Rockwell Automation 2711-ND3 PanelBuilder v2.60 Software User Manual - Manual (Page 157)

10–5 Creating Data Entry Controls
Publication 2711-6.0
Data Limits for a Scaled Value
If a scaled value exceeds the range for the selected data type, the
terminal will display a ‘Value Not In Range’ warning. When using
scaling, we recommend that you limit the minimum and maximum
values an operator can enter. These values are set in the Tag Editor
form view. (see page 19–5 ).
Calculate the range for scaled values before entering values in the
Tag Editor. Use the following formulas to determine scaled
minimum and maximum values:
Maximum Input Value =
Minimum Input Value =
(Maximum Value for Data Type x Scale) + Offset
(Minimum Value for Data Type x Scale) + Offset
For example:
•
Scale = 1.8 and Offset = 32 (Fahrenheit to Celsius conversion)
•
Data type is Signed Integer (-32,768 to +32,767)
The minimum / maximum values an operator can enter without
truncating:
Maximum Input Value =
Minimum Input Value =
32,767 x 1.8
-32,768 x 1.8
+ 32 = 59012
+ 32 = -58950
Initial Value of a Scaled Value
The initial value specified in the Tag Editor is written to the
controller on powerup or reset. This initial value is not scaled, so it
must be entered in units used by the logic controller.
For example, the terminal uses
_C and the controller uses _F. To
initialize the terminal to a value of 32
_F, the initial value in the Tag
Editor needs to be 32, not 0.
The terminal does not scale the initial value before sending it to the
controller if the specified tag has an:
•
initial value and
•
a scale and/or
•
offset
The value stored in the terminal may be different than the value sent
to the controller because of rounding that occurs during pre-scaling.
A warning message is displayed during validation if this occurs. If
the scaled initial value exceeds the range limits (because of a
rounding error), an error message is displayed.