Abstract:
An apparatus and method for measuring changes in pressure, temperature, speed, acceleration, vibration, or volume by detecting variations in one or more electrical circuits as the distance among a plurality of electrically conductive and magnetically permeable components changes. The invention utilizes changes in properties of electrical circuits induced by the variations in the intensity of a magnetic flux field resulting from spatial movements or displacement of the components. The components that make up the sensor may be electrically insulated from the electrical circuit that is the source of the magnetic flux field and detects the change and analyzes it as a measured change in pressure, temperature, speed, acceleration, vibration, volume, etc.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of and priority to U.S. Provisional Application No. 60/403,462 entitled “Displacement Sensing Measuring Device and Apparatus” and filed Aug. 14, 2003 
     
    
     
       BACKGROUND OF INVENTION  
         [0002]    1. Field of Use  
           [0003]    The present invention has many applications for measuring differing properties such as volume, pressure, temperature, velocity, acceleration, or impulse by detecting variations in one or more electromagnetic circuits maintained remote and insulated from the object of interest. The invention allows use of electrical instrumentation and recording devices in applications that have previously been inaccessible or hazardous due to factors including, but not limited to, corrosion, flame or spark hazards.  
           [0004]    2. Prior Art  
           [0005]    Various displacement measuring devices have been long known and reliably used in many applications. Typically, the displacement measuring devices involve some mechanically moveable component in conjunction with an active electrical circuit, e.g., floats to measure volume, etc. Previous to this invention, however, it has not been possible to accurately or reliably measure or monitor changes in certain objects by such traditional mechanical devices, where there exist harsh or extreme environments in which the mechanical device, particularly flexible or moveable components, are to operate over prolonged periods or where the components are inaccessible for routine inspection and maintenance. It also has not been possible to utilize common electrical sensors, where an electrical current creates an unacceptable risk of spark, fire or explosion due to volatile compounds or other hazardous environmental conditions. Common electrical sensors or mechanical devices have also been unsuitable or impracticable for metal containment vessels that may not be breached.  
         SUMMARY OF INVENTION  
         [0006]    The method and apparatus taught by the invention subject of this specification utilizes the ability to transmit a magnetic signal through electrically conductive and magnetically permeable materials or across distances that have previously not been achievable. The invention also utilizes the ability to transmit magnetic signals through materials that previously have been considered barriers to the transmission of magnetic energy. The applicant has previously disclosed (i) methods of transmitting electromagnetic signals through electrically conductive and magnetically permeable materials, i.e., EM barriers and detecting changes in electrical resistivity of media existing on the opposite side of the EM barrier; (ii) apparatus and methods for engaging EM barrier materials with magnetic energy, transmitting magnetic energy through a portion and then along the opposite surface of the material such that the material behaves similar to an electromagnetic antenna; (iii) methods and apparatus for saturating or partially saturating EM barrier material such that the magnetic permeability is sufficiently reduced to enhance electromagnetic energy engaging with and penetrating through EM barrier material. Reference is made to published U.S. patents or patent applications of the Applicant, Ser. Nos. 09/781,667, 09/981,775 and U.S. Pat. No. 6,392,421, which are hereby incorporated by reference.  
           [0007]    In the present specification, the applicant teaches use of some or all of these techniques to remotely create an insulated electric signal that can be detected by electrically insulated devices through one or more electrically conductive materials by the induction of magnetic energy.  
           [0008]    Therefore, it is a goal of the present invention to provide an apparatus and method for measuring or detecting changes in properties, including but not limited to volume, pressure, temperature, velocity, acceleration or impulse, by the interaction of electrically conductive objects controlled by at least one of these properties with a magnetic field and a resulting induced electric signal. The measurement can be made through various barriers or container walls, e.g., through the wall of a steel tank, without breach or perforation of the tank wall.  
           [0009]    It is a further goal to create a remote magnetic current or field that can be used to interact with moveable electrically conductive objects and generate an electric signal.  
           [0010]    It is a further goal of this invention to utilize changes in a magnetic field to induce changes in various properties of electrical circuits, e.g., changes in impedance, voltage, current amplitude and phase.  
           [0011]    It is yet another goal of this invention to utilize the detected change in magnetic energy to determine the quantity of the media or force of the phenomena responsible for the change in magnetic energy, e.g., change in temperature, vibration, acceleration, volume Or pressure. 
       
    
    
     SUMMARY OF DRAWINGS  
       [0012]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention. These drawings, together with the general description of the invention given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention.  
         [0013]    [0013]FIG. 1 schematically illustrates the components of one embodiment of the apparatus subject of the invention.  
         [0014]    [0014]FIG. 2 illustrates the embodiment of the invention used in the demonstration of the invention.  
         [0015]    [0015]FIG. 2A illustrates an induced magnetic circuit.  
         [0016]    [0016]FIGS. 2B and 2C illustrate the induced and bucking eddy currents within the magnetic circuit.  
         [0017]    [0017]FIG. 3 illustrates the electrically conductive plate structures of the apparatus depicted in FIGS. 2, 2A,  2 B and  2 C.  
         [0018]    [0018]FIG. 3A illustrates another embodiment of the plate structure.  
         [0019]    [0019]FIG. 4 illustrates the measured induced voltage change resulting from a change in water volume used in the demonstration of the invention.  
         [0020]    [0020]FIG. 5 illustrates another embodiment of the invention  
         [0021]    [0021]FIG. 6 illustrates a component of the invention  
         [0022]    [0022]FIG. 7 illustrates another embodiment of the invention.  
         [0023]    [0023]FIG. 8 illustrates an alternate embodiment of the invention.  
         [0024]    [0024]FIG. 9 depicts the results of the demonstration of the embodiment illustrated in FIG. 7 wherein increased pressure was placed upon a moveable disk adjacent to a steel pipe. 
     
    
       [0025]    The above general description and the following detailed description are merely illustrative of the subject invention, and additional modes, advantages and particulars of this invention will be readily suggested to those skilled in the art without departing from the spirit and scope of the invention.  
       DETAILED DESCRIPTION OF INVENTION  
       [0026]    It is well known that an oscillating (or changing) magnetic flux will induce an electrical current (“eddy current”) within an electrically conductive object located within the field of the changing flux. It is also well known that the movement of an electrically conductive material through a magnetic field, e.g., the constant magnetic field of a permanent magnet, will induce an electric current within the conductive material. The magnitude of induced current (eddy current) will, of course, be related in part, to the rate of change of magnetic flux, the conductivity or rate of movement of the material, and the intensity of the magnetic field. A change of either the induced electric current or magnetic flux causes an interaction with the other, and the result of the interaction can be detected. The detected signals are used to provide information concerning the material or the media existing on the opposite side of the material, e.g., measuring the volume (or change in volume) of the contents within a steel tank.  
         [0027]    One embodiment of the present invention utilizes measured changes in impedance of an electric circuit resulting from a change or movement in a magnetic flux or an electrically conductive material to determine, for example, the volume of liquid in a tank. This example would rely upon the changes in volume causing a discernible change in the separation among separate and electrically insulated components. The change in distance would be detected by the change in impedance, voltage or current of one or more electric circuits.  
         [0028]    It will be appreciated that the relationship between distance of the materials and the volume or other properties can be controlled by known and conventional methods. A change in volume of a liquid may cause the distance between two components (for example, two electrically conductive plates located in a magnetic field or magnetic circuit) to move in relation to the other. For example, if the quantity of a liquid in a fixed wall container increases, the level of the liquid rises within the container. The increased height increases the weight of the liquid above the device, there by causing a space between the two plates to contract by various and well known methods. As the space between the first and second materials changes in response to the change in weight or pressure, a change in the magnetic field or electric current can be detected. For example, the compression of a gap between two electrically conductive plates or disks within a steel tank may cause a detectable change in an electric current used to induce a magnetic field in one of the conductive disks. The detected change may be changed impedance, current or voltage. Useful information can be extrapolated from the change in one of these factors when the other variables are known or constant.  
         [0029]    [0029]FIG. 1 schematically illustrates the components of one embodiment of the apparatus subject of the invention. It will be appreciated that the depicted apparatus includes a separate, constant or low frequency magnetic flux generating component  560  connected by conductive wires to one or more flux coils  501 A and  501 B that are coupled with a magnetically permeable and electrically conductive, e.g., ferromagnetic, rod  100 . This constant or low frequency magnetic flux can be used to reduce the permeability of the rod  100  to facilitate a separate and oscillating or pulsed flux, illustrated to be generated by a separate oscillating or pulsed power supply  585  to couple with the rod  100  by means of a separate component  300 . The voltage or effective current may be maintained constant. It is preferred that this second flux oscillates at a frequency higher than the first flux.  
         [0030]    The second and higher frequency oscillating magnetic flux generating component  300  contains an electrically energized coil  301 . This component is termed a transmitter or transmitter coil. The energized coil  301  induces an oscillating flux engaging with the ferromagnetic rod  100 . By well known methods, the oscillating magnetic flux may conduct through or along the ferromagnetic rod, thereby creating an induced magnetic circuit (not shown.)  
         [0031]    [0031]FIG. 2 illustrates an embodiment of the invention used in the recording the information discussed herein. The apparatus consists of two saturation coils  501 A and  501 B wound around a carbon steel (ferromagnetic) rod  100 . The coils are electrically insulated from the rod. Between the two saturation coil is a single transmitter coil  301 , also electrically insulated from the steel rod. At the end of the rod is an electrically conductive object, i.e., a steel disk  105  approximately 2 inches in diameter and ¼ inch thick. A second disk (i.e., an electrically conductive object) of similar size  115  is located on a substantially parallel plane  116  to the plane  106  of the first disk  105 . This second disk is attached to a rod  110  that is pivotably mounted  120  to a piece  125  rigidly connected to the first rod  100 . A spring  130 , located between each rod  100  and  110 , is used to separate the surface  105 A of the first disk  105  from the opposing surface  115 A of the second disk  115 . It will be appreciated by persons skilled in the art that the spring is also electrically insulated from the surface of either rod and thereby does not serve as an electrical conductor. A voltage measuring device is utilized to measure changes in the voltage in response to the constant effective current.  
         [0032]    It is, of course, well known that the lines of magnetic flux generated by the transmitter coil  301  must form a closed loop. It will be appreciated that all or a substantial portion of the oscillating flux will travel along the magnetically permeable rod  100  to a first plate or disk  105  configured to facilitate the induction of eddy currents. It will be further appreciated that the components comprising the first rod  100 , the first disk  105 , the space  950  between the first disk  105  and a second disk  115 , a second rod  110 , hinge  120 , and connector rod  125  form a magnetic circuit. The magnetic flux  140  and  141  travels through or along this circuit as shown in FIG. 2A. FIG. 2A illustrates the “flow” of this magnetic circuit.  
         [0033]    The saturation coils  501 A and  501 B are powered by a constant dc power source  560 . The ac power cables are attached to an alternating current source  585  (oscillating at approximately 19 kHz), transmitter coil  301  and a voltage or amp meter  590 .  
         [0034]    There may be multiple transmitter coils. One or more of the transmitter coils may also serve as the component (receiver) that detects the changed signal received as a result of the variable strength eddy currents oscillating within a second plate  115  and the resulting the opposing directionality of eddy currents, i.e., bucking, within the first plate  105 .  
         [0035]    [0035]FIGS. 2B and 2C illustrates the bucking of eddy currents  161  and  162 , in conjunction with the closed loop magnetic field lines comprising the magnetic circuit. The magnetic circuit includes the portion of the magnetic circuit  142  flowing across the variable sized gap or space  950  between plates  105  and  115 . Proximate to the first plate, and preferably in a parallel plane, is the second similar plate or disk  115 . This plate is rigidly attached to a second rod  110 . This rod is pivotably attached  120  in relation to the first rod  100 , thereby allowing the distance between  105  and  115  to fluctuate. A significant portion of the oscillating flux will be expected to travel across the relatively short gap  950  between  105  and  115 . Change in the distance  950  between the opposing surfaces  105 A and  115 A will vary the induced eddy currents of each disk, resulting in a change in measured voltage or amperage.  
         [0036]    [0036]FIG. 3 illustrates the invention wherein a flexible seal  170  creates a cavity  970  that is maintained between plates  105  and  115 . The cavity  970  will be decreased and the spacing  950  narrowed as a result, for example, of the increased weight of a greater liquid volume levels above the device  500 . Alternatively, the space  950  could vary as a result of movement of a temperature sensitive bimetallic coil in response to temperature change. Of course, such coils are well known. Also the space could vary as a change in velocity, acceleration or impulse of the device.  
         [0037]    In the demonstration of the invention, the effective ac current and the dc current were maintained constant at all points illustrated. The distance between the disks varied as the depth of water surrounding the disks was raised. As the distance  950  changed with the fluctuation in water height, the measured voltage reading was recorded. FIG. 3 illustrates the direction of the compressive force  960  caused by the increased volume of water in a container with fixed sides (not shown). The disks are isolated from the water by use of water-tight bellow  170 . The increased depth of water caused increased compressive pressure on the disks maintained in a water tight, but flexible bellows  170  creating the cavity  970  between  105 A and  115 A. As the pressure increases, the distance  950  decreases between opposing surfaces  105 A and  115 A of  105  and  115  respectively.  
         [0038]    [0038]FIG. 3A illustrates an alternate embodiment for maintaining an opposing force to separate the plates. It will be appreciated that although both FIGS. 2 and 3A illustrate the use of a spring to maintain a separation between the conductive plates or objects (and a countervailing force to the property of interest, e.g., temperature, pressure, volume, etc.) other mechanisms or structure may be used without departing from the invention.  
         [0039]    [0039]FIG. 4 illustrates the recorded change in transmitter current voltage  280  as the distance between the disks is varied. A first voltage measurement of 9.93×10 −1  volts  411  was recorded with the water depth surrounding the disks,  105  and  115  in FIG. 2, was at 1 inch. The depth of water was then increased to two inches and the second voltage measurement of 8.7×10 −1  volts  412  was recorded. Similarly the voltage measurement of 7.7×10 −1    413  was recorded when the water depth was increased to 3 inches. The voltage measurement of 5.2×10 −1  volts  414  was recorded when the water depth was increased to 4 inches.  
         [0040]    The data illustrated in FIG. 4 illustrates that the measured voltage decreased as the distance between the disks was reduced by the increase water pressure. This is explained by the increasing proximity of the disks (contraction of the spacing  950  in FIG. 3) causing a larger inter-action between the magnetic circuit and the induced circuit within disk  115 . It will be appreciated that this interaction results in an increased dampening of the signal detectable by a decrease in voltage or current. This dampening will be detectable through a change in current or voltage within the circuit. The change can be measured by a volt or amp meter  590 .  
         [0041]    The relationship between the proximity or movement of the disks  105  and  115  and measured voltage or current has been consistently and repeatably shown. The recorded voltage (when the circuit utilizes a constant current) or amperage (when the circuit utilizes a constant voltage) can be reliably used to indicate the amount of separation between the two points. Further, the readings are created solely from the magnetic component of electromagnetic energy thereby reducing or minimizing error resulting from mechanical factors.  
         [0042]    It will be appreciated by persons skilled in the art that the apparatus can be configured to reflect changes in various environments, e.g., pressure, temperature, or properties, e.g. velocity, acceleration, vibration.  
         [0043]    Persons skilled in the art will also appreciate that the second disk  115  illustrated in FIG. 2 need not be part of the magnetic circuit. FIGS. 5 and 7 illustrate embodiments of the invention wherein the components  920 / 924  and  925  respectively comprise separate moveable components. Considering FIG. 5 first, the component  920 / 924  alter the measured voltage induced within the magnetic circuit comprised of  100 ,  115 ,  105 , and  110 . The component  920 / 924  may be maintained outside of the magnetic flux crossing (not shown) between  115  and  105  through the space  119 . The “tongue”  920  can be moved into space  119  in response to pressure or other force in the direction  960  or retracted by a spring force (not shown) or similar means in direction  970 . It will be readily appreciated that the movement of the tongue component  920 , comprised of an electrically conductive material, through or into the space  119  containing an oscillating magnetic flux, result in eddy currents being induced within the tongue. These eddy currents can be used to modify the voltage of the oscillating current induced by the transmitter coils  301  from the generator  585 .  
         [0044]    [0044]FIG. 6 illustrates an embodiment of the invention utilizing the tongue component  920  attached to a top plate  924 . The structure of the tongue contains varying spaced barriers  921 ,  922 , and  923  to eddy currents. It will be appreciated that the upper portion  926  of the tongue does not contain such eddy current barriers. Accordingly, as the tongue  920  is inserted further  960  into the space  119  between the plates  105  and  115 , there will be less impedance to the induction of eddy currents within the tongue that will alter the voltage induced by the magnetic circuit.  
         [0045]    [0045]FIG. 7 illustrates yet another embodiment of the invention. The magnetic flux generator  500  is separated from the moveable and electrically conductive plate  925  by a wall  128 . It will be appreciated that the wall may be comprised of magnetically permeable and electrically conductive material, e.g., a steel tank or pipe wall. In the illustrated embodiment, an electrically conductive disk  925  (obviously an electrically conductive object) is utilized in conjunction with the flux generator  500 . The flux generator is comprised of a transmitter coil  300 , alternating power supply  585  connected to the transmitter coil by means not shown, amp meter (not shown), four (4) saturation flux generating coils  552  wrapped around saturation cores (not shown), a magnetic culminator  555  and two poles  504  and  505  of like polarity (and having polarity opposite that of the culminator  555 ). It will be appreciated that the culminator, saturation flux cores and poles are comprised of highly magnetically permeable material. The saturation flux generator is located proximate to the side  129  of the wall opposite the remote electrically conductive disk  925 . In a preferred embodiment both the disk  925  and culminator  555  have substantially the same center axis C/L. Accordingly, the space  955  may be minimal or non-existent.  
         [0046]    The saturation flux generator can be powered by a dc power source or low frequency ac power source (not shown). The magnetic flux emitted from culminator  555 , and magnetic poles  504  and  505  are used to create a Metallic Transparency™ within a portion of the wall  128 . The transparency will permeate through the thickness  127  of the wall  128 . In conjunction with the creation of this transparency, the transmitter coil is energized with ac power (or pulsed dc power) that will create an oscillating or variable magnetic flux to be emitted from the side of the culminator  555  adjacent to the side  129  of the wall  128 . A portion of the oscillating magnetic flux (not shown) will couple with and permeate through the thickness  127  of the steel tank wall proximate to the area of the Metallic Transparency. The remote and electrically conductive component disk  925  may intersect some of the field lines generated by the transmitter coil. The number of field lines intersected by component disk  925  will increased when the disk moves toward the wall  128  in direction  960  due to increased pressure or other mechanical force. (It will also be appreciated that the remote component disk  925  may also move in the opposite direction  965  as a result of another force, such as buoyancy (as a float) or spring pressure, or in response to a lessening of pressure or other mechanical force.) Examples of forces causing movement of remote component  925  in direction  960  or  965  may also include varying factors such as change in the internal tank pressure, liquid level in the tank, change in temperature, movement of the tank or tank contents, etc. In a preferred embodiment, the distance  955  between the magnetic flux generator  500  and the first surface  129  of the wall  128  is fixed or constant. The proximity of the remote disk  925  to the wall  128 , and hence the transmitter  300 , will influence the quantity of flux density or number or magnetic field lines intersected by the remote disk. As this quantity changes, the interaction with the magnetic field can be detected and measured by change in voltage or amperage of electrical current energizing the transmitter coil  300 .  
         [0047]    In an alternate method, the interaction can be detected by a separate receiver coil  580 . In a preferred embodiment, the receiver is located in an annulus  553  located within the culminator  555  and approximately axially centered with respect to the transmitter coil  300 .  
         [0048]    Of course, a constant magnetic force, supplied by a permanent magnet or dc power source may be sufficient for the operation of the invention. The movement of the electrically conductive disk (object)  115 , depicted in FIG. 2, or component plate  925 , shown in FIG. 7, within a constant magnetic field will generate an electric current that may be detected.  
         [0049]    [0049]FIG. 8 illustrates another embodiment for creating a space  950  between the opposing surfaces  105 A and  115 A of the disks  105  and  115 . A spring  130  is placed between the disks.  
         [0050]    [0050]FIG. 9 illustrates the recorded changes of current as the pressure (in ounces) was increased on the surface of  925 , causing the electrically conductive disk (object)  925  to move toward the surface of a carbon steel pipe wall in the direction  965 . The recorded data was processed by standard or known polynomial expressions and curve fitting techniques. The resulting data shows a clear ability to monitor or measure the force of the pressure by means of the recorded change in current. For example, the change in position along curve  400  between  412  and  415  is the result of an increase of 4 ounces per unit area of pressure.  
         [0051]    This specification is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the manner of carrying out the invention. It is to be understood that the forms of the invention herein shown and describe are to be taken as the presently preferred embodiments. As already stated, various changes may be made in the shape, size and arrangement of components or adjustments made in the steps of the method without departing from the scope of this invention. For example, equivalent elements may be substituted for those illustrated and described herein and certain features of the invention may be utilized independently of the use of other features, all as would be apparent to one skilled in the art after having the benefit of this description of the invention.  
         [0052]    Further modifications and alternative embodiments of this invention will be apparent to those skilled in the art in view of this specification.