US3742357A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Noncontact electric apparatus for magnetically measuring strains
Assignee: Toshiba Corp
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Filing: 1971-12-28
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Granted: 1973-06-26
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Expires: 1991-12-28
Abstract
Abstract The apparatus of this invention includes a sensor unit having its substantially U-shaped core wound with primary and secondary coils and the ends of both legs of the core bridged by a nonmagnetic material wound with a leakage magnetic flux pickup coil. The sensor unit is disposed on one side of a magnetic or eddy current conductive sample with two opposite sides sufficiently close thereto for magnetic linkage. The primary coil of the sensor unit is magnetized by an A.C. source for controlling the electromotive force to be induced in the sample by magnetic fluxes passing through the sample from the sensor unit so as to keep it constant. Outputs from both secondary coil and leakage magnetic flux pickup coil of the sensor unit are supplied to a differential amplifier for producing output voltage corresponding to the varying magnetic flux passing through the sample by a difference between the two outputs. Output from the leakage magnetic flux pickup coil of the sensor unit and output proportionate to the voltage induced across the primary excited coil are impressed on a differential amplifier for producing output proportionate to magnetization current flowing through the sample by a difference between both outputs. Outputs from both differential amplifiers are supplied to a sampling circuit for detecting the varying coercive force conducted through the sample. Thus the apparatus is designed to detect by output from the sampling circuit variations in the mechanical stresses applied to the sample in the direction of the magnetic axis of the sensor unit, thereby measuring the amounts of strains occurring across the sample.
Inventors
- 👤 M Kubo
- 👤 K Asano
- 👤 M Obama
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 15:11
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/72; G01L; G01L1/00; G01L1/12; G01L1/125; G01L1/127; G01L5/00; G01L5/04; G01L5/045
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
286 words
A noncontact type electric apparatus for magnetically measuring strains in a magnetic or eddy current conductive sample with two opposite sides comprising: at least one sensor unit which includes a magnetic core provided with at least two legs and wound with primary and secondary coils and a leakage magnetic flux pickup coil wound around a nonmagnetic member bridging the open ends of the core legs to pick up that leakage component of a magnetic flux generated from said sensor unit which passes through an air gap between the sample and said sensor unit; means for locating said sensor unit on one side of the sample sufficiently close thereto for magnetic linkage to produce a magnetic flux which extends therethrough in a first direction; and a first differential amplifier having its two inputs supplied with outputs from said secondary coil and the leakage magnetic flux pickup coil of said sensor unit; and a second differential amplifier having its two inputs supplied with a rectified output from said first differential amplifier and an output from a preset D.C. reference voltage source; an A.C. source of variable amplitude connected between the output of said second differential amplifier and the primary coil of said sensor unit to supply excitation current to said primary coil; a third differential amplifier having its two inputs supplied with an output voltage from a voltage source for generating a voltage proportionate to the excitation current passing through said primary coil of said sensor unit and also with an output voltage from said leakage magnetic flux pickup coil thereof; and a sampling circuit for sampling output signals from said third differential amplifier under control of sampling signals consisting of output signals from said first differential amplifier.
Claim 2
Dependent Claim
286 words
A noncontact type electric apparatus for magnetically measuring strains in a magnetic or eddy current conductive sample with two opposite sides comprising: at least one sensor unit which includes a magnetic core provided with at least two legs and wound with primary and secondary coils and a leakage magnetic flux pickup coil wound around a nonmagnetic member bridging the open ends of the core legs to pick up that leakage component of a magnetic flux generated from said sensor unit which passes through an air gap between the sample and said sensor unit; means for locating said sensor unit on one side of the sample sufficiently close thereto for magnetic linkage to produce a magnetic flux which extends therethrough in a first direction; and a first differential amplifier having its two inputs supplied with outputs from said secondary coil and the leakage magnetic flux pickup coil of said sensor unit; and a second differential amplifier having its two inputs supplied with a rectified output from said first differential amplifier and an output from a preset D.C. reference voltage source; an A.C. source of variable amplitude connected between the output of said second differential amplifier and the primary coil of said sensor unit to supply excitation current to said primary coil; a third differential amplifier having its two inputs supplied with an output voltage from a voltage source for generating a voltage proportionate to the excitation current passing through said primary coil of said sensor unit and also with an output voltage from said leakage magnetic flux pickup coil thereof; and a sampling circuit for sampling output signals from said third differential amplifier under control of sampling signals consisting of output signals from said first differential amplifier.
Claim 3
Dependent Claim
51 words
An apparatus according to claim 1, wherein at least one divider is provided on the output side of said sampling circuit for dividing the output voltage from said sampling circuit by a D.C. voltage corresponding to an output from said sampling circuit when the sample is not under any mechanical stress.
Claim 4
Dependent Claim
44 words
An apparatus according to claim 1, wherein there are two sensor units, one being arranged to generate a magnetic flux in the first direction and the other being arranged to generate a magnetic flux in a second direction substantially transverse to said first direction.
Claim 5
Dependent Claim
74 words
An apparatus according to claim 1, wherein a nonlinear circuit is connected between the output terminal of the leakage magnetic flux pickup coil of said sensor unit and said first differential amplifier to enable both input voltages of said first differential amplifier to present the same variation characteristics with respect to variations in a mechanical stress applied to the sample as well as in the air gap between the sample and said sensor unit.
Claim 6
Dependent Claim
35 words
An apparatus according to claim 1, wherein said A.C. source of variable amplitude comprises a multiplier for multiplying an output from said second differential amplifier with an output from an A.C. source of constant amplitude.
Claim 7
Dependent Claim
96 words
An apparatus according to claim 1, wherein said sampling circuit comprises a sampling pulse generating circuit including a comparator impressed with an output from said first differential amplifier, a differentiation circuit supplied with an output from said comparator, and a one-shot multivibrator connected to an output from said differentiation circuit; a gate circuit for gating an output from said third differential amplifier by sampling pulses generated by said sampling pulse generating circuit; and an operational amplifier having a capacitor connected between the input and output terminals thereof and connected to an output from said gate circuit.
Claim 8
Dependent Claim
78 words
An apparatus according to claim 2, wherein there are two sensor units and signal processing circuits, one being arranged to generate a magnetic flux in the first direction and the other being arranged to generate magnetic flux in a second direction substantially transverse to said first direction, a second divider being provided with said second sensor unit, and wherein there is further provided a fourth differential amplifier having its two inputs supplied with both outputs from said dividers.
Claim 9
Dependent Claim
41 words
An apparatus according to claim 1 wherein said core of the sensor unit has a substantially U-shaped and the leakage magnetic flux pickup coil is wound about a nonmagnetic material bridged across the ends of the two legs of said core.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-06-25 | 1976-12-25 | 1977-06-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-06-25 | 1980-12-25 | 1981-06-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-06-25 | 1984-12-25 | 1985-06-26 | $7700.00 | Window Closed / Lapsed |