US5144231A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Eddy current detector for detecting an object with offset compensation
Assignee: Aisin Corp
•
Filing: 1991-04-23
•
Granted: 1992-09-01
•
Expires: 2011-04-23
Abstract
Abstract An RF oscillator induces eddy currents to be measured in an object. An eddy current probe senses alterations, such as teeth on a disc, for example, in the object which are represented as eddy current signals sensed by an eddy current probe. The present invention separates alteration current signals from offset currents in the eddy current signal to aid in discriminating levels in the alteration current signals. The alteration currents are separated from the offset currents by AC coupling with a high pass filter or separated by a microprocessor as part of a data processing detection routine.
Inventors
- 👤 Jeffrey Tenenbaum
- 👤 Peter A. Hochstein
- 👤 Teiji Okuyama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:30
CPC Classifications
G; G01; G01P; G01P3/00; G01P3/42; G01P3/44; G01P3/49; H; H03; H03B; H03B5/00; H03B5/08; H03B5/12; H03B5/1203; H03B5/1228; H03B2200/00; H03B2200/0002; H03B2200/0008
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
189 words
An eddy current detector capable of detecting a condition of movement of an object having surface variations, said detector comprising: a sensing probe adapted to be aligned to said object for inducing eddy currents in said object and sensing said eddy currents and providing a corresponding sensing signal; an RF oscillator coupled to said sensing probe for providing current for inducing said eddy currents in said object; demodulating means coupled to said sensing probe for demodulating said sensing signal; separating means for separating out any components of said sensing signal caused by said surface variations; said separating means including: a) a high pass filter coupled to said demodulating means for filtering an output of said demodulating means; b) an amplifier coupled to said high pass filter for amplifying an output of said high pass filter; and c) a high frequency roll-off capacitor coupled to said amplifier and located in a feedback loop of said amplifier for attenuating any residual RF components in said sensing signal; and discriminating means coupled to said separating means for discriminating the level of said sensing signal to indicate the present of said surface variations.
Claim 2
Dependent Claim
189 words
An eddy current detector capable of detecting a condition of movement of an object having surface variations, said detector comprising: a sensing probe adapted to be aligned to said object for inducing eddy currents in said object and sensing said eddy currents and providing a corresponding sensing signal; an RF oscillator coupled to said sensing probe for providing current for inducing said eddy currents in said object; demodulating means coupled to said sensing probe for demodulating said sensing signal; separating means for separating out any components of said sensing signal caused by said surface variations; said separating means including: a) a high pass filter coupled to said demodulating means for filtering an output of said demodulating means; b) an amplifier coupled to said high pass filter for amplifying an output of said high pass filter; and c) a high frequency roll-off capacitor coupled to said amplifier and located in a feedback loop of said amplifier for attenuating any residual RF components in said sensing signal; and discriminating means coupled to said separating means for discriminating the level of said sensing signal to indicate the present of said surface variations.
Claim 3
Dependent Claim
22 words
The eddy current detector of claim 1, wherein said high pass filter has a roll-off near the frequency of sensed eddy currents.
Claim 4
Dependent Claim
37 words
The eddy current detector of claim 1 further comprising switch means for selecting a desired data rate of sensing said eddy currents per unit time, said selection being dependent upon said condition of movement of said object.
Claim 5
Dependent Claim
213 words
An eddy current detector capable of inducing an eddy current signal in a region of a conductor and detecting surface variations of said conductor over time by detecting changes of said eddy current signal in said region of the conductor, comprising: oscillator means for providing RF signals to induce in said conductor; probe means coupled to said oscillator means for inducing said RF signals in said conductor to produce eddy currents; sensing means coupled to said probe means for sensing said eddy currents induced in said conductor and providing a corresponding sensing signal; separating means coupled to said sensing means for separating out any high frequency components of said sensing signal caused by said surface variations from lower frequency components sensed by the sensing means; said separating means including: a) a high pass filter coupled to said demodulating means for filtering an output of said demodulating means; b) an amplifier coupled to said high pass filter for amplifying an output of said high pass filter; and c) a high frequency roll-off capacitor coupled to said amplifier and located in a feedback loop of said amplifier for attenuating any residual RF components in said sensing signal; and discriminating means for discriminating levels in said sensing signal to indicate the occurrence of said surface variations.
Claim 6
Dependent Claim
213 words
An eddy current detector capable of inducing an eddy current signal in a region of a conductor and detecting surface variations of said conductor over time by detecting changes of said eddy current signal in said region of the conductor, comprising: oscillator means for providing RF signals to induce in said conductor; probe means coupled to said oscillator means for inducing said RF signals in said conductor to produce eddy currents; sensing means coupled to said probe means for sensing said eddy currents induced in said conductor and providing a corresponding sensing signal; separating means coupled to said sensing means for separating out any high frequency components of said sensing signal caused by said surface variations from lower frequency components sensed by the sensing means; said separating means including: a) a high pass filter coupled to said demodulating means for filtering an output of said demodulating means; b) an amplifier coupled to said high pass filter for amplifying an output of said high pass filter; and c) a high frequency roll-off capacitor coupled to said amplifier and located in a feedback loop of said amplifier for attenuating any residual RF components in said sensing signal; and discriminating means for discriminating levels in said sensing signal to indicate the occurrence of said surface variations.
Claim 7
Dependent Claim
22 words
The eddy current detector of claim 4, wherein said high pass filter has a roll-off near the frequency of sensed eddy currents.
Claim 8
Dependent Claim
25 words
The eddy current detector of claim 4 further comprising switch means for selecting a desired data rate of sensing said eddy currents per unit time.
References Cited (Backward Citations)
US3394303A
Cited
US3611120A
Cited
US3715659A
Cited
US3776606A
Cited
US3934200A
Cited
US4263551A
Cited
US4142153A
Cited
US4473799A
Cited
US4331920A
Cited
JPS55121110A
Cited
US4341996A
Cited
GB2107470A
Cited
US4465976A
Cited
US4556846A
Cited
US4543527A
Cited
US4574237A
Cited
US4678992A
Cited
US4647853A
Cited
US4605889A
Cited
US4799011A
Cited
US4761609A
Cited
US4875007A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-09-01 | 1996-03-02 | 1996-09-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-09-01 | 2000-03-02 | 2000-09-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-09-01 | 2004-03-02 | 2004-09-01 | $7700.00 | Window Closed / Lapsed |