Menu Location: Controller Blocks

Functional Description:
The Set-Point Tracking operator is designed for use with the PD, PI, and PID Controller blocks. It provides a means to match the controller set point to the process variable while the controller is operating in manual mode. This strategy is sometimes used to achieve bumpless transfer when the controller is switched from manual to automatic.

The Set-Point Tracking operator has one analog input, x, one digital input b, and one analog output y. When the digital input is high (b=1), the operator tracks the analog input, i.e.,

where limiting values y_min and y_max, are user-defined operator properties. When the digital input is low (b=0), the operator output is adjustable only from the front panel. In other words, the output maintains its value until modified via the Set Menu with the UP/DOWN arrow keys on the controller faceplate. The magnitude of output adjustment is a user-defined property of the operator.

A typical configuration of the Set-Point Tracking operator with the PID Controller block is shown in the following figure. In the figure, the Set-Point Tracking operator tracks analog input 2 (the process variable). The output of the Set-Point Tracking operator feeds the set point input (SP) of the PID Controller block. With this arrangement, the process set point will be adjustable from the controller front panel while the PID block operates in automatic mode. When the PID block operates in manual mode, the set point will match the process variable.

Design Pad will issue an error on processing if either input pin is not connected.

User-Defined Properties:
Object name.A string label that identifies the operator.

Initial value.The output value on startup (at time t=0).

Minimum value.The minimum output value, y_min.

Maximum value.The maximum output value, y_max.

Increment magnitude.The magnitude of output value increments when modified from the FAC-2x00 front panel (when input b is low).

Comments: None.

See Also:
PD ControllerIDH_PD_CONTROLLER, PI ControllerIDH_PI_CONTROLLER, PID Controller

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