Lift off compensation of eddy current crack detection system by controlling damping resistance of oscillator
Patent 4609870 Issued on September 2, 1986. Estimated Expiration Date: 
September 13, 2004. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
September 13, 2004. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3396193 Dual channel apparatus for detecting surface defects in elongate metallic members with liftoff compensation Method and apparatus for testing a metallic workpiece by inducing eddy currents therein Patent #: 4387338 InventorsAssigneeApplicationNo. 06/650667 filed on 09/13/1984US Classes:324/225, With compensation for test variable324/237, Material flaw testing331/109, Amplitude stabilization and control331/65WITH DEVICE RESPONSIVE TO EXTERNAL PHYSICAL CONDITIONExaminersPrimary: Karlsen, Ernest F.Assistant: Snow, Walter E. Attorney, Agent or FirmInternational ClassG01N 27/90 (20060101)Foreign Application Priority Data1981-03-27 GBAbstractAn eddy current crack detection system has an inductive probe coil forming part of an oscillatory circuit. The coil voltage is fed to a measuring device a change in amplitude of the coil voltage being used as an indication of a crack. In order to compensate for lift-off in the amplitude of the coil voltage, a control signal is generated related to the magnitude of lift-off, and controls the value of a variable damping resistor in the oscillatory circuit. | |
