US3815020A
Expired / Lapsed
US
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Capacitance/inductance distance measurement device
Assignee: LABOR D ELECTRONIQUE ET D AUTOMATIQUE DAUPHINOIS LEAD FR
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Filing: 1972-11-24
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Granted: 1974-06-04
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Expires: 1992-11-24
Abstract
Abstract A non-contact relative range measuring device for gauging the distance between a remote sensing device and an object. A remote sensing element and a reference sensing element are alternately connected to a source of signals capable of creating an electromagnetic field and a reference field, respectively. The two fields, when alternately created, also modify the signal from the signal source. The modified signal is applied to a measuring device capable of developing a measure of the difference in the modified signal due to the electromagnetic field and the reference field.
Inventors
- 👤 F Mayer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 20:21
CPC Classifications
G; G01; G01B; G01B7/00; G01B7/02; G01B7/06; G01B7/08; G01B7/30; G01B7/31
Claims Analysis
Total Claims: 33
Claim 1
Independent Claim
140 words
A non-contact relative range measurement device in which an electromagnetic field is established between a workpiece and at least one remote sensing element separated therefrom at a distance To be gauged, said electromagnetic field changing as the unknown distance changes, comprising, a. a signal source means for supplying a signal to establish said electromagnetic field, b. at least one reference sensor associated with said remote sensing element and adapted to provide an adjustable reference field, c. switching device means for alternately connecting said signal source to said remote and reference sensing elements to cause said signal to be modified alternately by said electromagnetic and reference fields, d. measuring device means, connected to receive said signal after being modified, for measuring the difference between the two periodically alternating components of said modified signal caused by said electromagnetic and reference fields, respectively.
Claim 2
Dependent Claim
140 words
A non-contact relative range measurement device in which an electromagnetic field is established between a workpiece and at least one remote sensing element separated therefrom at a distance To be gauged, said electromagnetic field changing as the unknown distance changes, comprising, a. a signal source means for supplying a signal to establish said electromagnetic field, b. at least one reference sensor associated with said remote sensing element and adapted to provide an adjustable reference field, c. switching device means for alternately connecting said signal source to said remote and reference sensing elements to cause said signal to be modified alternately by said electromagnetic and reference fields, d. measuring device means, connected to receive said signal after being modified, for measuring the difference between the two periodically alternating components of said modified signal caused by said electromagnetic and reference fields, respectively.
Claim 3
Dependent Claim
16 words
A device according to claim 1 wherein said signal source means is a variable frequency oscillator.
Claim 4
Dependent Claim
27 words
A device according to claim 1 wherein the frequency of the signal for establishing the field is substantially greater than the switching frequency of said switching device.
Claim 5
Dependent Claim
14 words
A device according to claim 1 wherein said switching device is a mechanical switch.
Claim 6
Dependent Claim
36 words
A device according to claim 1 wherein the signal for establishing a field has a frequency of 10 MHz and that the switching device is activated at a switching frequency in the order of 1 Hz.
Claim 7
Dependent Claim
51 words
A device according to claim 1 characterized in that, when a relatively low frequency of the oscillator (19), is used, a frequency stable pilot frequency generator (24), is provided, said pilot frequency generator being freed during a period of half period of the oscillator (19) and acting on the counter (23).
Claim 8
Dependent Claim
64 words
A device according to claim 1 further comprising a compensating device for automatically compensating the difference between the version of the signal from the signal source modified by said remote sensing element and the version of the signal from the signal source modified by said reference sensor; the measure required to achieve compensation being used as a criterion for the distance to be gauged.
Claim 9
Dependent Claim
40 words
A device according to claim 33 wherein said remote sensing element is a capacitive remote sensing element, said reference sensor is a capacitive reference sensor and an inductance is connected between said signal source means and said switching device means.
Claim 10
Dependent Claim
22 words
A device according to claim 8, wherein said remote sensing element and said reference sensor are in the form of flat plates.
Claim 11
Dependent Claim
14 words
A device according to claim 8, wherein said reference sensor is a variable condenser.
Claim 12
Dependent Claim
48 words
A device according to claim 8 further comprising a first inductance connected in between said switching device means and said remote sensing element and a second inductance connected in between said switching device means and said reference sensor a predetermined ratio existing between said first and second inductances.
Claim 13
Dependent Claim
16 words
A device according to claim 11, characterized in that, said ratio is a multiple of ten.
Claim 14
Dependent Claim
23 words
A device according to claim 11, characterized in that, said ratio between the first and second inductance may be converted into binary stages.
Claim 15
Dependent Claim
74 words
A device as claimed in claim 11, further comprising: a. a plurality of additional different reference sensors, b. a like plurality of decoupling diodes for connecting said reference sensors, respectively, to said switching device means, and c. automatic compensating device means connected to said measuring device means and to said decoupling diodes for selecting the one of said reference sensors from said plurality of reference sensors which corresponds most closely to said remote sensor.
Claim 16
Dependent Claim
48 words
A device according to claim 1 wherein said measuring device means comprises a means for detecting the difference, during a switching period, between the number of periods of said signal modified by said electromagnetic field and the number of periods of said signal modified by said reference field.
Claim 17
Dependent Claim
59 words
A device according to claim 15, wheRein said detecting means comprises a reversing counter adapted to count up during the switching in period of the remote sensing element and to count down during the switching in period of the reference sensor and means for reversing the direction in which said counter counts in switching rythm with said biasing means.
Claim 18
Dependent Claim
75 words
A device according to claim 1 wherein said remote sensing element and said reference sensor are arranged in a hole at a fixed distance from each other with their surfaces substantially parallel to the inner wall of the hole, the assembly consisting of the remote sensing element and the reference sensor being symmetrical and adapted to be centered in respect of the hole, such that the remote sensing element and the reference sensor are interchangeable.
Claim 19
Dependent Claim
53 words
A device according to claim 17, wherein a plurality of sensor pairs consisting of a remote sensing element and a reference sensor are arranged in plane perpendicular to the axis of the hole, and that the signal for establishing a field is applied in a cyclical manner to the individual pairs of sensors.
Claim 20
Dependent Claim
23 words
A device according to claim 18, wherein three pairs of sensors which are staggered in respect of each other by 120*, are provided.
Claim 21
Dependent Claim
92 words
A device according to claim 1 wherein said switching device means comprises, a. a first diode for connecting said signal from said signal source to said remote sensor when said first diode is biased in a conducting direction, b. a second diode for connecting said signal from said signal source to said reference sensor when said second diode is biased in a conducting direction, and c. means for alternately biasing said first and scond diodes in said conducting direction whereby the first diode is conducting when the second is blocked and vice-versa.
Claim 22
Dependent Claim
19 words
A device according to claim 20 wherein said first and second diodes are connected in opposition to one another.
Claim 23
Dependent Claim
49 words
A device according to claim 21, wherein said means for biasing comprises a square-wave generator connected to said two switching diodes, the positive square-wave pulses putting one of the switching diodes into the conductive state and the negative square-wave pulses putting the other switching diode into said conducting state.
Claim 24
Dependent Claim
75 words
A device according to claim 20 wherein first switching diode is connected to said biasing means via a first choke coil and said second switching diode is connected to said biasing means via a second choke coil, and wherein the inductance of said choke coils is selected to provide a low impedance at the switching frequency of the switching device and a very high, substantially blocking, impedance to the electrical signal for establishing the field.
Claim 25
Dependent Claim
39 words
A device according to claim 23 wherein each said switching diode has an impedance in the forward direction of approximately 3 ohm at maximum and has a capacitance in the blocking direction (ca. 30 volts) of approximately 0.1 picofarad.
Claim 26
Dependent Claim
27 words
A device according to claim 24 wherein the transition of the diodes from the conductive state to the blocked state takes place in a relatively short time.
Claim 27
Dependent Claim
36 words
A device according to claim 25 wherein the bias voltages of the diodes may be regulated in such a manner that the dissymmetry of their blocking capacitances may be controlled by an adjustable bias voltage dissymmetry.
Claim 28
Dependent Claim
126 words
A device according to claim 20, wherein said switching diodes are each switched in response to a square-wave voltage having an adjustable pulse mark-to-space ratio from a square-wave generator; and wherein said measuring device comprises a parallel circuit having connected in series in each of its branches, a gate, a frequency discriminator and a filter, said gates being controlled by said square-wave generator in such a manner that the said first gate is open and the said second gate closed when the signal source is connected to the remote sensing element, and the second gate is open and the first gate closed when the signal source is connected To the reference sensor; and an analog indicator device connected to receive the outputs of both said gates.
Claim 29
Dependent Claim
13 words
A device according to claim 27 wherein said frequency discriminators have inverse characteristics.
Claim 30
Dependent Claim
87 words
A device according to claim 20, wherein said switching diodes are each switched by a square-wave voltage having a regulatable pulse mark-to-space ratio, and wherein said measuring device comprises a frequency discriminator connected to receive said modified signal, a modulator connected in series with said discriminator, said modulator being controlled in such a manner that the signal components are each multiplied by a positive and negative voltage, an integrator connected to the output of said modulator and an analog indicator connected to the output of said integrator.
Claim 31
Dependent Claim
17 words
A device according to claim 29, wherein the pulse mark-to-space ratio of the square-wave voltage is ''''one''''.
Claim 32
Dependent Claim
20 words
A device according to claim 29 wherein said square-wave voltage is supplied by a square-wave generator with two symmetrical outputs.
Claim 33
Dependent Claim
22 words
A device according to claim 31, characterized in that the zero passages of the square-wave generator and of the oscillator are synchronized.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-06-03 | 1977-12-03 | 1978-06-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-06-03 | 1981-12-03 | 1982-06-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-06-03 | 1985-12-03 | 1986-06-04 | $7700.00 | Window Closed / Lapsed |