The present invention relates to a method and apparatus for determining the direction or magnitude of rotation, or both, of a rotating magnetic field. More specifically, the present invention determines the direction of rotation of a rotating magnetic field by sensing the changes in polarity of magnetic flux occurring at two locations within the rotating magnetic field and comparing these changes to determine the direction of rotation. In addition, the rate or number of revolutions may also be measured. In one exemplary embodiment of the present invention, a fluid meter is provided that determines the magnitude and direction of a flowing fluid. The kinetic energy of the moving fluid is translated into a rotating magnetic field. Two sensors are placed within the magnetic field to determine the changes in magnetic flux polarity occurring at two different locations within the field. The direction of fluid flow is determined by comparing and interpreting the signals. The volume or rate of flow may also be determined.
Conventional devices for fluid measurement are known. In general, such devices may be limited to measuring flow rates or may also be configured for totalizing the volume of fluid flow. While various devices and techniques for fluid measurement have been applied, many utilize a rotating element placed in the path of fluid flow. The kinetic energy of the moving fluid is harnessed to cause an element, such as a turbine, to rotate upon a shaft. Means are provided for detecting the rotational speed of the element and, in some devices, to determine the total number of revolutions. The volume of fluid displaced during one revolution is usually predetermined through calibration or calculations based upon the geometry of the rotatable element and the associated fluid passageway.
Various means exist for detecting the rotations of an element and converting the same into a recordable measurement. Such means include registers that are mechanically or magnetically coupled with the rotating element. U.S. Pat. No. 5,187,989, issued to Bulteau and commonly owned with the present application, discloses one example of an apparatus for detecting the rotation of the spinner of a water meter. In one embodiment, sensors in the form of oscillator circuits are disposed on two opposite radial directions about a disk. The disk is constructed of a non-metallic material but includes a metallized radial sector on the disk. As the disk rotates due to the flow of water through the meter, the oscillator circuits are used to detect the passage of the sector. The number of turns completed by the disk, and thus the flow of fluid through the meter, may then be totaled by associated circuitry to provide a measurement.
Sensors capable of detecting a changing magnetic field created from the rotation of a measuring element have also been applied. U.S. Pat. No. 4,579,008, issued to Bohm et al., discloses a flow meter that uses a plurality of sensors to detect the changing magnetic field created by placing a pair of magnets into the ends, respectively, of oval measuring gears. A plurality of sensing elements are required, and a nonuniform distribution of the sensors is utilized to compensate for the nonuniform rotation of the oval measuring gears.
U.S. Pat. No. 5,530,298, issued to Gerhold, discloses a natural gas volume meter. A magnetic sensor is located in close proximity to a magnet that is mounted upon a rotatable element in the gas meter. As the kinetic energy of the moving gas causes the element to rotate, a single magnet also rotates to create a magnetic field of changing flux. As only a single magnet is utilized, the resolution of this apparatus is limited to one change in magnetic flux, or signal, per each 180 degrees of revolution. Furthermore, specific physical configurations of the sensor and magnet are not taught.
The entire disclosures of the U.S. Patents noted above are herein incorporated by reference into the subject disclosure.
While the above referenced disclosures discuss means for detecting the rotation of an element for measuring the amount of flow, these references do not provide means for determining the direction of flow. In many applications, the ability to determine not only the amount or rate of flow but also the direction of flow would be advantageous.
The present invention provides for determining both the direction of rotation and magnitude of a rotating magnetic field. In application, the present invention provides for the measurement of certain physical events where the rotating magnetic field is generated in a known relationship to the event. The rotations of the magnetic field, for example, may be created by translating the kinetic energy of a moving fluid. Knowing the volume of fluid displaced per rotation of the magnetic field, the present invention allows for the determination of both the direction of flow and magnitude (rate or volume) of flow.
The present invention provides numerous embodiments for determining the direction of rotation of a rotating magnetic field. Examples will now be provided; others will be apparent to those of ordinary skill in the art using the techniques disclosed herein. In one exemplary embodiment, a method of determining the direction of rotation of a magnetic field includes sensing the change in polarity of magnetic flux encountered at a first point and at a second point located within a rotating magnetic field. The second point is located within the magnetic field at a position that is subsequent in the direction of rotation from the location of the first point. For example, if the magnetic field is rotating counter-clockwise, a change in magnetic flux encountered at the first point would be detected subsequent in time at the second point. In the event the direction of rotation changes from counter-clockwise to clockwise, the change in polarity of magnetic flux encountered at the second point would then be detected subsequent in time at the first point. By comparing the changes in polarity of magnetic flux detected at the first point and the second point, the direction of rotation of the rotating magnetic field may be determined.
Stated alternatively, the first point and second point are located at an angle, or subsequent in the direction of rotation, from one another. For example, assume a first plane is defined by the plane that is coincident with the axis of the rotating magnetic field and the location of the first point. Accordingly, the second point is located within a second plane that is coincident with the axis about which the magnetic field is rotating and positioned such that the second plane and first plane form a positive angle from each other. By way of example only, the angle between the first plane and second plane may be 45 degrees or multiples thereof such as 135, 225, and 315 degrees. Importantly, the angle between the first plane and second plane should be greater than 0 degrees. Otherwise, the change in magnetic flux polarity being detected at the first point and second point will be identical and thereby preclude a determination of the direction of rotation.
The rotating magnetic field may be created by the rotation of a magnet mechanically coupled with a measuring element located in the path of a flowing fluid. By way of example only, the rotating magnet may be connected to a turbine or nutating disk within a fluid meter. Water flowing through the meter causes the magnet to rotate by acting upon the turbine. The magnet may be configured from a variety of shapes. For example, the magnet may be cylindrical in shape and contain four quadrants of polarity within the cylindrical shape.
In another exemplary embodiment, the present invention provides a method of sensing the rotation and direction of a rotating magnetic field as follows. Within the rotating magnetic field, the changes in polarity of magnetic flux are detected at a first point. These changes are used to create a corresponding first stream of electrical pulses that alternate in polarity. The alternations in polarity correspond to the changes in polarity in magnetic flux detected at the first point. The changes in polarity of magnetic flux occurring within the rotating magnetic field are also detected at a second point. The second point is located at a position that is subsequent in the direction of rotation from the first point. A second stream of electrical pulses is created that corresponds to the changes in polarity of magnetic flux detected at the second point. The first and second stream of electrical pulses are each converted, respectively, into a first and a second alternating high and low signal. The alternating high and low signals are then decoded to determine the number of rotations and direction of the rotating magnetic field. As stated, the present invention requires that the second point is located subsequent in the direction of rotation from the first point. This limitation ensures that the first and second points are located relative to each other such that a given change in polarity of magnetic flux does not occur at said first point and said second point at exactly the same time.
In another exemplary embodiment, the present invention includes generating a first series of alternating electrical signals that are in sequence with the alternating changes in magnetic flux polarity occurring at a first position located within a rotating magnetic field. The first series of alternating electrical signals are created as the changes in magnetic flux polarity occur and alternate in polarity with the changes in magnetic flux. Simultaneously, a second series of alternating electrical signals are generated that are in sequence with the alternating changes in magnetic flux polarity occurring at a second position located within the rotating magnetic field. The second series of signals are generated as the changes in magnetic flux polarity occur and the signals are of alternating polarity. The second position is located subsequent in the direction of rotation from the first position such that a given change in magnetic flux polarity does not occur at the first position and the second position at the same time. The resulting first and second signal are combined to create a first output indicating the amount of rotation of the magnetic field and a second output indicating the direction of rotation of the rotating magnetic field.
The step of combining the first signal and second signal may be accomplished by converting the first series of alternating electrical signals into a first pulse train of positive pulses and converting the second series of alternating electrical signals into a second pulse train of positive pulses. The first pulse train is translated into a first channel of alternating high and low output that is in sequence with the positive pulses of the first pulse train. The second pulse train is also translated into a second channel of alternating high and low output that is in sequence with the positive pulses of the second pulse train. By decoding the first and second channels of alternating high and low output, the direction and amount of rotation of the rotating magnetic field may be determined and provided as a first and second output, respectively.
In another exemplary embodiment, the present invention provides a fluid meter for determining the rate and direction of fluid flow. A magnet is provided that is rotatable about an axis. During rotations, the magnet is configured such that a field of changing magnetic flux polarity is created. The rotation of the magnet is created by having the magnet in mechanical communication with a measuring element. Upon being placed into the path of fluid flow, the measuring element is configured such that it will translate the kinetic energy of the moving fluid so as to cause the magnet to rotate about its axis.
Within the field of changing magnetic flux polarity created by the magnet, a first sensor is located and is configured for detecting the changes in magnetic flux polarity. The first sensor provides a first series of signals that represent the changes in magnetic flux polarity being detected by the first sensor. The first sensor is physically located within a first plane that is coincident with the axis about which the magnet rotates.
A second sensor is also placed within the field of changing magnetic flux polarity created by the rotating magnet. The sensor is configured for detecting the changes in magnetic flux polarity and providing a corresponding second series of signals that represents the changes in magnetic flux polarity. The second sensor is located with a plane that is coincident with the axis about which the magnet rotates. The first plane described above and the second plane form an angle with each other that is greater than 0 degrees. Means are provided and configured for receiving and interpreting the first and second series of signals so as to determine both the direction and amount of fluid flow.
The means for receiving and interpreting the first and second series of signals may include a first rectifier that receives the first series of signals ands converts the same into a first pulse train and a second pulse train of positive pulses, which collectively represent the first series of signals. A second rectifier receives the second series of signals and similarly converts the second series of signals into a third and a fourth pulse train of positive pulses which represent the second series of signals. A first translator is provided that includes circuitry for receiving both the first and second pulse train and translating the same into a first channel of alternating high and low signals which represent and correspond to said first and second pulse train. A second translator is provided that includes circuitry for receiving the third and fourth pulse train and translating the same into a second channel of alternating high and low signals which represent and correspond to the third and fourth pulse train. Decoding circuitry receives the first and second channel of alternating high and low signals and determines the direction and amount of fluid flow by decoding the first and second channel.
In another exemplary embodiment of the present invention, a device is provided for measuring fluid flow. The device includes a first chamber that defines both a fluid inlet and a fluid outlet. A measuring element is configured within the first chamber such that when a fluid passes through the first chamber it causes the measuring element to rotate. The measuring element is in mechanical communication with a magnet having a centerline. As the measuring element rotates, it causes the magnet to also rotate about its centerline. A second chamber is attached to the first chamber. The attachment may be permanent or may be interchangeable. Within the second chamber, a first sensor is positioned such that the first sensor is within the field of magnetic flux of said magnet. Accordingly, upon said magnet rotating with the measuring element, the first sensor detects the resulting changes in polarity of magnetic flux occurring at the position of the first sensor. The first sensor provides a first series of alternating electrical pulses that correspond to the changes in polarity of magnetic flux detected by the first sensor. A second sensor is also positioned within the second chamber. The second sensor is located or positioned relative to the first sensor such that the second sensor does not simultaneously detect the same change in magnetic flux being detected by the first sensor. Upon the magnet rotating, the second sensor detects the resulting changes in polarity of magnetic flux occurring at the location of the second sensor and provides a second series of alternating electrical pulses that correspond to the changes in polarity being detected. Means are provided for receiving and interpreting the first and second series of electrical pulses so as to determine the direction and magnitude of fluid flow.
The means for determining the direction and magnitude of fluid flow may include a first circuit for transposing the first series of alternating electrical pulses into a first pulse train of positive pulses and a second pulse train of positive pulses both of which correspond to the first series of alternating electrical pulses. A second circuit transposes the second series of alternating electrical pulses into a third and fourth pulse train of positive pulses which correspond to the second series of alternating electrical pulses. A third circuit converts the first and second pulse train into a first channel of alternating high and low states that represents the first and second pulse train. A fourth circuit converts the third and fourth pulse train into a second channel of alternating high and low states representing the third and fourth pulse train. A fifth circuit receives the first and second channel and determines the direction and magnitude of flow from the information received from the first and second channel.
In another exemplary embodiment, the present invention includes a housing that defines a fluid inlet and a fluid outlet. A magnet, rotatable about an axis, is located within the housing. Means are provided for causing the magnet to rotate about the axis as a fluid flows through the housing. Within the field of magnetic flux of the magnet, a first magnetic flux sensor is positioned. The first magnetic flux sensor is located within a first plane that is coincident with the axis about which the magnet rotates. A second magnetic flux sensor is also positioned within the field of magnetic flux of the magnet. The second magnetic flux sensor is located within a second plane coincident with the axis about which the magnet rotates. The first plane and second plane form an angle that is greater than 0 degrees so that the first and second magnetic flux sensors do not simultaneously detect the same change in magnetic flux polarity caused by the rotation of the magnet. In communication with the first and second magnetic flux sensors, circuitry is provided and configured such that the magnitude of rotation and direction of rotation of the magnet may be determined. The magnet may assume a variety of shapes. For example, the magnet may be cylindrically shaped and include four quadrants of polarity.
In still another exemplary embodiment of the present invention, a first chamber is provided and defines a fluid inlet and fluid outlet. Within the first chamber a rotatable magnetic member is configured such that when a fluid passes through the first chamber the member is caused to rotate about an axis. A second chamber is attached to the first chamber. The second chamber may be permanently attached or may be interchangeable. A first magnetic flux sensor is positioned within the second chamber and is configured for sensing and detecting the changes in polarity of magnetic flux generated by the rotation of the magnetic member. The first magnetic flux sensor is located within a first plane that is coincident with the axis about which the magnetic member is rotatable. A second flux sensor is also positioned within the second chamber and is configured for sensing and detecting the changes in polarity of magnetic flux generated by the rotation of the magnetic member. The second magnetic flux sensor is located within a second plane that is coincident with the axis about which the magnetic member is rotatable. The first plane and second plane form an angle greater than 0 degrees. This angle ensures that the first and second magnetic flux sensor do not simultaneously detect the same change in magnetic flux polarity caused by the rotations of the magnetic member. Circuitry is provided in communication with said first and second magnetic flux sensors. The circuitry is configured such that the magnitude of rotation or direction of rotation, or both, of the rotatable magnetic member may be determined.
Finally, in still another exemplary embodiment of the present invention, a first housing is provided that defines a fluid inlet and a fluid outlet. A first magnet is configured within the first housing such that a fluid passing through the first housing causes the first magnet to rotate. A second housing is attached to the first housing. The second housing may be permanently attached or may be interchangeable. Within the second housing a second magnet is located and configured such that it is in magnetic communication with the first magnet. Accordingly, upon said first magnet rotating, said second magnet rotates about an axis. A first magnetic flux sensor is positioned within the second housing and is configured for detecting the changes in polarity of magnetic flux generated upon the rotation of said second magnet about its axis. The first magnetic flux sensor is located within a first plane that is coincident with the axis about which said second magnet rotates. The second magnetic flux sensor is also positioned within the second housing and is configured for detecting the changes in magnetic flux polarity occurring upon the rotation of said second magnet about its axis. The second magnet is located within a second plane that is also coincident with the axis about which the second magnet rotates. The first plane and the second plane form an angle greater than 0 degrees. Circuitry is provided that is in communication with the first and second magnetic flux sensors and is configured such that the magnitude of rotation and direction of rotation may be determined.
As above described, each embodiment of the invention requires that the changes in magnetic flux polarity created by a rotating magnetic field be sensed or detected at two positions within the field. Any sensor capable of detecting a change in magnetic field may be used. By way of example only, one type of sensor that may be used to detect changes in magnetic flux polarity is disclosed in U.S. Pat. No. 3,820,090 issued to Wiegand. This reference discloses a magnetic sensor that may be formed by cold working a wire constructed from iron, cobalt, and vanadium. When placed in the presence of a changing magnetic field, the wire will produce an electrical pulse that may be detected by appropriate circuitry. Alternatively, when placed in the presence of a changing magnetic field, the wire will also induce a voltage across a coil located near the wire. This resulting signal may be also captured by appropriate circuitry. The entire disclosure of U.S. Pat. No. 3,820,090 is incorporated herein by reference.
It is to be understood that exemplary embodiments of the subject invention equally involve methodology as well as apparatus disclosed herewith.
Additional objects and advantages of the invention are set forth, or will be apparent to, those of ordinary skill in the art from the detailed description as follows. Also it should be further appreciated that modifications and variations to the specifically illustrated and discussed features and materials hereof may be practiced in various embodiments and uses of this invention without departing from the spirit and scope thereof, by virtue of present reference thereto. Such variations may include, but are not limited to, substitutions of the equivalent means, features, steps, and materials for those shown or discussed, and the functional or positional reversal of various parts, features, steps, or the like.
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