Question

a controller compares the process value to the blank and signals the blank.
options: set point, final control element, retentate, dead band

Explanation:

Analyze the role of a controller

In industrial instrumentation and process control, a controller is the central decision-making device of a feedback control loop. Its primary function is to maintain a process variable at a desired value.

Identify the comparison reference

To make a decision, the controller must compare the actual measured value of the process (the process value or PV) to the desired target value. This target value is known as the set point (SP). The difference between the process value and the set point is the error.

Identify the target of the control signal

Based on the calculated error, the controller computes an output signal. This signal is sent to an actuator or device that directly adjusts the process (such as a control valve, variable speed drive, or heater). This physical device that directly alters the process is called the final control element (FCE).

Evaluate the remaining options

• retentate: This is a term used in filtration processes (the substance retained by the membrane) and is unrelated to basic control loop functions.
• dead band: This is a range of input values where no action occurs, which is a characteristic of some controllers but not what the controller compares the process value to or signals directly.

Answer:

A controller compares the process value to the <blank>set point</blank> and signals the <blank>final control element</blank>.