US 5,633,583 AGranted

Magnetic telescope with enhanced noise suppression

AssigneeGas Research Institute

InventorWalter N. Podney

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Abstract

A magnetic telescope utilized to detect flaws in underground articles such as underground piping, implements multiple stages in the form of geometric and electronic configurations to enhance noise suppression. The geometric configuration includes a differential configuration of two pair of source coils which generate the magnetic flux, and gradiometers which pick-up the magnetic flux. A superconducting quantum interference device (SQUID) is utilized to detect the magnetic flux. The electronic configuration includes circuitry to adjust the current in the source coil pairs to minimize the signal seen by the SQUID when no underground article is present. The electronic configuration also includes feedback circuitry to feed back magnetic flux to the SQUID based on the signal detected by the SQUID. Combining the geometric and electronic configurations provides enhanced noise suppression so that the SQUID is capable of detecting smaller flaws in the underground piping for the same amount of source magnetic flux.

Claims11

Dependent claims

A magnetic telescope having enhanced noise suppression, the magnetic telescope utilized for detecting ferrous metal discontinuities through an overburden, the magnetic telescope comprising:

means for transmitting a first signal through the overburden to the discontinuity, said means for transmitting having at least two pairs of spaced source coils;
said at least two source coil pairs each having an outer coil which substantially encompasses an inner coil, said outer and inner coils having substantially the same axis;
means, substantially located within said means for transmitting said first signal, for receiving a second signal induced by the first signal, but having noise thereon, said means for receiving being substantially located within said inner coils near the axis, said means for receiving including at least two gradiometers, each of said gradiometers having a coplanar pair of oppositely wound semicircles with a substantially common diameter;
and
means for electronically suppressing said noise in the second signal, said noise suppressing means including means for adjusting a characteristic of said second signal to suppress noise in the second signal, said means for adjusting a characteristic of said second signal having means for adjusting said second signal by using a feedback current in said noise suppressing means and related to said noise of said second signal, said noise suppressing means further having circuitry for substantially cancelling said first signal near the axis.

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Dependencies are inferred from the claim text.