Transient electromagnetics

Transient electromagnetics, (also time-domain electromagnetics / TDEM), is a geophysical exploration technique in which electric and magnetic fields are induced by transient pulses of electric current and the subsequent decay response measured.

At the surface, the change in magnetic field [flux] with time is measured.

The paper by McNeill is freely available from the Geonics website[4] explaining the basics of the method.

Low-power TEM/TDEM instruments can operate using C-cell batteries, and mid-range systems (approx.

2.5 kW) can operate with automotive batteries; more powerful systems (20 kW~150 kW) require a separate generator usually mounted on a truck, plane, or helicopter to provide the necessary current for deep investigations.