What tool can be used to measure the diameter of a motor shaft?

The tool best suited for measuring the diameter of a motor shaft is a caliper. Calipers are precision measuring instruments that can take internal and external measurements with high accuracy. They come in various forms, including vernier, dial, and digital calipers, allowing the user to read measurements with ease.

When measuring the diameter of a motor shaft, a caliper can conveniently wrap around the shaft, providing a direct reading of its width. This accuracy is critical in mechanical applications where precise dimensions ensure proper fit and function in assemblies.

Other tools, such as a voltage meter or an oscilloscope, are designed for electrical measurements and would not provide any measurement of physical dimensions like diameter. A digital scale measures weight, not dimensions, making it unsuitable for measuring the diameter of a motor shaft as well. Thus, the caliper stands out as the appropriate choice for this task.