Which valve transforms an analog electrical input signal into proportional opening cross-sections at the outputs?

• A. 4/3-way proportional valve
• B. 4/3-way regulating valve
• C. 4/2-way directional valve
• D. 4/2-way proportional valve

Answer: (A)

The main idea is that this question tests proportional electro-hydraulic control: turning an analog electrical signal into a continuous, proportional change in hydraulic flow by adjusting the size of the openings in the valve’s output paths. A four-/three-way proportional valve does exactly that: its spool position is moved in proportion to the input signal, so the flow paths to the outputs open by amounts that match the control signal. With this setup, the cross-sections of the output paths vary smoothly, giving proportional control of the actuators or loads connected to those outputs. The other valve types either switch between fixed states or regulate pressure without providing the same continuous, proportional modulation of multiple output openings, so they don’t fit the requirement as well.