What device would be used to measure AC current flow in a large diameter conductor?

A clamp-on type ammeter is the most suitable device for measuring AC current flow in a large diameter conductor. This type of ammeter is designed to be clamped around the conductor without the need to physically disconnect it from the circuit. This is particularly important for large diameter conductors, as it can be challenging and impractical to attach probes or leads directly to them.

The clamp-on ammeter operates by measuring the magnetic field generated by the AC current flowing through the conductor. This approach provides a non-intrusive way to take measurements, which is essential for safety and convenience in electrical systems where high currents may be present.

In contrast, a digital multimeter, while versatile, typically requires direct contact with the circuit and may not be able to handle large currents effectively without the appropriate settings or probes. A voltmeter measures voltage, not current, and a resistance meter is used to evaluate resistance rather than current flow. Therefore, the clamp-on type ammeter is the ideal choice for measuring AC current in this situation.