Campbell Scientific CSIOPC Software - Manual (Page 11)

CSIOPCServer
The format may vary somewhat from the examples given above,
depending upon the client. NOTE
4.2 CSIOPCServer Browser
The CSIOPCServer allows OPC Universal Tag compliant browsing so that
data tag names can be searched for from within an OPC application. The
browser provides a list of all dataloggers in the network map and their
associated data tables. The datalogger devices and their tables are presented in
a directory-tree type structure, with variable names displayed under their
respective tables. Multi-dimensional variables are presented with the name of
the dimensioned variable as part of the directory-tree structure, with each
variable in the array listed as a separate element.
The browser is a tool of convenience—it is not necessary to
assign data tags using the browser. Data tag names can be typed
in directly, in the format described above. NOTE
5. Data Reliability
5.1 OPC Technology and Campbell Scientific Dataloggers
OPC technology relies on consistent data from the OPC server. It expects that
the structure of the data being passed from the server will not change.
Therefore, it does not readily accommodate changes that occur if a new
program is downloaded to a datalogger.
If changes are made to the datalogger program or the LoggerNet device map, it
may be necessary to shut down and restart the OPC client before the client will
recognize the data from the new device. Whether or not this is necessary will
depend upon whether the OPC client stores device and table information or
queries the server for the information at regular intervals.
The OPC Data Access Specification 2.05a supported by the CSIOPCServer is
designed for real-time monitoring and control. It does not lend itself very well
to historical trending. The data value passed to the OPC client is always the
most recent value stored in the data cache. Because of this, if data is stored in a
datalogger on a one-second interval, and that data is being collected using
LoggerNet on a five-second interval, then the information passed to the OPC
client will be missing some data points. If viewing historical trends is
important, then the data should be exported to a file or one of the other
LoggerNet clients should be used instead of CSIOPCServer.
5.2 Data Quality
CSIOPCServer will assign the data quality of "Bad" to any value that it
determines is missing or stale. Situations that may return a "Bad" data quality
include:
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