FAQ - OPC Server
The update time is not very fast. Do I have a
problem?
I lowered the polling cycle and the Tag updates
became faster.
I lowered it again but found no difference in
the update time. What is wrong?
Can I use serial port expansions (Digiboard,
etc.) to communicate with a device?
Is there a way of increasing productivity when I
am entering a large number of Tags?
Why does the server start automatically
sometimes, even when I am not using any client on my computer?
I started the server but I cannot see any Tags
when I am browsing with my OPC client. Why?
I cannot have access to the OPC server from a
remote computer. Why?
Is OPC an extension of OLE? If so, what are the functions specific to OPC?
The update time is not very fast. Do I have a problem?
The polling cycle may be set to a large time interval. Try to lower the
polling cycle to get the desired response time.
I lowered the polling cycle and the Tag
updates became faster.
I lowered it again but found no difference in the update time. What is
wrong?
There is nothing wrong: the device with which the server is communicating
has its own response cycle. If you go beyond the answering capability of the
device, there is no improvement of the refresh time.
Can I use serial port expansions (Digiboard, etc.) to communicate with
a device?
Yes, as long as Windows® sees the ports as COM devices.
Is there a way of increasing productivity when I am entering a large
number of Tags?
Yes, you can use cut, copy and paste for Devices and Tags to speed up the
configuration job, and then you change the required parameters.
Why does the server start automatically sometimes, even when I am not
using any client on my computer?
The OPC server is based on DCOM object standards. A client is requesting
the connection to the server from a remote computer on the LAN.
I started the server but I cannot see any Tags when I am browsing with
my OPC client. Why?
The server has to be put in Online mode in order to an OPC client to
browse its Tags.
I cannot have access to the OPC server from a remote computer. Why?
To have access to the remote server you have to adjust the security. Run
“dcomcnfg.exe" and choose the appropriate Cybectec OPC server. Click on
Properties. Select “Interactive User” on the Identity Tab.
Is OPC an extension of OLE? If so, what are the functions specific to
OPC?
OPC initially meant “OLE for Process Control”, where OLE stands for
“Object Linking and Embedding”. OLE has since been restructured from
object-oriented to object-based, and renamed Active X. We can consider OLE
(now ActiveX) as a set of DCOM interfaces that are useful for many
applications in general. These interfaces support functions such as compound
documents, data transfer, persistent storage, etc. OPC defines an additional
set of DCOM interfaces to support process control applications. The OPC
interface supports functions such as process data access, alarms and events,
and process history data access. |
