Acoustic method and apparatus for measuring thickness of a coating layer on a substrate
First Claim
1. Method of determining the thickness of a coating layer on a substrate, comprising the steps oftransmitting acoustic energy through said substrate and coating layer transversely to said coating layer,sweeping the frequency of said transmitted acoustic energy over a predetermined range of frequencies,receiving reflected acoustic energy from the boundaries between said substrate and coating layer and between said coating layer and beyond, anddetermining the frequencies at which minimum acoustic energy transmissions occur whereby said coating layer thickness is determined.
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Accused Products
Abstract
A method or system for measuring thickness of a coating layer on a substrate. It employs acoustic energy and involves transmitting a sweep of frequencies covering a predetermined range through the substrate and its coating. The energies reflected back by the substrate and coating are determined as a function of the frequencies in said range, and the transmission pattern provides a basis for determining the coating thickness.
67 Citations
13 Claims
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1. Method of determining the thickness of a coating layer on a substrate, comprising the steps of
transmitting acoustic energy through said substrate and coating layer transversely to said coating layer, sweeping the frequency of said transmitted acoustic energy over a predetermined range of frequencies, receiving reflected acoustic energy from the boundaries between said substrate and coating layer and between said coating layer and beyond, and determining the frequencies at which minimum acoustic energy transmissions occur whereby said coating layer thickness is determined.
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2. System for determining thickness of a layer of coating on a substrate, comprising in combination
means for transmitting a predetermined range of frequencies of acoustic energy through said substrate and coating, means for receiving reflections of said transmitted range of acoustic energy, means for determining the amplitude of said reflections over said predetermined range of frequencies whereby said coating thickness is determined from the transmissibility pattern over said frequency range.
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7. System for determining thickness of a layer of coating on a substrate, comprising in combination
a first piezeoelectric transducer for transmitting a range of frequencies of 20-120 KHz of acoustic energy through said substrate and coating, a voltage controlled variable frequency oscillator and first circuit means for introducing a voltage to sweep said oscillator over said range of frequencies and for connecting said oscillator to energize said first transducer, a second piezoelectric transducer for receiving reflections of said transmitted range of acoustic energy and for generating signals in accordance therewith, and second circuit means comprising a microprocessor for determining the amplitude of said reflection signals whereby said coating thickness is determined from the transmissibility pattern over said frequency range.
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8. Method of measuring thickness of a concrete layer on a subsea pipeline, wherein said pipeline includes a pipe coated with a layer of concrete, comprising
transmitting a frequency sweep of acoustic energy through a wall of said coated pipe, receiving reflected acoustic energy returned over said frequency sweep, and determining the acoustic transmissibility through said wall of coated pipe over said frequency sweep whereby said concrete layer thickness is determined.
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10. System for measuring thickness of a coating on a pipe, comprising in combination
means for transmitting a frequency sweep of acoustic energy through a wall of said pipe, means for receiving reflected energy from said transmitted sweep, and means for determining the transmissibility of said acoustic energy over said frequency sweep whereby said coating thickness is determined.
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13. System for measuring thickness of a concrete coating on a subsea pipeline, comprising in combination
a first piezoelectric transducer adapted for transmitting a sweep of acoustic energy over a range of 20-120 KHz through the wall of said pipe and concrete coating into said sea, a second piezoelectric transducer adapted for receiving said sweep of acoustic energy reflected from the boundaries of said pipe wall and concrete coating, first circuit means for energizing said first transducer, second circuit means for amplifying signals generated by said second transducer, a variable frequency oscillator for generating a sweep of frequencies over said range of 20-120 KHz, third circuit means for connecting the output of said oscillator to said first transducer, means for measuring the amplitudes of said transmitted and received acoustic energies, a microprocessor; -
fourth circuit means for connecting said microprocessor to control said oscillator, and fifth circuit means for connecting said amplitude measuring means to said microprocessor whereby the ratio of said measured amplitudes over said range of frequencies is determined and the thickness of said concrete coating measured.
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Specification