My question relates to pulsed induction (PI) metal detection in particular.
It is my understanding that in a DC circuit an inductor acts as a conductor with little to no energy stored in a magnetic field. You will usually see them in DC circuits to help attenuate any high frequency noise components.
With a PI metal inductor, a short pulse of current for a few µs is supplied to a coil of wire. This pulse generates a magnetic field around the coil. The magnetic field around the coil excites eddy currents on the surface of surrounding metals which in turn induces a small magnetic field around these materials also.
When the current supply is removed from the coil (e.g. the end of the pulse) the magnetic field collapses and back-EMF is generated. The length of time it takes for the back-EMF to settle is determined by the amount of surrounding metal, as it will take a short amount of time after the field around the coil collapses for the induced magnetic field around the materials to collapse and these interfere with the EMF present in the coil.
How is a magnetic field generated and maintained during a pulse around an inductor? As far as the inductor is concerned, during that time when the pulse is settled, isn't it effectively just the same as DC?
Here is a little bit more on the subject of PI if needed.