Patent ID: 6968727

Claim:
A method of calibrating long range guided wave signals from a pipe under test consisting of the following steps: first generating near a test area a first guided wave in said pipe under test by a transmitter probe and guided-wave instrumentation; first propagating said first guided wave along said pipe under test; first detecting in said pipe under test by a receiver probe and said guided-wave instrumentation first reflected signals from defects, if any; placing a first reference reflector on said pipe under test near said test area, but outside a dead zone for guided waves; generating a second guided wave in said pipe under test by said transmitter probe and said guided-wave instrumentation; second propagating said second guided wave along said pipe under test; second detecting in said pipe under test by said receiver probe and said guided-wave instrumentation second reflected signals from said first reference reflector and defect signals from said defects, if any; correcting for attenuation in said reflected signals and said defect signals; and calculating size of said defects using said first reflected signals and said second reflected signals.