To check whether a winding in a split-phase motor is grounded, which tool should you use?

Using a megohmmeter is the best choice for checking whether a winding in a split-phase motor is grounded. This tool measures high resistance values and is particularly effective for detecting insulation failures and grounding issues within motor windings. When testing with a megohmmeter, it applies a high-voltage DC signal to the winding, allowing the user to evaluate the resistance of the winding's insulation. If the winding is grounded, the megohmmeter will indicate a low resistance reading, revealing a fault that needs to be addressed.

In contrast, a voltmeter is primarily used for measuring voltage levels, which would not directly indicate whether a winding is grounded. An ammeter measures current flow, which also does not provide information about insulation condition or grounding. An oscilloscope is generally used to observe waveforms and signals rather than for insulation resistance testing. Thus, the megohmmeter stands out as the appropriate tool for diagnosing grounding issues in motor windings.