Rockwell Automation T7480 ICS Regent+Plus Guarded Analog Output Modules - Manual (Page 15)

Guarded Analog Output Modules (T7480)
P D - 7 0 2 6 M a r - 0 6
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control logic, you maintain the full resolution of the analog
output (1 part in 4096) and have a convenient engineering
range that represents 0.00 to 100.00% (the two decimal places
are implied).
Programming Fault Tolerant Guarded Analog Outputs
To program guarded analog outputs in a fault tolerant
configuration, you should create control logic to calculate the
value for one of the guarded analog outputs and copy this
calculated value to the redundant guarded analog output. If
you use the unscale entry in the analog scaling function block
you should place this “copy logic” after the analog scaling
function block in your application program. Figure 9
illustrates how the Assign instruction in ladder logic can be
used.
Figure 9. Programming Fault Tolerant Outputs.
In this example GAO1A is the name of the analog output that
has been set by your control logic, and GAO1B is the
redundant analog output. When power flows to the Assign
element, it reads the value of GAO1A and stores that value to
GAO1B, so that both of the redundant analog outputs have
the same value.
Maintenance
There are no user replaceable parts inside the Guarded
analog output module. Re-calibration is recommended once
per year, in order to maintain the rated accuracy of the analog
output signals over an extended period of time. The following
procedure describes the equipment and steps necessary to
calibrate the Guarded analog output module.
Calibration Procedure
Equipment Required
· A 5½-digit voltmeter.
·
Six 250 ohm, 0.005%, 5 ppm/ ° C resistors to convert the six
output signals from a current to a voltage.