opc

Hi, can anyone tell me what the difference is between an OPC-server and I/O server? I've seen those names somewhere but don't know what the difference is. I know OPC stands for Ole for Process Control but thats it.
Thanks

ungaro,

an OPC server is a program used to transmit data between dedicated hardware(PLC, controllers, etc) and general applications (such as Excel, SQL databases or visualisation packages).

As far as I know, an IO server is a computer in a network used to transmit data from and to the PLCs and controllers. In most SCADA systems you can use more than one computer in a project. Some of these computers are simple display clients, others are IO servers, alarm servers or combinations of the three. A stand alone computer running a SCADA system does perform the three functions: it's a display client, an IO server and, if the functionality is needed (which is mostly the case), an alarmserver as well.

Sometimes an IO server uses an OPC server to get the communication going between the SCADA system and the PLCs/controllers. That is the case if no native driver is included in the SCADA package.

Kind regards,

Two terms:

OLE stands for Object Linking and Embedding - its a function provided by your operating system that allows applications that are very different to share the same data - and if the data changes at the source, it will change also in the application in which it is embedded. Try this: Open excel, type a number in a cell, and save it, don't close Excel. Open a word document, select insert -> object - from file, browse to the excel file you just saved, and check the link box. YOu will see the spreadsheet in Word. Now change the number in Excel. Look at Word, notice that the number changed. You can do the same with Quatro-Pro and Word if you want to see that you can mix an MS app with a non-MS app. Try it with a few other applications, like ACAD and Word.

OPC stands for OLE for Process Control or
Object Linking and Embedding for Process Control.

Trivia: OPC was the worlds first Three Letter Acronym embedded in a TLA.
Regards Alan Case