Control System Terminology

1. CONTROLLED VARIABLE: Process output variable that is maintained between specified limits.

2. MEASURED VALUE: Actual value of the controlled variable, as determined by the instrumentation.

3. DESIRED VALUE: Required value of the controlled variable (set point).

4. ERROR : The difference between the desired value and the measured value.

5. MANIPULATED VARIABLE: Process input variable that is adjusted, to steer the controlled variable towards the desired value.

6. DISTURBANCE VARIABLE: Process input variable that can cause the controlled variable to deviate from the desired value.