Rockwell Automation 2707-NP DTAM Programming Software - Manual (Page 30)

Chapter 3
Designing DTAM Plus and
DTAM Micro Applications
3–6
Data entered by an operator can be scaled from engineering units such as
gallons or PSI to machine control values. Likewise, data displays can
take raw numeric values and scale them so they are displayed in
engineering units.
Scaling of data is accomplished by defining a proportional ratio between the
register value range and the display or entry value range. If a 1:1 ratio exists,
the DTAM displayed or entered value equals the controller register value.
Here is an example of scaling using a data display to scale a register data
range of 0 to 4,095 to a DTAM display range of -100 to +300.
Controller
Register Limits
0
4,095
DTAM
Display Limits
4,095
-100
+300
This Value
Is Displayed:
0
-100
4,095
+300
+100
2,047
If the Display
Register Contains:
When the ratio between the controller register values and DTAM display or
entry values is not a multiple of 2, the value is rounded. Rounding may
result in a 1 count error. Depending upon the direction of the scaling, this
means that:
•
The DTAM display value may be off by 1 when the controller register
value is scaled
•
The controller register value may be off by one when a DTAM data entry
is scaled.
An error screen appears if a rounding error occurs at the end points of a data
range. You must either increase the minimum or decrease the maximum
range of either the controller register or display ranges.
Data Scaling