Re: [foxboro] OPC and DDE
- From: "Johnson, Alex (Foxboro)" <ajohnson@xxxxxxxxxxx>
- To: foxboro@xxxxxxxxxxxxx
- Date: Wed, 2 Oct 2002 11:38:17 -0400
I meant to add that
* the AW70 was a 300 MHz machine
* the PCs were typically 500 MHz machines
* RAM was sufficient
Obviously, your mileage will vary with the type of machines you will use.
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: Johnson, Alex (Foxboro)
Sent: Wednesday, October 02, 2002 10:36 AM
To: 'foxboro@xxxxxxxxxxxxx'
Subject: RE: [foxboro] OPC and DDE
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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