High-speed supervision of process variables

IMAGINE an instrument which scans rapidly through 50 primary elements in less than five seconds. It has no scale but has 50 bull´s-eyes on the front of its case. Suddenly one of these bull´s-eyes lights up and a howler sounds. A nearby recorder moves into action. The operator on duty notes the generator involved and presses a button to silence the howler, then leaves to inspect the stator of that generator. The bull´s-eye remains lit and the recorder remains active. The temperature is dropping back toward a safe condition because the operator has increased the water flow to the hydrogen cooler. Next the light goes out and the recorder runs down scale and stops.