وهذه التعريفات منقوله من موقع wikipedia
“OPC”
is not really a protocol, in the sense that you think of the word protocol.
It means “OLE for Process Control”.
The term OLE means “****** Linking and Embedding”.
OLE is a set of rules for programs that run on Windows PCs to allow them to communicate with each other, on the same PC.
The idea is that you can design a program that does some general purpose function, like fancy printing, graphing, calculating, special communication etc. and then allow other programs to use your functions easily. This is part of the ****** mechanism in Windows now.
Some years ago, a number of manufacturers in the Process Control industry were having problems with integration because they all used different proprietary kinds of programs.
والمقصود بكلمة proprietary إمتلاكي
They got together and developed this concept called OLE for Process Control (OPC).
OPC is a set of rules for programs to talk to each other to do common kinds of functions that are needed in process control. Mostly what we would call reading and writing of points. So if I design a graphic display program that can be an OPC “Client” that asks questions (like read a point), and you design a communication program that knows your proprietary communication protocol and acts as an OPC “Server” then those two programs can interact with each other on the same Windows PC.
This is great for process control where it is common to have small point count and centralized operation of everything.
That’s not usually a good strategy for BMS interoperability because every translation is limited to the central PC. Also, because it is very general purpose, OPC is limited in the functions that it provides access to. For example, in OPC the concept of alarming is based on having an OPC client that periodically reads a point and makes a logic decision about whether the value is an “alarm.” There is no distributed alarm notification concept as in BACnet.
So, you can use OPC as a way to integrate various kinds of BMS together with some industrial types of equipment, if you can accept the following:
1. the centralization
2. single point of failure
3. slower operation of that kind of system.
With BACnet , the interoperability takes place into the controllers themselves. From a modern BMS perspective those are required features and flexibility that protect the owner’s investment and provide more flexible bidding for future expansion etc.
_________________
I am so far behind, I think i am first
موضوع: Communication via OPC 
الإثنين 14 مارس 2011 - 12:31
