How must the circuit be tested if using millisecond delay detonators?

The correct method for testing a circuit that employs millisecond delay detonators is to use a galvanometer. A galvanometer is specifically designed to measure small electrical currents, which is essential in confirming the integrity of the circuit before detonators are activated. This precise measurement capability ensures that any current flowing through the detonator can be accurately detected, allowing for safe and effective initiation of blasting operations.

In the context of using millisecond delay detonators, the importance of measuring small currents cannot be overstated. They require immediate and precise evaluation to ensure that they are functioning correctly and that there are no issues with the circuit that could lead to a misfire or unsafe conditions. The galvanometer's sensitivity is crucial in this scenario.

Other methods such as a multimeter, voltmeter, or standard light bulb are less suitable for this specific application. While a multimeter or voltmeter could measure voltage or general current flow, they may not provide the same level of sensitivity needed for detonators. A light bulb wouldn’t effectively indicate whether a circuit is complete or if the required current levels for detonation are being met, as it would only light up with a sufficient current, potentially masking issues that need attention.