Rockwell Automation FactoryTalk View Machine Edition Users Guide - Manual (Page 528)

F ACTORY T ALK V IEW M ACHINE E DITION U SER ’ S G UIDE
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Log on change
On-change logging is used to log only tags whose values have changed.
For HMI tags, before logging occurs, the change must equal a specified percentage of
change in the tag value. The percentage is based on HMI tags’ minimum and maximum
values as set up in the Tags editor. Only the tags that change by the specified percentage
are logged. If you specify a percentage of 0, all changes are logged.
If a tag does not have a minimum or maximum attribute (for example a data server tag in
Logix5000), when you specify on-change logging, all changes are logged for that tag. You
don’t need to specify a percentage.
Use a heartbeat rate
You can also specify a heartbeat rate, to log values at specified times even if no tag value
changes have occurred. The heartbeat ensures that the data in the log file is current. The
heartbeat is also a good way to ensure that data logging is working and acquiring valid
data.
The heartbeat cannot be less than the maximum update rate, which is the rate at which
data servers send tag values to FactoryTalk View.
If you specify a heartbeat of 0, the heartbeat is not used.
Tags in the data log model
The data log model can contain up to 100 analog or digital tags, including both HMI and
data server tags.
You cannot use string tags, array tags, tag placeholders, parameters, or expressions in your
data log model.
Delete tags from the model
If you delete a tag from the data log model, previously logged data for the tag is not
accessible unless you add the tag back to the model.
Change the data log model used at run time
Your application can run only one data log model at a time. Follow this procedure to
switch data log models.
To run a different data log model
1. Shut down the application.
2. Start FactoryTalk View Studio and open the application.
3. In the Startup editor, specify the new data log model.