Rockwell Automation 1395 Digital DC Drive FRN 5-10.10/9.30 User Manual
Page 105
Chapter 5
Functional Description
5-19
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Once a trend buffer is activated, it continuously samples the selected
parameter. When it is triggered, each buffer will take an additional
number of samples as specified by the Post Sample Parameter. When
finished sampling, the data is transferred to an output buffer where it
can be displayed or sent to an external device.
An example of a typical trend buffer is shown below:
Parameter to be monitored:
Parameter 106 (Velocity feedback)
Trend Trigger operand X
Parameter106
Trend Trigger operand Y
Parameter 900 (signed trend constant).
The value in 900 will be set to 100
RPM (Actual value is entered in
Internal Units)
Trend Operator
Greater than (.GT)
Samples after trigger
80
Trend sample rate
Trend buffer sample rate, this will be
set to 24 ms.
Continuous trigger
One shot, the trend will have to be
reset after each trigger.
Trend Enable
Activate
Trend Output Rate
Output buffer data rate.
When setting up a trend buffer, the following equation is used for
comparison of operand X and Y.
[operand X] [operator] [operand Y]
The example above would result in the following formula:
When [Parameter 106] is [greater than] [Parameter 900] the trend buffer
will be triggered.
Using the setup above, parameter 106 would be monitored. When its value
exceeded 100 RPM the trend buffer would be triggered and 80 more
samples (at a rate of 1 every 24 ms) would be taken. Once the sampling is
complete the data would be transferred to the output buffer and the trend
would be deactivated.
Trend Setup Description – This procedure describes how to setup trend
buffers using a 1395 Program Terminal. For information on setting up
trend buffers from an Allen-Bradley PLC refer to the 1395 Node Adapter
publication.