Rotor-to-stator air gap readings should be periodically taken for electrical generation equipment. What is the best tool to use to take these measurements?

Correct Answer: Option C — tapered, long blade, feeler gage

A tapered, long blade feeler gage provides precise physical clearance measurements within the restricted geometric confines between the rotating armature/rotor and stationary stator frame. Per IEEE 45, this ensures concentricity and prevents catastrophic magnetic rub conditions during operation.