Stroboscope application in rotating machinery A stroboscope is commonly used in industry to measure which quantity without mechanical contact?

Introduction / Context:
A stroboscope emits flashes of light at a controllable frequency. When this frequency synchronizes with a rotating object’s apparent motion, the object appears stationary. This visual “freezing” enables non-contact speed measurements on shafts, fans, and flywheels — a staple of maintenance and balancing work.

Given Data / Assumptions:

• Instrument: portable electronic stroboscope.
• Rotating target with a visible mark or blade.
• No physical tachometer pickup is used.

Concept / Approach:
Adjust flash rate until the mark appears stationary. The flash frequency at that point corresponds to the rotational frequency (allowing for harmonics). Converting from flashes per second to revolutions per minute is straightforward: rpm = 60 * flashes per second (for the fundamental stationary image).

Step-by-Step Solution:

Verification / Alternative check:
Cross-check the displayed rpm with a contact tachometer or a laser optical tach; readings match when the fundamental stationary image (not a harmonic) is used.

Why Other Options Are Wrong:

Common Pitfalls:
Misreading harmonic locks (e.g., 2×, 3×). Always verify by checking multiple flash rates and ensuring the mark’s apparent position and count are consistent.

Final Answer:
rpm of a flywheel