Rockwell Automation 1395 Digital DC Drive FRN 5-10.10/9.30 - Manual (Page 107)

Chapter 5
Functional Description
5-21
Programming a Trend Buffer Determining What to Trend – The first step to programming a Trend
Buffer is to determine which parameter you want to monitor or trend. The
parameter you select to trend must be a fast parameter because you will
establish a configuration link to that parameter. This link will be made
between the parameter to be trended and the Trend Input Parameter
(Parameters. 50 through 53).
NOTE: If you are not familiar with Drive configuration links refer to the
Programming Terminal manual section detailing Drive Setup.
Setting up the Trend Trigger – In order for a trend to operate you must
tell it what conditions (trigger) will cause it to store data. These conditions
are setup by three parameters: Trend Operand X, Trend Operand Y, and
Trend Operator. The following Equation is used to evaluate a trend trigger
condition.:
If [Operand X] [Operator] [Operand Y] then trigger.
In other words, the value of parameter specified by Operand X is compared
to the value of the parameter specified Operand Y. If the conditions
specified by the Operator are satisfied, then the trend is triggered and
begins storing data samples.
Operand X and Operand Y can be any parameter number from 1 to 947. If
a constant value is required, the Trend constant parameters (Parmeters 900
through 909) can be used.
IMPORTANT: Attempting to compare a signed parameter with an
unsigned parameter will result in unpredictable trend operation. All
attempts should be made to keep both Operand X and Operand Y signed or
unsigned.
1. Greater Than (.GT.) – Compares the data value for the parameter
specified by Operand X to the data value for the parameter
specified by Operand Y. If the comparison is positive, the trend is
triggered
2. Less Than (.LT.) – Compares the data value for the parameter
specified by Operand X to the data value for the parameter
specified by Operand Y. If the comparison is positive, the trend is
triggered
3. Equal (.EQ.) – Compares the data value for the parameter
specified by Operand X to the data value for the parameter
specified by Operand Y. If the comparison is equal, the trend is
triggered
4. Not Equal (.NOT EQ.) – Compares the data value for the
parameter specified by Operand X to the data value for the
parameter specified by Operand Y. If the comparison isn’t equal,
the trend is triggered.