Simplified inductive position sensor and circuit configuration
First Claim
1. A device for the measurement of position along a linear, rotary, or curved motion axis, the device comprising a sensing element, a core assembly, and a drive oscillator, the drive oscillator driving the sensing element with an alternatine current at a variable frequency,the sensing element comprising at least one electrically nonconductive substrate and at least two planar conductor patterns, the conductor patterns forming at least two inductances, at least two of the inductances connected together in series,the core assembly comprising at least one electrically conductive or ferromagnetic structure, the structure moving essentially in parallel to a surface of the substrate such that it becomes more aligned over a given conductor pattern as a measured position varies along the motion axis, at least one structure shaped to cause a variation in the inductance of the conductor pattern over which it is more closely aligned, the magnitude of at least one inductance providing an informative signal that is indicative of the measured position.
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Abstract
Inductive position sensors and circuit configurations are disclosed for the measurement of linear, rotary, or curved position along a motion axis. The simplified sensor structures combine one or two parts of a movable core element with a simple planar substrate having first and second inductances connected in series. Movement of the core element in parallel to the planar substrate causing the impedance of at least one of the inductances to change. Simple circuit configurations are taught by which the impedance change is converted into a useful output signal that indicates position along the motion axis.
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Citations
14 Claims
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1. A device for the measurement of position along a linear, rotary, or curved motion axis, the device comprising a sensing element, a core assembly, and a drive oscillator, the drive oscillator driving the sensing element with an alternatine current at a variable frequency,
the sensing element comprising at least one electrically nonconductive substrate and at least two planar conductor patterns, the conductor patterns forming at least two inductances, at least two of the inductances connected together in series, the core assembly comprising at least one electrically conductive or ferromagnetic structure, the structure moving essentially in parallel to a surface of the substrate such that it becomes more aligned over a given conductor pattern as a measured position varies along the motion axis, at least one structure shaped to cause a variation in the inductance of the conductor pattern over which it is more closely aligned, the magnitude of at least one inductance providing an informative signal that is indicative of the measured position.
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8. A transducer for measuring linear, rotary, or curved position along a motion axis, the transducer comprising a sensing element, a core assembly, and an electronics module, the electronics module including a drive oscillator, the drive oscillator driving the sensing element with an alternating current at a variable frequency,
the sensing element formed of one planar, electrically nonconductive substrate and at least two conductor patterns, the conductor patterns forming two inductances, the two inductances connected together in series, the core assembly having at least two one electrically conductive or ferromagnetic structures that moves with respect to the sensing element in response to changes in position along the motion axis, the electronics module driving the sensing element at a sufficiently high frequency to induce an eddy current to flow within the core assembly, the electronics module receiving a signal from the sensing element, the signal being informative of a measured position, the electronics module providing an electrical output indicative of the measured position along the motion axis.
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11. A position sensor for measuring position along a motion axis, the sensor comprising a planar sensing element, a drive oscillator and a core assembly, the sensing element comprising one electrically nonconductive substrate and at least two planar conductor patterns, the substrate having first and second sides, the conductor patterns forming first and second inductances connected together in series, the inductances each having an inductive reactance,
the core assembly having electrically conductive or ferromagnetic first and second parts that move one with the other and with changes in the measured position along the motion axis, the core assembly first part disposed proximate the first side of the substrate, the core assembly second part disposed proximate the second side of the substrate, the inductance of at least one conductor pattern changing in response to the approach of the core assembly such that a surface of the core assembly is more closely aligned with the conductor pattern, the drive oscillator driving the sensing element with an alternating current at a variable frequency.
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14. A device for the measurement of a physical parameter, the device having a sensing element and a drive circuit, the sensing element providing an informative signal of the measured parameter, the drive circuit providing an alternating current drive signal to the sensing element at a drive frequency, a control signal connected to the drive circuit and introducing a variation into the drive frequency, the variation having a range, a direction, and a scan rate, the range being the difference between the highest and lowest drive frequencies, the direction being increasing or decreasing in frequency, the scan rate being the frequency at which the variation changes from increasing to decreasing frequency, the range having a midpoint frequency that is halfway between the highest and lowest drive frequencies, the range being less than fifty percent of the midpoint frequency, and the scan rate being less than fifty percent of the midpoint frequency.
Specification