Question

For a hot water heater, define the following:

Controlled Variable:

Manipulated Variable:

Sensor:

Controller:

Final Control Element:

Answer 1

1) Control variable: The variable that has to be controlled. In this case, it is T, the outlet temperature of water.

2) Manipulated variable: The variable that has to be changed to control the control variable. Here, it is the current to the electric heater to produce more or less heat.

3) Sensor: That which will detect the changes in the control variable. Here, we need a sensor like thermocouple to detect or measure the temperature of the outlet temperature T.

4) Controller: The computer program which decides what action to take. Here, we can use a feedback controller to control the outlet temperature T.

5) Final control element: That which takes the necessary action to control. Here, the FCE increases the current flow, disspitating more heat if the temperature has dropped and vice versa. This changes affects the manipulated variable.