Estell R Lopez

US Patent:

6798197, Sep 28, 2004

Filed:

Oct 8, 2002

Appl. No.:

10/266845

Inventors:

Estell Lopez - Issaquah WA

Assignee:

Zetec, Inc. - Issaquah WA

International Classification:

G01N 2782

US Classification:

324238, 324242

Abstract:

A method and apparatus of a digital synthesizer generating an electrical digital carrier that is converted to analog and driven a probe coil to generate an electromagnetic wave propagated into a test material proximate the probe coil. A return electromagnetic wave generated by eddy currents in the material includes signatures of material defects modulated on the return carrier electromagnetic wave. The return wave is detected by one or more probe coils and amplified. A second amplifier is applied selectively amplifying the signal in segments such that each segment exploits the input range of the analog to digital converter. The signal is then converted from an analog signal to a digital signal and then digitally mixed with digital sine and cosine functions also generated by the digital synthesizer to yield sum and difference values. A gain scaling stage then trims the signal to overcome circuit imprecision such that the amplification in each respective segment is a power of two. A low pass filter then removes all but the difference values, leaving only the small eddy current signal.

US Patent:

6809671, Oct 26, 2004

Filed:

Mar 26, 2004

Appl. No.:

10/809964

Inventors:

Estell Lopez - Issaquah WA

Assignee:

Zetec, Inc. - Issaquah WA

International Classification:

H03M 162

US Classification:

341139, 324234

Abstract:

A digital synthesizer generates an electrical digital carrier that is converted to analog and driven a probe coil to generate an electromagnetic wave propagated into a test material proximate the probe coil. A return electromagnetic wave generated by eddy currents in the material includes signatures of material defects modulated on the return carrier electromagnetic wave. The return wave is detected by one or more probe coils and amplified. A second amplifier is applied selectively amplifying the signal in segments such that each segment exploits the input range of the analog to digital converter. The signal is then converted from an analog signal to a digital signal and then digitally mixed with digital sine and cosine functions also generated by the digital synthesizer to yield sum and difference values. A gain scaling stage then trims the signal to overcome circuit imprecision such that the amplification in each respective segment is a power of two. A low pass filter then removes all but the difference values, leaving only the small eddy current signal.

US Patent:

20030227288, Dec 11, 2003

Filed:

Jun 11, 2002

Appl. No.:

10/167166

Inventors:

Estell Lopez - Issaquah WA, US

International Classification:

G01R033/04

US Classification:

324/255000

Abstract:

A digital synthesizer generates an electrical digital carrier that drives probe coil to generate an electromagnetic wave propagated into a test material proximate the probe coil. A return electromagnetic wave generated by eddy currents in the material includes signatures of material defects modulated on the return carrier electromagnetic wave. The return wave is detected by one or more probe coils, amplified, converted from an analog signal to a digital signal and then digitally mixed with digital sine and cosine functions also generated by the digital synthesizer to yield sum and difference values, mathematically expressing various eddy current signals received by the probe in a complete set of orthogonal functions. A low pass filter then removes all but the difference values. A direct current reference component is subtracted from the mixed digital signal, which translates the signal to center about a zero axis for ease of display and analysis.