Abstract: The present invention relates to a SQUID device for magnetic field measurement. The device is comprised of a body of superconducting material. First and second holes are located therein. A slot is provided joining the first and second holes. A contact unit is provided which is located in the slot thereby forming a weak link across the slot. The dimensions of the first and second holes produce first and second inductances respectively. These inductances have unequal magnitude.

Abstract: A device and method producing a compensated gradiometer signal from an uncompensated gradiometer signal having at least one unwanted term which varies as a function of magnetic field. The device is comprised of a sensing unit for sensing the magnetic field. A generator is provided for producing a first vector signal which is representative of the magnetic field. A function generator is provided for producing a second vector signal which represents a component of one of the at least one unwanted term. A mixer is connected to the generator and the function generator for producing a vector output signal which is equal to the one of the at least one unwanted term. Finally, a subtractor unit is provided which is connected to the mixing means for subtracting the output vector signal from the uncompensated gradiometer signal to thereby produce the compensated gradiometer signal.

Abstract: The present invention relates to a system for the nondestructive testing of the thickness of boiler tubes. The system comprises a probe assembly which includes a mounting unit for mounting the assembly in a mud or water drum of a boiler at the location of a boiler tube to be tested. The probe assembly is comprised of an ultrasonic transducer for transmitting and receiving ultrasonic signals. The probe assembly further includes a motor drive connected to the transducer. A control unit is provided which includes a motor control portion connected to the motor drive to selectively position the transducer at a plurality of locations in the boiler tube to be tested. The control unit also includes an ultrasonic drive for producing an ultrasonic pulse for driving said transducer means. A water control is connected to the control unit, a source of water supply, a drain, and the probe assembly.