Electromagnetic power and communication link particularly adapted for drill collar mounted sensor systems

A method for interrogating a data storage device disposed in a mandrel, the mandrel disposed in a drill collar, comprising:

• sending an interrogation command signal through an external device clamped onto an exterior wall of the drill collar;
• electromagnetically transferring the signal between the external clamp-on device and an exterior wall of the drill collar;
• electromagnetically transferring the signal between an interior wall of the drill collar and an exterior wall of the mandrel;
• coupling the signal to a processor in the mandrel to cause the processor to export data in the storage device;
• electromagnetically transferring the data between the exterior wall of the mandrel and the interior wall of the collar;
• and
• electromagnetically transferring the data between the exterior wall of the collar and the external clamp-on device.

A method for operating a sensor, comprising:

• electromagnetically transferring electrical power from circuits in a mandrel disposed inside a drill collar between an exterior wall of the mandrel and an interior wall of the collar;
• conducting the electrical power to the sensor to operate the sensor;
• conducting signals generated by the sensor to a location proximate the interior wall of the collar;
• electromagnetically transferring the sensor signals between the interior wall of the collar and the exterior wall of the mandrel;
• and
• conducting the sensor signals to the circuits in the mandrel.

A sensor system, comprising:

• at least one sensor disposed in a wall of a drill collar;
• a signal processing and power conditioning circuit disposed in the wall of the drill collar and operatively coupled to the at least one sensor, the signal processing and power conditioning circuit adapted to provide operating power extracted from an electromagnetic link, the signal processing and power conditioning circuit adapted to digitize, locally store and transmit signals generated by the at least one sensor;
• and
• a first electromagnetic transducer disposed in the drill collar and adapted to transfer power and signals to a second electromagnetic transducer disposed in a mandrel when the mandrel is disposed at a selected position inside the drill collar, the second transducer operatively coupled to signal processing circuits in the mandrel.