Emerson ROC827 Proportional, Integral, and Derivative PID, Function Sequence Table FST

ROC827 Instruction Manual

the user. The ROC827 wakes from Standby mode when it needs to perform a task.

ƒSleep

The ROC827 uses this mode if it detects a low battery voltage. The System AI Battery Point Number 1 measures the battery voltage and compares it to the LoLo Alarm limit associated with this point. (The default value for the LoLo Alarm limit is 10.6 Volts dc.) When in Sleep mode, AUXsw is turned off. For information on configuring alarms and System AI points, refer to the ROCLINK 800 Configuration Software User Manual (Form A6121).

Note: Sleep mode applies only to ROC827s using the 12 V dc Power Input module (PM-12).

1.4.6Proportional, Integral, and Derivative (PID)

The PID Control applications firmware provides Proportional, Integral, and Derivative (PID) gain control for the ROC827 and enables the stable operation of 16 PID loops that employ a regulating device, such as a control valve.

The firmware sets up an independent PID algorithm (loop) in the ROC827. The PID loop has its own user-defined input, output, and override capability.

The typical use for PID control is to maintain a Process Variable at a setpoint. If you configure PID override control, the primary loop is normally in control of the regulating device. When the change in output for the primary loop becomes less or greater (user-definable) than the change in output calculated for the secondary (override) loop, the override loop takes control of the regulating device. When the switchover conditions are no longer met, the primary loop regains control of the device. Parameters are also available to force the PID into either loop or force it to stay in one loop.

1.4.7 Function Sequence Table (FST)

The Function Sequence Table (FST) applications firmware gives analog and discrete sequencing control capability to the ROC827. This programmable control is implemented in an FST, which defines the actions the ROC827 performs using a series of functions. To develop FSTs, you use the FST Editor in the ROCLINK 800 Configuration software.

The function is the basic building block of an FST. You organize functions in a sequence of steps to form a control algorithm. Each function step can consist of a label, a command, and associated arguments. Use labels to identify functions and allow branching to specific steps within an FST. You select commands from a library of mathematical, logical, and other command options. Command names consist of up to three characters

Issued Mar-06 General Information 1-14