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5.4.0 External Command Considerations
5.4.1.0 External Command Activity
The External Command activity accommodates program inputs from an external programmer or controller.
Before you can use an External Command activity, you must:
1. Connect the external command source to your controller.
2. Use the Station Builder application to allocate an analog input resource for the command input signal.
3. Adjust the command input signals with the Station Manager application.
4. When you define the properties of an External Command activity, you must define which channel(s) the
process will control.
5.4.2.0 Starting External Commands
The external command must be running when the MPE application starts the External Command activity. To
ensure that your external program is running when it is needed, do one of the following:
•
Start your external program source before you start your MPE procedure. This ensures that the external
command is running when the External Command activity starts and limits unwanted bumps in your
command signal.
•
If your external programmer supports digital input and output signals, configure a Digital Output activity
to start the external program, and a Digital Input Detector activity to start the External Command activity.
5.4.3.0 Stopping External Command Activity
Typically, you use a Data Limit Detector activity or Digital Input Detector activity to end the External Command
activity.
•
Use a Limit Detection activity to interrupt the External Command activity after a specified time period or
when specified signal limits are reached.
•
If your external programmer can issue a signal when the program is complete, you can use a Digital Input
activity to interrupt the External Command activity.
•
Stop the External Command activity manually by clicking the Stop control on the MPE Test panel. This
stops the activity and the procedure.
•
Resume the External Command activity by clicking the Run control on the MPE Test panel.
•
If you click Run after stopping the command, the process either ramps to the specified setpoint and then
tapers up to the defined amplitude (if Enable Ramp is selected), or tapers directly up to the defined
amplitude (if Enable Ramp is not selected).
Multipurpose Elite Test Design Guide 69
5.0 Creating Tests