What is the simplest meter to use for measuring current flow in a circuit?

A clamp-on ammeter is the simplest meter to use for measuring current flow in a circuit because it allows for non-intrusive measurement. This tool can be clamped around a conductor without the need to disconnect the circuit or interrupt the current flow, making it highly convenient for practical use.

Unlike a voltmeter, which measures voltage and requires two points in a circuit to take a reading, or an ohmmeter, which measures resistance and requires the circuit to be powered off and isolated, a clamp-on ammeter operates simply by clamping around the wire. This significantly reduces the complexity and risk associated with measuring current, especially in live circuits.

A manometer, which measures pressure rather than electrical properties, is not applicable in this context. Hence, the clamp-on ammeter stands out as the most straightforward and effective tool for current measurement in various situations.