Six induction coils are available, each most appropriate for certain depths and applications. For shallow resistivity soundings, the high bandwidth of the high frequency coils is needed for the rapidly changing early-time signal. Comparatively, for deeper soundings, or for measuring late-time signal from conductive ore bodies, the larger effective area of the low frequency coils amplifies the very low amplitude late-time signals to measureable levels.

When the stratigraphy of the survey environment is effectively flat-lying, a single component coil is generally appropriate. The response from sub-vertical structure, however, is three dimensional; in these environments, the measurement of all three components will result in an easier and more accurate interpretation. Both high and low frequency coils are available in both single component (1D) and three component (3D) versions.

Geonics induction coils are air-cored, rather than ferrite-cored, offering two significant advantages: most ferrite materials exhibit some self-response when subject to strong primary magnetic fields, which can unnecessarily add noise to the data. Second, ferrite-cored coils are long and thin in design which tends to make them sensitive to noise from wind-induced vibration; air-cored coils with “flat” geometry are much less sensitive to this effect.

Some ore bodies can be so conductive that induced eddy currents decay exceedingly slowly, in which case voltage induced in an induction coil may be too small to measure. The actual magnetic field amplitude associated with such ore bodies, however, will be quite high. Overburden or other lesser conductors will produce relatively weak magnetic fields that decay rapidly leaving, by late time, only fields from the more conductive targets. For such circumstances, a three component (3D) fluxgate magnetometer sensor is available.