Voltage source

Measures current by magnetic field induced into the clamp. You need to clamp a single conductor. For example you couldn't just clamp a lamp cord since it has two conductors and the current is going in opposite directions and the fields cancel each other out.

A DC clamp meter works by measuring the magnetic field produced by the flow of direct current in a conductor. When the clamp is placed around the conductor, it detects the magnetic field and converts it into a direct current measurement. This measurement is then displayed on the meter's screen.

they are used to separate magnetic metals and non-magnetic metals in a scrapyard and are used as well to lock gates shut by forming a clamp and holdong tight.

A clamp-on meter works by measuring the magnetic field set up around a conductor. Because the currents in the line and neutral conductors flow in opposite directions, their fields cancel and the clamp-on meter has nothing to monitor. So it must be placed around either the line OR the neutral conductor -not both!