When you need to measure current flow through a wire, the normal method is to insert an ammeter in series with the cable. Using a clamp-on ammeter, or “Amp-clamp,” you don’t need to break the circuit. The more basic versions of the Amp-clamp can only measure AC current flow because they use sensors that respond to AC only (i.e., they work on the same principle as a transformer). In order to measure DC current, we can use Hall sensors.