The valve's open and close signals are best described by which option?

• A. Opens at 3133 and closes at 3533.
• B. Opens at 3533 and never closes.
• C. Opens at 3533 and closes at 3233.
• D. Opens at 3533 and closes at 3133.

Answer: (D)

Valves are typically controlled with hysteresis: the signal that opens the valve is higher than the signal that closes it. This creates a safety margin so small fluctuations don’t cause constant on/off chatter.

In this case, the valve opens when the signal reaches 3533 and closes when it falls to 3133. That setup creates a clear open/close band—a 200-unit gap—so once the valve is opened, it will stay open until the input drops to 3133, and once closed, it will stay closed until the input rises to 3533. This stability is why opening at 3533 and closing at 3133 is the best description. Other patterns would either reverse the thresholds or remove the stabilizing margin, leading to less reliable operation.