Controlled variable

Definition

A controlled variable is a key element in process control that remains constant throughout an experiment or a process to ensure accurate and reliable results. By maintaining the controlled variable at a specific level, engineers can better observe the effects of other variables on the system, which helps in analyzing performance and stability.

5 Must Know Facts For Your Next Test

1. Controlled variables are crucial in experiments to eliminate confounding factors that could skew results.
2. In control systems, keeping controlled variables stable helps in achieving desired performance and reliability.
3. Common examples of controlled variables include temperature, pressure, and flow rate in chemical processes.
4. The effectiveness of control strategies often depends on how well controlled variables are maintained.
5. In feedback control systems, sensors monitor controlled variables to ensure they remain at their setpoints.

Review Questions

• How do controlled variables contribute to the reliability of experimental results?
  • Controlled variables help maintain consistency in experiments by keeping certain factors constant, which allows researchers to isolate the effects of manipulated variables. This consistency reduces variability in results and improves the accuracy of conclusions drawn from the data. By focusing on how changes in other variables impact the controlled variable, engineers can better understand and optimize system performance.
• Discuss the relationship between controlled variables, setpoints, and manipulated variables in a control system.
  • In a control system, controlled variables are maintained at predetermined setpoints, which represent the desired operational conditions. Manipulated variables are adjusted by the control system to achieve these setpoints despite any disturbances. The interaction between these elements is crucial; if controlled variables deviate from their setpoints due to disturbances, manipulated variables are altered to bring them back into alignment, ensuring optimal performance and stability.
• Evaluate the importance of controlling disturbance variables in maintaining stable controlled variables within chemical processes.
  • Controlling disturbance variables is vital for keeping controlled variables stable in chemical processes because disturbances can lead to fluctuations that negatively impact product quality and safety. Engineers must identify potential disturbances and implement strategies, such as feedback loops and feedforward controls, to mitigate their effects. By effectively managing disturbances, controlled variables can be maintained close to their setpoints, ensuring that processes run efficiently and meet desired specifications.

Related terms

manipulated variable:

A manipulated variable is the input or control parameter that can be adjusted to influence the output of a process.

disturbance variable: A disturbance variable is an external factor that can affect the output of a process but is not controlled by the system.

setpoint:

A setpoint is the desired value for a controlled variable that the control system aims to maintain.