Which tool is essential for measuring electrical current?

The clamp meter is essential for measuring electrical current because it allows for a non-intrusive method of measuring the flow of current in a conductor without the need to disconnect it from the circuit. This is especially useful in situations where the circuit cannot be interrupted or where it would be unsafe to do so. The design of the clamp meter enables it to "clamp" around a wire or conductor, detecting the magnetic field generated by the electric current passing through it, thus providing an immediate reading of the current in amperes.

While other tools listed are valuable for electrical measurements—such as the voltage tester for checking voltage levels, the ohmmeter for measuring resistance, and the multimeter which can measure voltage, current, and resistance—they do not specialize in the specific task of measuring current in a live conductor as effectively as the clamp meter does. The clamp meter is particularly favored in both residential and industrial applications due to its convenience and safety features.