The Induction Sonde works by transmitting a high frequency current through a coil and measures the induced electromagnetic field 180 degrees out of phase at the receiver.

The Dual Induction Sonde has two receiver coils instead of one for a single induction.
This extra coil allows two points to be plotted instead of one which helps more accurately determine formation features.

The Dual Induction Sonde has two measurement coils which are labelled DEEP and
SHALLOW the DEEP channel is the lowest measurement in the borehole.

Units are written mmho which stands for milli-mho’s, a measurement of Conductivity. 1 milli-mho is simply 0.001mho and 1mho is 1/ohmmeter therefore 1k ohm-metre (resistance) is equal to 1mmho (conductivity). The conductance may also be quoted in units of Siemens or mS/m (milli Siemens per metre), where 1 Siemen equals 1 mho.

In borehole logging, the usual units are Ohm-metre for resistivity and mmho for
conductivity. The relationship is

Resistivity (Ohm-metres) = 1000 / Conductivity (mmho) 

Depth Offset    Mnemonic Unit Range Resolution
0.62m    ILD MMHO 2-2,000 mmho 0. 1mmho
0.77m      ILS MMHO 2-2,000 mmho 0. 1mmho