For working with electric motors, which meter is primarily used for insulation testing?

The meter primarily used for insulation testing in electric motors is the megohmmeter. This device is designed to measure high resistance values, typically in the megohm range, which is essential when assessing the insulation quality of electrical systems. Insulation testing helps determine whether the insulation of the motor windings is intact and able to prevent electrical currents from leaking out or causing short circuits. The megohmmeter applies a high voltage to the insulation and measures the resistance; high resistance values indicate good insulation, whereas low values can signal potential insulation failures or degradation.

In contrast, a multimeter is typically used for measuring lower voltage and current values, making it less suitable for insulation testing. A wattmeter measures the power consumed by an electrical circuit and is not used for testing insulation. A frequency meter measures the frequency of an electrical signal, which is not relevant to assessing the integrity of insulation in motors. Therefore, the megohmmeter is the correct choice due to its specific design for insulation resistance testing, crucial for ensuring the safety and longevity of electric motors.