Are control valves considered digital or analog?

Control valves are considered analog devices as they are designed to modulate and regulate the flow of fluids in a system by opening, closing, or partially opening based on changes in the input signal. This input signal is typically an analog signal, which can vary continuously within a range, allowing for precise control of the valve position.

Analog control valves respond to a continuous spectrum of input signals, enabling smooth and variable operation, which is crucial in many industrial applications where precise flow control is necessary. For instance, in a process control system, the valve can adjust its position in response to an analog signal from a controller, facilitating variable flow rates rather than just on/off states.

While digital signals represent discrete values (such as open/closed), they can be used indirectly with valves through the use of intermediate control devices (like electronic positioners) that convert them into an analog format. However, the fundamental operation of the valve itself is inherently analog due to its ability to adjust continuously.