For testing a valve supervisory system, what indicates movement from the control valve's normal position?

Choosing the first 2 revolutions as the indicator of movement from the control valve's normal position aligns with typical testing protocols that aim for early detection of discrepancies. When testing a valve supervisory system, the focus is on identifying the point at which the valve begins to move from its set position.

In many systems, the initial movements often signify the valve is on the verge of transitioning, making the first couple of revolutions the most critical for determining whether the valve is functioning as intended. Observing movement within this small range allows for timely intervention if the valve is not responding properly, ensuring system integrity and preventing potential issues.

In contrast, larger revolutions, like 3, 5, or 10, may provide information about the performance over a more extended range but may miss the critical early signs of malfunction. Thus, the first 2 revolutions serve as a proactive measure in valve testing, which is essential for maintaining safety and operational effectiveness in water-based fire protection systems.