Magnetic position indicator

Claim 2

Apparatus for indicating the position of a movable member, which comprises: signal generating means for producing a variable-phase oscillating electrical signal the phase of which uniquely indicates for a predetermined range of motion the position of the movable member, the signal generating means including means for simultaneously producing a plurality of variable-amplitude, constant-phase oscillating electrical signals, each associated with a different successive one of a plurality of contiguous portions of the predetermined range, having first and second limiting amplitude values, and varying therebetween in accordance with the position of the movable member while the movable member is in the associated portion, each pair of variable-amplitude signals associated with successive portions having a preselected constant phase between them, and means for forming the variable-phase signal from the variable-amplitude signals; and phase detecting and indicating means resPonsive to the variablephase signal for producing a direct current signal having a magnitude that varies in accordance with changes in phase of the variable-phase signal.

Claim 3

Apparatus according to claim 1, wherein the movable member is a ferromagnetic shaft that translates an elongated chamber, and wherein the signal generating means includes a plurality of magnetic transducers each to be disposed at a successive one of a plurality of spaced-apart locations adjacent the outside of the chamber and each having an output circuit for providing a different one of the variable-amplitude, constant-phase signals.

Claim 4

Apparatus according to claim 2, wherein the output circuit of each transducer comprises a coil and the means for forming the variable-phase signal comprises means connecting the coils in series-circuit relationship.

Claim 5

Apparatus according to claim 2, wherein each transducer includes an input circuit and has a variable gain from the input circuit to the output circuit for producing the corresponding variable-amplitude signal in response to excitation of the input circuit by a constant-amplitude oscillating voltage.

Claim 6

Apparatus according to claim 2, wherein each transducer includes a magnetic core, a primary coil wound around the core and forming an input circuit, and a secondary coil wound around the core and forming the output circuit, and wherein each transducer has a variable gain from the input circuit to the output circuit for producing the corresponding variable-amplitude signal in response to excitation of the input circuit by a constant-amplitude oscillating voltage.

Claim 7

Apparatus according to claim 5, wherein each core has a generally U-shaped portion and is to be supported with the U opening toward the chamber, and wherein the gain from the input circuit to the output circuit has a first limiting value when there is a high magnetic reluctance path between the tips of the U, a second limiting value when there is a low magnetic reluctance path between the tips of the U.

Claim 8

Apparatus according to claim 6, wherein the means for forming the variable-phase signal comprising means connecting the secondary coils in series-circuit relationship whereby the variable-phase signal has the amplitude and phase of the vector sum of the plurality of variable-amplitude signals, and wherein the phase detecting means includes a limiter circuit and a phase detector circuit, the limiter circuit providing in response to the variable-phase signal a substantially constant-amplitude, variable-phase square wave voltage to the detector circuit, and the phase detector circuit providing the direct current signal which has thereby a magnitude independent of the amplitude of the vector sum.

Claim 9

Apparatus for indicating the relative position, with respect to a reference position, of a ferromagnetic movable member, which comprises: electrical-signal generating means including means for producing a first oscillating electrical signal having an amplitude proportional to the permeability of the movable member and having a first constant phase relative to a reference phase, means including a magnetic transducer for producing a second oscillating electrical signal having an amplitude proportional to the product of the permeability and the relative position of the movable member and having a second, different, constant phase relative to the reference phase, and means responsive to the first and second signals for forming a third oscillating electrical signal having a substantially continuously variable phase that is substantially independent of the permeability and is proportional to the relative position; and phase detecting means for producing a direct current signal having a magnitude proportional to the difference in phase between the variable-phase signal and the reference phase to provide an indication of the relative position.

Claim 10

Apparatus for indicating the relative position, with respect to a reference position, of a ferromagnetic movable member, which comprises: electrical-signal generating means including means for producing a first oscillating electrical signal having an amplitude proportional to the permeability of the movable member and having a first constant phase relative to a reference phase, means including a magnetic transducer for producing a second oscillating electrical signal having an amplitude proportional to the product of the permeability and the relative position of the movable member and having a second, different, constant phase relative to the reference phase, and means responsive to the first and second signals for forming a third oscillating electrical signal having a substantially continuously variable phase that is substantially independent of the permeability and is proportional to the relative position; and phase detecting means for producing a direct current signal having a magnitude proportional to the difference in phase between the variable-phase signal and the reference phase to provide an indication of the relative position.

Claim 11

Apparatus according to claim 8 wherein the movable member is a shaft translating in an elongated chamber, the apparatus Being external to the chamber, and wherein the transducer means includes a magnetic core, a primary winding wound around the core for excitation by an oscillating voltage having a constant phase relative to the reference phase, and a secondary coil wound around the core for producing the second signal.

Claim 12

Apparatus according to claim 9, wherein the magnetic core has a generally U-shaped portion and is to be supported with the U opening toward the chamber, and wherein the transducer has from the primary winding to the secondary winding a variable gain that is a function of the permeability of the medium along a line between the tips of the U so that as the ferromagnetic shaft moves along the line the variable gain changes.

Claim 13

Apparatus for indicating the position of an end of an elongated, ferromagnetic shaft that translates in an elongated chamber, the apparatus being external to the chamber and comprising: a plurality of magnetic transducers, each to be disposed at a successive one of a plurality of longitudinally spaced-apart locations adjacent the outside of the chamber, and each having an input coil and a corresponding output coil; means for connecting the input coils for excitation by a multi-phase electrical source, each input coil being excited by a phase that is different from the phase exciting the input coil of an adjacent transducer, the excitation of the plurality of input coils generating a corresponding plurality of variable-strength magnetic circuits each having a path linking a different portion of the shaft travel; each output coil responding to the strength of its corresponding magnetic circuit to provide a respective one of a plurality of variable-amplitude, constant-phase oscillating voltages each having a maximum amplitude while the shaft is in any position such that a section of the shaft fully occupies the corresponding portion of shaft travel and provides a low reluctance path which increases the strength of the magnetic circuit, having a minimum amplitude value while the shaft is any position such that no section of the shaft occupies the corresponding portion of shaft travel, and having an intermediate amplitude value while the end section of the shaft partially occupies the corresponding portion of shaft travel; summing means for forming a variable-phase oscillating signal proportional to the vector sum of all the oscillating voltages provided by the output coils; and phase detecting means responsive to the variable-phase signal for producing a direct current signal having a magnitude that varies in accordance with the phase of the variable-phase signal.

Claim 14

Apparatus for indicating the position of an end of an elongated, ferromagnetic shaft that translates in an elongated chamber, the apparatus being external to the chamber and comprising: a plurality of magnetic transducers, each to be disposed at a successive one of a plurality of longitudinally spaced-apart locations adjacent the outside of the chamber, and each having an input coil and a corresponding output coil; means for connecting the input coils for excitation by a multi-phase electrical source, each input coil being excited by a phase that is different from the phase exciting the input coil of an adjacent transducer, the excitation of the plurality of input coils generating a corresponding plurality of variable-strength magnetic circuits each having a path linking a different portion of the shaft travel; each output coil responding to the strength of its corresponding magnetic circuit to provide a respective one of a plurality of variable-amplitude, constant-phase oscillating voltages each having a maximum amplitude while the shaft is in any position such that a section of the shaft fully occupies the corresponding portion of shaft travel and provides a low reluctance path which increases the strength of the magnetic circuit, having a minimum amplitude value while the shaft is any position such that no section of the shaft occupies the corresponding portion of shaft travel, and having an intermediate amplitude value while the end section of the shaft partially occupies the corresponding portion of shaft travel; summing means for forming a variable-phase oscillating signal proportional to the vector sum of all the oscillating voltages provided by the output coils; and phase detecting means responsive to the variable-phase signal for producing a direct current signal having a magnitude that varies in accordance with the phase of the variable-phase signal.