What equipment is used to test the condition of insulation in electrical apparatus?

The correct choice is a megohmmeter, which is specifically designed to measure the resistance of insulation in electrical systems. Insulation resistance testing is crucial for assessing the integrity of electrical apparatus and ensuring that it is safe and functioning effectively. A megohmmeter applies a high voltage, typically between 250 to 5,000 volts, across the insulation and measures how much current flows through it. This allows the user to determine the quality of the insulation; higher resistance values indicate good insulation, while lower values suggest potential issues.

Other devices mentioned, such as the multimeter, oscilloscope, and amperemeter, serve different purposes. A multimeter can measure voltage, current, and resistance but does not provide the high-voltage insulation testing that a megohmmeter does. An oscilloscope is used to visualize electrical signals over time, which is useful for analyzing waveforms but not for directly assessing insulation condition. An amperemeter measures the flow of electrical current in a circuit, which does not pertain to insulation testing. Thus, when evaluating insulation, the megohmmeter is the most appropriate and effective tool.