Patent ID: 6847207

Claim:
An instrument pig for determining the characteristics of a ferromagnetic pipeline through which it passes, comprising: a pig body coaxially supported and moving within the pipeline in response to fluid flow; first and second coaxial circumferential, spaced apart magnets of opposed polarities supported to said pig body and providing substantially complete magnetic saturation of an area of the pipeline between the magnets; first instruments supported by the pig body between said magnets and arranged to generate signals that are responsive to flux leakage servicing to provide first information as to anomalies in the pipeline interior and/or exterior surface; second instruments employing pulsed and sensing coil pairs supported by the pig body between said magnets and arranged to generate signals that are responsive to eddy currents induced in the pipeline interior surface servicing to provide second information as to anomalies in the pipeline interior surface; signal processing circuitry combining said first and second signals to indicate the magnitude and interior or exterior location of the pipeline anomalies; and wherein said second instruments are energized only in response to signals generated by said signal processing circuitry.