In a basic electric control system, which component serves as a controlled device?

In a basic electric control system, the fuel valve acts as the controlled device because it directly regulates the flow of fuel to the burners based on control signals from other components in the system. The purpose of the controlled device is to respond to specific conditions within the system, enabling it to maintain the desired operational parameters, such as temperature, pressure, or humidity.

The fuel valve operates in conjunction with sensors or controllers that monitor the system's performance. For example, if a thermostat detects that the temperature has fallen below a setpoint, it will send a signal to the fuel valve to open, allowing fuel to flow and thereby increasing the temperature. This feedback loop is essential for automated control systems in power engineering.

While the thermostat, pressure-stat, and humidistat are critical components in control systems, they primarily function as sensors or controllers rather than direct manipulators of a variable. The thermostat measures temperature, the pressure-stat monitors pressure levels, and the humidistat controls humidity, but they do not directly control the flow of fuel. Instead, they inform the fuel valve when action needs to be taken to achieve the desired outcomes.