Which device contains a paddle that moves when contacted by air or water flow?

• A. Flow switch
• B. Accumulator
• C. Digital output
• D. Pseudopoint

Answer: (A)

Flow switches use a movable element in the flow path to detect fluid movement. A paddle or vane sits in the air or water stream, and when the flow hits it, the paddle deflects and moves a linked switch mechanism. That movement changes the electrical state to indicate that flow is present. This mechanical interaction with the passing fluid is what makes a flow switch the correct choice. An accumulator isn’t a sensor, it just stores fluid energy. A digital output is a signaling method, not a sensing element. Pseudopoint isn’t a real device. So the paddle that moves with the flow identifies a flow switch.