Duel Guarded Resistivity Sonde The DLL3 sonde measures formation resistivity using a set of electrodes designed to allow for both a Deep and a Shallow investigation capability. The DLL3 sonde requires the use of an isolating bridle. The DLL3 is a superior alternative to the traditional Normal Resistivity sonde.

It offers the advantage of deeper penetration (particularly in conductive mud) and bettervertical resolution. The Dual Guard Sonde works on a principle that is similar to the standard nominal resistivity sonde. A measure current I0 is sent from a central electrode A0 to a remote return (the cable armour beyond the isolating bridle). This current is focussed by means of a Bucking current Ib which flows from the Guard Electrodes pairs which are connected together. The potential of the Guard Electrode pairs is held equal to the potential of the measure electrode A0.

This turns the sonde into an equipotential surface forcing current I0 to flow out perpendicularly as a disc with an initial thickness equal to the measure electrode A0. Sonde Dimensions: Sonde length 2.27 metres Sonde diameter 38 millimetres Sonde weight 7.5 Kg Sonde Output: Ohm/m