B&B Electronics VFG3000 - Manual - Manual (Page 171)

C ONFIGURING D ATA L OGGING D ATA L OG P ROPERTIES
R EVISION 1 P AGE 155
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ATA
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ROPERTIES
Each data log has the following properties…
• The Update Type property defines if this data log will record data continuously
or on a trigger edge. Continuous Sample data logging saves tags values at regular
time intervals, as define by the Update Rate property. Triggered Snapshot saves
tags values when the expression in the Log Trigger property goes from false to
true. Since the log trigger is looking at the change in the expression, only one set
of data will be recorded at the time of change, the expression has to return to
false and back to true again to save another set. Each set is a line of data in a
CSV file.
• The Update Rate property is used to indicate how often Fieldbus Gateway
Manager will take a sample of the data items to be logged. The fastest sample
rate is one second, but note that using such a high rate will produce very large
amounts of data! All of the tags in the log will be sampled at the same rate.
• The Each File Holds property is used to indicate how many samples will be
included in each log file. When this many samples have been recorded, a new
log file will be created using a different name. Typically, this value is set such
that each log file contains a sensible amount of data. For example, the log shown
above is configured to use a new log file each day.
• The Retain At Most property is used to indicate how many log files will be kept
on CompactFlash before the oldest file is deleted. This property should be set so
as to allow whatever is consuming the logged information to extract the data
from the Fieldbus Gateway before the information is deleted. The log shown
above is configured to retain a week’s worth of data.
• The Log Enable property is used to allow or inhibit logging. If the entered
expression is true, logging will be enabled. If the expression is false, logging will
be disabled. If no expression is entered, logging will be enabled by default.
• The Log Trigger property is used to log a single set of data when the expression
changes from false to true.