US20070164735A1 - Methods and systems for controlling the temperature stability of an inductor - Google Patents
Methods and systems for controlling the temperature stability of an inductor Download PDFInfo
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- US20070164735A1 US20070164735A1 US11/335,201 US33520106A US2007164735A1 US 20070164735 A1 US20070164735 A1 US 20070164735A1 US 33520106 A US33520106 A US 33520106A US 2007164735 A1 US2007164735 A1 US 2007164735A1
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- 238000000034 method Methods 0.000 title claims abstract description 19
- 239000000523 sample Substances 0.000 claims abstract description 92
- 230000005284 excitation Effects 0.000 claims abstract description 16
- 230000001419 dependent effect Effects 0.000 claims description 8
- 230000000694 effects Effects 0.000 claims description 6
- 238000012544 monitoring process Methods 0.000 description 11
- 239000004020 conductor Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 238000005259 measurement Methods 0.000 description 5
- 230000010355 oscillation Effects 0.000 description 4
- 238000005538 encapsulation Methods 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000012212 insulator Substances 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/02—General constructional details
- G01R1/06—Measuring leads; Measuring probes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
- G01B7/02—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness
- G01B7/023—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring length, width or thickness for measuring distance between sensor and object
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
- H03K17/945—Proximity switches
- H03K17/95—Proximity switches using a magnetic detector
- H03K17/9502—Measures for increasing reliability
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
- H03K17/945—Proximity switches
- H03K17/95—Proximity switches using a magnetic detector
- H03K17/9505—Constructional details
Definitions
- This invention relates generally to controlling the temperature stability of an inductor, and more particularly to methods and apparatus for controlling the temperature stability of a sensing coil of a proximity probe.
- At least some known rotating and reciprocating machinery use an eddy current or proximity probe to facilitate monitoring machine vibration or rotor position characteristics.
- the environment that the proximity probe operates may be relatively harsh.
- the proximity probe outputs a signal correlative to a spacing between a target object such as, a rotating shaft of a machine or an outer ring of a rolling element bearing and a sensing coil of the proximity probe.
- a target object such as, a rotating shaft of a machine or an outer ring of a rolling element bearing and a sensing coil of the proximity probe.
- the gap or spacing between the target and the sensing coil of the proximity probe needs to remain within the linear range of the proximity probe for providing accurate and reliable measurements of machine vibration characteristics. Accordingly, to provide accurate and reliable measurement, a proximity probe should remain in the linear range of operation under all operating environmental conditions.
- the electronics associated with the proximity probe typically incorporates an oscillation circuit whose amplitude of oscillations is dependent on the conductance of the sensing coil.
- the sensing coil When the circuit is oscillating, the sensing coil has an alternating current flowing therein which causes the sensing coil to radiate energy in the form of an alternating magnetic field.
- the target object absorbs some of the radiated energy from the sensing coil when it is placed within the alternating field emanating from the sensing coil. This absorption of energy is a result of the alternating field generating eddy currents in the object which circulate so as to oppose the alternating field which created them.
- the amount of energy absorbed by the target object is correlative to the spacing between the target object and the sensing coil.
- the amplitude of oscillations of the oscillation circuit will vary as a function of spacing between the sensing coil and the target.
- the ability to provide accurate and reliable measurements over a wide range of circuit and environmental conditions is dependent, at least partially on, the characteristics of the sensing coil including the material and diameter of the wire used to wind the coil, the operating frequency of the system and the electronics of the proximity probe system.
- the sensing coil and the remaining electronics usually have a wide range of tolerances, such as gain, bias voltage, bias current and temperature coefficients. Accordingly, each production unit has to be initially calibrated to incorporate those tolerances.
- the sensing coil of the proximity probe usually contains sources of temperature drift error which are attempted to be compensated for in the final product.
- a source of the temperature drift error in the sensing coil is due to a temperature dependent resistance of the coil and an inductance of the coil.
- This temperature dependent resistance and inductance of the sensing coil effects a source of temperature drift error resulting in inaccurate proximity probe measurements as a consequence of the false appearance of a gap change between the target and sensing coil.
- Such inconsistencies in temperature stability of the proximity probe result in unpredictable and unreliable measurements even when the proximity probe is functioning in its linear range of operation. Compensation for such inconsistencies is usually only partially effective to facilitate temperature dependent errors.
- a method of assembling a proximity probe includes determining a coil wire dimension and coil geometry for the probe such that a resistance versus temperature profile of the coil is approximately constant when the coil is excited with an excitation frequency of approximately 150 kilohertz to approximately 350 kilohertz, and adjusting the coil geometry such that a resistance versus temperature profile of the coil is substantially constant.
- a system for determining a gap defined between an eddy current proximity probe and a target includes a proximity probe including a coil configured to be located magnetically proximate the target on a first side of the coil such that an output signal correlative to a distance between the proximity probe and the target, said coil comprising a coil wire dimension and a coil geometry for the probe such that a resistance versus temperature profile of the coil is approximately constant when the coil is excited with an excitation frequency of approximately 150 kilohertz to approximately 350 kilohertz, and a tuning disk positioned proximate a second opposite side of the coil wherein a distance between the first coil and tuning disk is changeable to generate a predetermined scale factor for the coil.
- the system also includes an electronic circuit coupled to the proximity probe configured to transmit an excitation frequency to the proximity probe and to receive the output signal from the proximity probe.
- FIG. 1 is a schematic view of a proximity probe system
- FIG. 2 is an exploded perspective view of an exemplary proximity probe in accordance with an embodiment of the present invention.
- FIG. 3 is a flow chart of an exemplary method of assembling the proximity probe shown in FIG. 2 .
- FIG. 1 is a schematic view of a proximity probe system 100 .
- Proximity probe system 100 is configured to monitor a target object, for example, a rotating shaft 102 of a machine (not shown).
- Proximity probe system 100 includes a proximity probe 104 including a temperature stable inductor 106 , an electronic circuit 108 and a monitoring system 110 .
- proximity probe 104 is operatively coupled to electronic circuit 108 and is positioned adjacent rotating shaft 102 for monitoring the vibrational or rotor position characteristics thereof.
- Proximity probe 104 uses eddy currents to generate a signal indicative of a gap 112 between rotating shaft 102 and inductor 106 .
- Proximity probe 104 includes a tuning disk 114 magnetically coupled to inductor 106 for setting a scale range for the output of proximity probe 104 .
- Proximity probe 104 defines a common enclosure 116 housing both inductor 106 and tuning disk 114 .
- proximity probe 104 is formed from a cured monolith of molded material 118 defining an encapsulation having a front end 120 and a back end 122 .
- Inductor 106 is generally symmetrically positioned within proximity probe 104 .
- An integrally formed protective probe tip 124 of a substantially uniform thickness 126 is fabricated along a forwardmost portion of proximity probe 104 .
- Molded material 118 substantially surrounds inductor 106 proximate front end 120 and ensconces a portion of an electrical conduit 128 that emanates from back end 122 .
- Tuning disk 114 is adjustable such that a distance 138 between inductor 106 and tuning disk 114 may be selected and maintained to facilitate controlling the output characteristics of proximity probe 104 .
- electrical conduit 128 comprises a multi-axis cable including a center conductor 140 electrically connected to a first lead 142 of inductor 106 and a coaxial conductor 144 electrically connected to a second lead 146 of inductor 106 wherein the center conductor 72 and coaxial conductor 74 are separated by an insulator or dielectric 148 .
- a braided sheath 150 circumscribes coaxial conductor 144 and is separated therefrom by an insulator 152 . Braided sheath 150 provides additional shielding and mechanical integrity to electrical conduit 128 .
- Electrical conduit 128 extends out of the back end 116 of the encapsulation 118 and couples inductor 106 to electronic circuit 108 to provide signal output and power input therebetween.
- Electronic circuit 108 is operatively coupled to inductor 106 for radiating energy in the form of an alternating magnetic field 158 from inductor 106 to rotating shaft 102 and for receiving signals from inductor 106 .
- Rotating shaft 102 absorbs some of this radiated energy and the received signals by electronic circuit 108 , from inductor 106 , are a function of the spacing between rotating shaft 102 and inductor 106 .
- the closer rotating shaft 102 is to inductor 106 the more energy rotating shaft 102 will absorb as a result of the eddy currents induced in rotating shaft 102 .
- the absorption of the radiated energy by shaft 102 is a result of the alternating magnetic field 158 generating eddy currents in shaft 102 which circulate so as to oppose magnetic field 158 , which created them.
- This action causes the resistance of the coil to change.
- the mutual effect of the currents in the closely adjacent conductors, turns of inductor 106 produce a temperature dependent change in resistance in response to the alternating current.
- the mutual effect of the currents in the closely adjacent turns of inductor 106 and the effect of the currents in shaft 102 produce temperature drift and gain variations in response to the alternating current.
- dimensions of inductor 106 and the wire comprising inductor 106 are preselected based on system performance requirements and the environment where proximity probe 104 is to operate. For example, a distance 112 may determine a diameter of proximity probe 104 and inductor 106 .
- a system operating frequency is determined based on the dimensions of inductor 106 and the dimensions and electrical characteristics of the wire used to form inductor 106 .
- the system operates at a specified frequency in order to provide an acceptable level of temperature stability. This frequency is theoretically determined, for example, using a computer programmed to determine the frequency based on the wire composition, diameter, and the geometrical configuration of the coil windings. This provides a baseline frequency at which the system will operate.
- the system is tested iteratively over its operating temperature range to determine the optimal operating frequency.
- the eddy current system is temperature stable when operating at a frequency between 150 kilohertz and 350 kilohertz. Specifically, for a 50 millimeter diameter probe configured as described herein the system is temperature stable when operating at a frequency of approximately 267 kilohertz.
- a linearly of a resistance versus temperature curve is determined empirically.
- the inductance of inductor 106 is adjusted, for example, by adding or removing winding turns to inductor 106 such that temperature drift and gain variations generated by both inductor 106 and target object (i.e., shaft 102 ) for effecting the temperature stable inductor 10 are substantially canceled out which results in a temperature stable proximity probe 104 .
- the temperature compensated proximity probe maintains an accurate indication of the gap 112 between rotating shaft 102 and inductor 106 under the temperature variations found in the environment of machine monitoring.
- FIG. 2 is an exploded perspective view of an exemplary proximity probe 104 in accordance with an embodiment of the present invention.
- Proximity probe 104 includes common enclosure 116 housing inductor 106 and tuning disk 114 .
- proximity probe 104 is formed from molded material 118 defining an encapsulation having a front end 120 and a back end 122 .
- Inductor 106 is generally symmetrically positioned within proximity probe 104 .
- An integrally formed protective probe tip 124 of a substantially uniform thickness 126 is fabricated along a forwardmost portion of proximity probe 104 . Molded material 118 substantially surrounds inductor 106 proximate front end 120 .
- a feed through boss 202 extends from back end 122 to guide and protect electrical conduit 128 (not shown in FIG. 2 ) from inductor 106 .
- Boss 202 includes a bore 204 therethough and a threaded portion 206 configured to threadably engage a threaded portion 208 of tuning disk tuning disk 114 .
- Tuning disk tuning disk 114 is adjustable such that a distance between inductor 106 and tuning disk 114 may be selected and maintained to facilitate controlling the output characteristics of proximity probe 104 .
- a weld ring 210 facilitates sealing a case 212 to enclosure 116 .
- FIG. 3 is a flow chart of an exemplary method 300 of assembling proximity probe 104 (shown in FIG. 2 ).
- the method includes determining 302 a coil wire dimension and coil geometry for the probe such that a resistance versus temperature profile of the coil is approximately constant when the coil is excited with an excitation frequency of approximately 150 kilohertz to approximately 350 kilohertz, and adjusting 304 the coil geometry such that a resistance versus temperature profile of the coil is substantially constant.
- the coil geometry is selected based on an application for the proximity probe. In the exemplary embodiment, a fifty millimeter diameter probe is selected. Selecting the coil geometry also includes selecting a wire diameter and material. An excitation to be applied to the probe during operation is determined using for example, a computer-based algorithm that determines a frequency of operation that facilitates reducing a temperature dependence of the output of the probe. In the exemplary embodiment, the algorithm uses the selected coil geometry and the coil wire dimensions and electrical characteristics to determine an operating frequency between approximately 150 kilohertz to approximately 350 kilohertz. The coil is subjected to output tests at various gap distances between the coil and a target.
- the ambient temperature of the probe is varied between temperature extremes expected to be experienced in the particular application the probe will be used in.
- the coil geometry is iteratively adjusted to attain a resistance versus temperature profile of the coil is substantially constant. For example, coil turns are added or removed to control the coil inductance such that the excitation frequency changes correlatively. In the exemplary embodiment, an operating frequency of approximately 267 kilohertz is the final operating frequency.
- a tuning disk comprising, in the exemplary embodiment, a stainless steel disk is positioned on an opposite side of the coil from the target. The tuning disk is magnetically coupled to the coil when an excitation signal is applied to the coil. The tuning disk is threadably coupled to a boss extending from the side of the coil enclosure. The scale factor of the coil is controlled by threading the tuning disk closer to the coil or further away from the coil. When the output scale factor is determined to be at the predetermined value, the tuning disk is locked in place and the proximity probe is further assembled.
- temperature stable proximity probe system provides a cost-effective and reliable means for monitoring machinery. More specifically, the coil of the proximity probe is fabricated such that an operating frequency is selected that substantially mitigates a temperature dependence of the output of the coil. As a result, an proximity based monitoring system is provided that facilitates improving the accuracy and repeatability of the proximity probe.
- monitoring system components illustrated are not limited to the specific embodiments described herein, but rather, components of each monitoring system may be utilized independently and separately from other components described herein.
- the monitoring system components described above may also be used in combination with other monitoring system.
Abstract
Description
- This invention relates generally to controlling the temperature stability of an inductor, and more particularly to methods and apparatus for controlling the temperature stability of a sensing coil of a proximity probe.
- At least some known rotating and reciprocating machinery use an eddy current or proximity probe to facilitate monitoring machine vibration or rotor position characteristics. The environment that the proximity probe operates may be relatively harsh.
- Typically, the proximity probe, outputs a signal correlative to a spacing between a target object such as, a rotating shaft of a machine or an outer ring of a rolling element bearing and a sensing coil of the proximity probe. The gap or spacing between the target and the sensing coil of the proximity probe needs to remain within the linear range of the proximity probe for providing accurate and reliable measurements of machine vibration characteristics. Accordingly, to provide accurate and reliable measurement, a proximity probe should remain in the linear range of operation under all operating environmental conditions.
- The electronics associated with the proximity probe typically incorporates an oscillation circuit whose amplitude of oscillations is dependent on the conductance of the sensing coil. When the circuit is oscillating, the sensing coil has an alternating current flowing therein which causes the sensing coil to radiate energy in the form of an alternating magnetic field. The target object absorbs some of the radiated energy from the sensing coil when it is placed within the alternating field emanating from the sensing coil. This absorption of energy is a result of the alternating field generating eddy currents in the object which circulate so as to oppose the alternating field which created them. The amount of energy absorbed by the target object is correlative to the spacing between the target object and the sensing coil. The closer the target is to the sensing coil, the more energy the target will absorb from the sensing coil as a result of the eddy current principle. Therefore, the amplitude of oscillations of the oscillation circuit will vary as a function of spacing between the sensing coil and the target.
- The ability to provide accurate and reliable measurements over a wide range of circuit and environmental conditions is dependent, at least partially on, the characteristics of the sensing coil including the material and diameter of the wire used to wind the coil, the operating frequency of the system and the electronics of the proximity probe system. The sensing coil and the remaining electronics usually have a wide range of tolerances, such as gain, bias voltage, bias current and temperature coefficients. Accordingly, each production unit has to be initially calibrated to incorporate those tolerances. Moreover, the sensing coil of the proximity probe usually contains sources of temperature drift error which are attempted to be compensated for in the final product.
- A source of the temperature drift error in the sensing coil is due to a temperature dependent resistance of the coil and an inductance of the coil. This temperature dependent resistance and inductance of the sensing coil effects a source of temperature drift error resulting in inaccurate proximity probe measurements as a consequence of the false appearance of a gap change between the target and sensing coil. Such inconsistencies in temperature stability of the proximity probe result in unpredictable and unreliable measurements even when the proximity probe is functioning in its linear range of operation. Compensation for such inconsistencies is usually only partially effective to facilitate temperature dependent errors.
- In one embodiment, a method of assembling a proximity probe includes determining a coil wire dimension and coil geometry for the probe such that a resistance versus temperature profile of the coil is approximately constant when the coil is excited with an excitation frequency of approximately 150 kilohertz to approximately 350 kilohertz, and adjusting the coil geometry such that a resistance versus temperature profile of the coil is substantially constant.
- In another embodiment, a proximity probe configured to monitor a rotatable machine by measuring a gap between the probe and a target associated with the rotatable machine includes a coil configured to be located magnetically proximate the target on a first side of the coil, said coil comprising a coil wire dimension and coil geometry for the probe such that a resistance versus temperature profile of the coil is approximately constant when the coil is excited with an excitation frequency of approximately 150 kilohertz to approximately 350 kilohertz and a tuning disk positioned proximate a second opposite side of the coil wherein a distance between the first coil and tuning disk is changeable to generate a predetermined scale factor for the coil.
- In yet another embodiment, a system for determining a gap defined between an eddy current proximity probe and a target includes a proximity probe including a coil configured to be located magnetically proximate the target on a first side of the coil such that an output signal correlative to a distance between the proximity probe and the target, said coil comprising a coil wire dimension and a coil geometry for the probe such that a resistance versus temperature profile of the coil is approximately constant when the coil is excited with an excitation frequency of approximately 150 kilohertz to approximately 350 kilohertz, and a tuning disk positioned proximate a second opposite side of the coil wherein a distance between the first coil and tuning disk is changeable to generate a predetermined scale factor for the coil. The system also includes an electronic circuit coupled to the proximity probe configured to transmit an excitation frequency to the proximity probe and to receive the output signal from the proximity probe.
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FIG. 1 is a schematic view of a proximity probe system; -
FIG. 2 is an exploded perspective view of an exemplary proximity probe in accordance with an embodiment of the present invention; and -
FIG. 3 is a flow chart of an exemplary method of assembling the proximity probe shown inFIG. 2 . -
FIG. 1 is a schematic view of aproximity probe system 100.Proximity probe system 100 is configured to monitor a target object, for example, arotating shaft 102 of a machine (not shown).Proximity probe system 100 includes aproximity probe 104 including a temperaturestable inductor 106, anelectronic circuit 108 and amonitoring system 110. Typically,proximity probe 104 is operatively coupled toelectronic circuit 108 and is positioned adjacent rotatingshaft 102 for monitoring the vibrational or rotor position characteristics thereof.Proximity probe 104 uses eddy currents to generate a signal indicative of agap 112 betweenrotating shaft 102 andinductor 106.Proximity probe 104 includes atuning disk 114 magnetically coupled toinductor 106 for setting a scale range for the output ofproximity probe 104. -
Proximity probe 104 defines acommon enclosure 116 housing bothinductor 106 andtuning disk 114. In the exemplary embodiment,proximity probe 104 is formed from a cured monolith of moldedmaterial 118 defining an encapsulation having afront end 120 and aback end 122.Inductor 106 is generally symmetrically positioned withinproximity probe 104. An integrally formedprotective probe tip 124 of a substantiallyuniform thickness 126 is fabricated along a forwardmost portion ofproximity probe 104.Molded material 118 substantially surroundsinductor 106proximate front end 120 and ensconces a portion of anelectrical conduit 128 that emanates fromback end 122.Tuning disk 114 is adjustable such that adistance 138 betweeninductor 106 andtuning disk 114 may be selected and maintained to facilitate controlling the output characteristics ofproximity probe 104. - In the exemplary embodiment,
electrical conduit 128 comprises a multi-axis cable including acenter conductor 140 electrically connected to afirst lead 142 ofinductor 106 and acoaxial conductor 144 electrically connected to asecond lead 146 ofinductor 106 wherein the center conductor 72 and coaxial conductor 74 are separated by an insulator or dielectric 148. In the exemplary embodiment, abraided sheath 150 circumscribescoaxial conductor 144 and is separated therefrom by aninsulator 152. Braidedsheath 150 provides additional shielding and mechanical integrity toelectrical conduit 128.Electrical conduit 128 extends out of theback end 116 of theencapsulation 118 andcouples inductor 106 toelectronic circuit 108 to provide signal output and power input therebetween. -
Electronic circuit 108 is operatively coupled toinductor 106 for radiating energy in the form of an alternatingmagnetic field 158 frominductor 106 to rotatingshaft 102 and for receiving signals frominductor 106.Rotating shaft 102 absorbs some of this radiated energy and the received signals byelectronic circuit 108, frominductor 106, are a function of the spacing between rotatingshaft 102 andinductor 106. Thus, the closer rotatingshaft 102 is toinductor 106, the moreenergy rotating shaft 102 will absorb as a result of the eddy currents induced in rotatingshaft 102. - Specifically, the absorption of the radiated energy by
shaft 102 is a result of the alternatingmagnetic field 158 generating eddy currents inshaft 102 which circulate so as to opposemagnetic field 158, which created them. This action causes the resistance of the coil to change. In addition, the mutual effect of the currents in the closely adjacent conductors, turns ofinductor 106, produce a temperature dependent change in resistance in response to the alternating current. Thus, the mutual effect of the currents in the closely adjacent turns ofinductor 106 and the effect of the currents inshaft 102 produce temperature drift and gain variations in response to the alternating current. In the exemplary embodiment, dimensions ofinductor 106 and thewire comprising inductor 106 are preselected based on system performance requirements and the environment whereproximity probe 104 is to operate. For example, adistance 112 may determine a diameter ofproximity probe 104 andinductor 106. A system operating frequency is determined based on the dimensions ofinductor 106 and the dimensions and electrical characteristics of the wire used to forminductor 106. The system operates at a specified frequency in order to provide an acceptable level of temperature stability. This frequency is theoretically determined, for example, using a computer programmed to determine the frequency based on the wire composition, diameter, and the geometrical configuration of the coil windings. This provides a baseline frequency at which the system will operate. The system is tested iteratively over its operating temperature range to determine the optimal operating frequency. In the exemplary embodiment, the eddy current system is temperature stable when operating at a frequency between 150 kilohertz and 350 kilohertz. Specifically, for a 50 millimeter diameter probe configured as described herein the system is temperature stable when operating at a frequency of approximately 267 kilohertz. - Using the determined frequency, a linearly of a resistance versus temperature curve is determined empirically. To improve the linearity of the resistance versus temperature curve over the desired range, the inductance of
inductor 106 is adjusted, for example, by adding or removing winding turns toinductor 106 such that temperature drift and gain variations generated by bothinductor 106 and target object (i.e., shaft 102) for effecting the temperature stable inductor 10 are substantially canceled out which results in a temperaturestable proximity probe 104. Thus, the temperature compensated proximity probe maintains an accurate indication of thegap 112 betweenrotating shaft 102 andinductor 106 under the temperature variations found in the environment of machine monitoring. -
FIG. 2 is an exploded perspective view of anexemplary proximity probe 104 in accordance with an embodiment of the present invention.Proximity probe 104 includescommon enclosure 116housing inductor 106 andtuning disk 114. In the exemplary embodiment,proximity probe 104 is formed from moldedmaterial 118 defining an encapsulation having afront end 120 and aback end 122.Inductor 106 is generally symmetrically positioned withinproximity probe 104. An integrally formedprotective probe tip 124 of a substantiallyuniform thickness 126 is fabricated along a forwardmost portion ofproximity probe 104. Moldedmaterial 118 substantially surroundsinductor 106 proximatefront end 120. A feed through boss 202 extends fromback end 122 to guide and protect electrical conduit 128 (not shown inFIG. 2 ) frominductor 106. Boss 202 includes abore 204 therethough and a threadedportion 206 configured to threadably engage a threadedportion 208 of tuningdisk tuning disk 114. Tuningdisk tuning disk 114 is adjustable such that a distance betweeninductor 106 andtuning disk 114 may be selected and maintained to facilitate controlling the output characteristics ofproximity probe 104. Aweld ring 210 facilitates sealing acase 212 toenclosure 116. -
FIG. 3 is a flow chart of anexemplary method 300 of assembling proximity probe 104 (shown inFIG. 2 ). The method includes determining 302 a coil wire dimension and coil geometry for the probe such that a resistance versus temperature profile of the coil is approximately constant when the coil is excited with an excitation frequency of approximately 150 kilohertz to approximately 350 kilohertz, and adjusting 304 the coil geometry such that a resistance versus temperature profile of the coil is substantially constant. - The coil geometry is selected based on an application for the proximity probe. In the exemplary embodiment, a fifty millimeter diameter probe is selected. Selecting the coil geometry also includes selecting a wire diameter and material. An excitation to be applied to the probe during operation is determined using for example, a computer-based algorithm that determines a frequency of operation that facilitates reducing a temperature dependence of the output of the probe. In the exemplary embodiment, the algorithm uses the selected coil geometry and the coil wire dimensions and electrical characteristics to determine an operating frequency between approximately 150 kilohertz to approximately 350 kilohertz. The coil is subjected to output tests at various gap distances between the coil and a target. In one such test, the ambient temperature of the probe is varied between temperature extremes expected to be experienced in the particular application the probe will be used in. The coil geometry is iteratively adjusted to attain a resistance versus temperature profile of the coil is substantially constant. For example, coil turns are added or removed to control the coil inductance such that the excitation frequency changes correlatively. In the exemplary embodiment, an operating frequency of approximately 267 kilohertz is the final operating frequency. Additionally, a tuning disk comprising, in the exemplary embodiment, a stainless steel disk is positioned on an opposite side of the coil from the target. The tuning disk is magnetically coupled to the coil when an excitation signal is applied to the coil. The tuning disk is threadably coupled to a boss extending from the side of the coil enclosure. The scale factor of the coil is controlled by threading the tuning disk closer to the coil or further away from the coil. When the output scale factor is determined to be at the predetermined value, the tuning disk is locked in place and the proximity probe is further assembled.
- The above-described embodiments of temperature stable proximity probe system provides a cost-effective and reliable means for monitoring machinery. More specifically, the coil of the proximity probe is fabricated such that an operating frequency is selected that substantially mitigates a temperature dependence of the output of the coil. As a result, an proximity based monitoring system is provided that facilitates improving the accuracy and repeatability of the proximity probe.
- Exemplary embodiments of monitoring systems are described above in detail. The monitoring system components illustrated are not limited to the specific embodiments described herein, but rather, components of each monitoring system may be utilized independently and separately from other components described herein. For example, the monitoring system components described above may also be used in combination with other monitoring system.
- While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
Claims (20)
Priority Applications (4)
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US11/335,201 US7239133B1 (en) | 2006-01-19 | 2006-01-19 | Methods and systems for controlling the temperature stability of an inductor |
KR1020070005728A KR101281221B1 (en) | 2006-01-19 | 2007-01-18 | Methods and systems for controlling the temperature stability of an inductor |
JP2007008872A JP5059422B2 (en) | 2006-01-19 | 2007-01-18 | Proximity probe and system for controlling the temperature stability of an inductor |
CNA2007101385105A CN101126647A (en) | 2006-01-19 | 2007-01-19 | Methods and systems for controlling the temperature stability of an inductor |
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US11/335,201 US7239133B1 (en) | 2006-01-19 | 2006-01-19 | Methods and systems for controlling the temperature stability of an inductor |
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US7239133B1 US7239133B1 (en) | 2007-07-03 |
US20070164735A1 true US20070164735A1 (en) | 2007-07-19 |
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US11/335,201 Active 2026-01-23 US7239133B1 (en) | 2006-01-19 | 2006-01-19 | Methods and systems for controlling the temperature stability of an inductor |
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MX341495B (en) | 2010-01-14 | 2016-08-23 | Neptco Inc * | Wind turbine rotor blade components and methods of making same. |
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US10564307B2 (en) | 2014-05-15 | 2020-02-18 | Witricity Corporation | Systems, methods, and apparatus for foreign object detection loop based on inductive thermal sensing |
Also Published As
Publication number | Publication date |
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CN101126647A (en) | 2008-02-20 |
KR101281221B1 (en) | 2013-07-02 |
JP5059422B2 (en) | 2012-10-24 |
KR20070077096A (en) | 2007-07-25 |
US7239133B1 (en) | 2007-07-03 |
JP2007199060A (en) | 2007-08-09 |
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