National Instruments BridgeVIEW 用户手册
Chapter 3
Tag Configuration
© National Instruments Corporation
3-23
Table 3-4. Operations Configuration Attributes
Attribute
Applies to
Data Types
Description
Update
Deadband
Deadband
all
Determines when the Real-Time Database (RTDB) updates the
value for this tag. It is used to improve system performance and
prevent unnecessary processing of tag values in the RTDB. The
field is expressed differently for analog, discrete, string, and bit
array tags. For analog tags, Update Deadband is a percent of full
scale. The database updates analog tags only when a new tag
value is different than the currently stored value by at least the
Update Deadband. Use 0% if you want each new value for the tag
to be saved in the RTDB. For discrete, string, and bit array tags,
Update Deadband is expressed as either Always or On Change.
value for this tag. It is used to improve system performance and
prevent unnecessary processing of tag values in the RTDB. The
field is expressed differently for analog, discrete, string, and bit
array tags. For analog tags, Update Deadband is a percent of full
scale. The database updates analog tags only when a new tag
value is different than the currently stored value by at least the
Update Deadband. Use 0% if you want each new value for the tag
to be saved in the RTDB. For discrete, string, and bit array tags,
Update Deadband is expressed as either Always or On Change.
Log Data
analog,
discrete,
bit array
discrete,
bit array
Determines whether a tag value is logged to historical files.
Log Data
Deadband
Deadband
analog,
discrete,
bit array
discrete,
bit array
Determines when tag values are logged to disk. It is used to
improve system performance and prevent unnecessary logging
of data to disk. Like Update Deadband, the field is expressed
differently for analog, discrete, and bit array tags. For analog
tags, Update Deadband is a percent of full scale. The
BridgeVIEW Engine writes new analog tag values to historical
files only when a new tag value is different than the last logged
value by at least the Log Data Deadband. Use 0% if you want
each new value for the tag to be logged. For discrete and bit
array tags, Update Deadband is expressed as either Always
or On Change.
improve system performance and prevent unnecessary logging
of data to disk. Like Update Deadband, the field is expressed
differently for analog, discrete, and bit array tags. For analog
tags, Update Deadband is a percent of full scale. The
BridgeVIEW Engine writes new analog tag values to historical
files only when a new tag value is different than the last logged
value by at least the Log Data Deadband. Use 0% if you want
each new value for the tag to be logged. For discrete and bit
array tags, Update Deadband is expressed as either Always
or On Change.
Log
Resolution
Resolution
analog
Determines the resolution in engineering units for logging a tag
value in the Citadel Historical Database. Tag values are written to
the database in a compressed format with the resolution specified
by Log Resolution. Use
value in the Citadel Historical Database. Tag values are written to
the database in a compressed format with the resolution specified
by Log Resolution. Use
0.0
if you want the exact value written
to the Citadel Historical Database. Notice that logging the exact
value requires more time and disk space. The default value
is
value requires more time and disk space. The default value
is
0.1
.
Log/Print
Events
Events
all
Determines whether events associated with the tag (for example,
changes in alarm state) are logged to event log files or printed to
a line printer.
changes in alarm state) are logged to event log files or printed to
a line printer.