Motor controlsQuestion 250 of 1506

How can a speed switch sense shaft speed without touching the shaft?

With a bimetal strip clamped on the shaft
With a non-contact optical or magnetic detector
With a float in an oil pan
With a liquid-filled bulb

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Correct answer: With a non-contact optical or magnetic detector

A speed switch can use a centrifugal weight on the shaft or a non-contact optical or magnetic detector.

Source: Lessons in Electric Circuits IV: Digital (Kuphaldt), 4.1: Switch Types

Questions last reviewed: 18 October 2026

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