Honeywell Minitrend QX, Руководство пользователя

Страница: 238 / 324

232 43-TV-25-30 Iss.6 GLO Aug 07 UK
OPC Interface - Open Process Control
OPC Server connection must be enabled in the recorder by selecting the OPC option in
“Credits”
on page 102. Many types of OPC Server software packages are available and are com-
patible with the recorders. OPC server supports OPC DA version 3 and OPC AE (Alarm and
Events). Use the name of the OPC server as it appears in the client software.
OPC limitations
Technically speaking there are no restrictions on the number of clients that can connect to
OPC DA or OPC A&E servers. Some software limits are in place:
OPC DA Server
Maximum number of groups that can be added per client is 3.
Maximum number of unique items that a OPC DA server supports is 100. I.e.(Number of
pens + Number of tota Number of communication variable) spread across 3 groups
per client. Recommended number of clients that can connect a OPC DA server is 3.
OPC A&E Server
Number of active alarm that is maintained at a given time is 576. Includes pens having active
alarms and pens which have normal but unacknowledged alarms if latch enabled.
Recommended maximum number of event subscriptions is 3
Not only can pen and alarm values be imported from the recorder but CV values can be sent
to the recorder from the OPC software.
How OPC works
When data acquisition devices conform to the OPC standard, you can use them with any
OPC-enabled software application, and vice versa. You can therefore easily combine differ-
ent devices from different manufacturers in one system. OPC gives you the freedom to add
new hardware from third-party vendors to existing set-ups, or to replace a device, without
worrying about compatibility with your chosen software.
The measurement and control hardware, such as a recorder, provides front-line data acqui-
sition. As soon as the hardware device has collected the data it makes it available to soft-
ware applications running under Windows. It presents the data according to the OPC
standard, and is thus known as an OPC server. Each OPC server offers data in the same
way. If the software application can understand the OPC format it can therefore access data
from any OPC server device, making individual drivers for each piece of equipment obso-
lete.
OPC-enabled software include spread sheets, databases, virtual instruments and SCADA
(supervisory control and data acquisition) interfaces. These applications are known as OPC
client software.
Each OPC server can simultaneously provide data for any number of OPC clients. Likewise
multiple clients can at the same moment access any server: a robust method of communi-
cation. With OPC, measurement and control systems can share information and co-operate
with other installations across factories, offices, laboratories, etc. The same data is therefore
readily available to engineering, maintenance, management...in fact to anyone that requires
up-to-the-minute data on which to base their decisions.
OPC allows "plug-and-play". All OPC devices will connect together and immediately work
with the OPC client software. This has the potential to massively reduce installation and sys-
tem configuration time. It also means that you can add devices without shutting down exist-
ing systems.