blown DCS systems already had ways, (such as Foxboro's Object
Manager), to pass alarm and process data to their own proprietary
applications and most already had a way to import external data, (often
using Modbus), so OPC was no big deal for them.
We looked at and avoided getting sucked into the OPC vacuum
after seeing how temperamental it was even as the SCADA folks mentioned
above continued to sing its praises, but I do think with so many people
focusing on making it a useful cross platform tool, that it has a chance
of being a good data acquisition tool, even for DCS systems, someday.
That day is not today, but I'll keep watching with interest.
Cheers,
Tom VandeWater
Control Systems Developer/Analyst
Dow Corning Corporation
Carrollton, KY USA
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