問題文
A static threshold detector has three options for trigger sensitivity. An engineer must choose one for a signal that regularly spikes above the threshold for a few seconds. Which option correctly describes the three and identifies the appropriate choice?
選択肢
- The percentage refers to the share of received data points, so a signal that spikes for a few seconds is best served by raising the percentage until those short spikes fall below it, which leaves the duration free to stay short for everything else.
- Immediately is the least sensitive because it requires the very next data point to also be anomalous; Duration is the most sensitive; Percent of duration is equivalent to Duration with the percentage fixed at one hundred, so a spiky signal calls for Immediately, and the percentage field is therefore only a display detail that never changes when the detector fires at all.
- Duration and Percent of duration are two names for the same setting, and the only real choice is between firing immediately and firing after a delay, so a spiky signal calls for any of the delayed forms, while the percentage field beside the duration is a leftover from an earlier version of the condition.
- Immediately fires as soon as the threshold is met and is the most sensitive; Duration requires the condition to hold for a period and fires nothing if any data point is missing in that period; Percent of duration fires when the required share of the expected points met the threshold, so it tolerates some missing points, and it suits a spiky signal.