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With a clamp meter, the conductor through which current is flowing is clamped with the transformer core, in order to measure electrical current without breaking the circuit. The measuring principle is that the electromagnetic field generated around the wire through which current is flowing is picked up by the clamp meter’s transformer core, and the current generated in the coil wrapped around the core is measured. Rules such as Coulomb’s Law and Fleming’s Law, etc., apply to this principle, and, in the case of clamp meters that can also measure direct current, Hall elements are built into the transformer and micro electrical current applied to these elements in advance so that direct current can be measured.
AC measurement is real easy by flemings rule.
DC is tricky since it saturates the clamp meter's transformer core. so2 methods are used.
1. An oscillator ckt produces low frequency, Low voltage AC ( triangular or trapezoidal waweform will do) . TheDC will offset this AC, but still leaves it as AC, just offseted which will not saturate the core.
no just measure the offset.
2. Some clamp meters use HALL EFFECT TRANSDUCERS to measure DC
