Patent ID: 7703507

Claim:
An apparatus comprising: a wellbore commencing at a surface and confining a well casing; a depth determination device in sliding communication with said well casing, said depth determination device providing a module attachment portion configured for direct attachment and detachment of a down hole tool to said depth determination device, and a hermetically sealed electronics compartment; a processor secured within said hermetically sealed electronics compartment; an electronic location sensing system integrated within said hermetically sealed electronics compartment, and communicating with said processor, said electronic location sensing system interacting exclusively with features of said well casing to electronically determine a location of said depth determination device within said well casing, in which said depth determination device is physically connected with said surface via at most a fluidic material, and further in which said electronically determined location of said depth determination device within said well casing is data used by said processor and wherein said electronically determined location of said depth determination device within said well casing is available at said surface only upon retrieval of said depth determination device from said well casing to said surface; and a hermetically sealed communication port provided by said module attachment portion accommodating a communication of operational commands from said processor to said downhole tool when said downhole tool is attached to said module attachment portion.