Monitoring the PID Loop

Cogent Tools Demo and Tutorials: Version 4.0
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# 2.2. Monitoring the PID Loop

When you click the Monitor button in the Controller the Monitor window will appear, as shown here. The Monitor shows what's happening in the PID Emulator.

The Monitor in GTK |  | The Monitor in Photon 2

The demo starts with the PID Emulator (`emul.g`) in automatic mode, with the set point (SP) scale's slider moving at random every 8 or 10 seconds. The MV and PV progress bars move in response, emulating a poorly-timed PID loop. You can click off the Auto mode button to put the demo into manual mode; or you can adjust the rate of change with the Delay spin button. To modify the PID Emulator's behavior, you can click the Good, Oscillating, or Out-of-control buttons at the bottom of the window, or you can adjust any of the variables using the Kp, Ki, Kd INT, or PROP spin buttons.

| The QNX versions of the Monitor have a trend widget that displays `SP`, `MV` and `PV` data graphically. This widget is not available in Linux, but the functionality is emulated in the Linux version of the Log program (`gtklog.g`) using gnuplot.

The Monitor serves as an interface for the PID Emulator, with the Cascade DataHub passing data between the two. To get a better view of the data, you can use the DataHub Viewer as explained in the next section.

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