Rockwell Automation 1746-NO8V SLC 500 8-Point Analog Output Module/ User Manual - Manual (Page 36)

Publication 1746-UM026A-EN-P - September 2003
4-12 Configuring the Module
Setting the Parameter
Option Values (Class 3
Only)
User-Defined Scale
For special applications, the module allows definition of a custom
data format. This “user-defined scale” is very similar to the
“proportional counts” data format, except that instead of converting
the output data to an output signal using a previously defined scale
(-32,768 to 32,767), the module converts the output data using a scale
defined by “low limit of scale” (output word 16) and “high limit of
scale” (output word 24) for Channel 0.
You select the data format for each channel using that channel’s
configuration bits, described in the previous subsection, Data Format
(configuration bits 4 to 6) on page 4-8.
The user low value (Output Data Parameter 1) is the value that will set
the output to the selected output range’s minimum value. Similarly,
the user high value (Output Data Parameter 2) is the output data value
that will set the output range’s maximum value.
EXAMPLE 1: User-Defined Scale
Suppose you have a valve connected to Channel 0 with a 4 to 20
mA range, and you want your scale to go from 100 to 9999 counts.
For a 4 to 20 mA output with user-defined scaling, your module sets
the signal limits to 3.5 mA and 20.5 mA (see Table 4.3 on page 4-8).
Enter 100 and 9999 into output words 16 and 24, respectively.
O:e.16, value = 100 decimal (Channel 0 Data Parameter 1)
O:e.24, value = 9999 decimal (Channel 0 Data Parameter 2)
TIP
Once the Data Parameters have valid values and bits
9 to 11 are set; then set bit 8 (set optional feature) to
set the feature, or set bit 7 (clear optional feature) to
clear the feature.
IMPORTANT
The high limit value must be greater than the low
limit value for proper operation. Also, the difference
between the low and high values should be greater
than 1024 counts. If the difference between the low
and high values is less than 1024 counts, unexpected
results can occur (especially at the extreme ends of
the range).