Re: [foxboro] OPC and DDE
- From: "Johnson, Alex (Foxboro)" <ajohnson@xxxxxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Wed, 2 Oct 2002 11:36:44 -0400
There are all kinds of ramifications to this question. I'll try a few.
If you are interested in how long it takes to get a value from the field to
an OPC Client, you have to consider:
FBM conversion time (10s of ms)
FBM scan time (ECB period and phase)
Block scan time (AIN period and phase)
Time in OM Scanner (ms)
OM scan time (0.5s)
Value transfer delay across the network
Time in OM Client (ms)
AIS scan time (rsr usually 0.5s)
Time in OPC Server (unknown to me)
Transit to the OPC Client (unknown to me)
Time in OPC Client (unknown to me)
With regard to how many points per second the OPC Server can supply, tests
have been run in a variety of configurations, e.g., OPC Server and Client in
same machine, OPC Server and Client in different machines, OPC Server, OPC
Client, and AIM*API server in the same AW-70.
At 5000 points per second transferred, but the CPU time has been as high as
55% (everything in the AW70) in support of that rate and as low as 10%
(different boxes for AIM*API, OPC Server, and OPC Client).
At 500 points per second transferred, the load was about 3% in each box
involved in the process.
Hope this gives you some of the information that you need.
Regards,
Alex Johnson
Invensys
10707 Haddington
Houston, TX 77063
713.722.2859 (office)
713.722.2700 (switchboard)
713.932.0222 (fax)
ajohnson@xxxxxxxxxxx <mailto:ajohnson@xxxxxxxxxxx>
For the latest information on ArchestrA, go to
www.invensys.com/divisions/Archestra.html
<http://www.invensys.com/divisions/Archestra.html>
-----Original Message-----
From: Murphy, Daniel J (COR) [SMTP:murphydj@xxxxxx]
Sent: Wednesday, October 02, 2002 9:41 AM
To: 'foxboro@xxxxxxxxxxxxx'
Subject: [foxboro] OPC and DDE
Does anyone have experience using OPC or DDE communications protocol
with
AIM*AT? What is the speed of data transfer for about 400 signals
(less than
a second, more than a few seconds) ?
Specifically, I wish to pass about 400 digital signals from the
Foxboro DCS
to a PC-based Rochester alarm system. One way of doing this is via
FBM
outputs wired directly up to Rochester terminal racks. Another way
is to use
a modbus gateway link. I am looking for a cheaper option and am
investigating the possibility of using OPC or DDE.
Regards,
Dan
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