Is the difference between the set point of a process variable and its actual value?

Skip Navigation

Navigation

  • Home

    • Site pages

      • Tags

      • Calendar

      • Site news

    • Current course

      • Instrumentation and Process Control

        • Participants

        • General

        • 20 February - 26 February

        • 27 February - 5 March

        • 6 March - 12 March

        • 13 March - 19 March

        • 20 March - 26 March

        • 27 March - 2 April

          • Lesson 27. ELEMENTS OF GENERALIZED PROCESS CONTROL

          • Quiz 27

          • Lesson 28. CONTROL SYSTEM PARAMETERS

          • Quiz 28

          • Lesson 29. TYPES OF CONTROLLER MODES

          • Quiz 29

          • Lesson 30. FINAL CONTROL ELEMENTS AND ACTUATORS

          • Quiz 30

          • Lesson 31. INSTRUMENTATION AND CONTROLS IN DAIRY P...

          • Quiz 31

          • Lesson 32. INSTRUMENTATION AND CONTROLS IN CIP CLE...

          • Quiz 32

        • 3 April - 9 April

        • 10 April - 16 April

        • 17 April - 23 April

        • 24 April - 30 April

    • Courses

You are currently using guest access (Log in)

A standard control loop is shown in the figure below. A controller tries to steer a process in a way that minimizes the difference between a given setpoint and the output of that process. In other words, the controller tries to get the process output as close as possible to the given setpoint.

Setpoint

The setpoint (SP) is where the process output should match. It can be a static value (e.g. the desired temperature of a room) or a varying value (e.g. the desired position of a robot-tip).

The setpoint is where you would like the measurement to be. Error is defined as the difference between set-point and measurement.

Process

The process is the system that should be controlled. It is sometimes referred to as plant or system. The process should have has at least one impute to control its behavior and at least one output that is a measure of its behavior. Consider for example a gas heated house as process. The heater feed could be the process input and the measured room temperature the process output.

The process input is connected to the controller output or controller variable (CV). It is mostly the input for an actuator that can drive the process to a desired setpoint.

The process output is commonly known as process variable (PV), or measured variable (MV). Other names of the process output are system output and measurement.

Error

The error is defined as the setpoint minus the process output. It is a measure for how much the process deviates from the desired setpoint, and thus how much the controller should respond to get the process back to the desired setpoint.

Setpoint Weighting

For many controllers the controller input is equal to the error signal. Some controllers, however use specialized inputs for their proportional, integral and derivative parts (setpoint weighting). They have two inputs, one for the setpoint and one for the measured variable and are therefore also described as 2-DOF controllers.

What is the difference between the process variable and the set point?

Common process variables include – level, flow, temperature, density, PH(acidity or alkalinity), mass, conductivity etc. The SETPOINT is the target value of the process variable that is desired to be maintained. For example, if a process temperature needs to be kept within 5 °C of 100 °C, then the SETPOINT is 100 °C.

What is the difference between the desired value of a variable and the controlled actual value?

The difference between actual and desired value of the process variable, called the error signal, or SP-PV error, is applied as feedback to generate a control action to bring the controlled process variable to the same value as the set point. Other aspects which are also studied are controllability and observability.

What is a set point in process control?

In cybernetics and control theory, a setpoint (also set point) is the desired or target value for an essential variable, or process value of a system. Departure of such a variable from its setpoint is one basis for error-controlled regulation using negative feedback for automatic control.

What is a set point variable?

Definition(s): An input variable that sets the desired value of the controlled variable. This variable may be manually set, automatically set, or programmed.

Toplist

Neuester Beitrag

Stichworte