Abstract:
An orientation sensor capable of generating at least one output signal indicative of a particular orientation parameter is described. The orientation sensor comprises a sensor housing defining a closed internal chamber including a first internal surface. The first internal surface supports a first electrically conductive pattern which itself forms part of a sensing arrangement. The first electrically conductive pattern includes an arrangement of electrically isolated segments in a predetermined configuration. A flowable material is contained within the internal chamber, which flowable material contacts a portion of the first internal surface dependent upon the value of the particular orientation parameter. An electrical property is measurable between the segments such that the orientation parameter can be determined using the output signal based only on the electrical property and, therefore, only on the portion of the first internal surface contacted by the flowable material. Thus, intra-pattern measurements yield the measured property without the need for conductive members distributed along the length of the chamber. A combination pitch/roll sensor is described in which a single electrically conductive pattern cooperates with the flowable material so as to produce independent electrical signals corresponding to the pitch and roll of the housing. In one aspect, first and second electrically conductive patterns are provided at opposing ends of a flowable material chamber. Use of signals from the patterns results in ratiometric cancellation of temperature error.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to the field of orientation sensors and, more particularly, to an orientation sensor including a conductive pattern including isolated conductive segments configured for segment to segment (hereinafter intra-pattern) property measurements useful in establishing one or more orientation parameters. The sensor is suitable for use in applications such as, for example, monitoring a remotely controlled underground boring device.  
           [0002]    A number of orientation sensors have been designed especially for use in remote controlled underground boring devices. As will be seen, these prior art devices have shared a basic design concept.  
           [0003]    One example of a prior art orientation sensor in the form of a roll sensor is disclosed in U.S. Pat. No. 5,174,033 (Rider). FIGS. 1 and 2 are partial reproductions of FIGS. 4 and 5, respectively, of the Rider patent. FIG. 1 shows a roll sensor generally indicated by the reference number  10 . Sensor  10  includes a substrate  12  and a cup-shaped member  14  which is sealed to substrate  12  by an O-ring  16  in a way which defines a cavity  18 . A conductive fluid  20  is contained by cavity  18 .  
           [0004]    Attention is now directed to FIG. 2 in conjunction with FIG. 1. FIG. 2 illustrates a plurality of capacitor electrode plates  22  which are formed on the inner surface of substrate  12 . Electrical connections to capacitor electrode plates  22  are accomplished via a plurality of electrically conductive leads  24 . Cup-shaped member  14  serves as a grounded electrode common to all of electrode plates  22 . During operation, roll sensor  10  is designed to spin in the plane of FIG. 2, oriented such that gravity causes fluid  20  to continuously flow into the bottom portion of the cavity (FIG. 1). The roll orientation of sensor  10  is determined by measuring the capacitance between individual electrode plates  22  and cup-shaped member  14  as influenced by fluid  20 . It is important to note that measurements are taken, in essence, between the ends of the device. Moreover, it is submitted that prior art orientation sensors, in general, operate under the concept of using measurements taken along the length of the device. That is, by using electrically conductive members positioned at least at the ends of the device and/or centered therebetween or at other intermediate locations. For other examples, see U.S. Pat. Nos. 4,674,579, 4,714,118 and 5,726,359. As will be seen, the present invention eliminates the need for an implementation having electrodes at both ends of a device or spaced apart therebetween, introducing a highly advantageous and heretofore unseen configuration useful in measuring pitch and/or roll.  
         SUMMARY OF THE INVENTION  
         [0005]    As will be described in more detail hereinafter, there is disclosed herein an orientation sensor capable of generating at least one output signal indicative of a particular orientation parameter. The orientation sensor comprises a sensor housing defining a closed internal chamber including a first internal surface. The first internal surface supports a first electrically conductive pattern which itself forms part of a sensing arrangement. The first electrically conductive pattern includes an arrangement of electrically isolated segments in a predetermined configuration. A flowable material is contained within the internal chamber, which flowable material contacts a portion of the first internal surface dependent upon the value of the particular orientation parameter.  
           [0006]    In one aspect of the invention, an electrical property is measurable between the segments such that the orientation parameter can be determined using the output signal based only on the electrical property and, therefore, only on the portion of the first internal surface contacted by the flowable material. Thus, intra-pattern measurements yield the measured property without the need for conductive members distributed along the length of the chamber.  
           [0007]    In another aspect of the invention, the particular orientation parameter is pitch. In this instance, a first electrically conductive pattern includes first and second electrically isolated segments defining a gap therebetween on the first internal surface such that the value of the electrical property is in proportion to an area of the gap covered by the flowable material between the first and second segments which, in turn, is in proportion to the pitch so as to cause the value of the electrical property between the first and second segments to change in response to changes in pitch.  
           [0008]    In still another aspect of the invention, the particular orientation parameter is roll angle. In this instance, the first electrically conductive pattern includes at least first and second electrically isolated segments defining a first roll sensing gap therebetween on the first internal surface such that the value of the electrical property is in proportion to an area of the roll sensing gap covered by the flowable material between the first and second segments which, in turn, is in proportion to the roll so as to cause the value of the electrical property between the first and second segments to change in response to changes in roll. In one feature, the electrically conductive pattern defines a plurality of roll sensing gaps, each of which covers a particular range of roll positions of the orientation sensor. In one preferred embodiment, the electrically conductive pattern defines three roll sensing gaps that are configured so as to substantially surround a common center point about which the orientation sensor experiences roll. Each roll sensing gap is used to produce an output such that the roll position of the orientation sensor is unambiguously identifiable either statically or dynamically.  
           [0009]    In yet another aspect of the present invention, an orientation sensor is provided which is capable of generating at least two output signals indicative of a particular orientation parameter. The orientation sensor comprises a sensor housing defining a closed internal chamber having first and second opposing internal surfaces. A first electrically conductive pattern is supported by the first internal surface and a second electrically conductive pattern is supported by the second internal surface. The first electrically conductive pattern includes a first plurality of electrically isolated segments in a first predetermined configuration while the second electrically conductive pattern includes a second plurality of electrically isolated segments in a second predetermined configuration. A flowable material is contained within the internal chamber such that the flowable material contacts first and second portions, respectively, of the first and second internal surfaces. The respective areas of the first and second portions contacted by the flowable material are dependent upon the value of the particular orientation parameter in a way which influences an electrical property measurable between the segments disposed on the first and second surfaces such that the first electrically conductive pattern produces at least a first output signal and the second electrically conductive pattern produces at least a second output signal. In one feature of the present invention, each pattern produces its output signal substantially independent of the other pattern based on contact with the flowable material.  
           [0010]    In another feature of the present invention, the first and second electrically conductive patterns are identical and identically oriented such that combined use of the output signals to determine the value of the orientation parameter produces ratiometric cancellation of temperature error.  
           [0011]    In one implementation according to the present invention, a combination pitch and roll orientation sensor is provided having a housing containing a flowable material which flows in the housing in response to the pitch and roll orientation of the housing. An electrical arrangement includes a single electrically conductive pattern cooperating with the flowable material so as to produce independent electrical signals corresponding to the pitch and roll of the housing. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The present invention may be understood by reference to the following detailed description taken in conjunction with the drawings briefly described below.  
         [0013]    [0013]FIGS. 1 and 2 are prior art figures taken directly from U.S. Pat. No. 5,174,033 for use in conjunction with the discussion of the prior art appearing above.  
         [0014]    [0014]FIG. 3 is a diagrammatic side view of an orientation sensor manufactured in accordance with the present invention, shown here to illustrate general aspects of its highly advantageous structure.  
         [0015]    [0015]FIG. 4 is a diagrammatic illustration of one of two identical printed circuit boards used in the orientation sensor of FIG. 3, shown here to illustrate the overall outline of the boards in conjunction with a highly advantageous electrically conductive sensing pattern that is defined on the depicted side of each board.  
         [0016]    [0016]FIG. 5 is a diagrammatic illustration showing an electrically conductive pattern formed on the side of the printed circuit boards opposing the side depicted in FIG. 4.  
         [0017]    [0017]FIG. 6 is a diagrammatic/schematic illustration showing one highly advantageous manner of electrically interconnecting the printed circuit boards of the orientation sensor of FIG. 3 for purposes of measuring pitch orientation.  
         [0018]    [0018]FIG. 7 is a diagrammatic/schematic illustration showing one highly advantageous manner of electrically interfacing with the printed circuit boards of the orientation sensor of FIG. 3 for purposes of measuring roll orientation, which simultaneously permits the use of the pitch measurement scheme shown in FIG. 6.  
         [0019]    [0019]FIG. 8 is a plot illustrating normalized roll output signals from the orientation sensor and associated circuitry of FIG. 7. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    Having described FIGS. 1 and 2 previously, attention is immediately directed to FIG. 3 which illustrates an orientation sensor manufactured in accordance with the present invention and generally indicated by the reference numeral  100 . It is noted that dimensions in FIG. 3 have been exaggerated for illustrative purposes. Sensor  100  is made up of first and second printed circuit boards  102   a  and  102   b , respectively. A cylindrical tube  106  includes openings which are sealed to the inner facing surfaces  108   a  and  108   b  of each of the printed circuit boards so as to define a cavity  110 . Tube  106  may be formed, for example, from quartz or from other such suitable materials. In this preferred embodiment, printed circuit boards  102   a  and  102   b  are identical to one another, as well as being identically oriented at either end of tube  106 . It is to be understood, however, that an effective orientation sensor may be produced using only one of these printed circuit boards by sealing off tube  106 , for example, at the location of a dashed line  112 , which is described in further detail below.  
         [0021]    Attention is now directed to FIGS. 3 and 4. The latter figure illustrates a printed circuit board pattern  114  that is formed on inner sides  108   a  and  108   b  of each of printed circuit boards  102   a  and  102   b . The overall outline of the printed circuit boards is a “tombstone” configuration, however, it should be appreciated that any suitable outline may be used so long as measurements can be obtained in accordance with the teachings herein. Pattern  114  defines a highly advantageous configuration made up of individual, electrically isolated segments including one combination of segments for sensing pitch and another combination of segments for sensing roll. Specifically, a first segment  120  and a second segment  122  comprise a pitch sensing arrangement defining a pitch sensing gap  124 . The first segment comprises a circular shape with its center located at center point  128 . Alternatively, segment  120  could comprise a ring shape or other such suitable form. Second segment  122  comprises a ring shape which is likewise centered on center point  128  such that its innermost edge is equidistant from the edge of segment  120  about its periphery. During operation, orientation sensor  100  is designed to be mounted, for example, in the drill head of a boring tool such that roll takes place about an axis  126  (FIG. 3) which passes through the center point  128  (FIG. 3) of each of printed circuit boards  102   a  and  102   b . Pitch, on the other hand, is measured in terms of the angle φ, as indicated in FIG. 3, wherein an arrow  130  represents a horizontal orientation.  
         [0022]    Still referring to FIGS. 3 and 4, the roll sensing combination of segments comprises segment  122  along with segments  132   a - c  so as to define first, second and third roll sensing gaps  134   a - c , respectively, which serve to surround center point  128 . Each of segments  132   a - c  is spaced uniformly apart from segment  122  by virtue of an appropriate radius centered upon center point  128 . Therefore, each roll sensing gap covers an arc of somewhat less than 120° and is arcuate in form having a constant width. External connections are made via connection pads  136   a - c  wherein pads  136   a - c  are connected to roll sensing segments  132   a - c  while pad  137  is connected to segment  122 . The connection pads are electrically connected with their associated segments by appropriately configured traces. For purposes of clarity, the traces are identified using the appropriate connection pad reference number. It is noted that segment  122  includes projections  138   a  and  138   b . These projections serve to equalize roll signals obtained from the different roll sensing segments by approximating that portion of trace  137  which extends between roll sensing segments  132   b  and  132   c.    
         [0023]    Attention is now directed to FIGS.  3 - 5 . FIG. 5 illustrates an electrically conductive pattern  140  formed on outer sides  142   a  and  142   b  of printed circuit boards  102   a  and  102   b , respectively. A feed-through  144  defining a through-hole is positioned encompassing center point  128  whereby to electrically connect a trace  146  and associated connection pad with segment  120  of pattern  114  on the opposite side of the printed circuit board. Connection pad  146  is arranged so as to be positioned laterally between connection pads  136   a  and  136   c  of pattern  114  (comparing FIGS. 4 and 5) for purposes of maintaining signal isolation between segment  120  and the various other segments. This purpose is also furthered by a ground segment  148  which covers essentially all of outer sides  142 , but for trace/pad  146  and a space  150  defined between ground segment  148  and trace/pad  146 . It is noted that patterns  114  and  140  may be modified in any suitable manner in accordance with the present invention. For example, in pattern  114 , roll sensing segments  132   a - c  may be positioned (not shown) within the interior of segment  122  while segment  120  may surround (not shown) the outer periphery of segment  122 .  
         [0024]    Still referring to FIGS.  3 - 5 , chamber  14  is partially filled with a flowable material such as, for example, a suitable conductive fluid  152  which is selected to function in the manner to be described. The fluid may readily be injected, for example, into chamber  106  through feed-through  144  of printed circuit board  102   a  while air is allowed to escape from the feed-through of printed circuit board  102   b . Thereafter, the feed-throughs may be sealed using any suitable material such as, for example, silicone sealant. One useful conductive fluid has been found to be glycerin with a small quantity of saline solution added to provide for conductivity, as described in U.S. Pat. Nos. 5,155,442, 5,337,002, 5,444,382 and 5,726,359 which are incorporated herein by reference. In order to function in the manner intended, and at the same time, optimize contact with patterns  114  on surfaces  108   a  and  108   b , chamber  106  is filled with conductive fluid  152  to a predetermined level. As will be seen, the predetermined fluid level should be selected in view of several considerations with regard to establishing an operational range of orientations to be detected. Thus, conductivity, as measured between any pair of segments defining a sensing gap, will vary based upon the portion of the sensing gap in direct contact with the conductive fluid. It is important to understand that flowable materials that enable measurement of electrical characteristics other than conductivity (such as capacitance and inductance) may also be used in chamber  110 . For instance, materials having dielectric characteristics are well suited wherein capacitance measured between the segments of electrically conductive pattern  114  varies in accordance with the portion of the fluid contacting the respective sensing gap. One example of a material having such dielectric characteristics is liquid silicone.  
         [0025]    Having generally described the structure of orientation sensor  100 , the pitch aspect of its operation will be described with reference to FIGS. 3 and 6. For any particular pitch orientation within a predetermined operational range, some portion of each pitch sensing gap  124  will be contacted by conductive fluid  152 . FIG. 6 diagrammatically illustrates printed circuit boards  102   a  and  102   b  along with external electrical connections in a configuration for purposes of sensing pitch. The illustrated pitch measurement configuration utilizes a voltage source  160  having a positive (+) terminal electrically connected to connection pad  137  of printed circuit board  102   b  and a negative terminal (−) connected to pad  137  of printed circuit board  102   a . For purposes of illustrations only this is shown as a direct current source. In actual practice, the source would be alternating in order to avoid electrolytic damage to the conductive fluid  152  and/or other parts of the orientation sensor  100 . Connection pads  146  of printed circuit boards  102   a  and  102   b  are electrically connected with one another and a pitch output  162  is taken from this connection. The variable resistivities between segments  120  and  122  of printed circuit boards  102   a  and  102   b  caused by contact of conductive fluid  152  with pitch sensing gaps  124  of the respective printed circuit boards are illustrated by equivalent variable resistors ER 164  and ER 166 . It is to be understood that these equivalent variable resistors each represent a lumped resistance corresponding to the actual, distributed resistance produced by the corresponding pitch sensing gap in contact with conductive fluid  152 . Thus, in operation, the sensor illustrated in FIG. 6 functions as equivalent variable resistors ER 164  and ER 166  connected in series with one another across voltage source  160 .  
         [0026]    Continuing to refer to FIGS.  3 - 5 , it should be appreciated that the illustrated pitch sensing arrangement is highly advantageous. Specifically, orientation sensor  100  is configured for roll about axis  126 . Segments  120  and  122  of each printed circuit board, therefore, define pitch sensing gap  124  in such a way that the gap surrounds center point  128 . Additionally, pitch sensing gap  124  is circular in configuration and centered on center point  128  so that contact of the pitch sensing gap with conductive fluid  152  is constant irrespective of roll about axis  126  (assuming the proper characteristics of fluid  152 , as described above). Therefore, printed circuit boards  102   a  and  102   b  provide a constant pitch output signal for a fixed pitch orientation, which output signal is independent of roll. It should be appreciated that the pitch sensing gap may be configured depending on the specific intended application. For example, in a pitch sensor which is not subjected to roll, in normal use the pitch sensing gap may be defined as a “stripe” having a vertical component of orientation. Any configuration of pitch sensing gap is suitable in this regard so long as the area of the gap contacted by conductive fluid  152  is proportional to pitch orientation.  
         [0027]    Still considering the pitch orientation measurement configuration illustrated in FIG. 6, it is important to understand that each printed circuit board produces a pitch signal independent of the other board. That is, each board measures pitch based solely on the resistivity present between segments  120  and  122  of pattern  114 . In essence, the measurements are taken in the plane of each printed circuit pattern. Therefore, as mentioned previously, only one of printed circuit boards  102   a  and  102   b  is necessary for producing a pitch measurement. Applicants submit that such a configuration has not been seen in the prior art. Accordingly, an effective pitch sensor may be implemented by closing chamber  110  at aforementioned line  112  such that the chamber is defined between this line and printed circuit board  102   a . The concept of independently produced measurements provides significant advantages over the prior art for reasons to be described.  
         [0028]    As discussed above, prior art orientation sensors require electrodes that are positioned at opposing ends of a chamber (see FIGS. 1 and 2) and possibly centered or at other intermediate positions between the ends of the chamber (not shown). Accordingly, such prior art arrangements measure the electrical property of interest as distributed along the length of the chamber. The entirety of the chamber is thus involved in obtaining the desired measurement. In contrast, because the electrically conductive pattern of the present invention independently produces its measurement, the entirety of the flowable medium chamber is not involved in generating the desired orientation signal. That is, measurements are localized at each printed circuit board. In and by itself, it is submitted that this feature provides a heretofore unseen opportunity for improvement in the accuracy of an orientation sensor using a single flowable medium chamber. The significance of such independent readings will be described immediately hereinafter.  
         [0029]    Referring again to FIGS.  3 - 5 , it should be appreciated that the electrical interconnection of printed circuit boards  102   a  and  102   b  in FIG. 6 utilizes the independently produced pitch signal of each board in a highly advantageous way. Specifically, as noted above, equivalent resistance  164  of circuit board  102   a  and equivalent resistance  166  of circuit board  102   b  are connected in series across voltage source  160  with pitch output  162  being taken at the common connection between the equivalent resistances. It should also be appreciated that measurements taken from each of the printed circuit boards are affected as a result of changes in conductivity of electrically conductive fluid  152  resulting from temperature changes. If only one printed circuit board were used, such temperature effects should be given consideration. However, in the circuit of FIG. 6, temperature equally affects the pitch signal produced by each printed circuit board. Therefore, as a result of the series connection of equivalent resistances  164  and  166 , the temperature produced resistance changes are seen to essentially cancel one another. No provision other than the use of the illustrated interconnection is required in order to realize this advantage. Therefore, in accordance with the present invention, this configuration is substantially immune to temperature induced error. It should be appreciated that the described temperature cancellation effects are ratiometric in nature and are not limited to this specific configuration. That is, ratiometric cancellation will be exhibited whenever a ratio is taken between measurements produced by the printed circuit boards  102   a  and  102   b  at either end of the orientation sensor.  
         [0030]    Although the pitch measurements produced by printed circuit boards  102   a  and  102   b  are independent of each other, it should be appreciated that, for any particular pitch angle, the different portions of each printed circuit pattern contacted by conductive fluid  152  are, in fact, interdependent. For this reason, pitch output  162  is unique for any particular pitch orientation within a specified operational range of pitch angles. Specific details will be provided for establishing a particular operational range at an appropriate point below. It should be noted that the sensitivity of the orientation sensor is proportional to the length of tube  106  (FIG. 3).  
         [0031]    Attention is now directed to FIG. 7 in conjunction with FIGS.  3 - 5 . FIG. 7 diagrammatically illustrates orientation sensor  100  including external electrical connections made to printed circuit boards  102   a  and  102   b  for use in sensing roll orientation. As mentioned previously, roll orientation sensing is accomplished using a particular combination of segments including segments  132   a - c  and segment  122 , all of which cooperatively define roll sensing gaps  134   a - c . The external circuitry configuration of FIG. 7 may be used simultaneously with the pitch sensing configuration of FIG. 6 such that each of printed circuit boards  102   a  and  102   b  independently produces a pitch signal, but also independently produces roll signals. To this end, voltage source  160  is applied to connection pad  137  of each printed circuit board  102   a  and  102   b , as originally shown in FIG. 6 so as to apply voltage to segment  122  of each printed circuit board  102   a  and  102   b . Each one of connection pads  136   a - c  for each printed circuit board  102   a  and  102   b  is connected to a circuit ground  170  through one of a plurality of resistors indicated by the reference numbers R 172   a - f , all of which have the same value. Equivalent resistances of roll sensing gaps  134   a - c  for printed circuit board  102   a  are indicated by the reference numbers ER 174 , ER 176  and ER 178 , respectively, while equivalent resistances of roll sensing gaps  134   a - c  for printed circuit board  102   b  are indicated by the reference numbers ER 180 , ER 182  and ER 184 , respectively. Once again, it is to be understood that each of these equivalent variable resistors represents a lumped resistance corresponding to the actual, distributed resistance produced by the corresponding roll sensing gap in contact with conductive fluid  152 . Therefore, a voltage divider is formed for each roll sensing gap comprising the resistance of the pitch sensing gap in series with one of resistors R 172 . Six roll outputs are indicated as ROLL a-f . For example, roll sensing gap  134   a  of printed circuit board  102   a , having an equivalent resistance represented by ER 174 , is in series with resistor R 172   a . The corresponding roll output, ROLL a , is taken from the connection of R 172   a  and connection pad  136   a.    
         [0032]    Attention is now directed to FIGS. 7 and 8. FIG. 8 illustrates output signals ROLL a-c  for counterclockwise roll in the direction indicated by an arrow  190 . For purposes of clarity, output signals ROLL d-f  (independently produced by printed circuit board  102   b ) have not been illustrated. The specific position of printed circuit boards  102   a  and  102   b  in FIG. 7 correspond to the roll position of 0° in FIG. 8. Chamber  106  and the level of fluid  152  are also diagrammatically shown between the two printed circuit boards. In the position shown in FIG. 7, roll sensing gap  134   c  is completely immersed in fluid  152 . Roll sensing gap  134   a  is partially immersed in the fluid and is being further immersed by continuing rotation. Therefore, ROLL a  exhibits a positive slope at the 0° roll position. Roll sensing gap  134   b  is also partially immersed in fluid, but is emerging from the fluid with rotation such that ROLL b  exhibits a negative slope at the 0° roll position. It is apparent from FIG. 8 that the combination of these three roll signals unambiguously identifies the roll position of orientation sensor  100  for any particular roll orientation under both static and dynamic conditions. Moreover, the roll output waveforms of FIG. 8 contemplate the level of fluid  152  as being above center point  128  of printed circuit board  102   a  since positive plateaus  192  of the roll signal waveforms are longer in duration than negative plateaus  194 . That is, the orientation sensor is pitched such that the roll sensing gaps are completely immersed in fluid  152  over an arc that is longer than the arc over which the roll sensing gaps are completely out of contact with the fluid. This condition may be caused, for example, by a pitch, φ, of approximately −10% grade as indicated by fluid  152  which causes a greater proportion of fluid to contact printed circuit board  102   a  compared with the portion contacting printed circuit board  102   b . The usefulness of roll signals from the second printed circuit board will be described immediately below.  
         [0033]    Referring to FIGS. 3 and 4, the operational range of orientations over which orientation sensor  100  is useful depends upon a number of different factors including the level of fluid  152 , the length, L, of chamber  110  (tube  106 ), the A diameter of tube  106  and the widths of the various pitch and roll sensing gaps. In this regard, the overall combination of these factors cooperate interactively to establish the operational range of the sensor. An orientation sensor has been produced in accordance with this disclosure for use in a horizontal directional drilling application anticipating an operational pitch range of approximately ±100% grade. Specific dimensions of this working embodiment include tube  106  having a length, L, of approximately 0.188 inches and an inside diameter of approximately 0.375 inches. Pitch sensing gap  124  includes inner and outer diameters of approximately 0.195 inches and 0.234 inches, respectively. Roll sensing gaps  134   a - c  include inner and outer diameters of approximately 0.275 inches and 0.313 inches, respectively. These dimensions may be modified in any suitable way depending upon a specific application. For example, L may be increased so as to increase the pitch sensitivity of the orientation sensor. Likewise, pitch sensitivity is increased by lowering the relative level of fluid  152 . However, the effect of any modification should be considered with regard to other factors. For instance, if L is inordinately increased, the range over which fluid  152  contacts both printed circuit boards  102   a  and  102   b  will be decreased. The net result, at high pitch, may be one printed circuit board completely covered by fluid  152  while the opposing board makes no contact with fluid  152 .  
         [0034]    It should be appreciated that the roll output signals of printed circuit board  102   b  will essentially be identical to those obtained from printed circuit board  102   a  when pitch angle φ is equal to zero. In instances where φ is not equal to zero, the output signals obtained from one printed circuit board will vary from those of the other printed circuit board dependent upon the specific value of φ. Because the rotational motion of inner sides  108   a  and  108   b  of printed circuit boards  102   a  and  102   b  relative to axis  126  is opposite to one another, ROLL a  of printed circuit board  102   a  corresponds to ROLL b  of printed circuit board  102   b  while ROLL b  of printed circuit board  102   a  corresponds to ROLL a  of printed circuit board  102   b . While both printed circuit boards  102   a  and  102   b  independently produce roll signals, the overall accuracy of orientation sensor  100  can be improved even further by utilizing the roll signals available from both printed circuit boards. For example, all six of the roll signals may be converted to digital signals using an analog to digital converter (not shown), provided to a microprocessor (not shown), and thereafter provided to a suitable arrangement, such as a display (not shown) for calculation and display of the roll position of the orientation sensor.  
         [0035]    The roll sensing configuration disclosed in FIG. 7 herein may be modified in an unlimited number of ways according to the present invention. For example, any number of two or more roll sensing gaps may be utilized. In the instance where only roll is dynamically measured, as little as a single roll sensing gap is useful. For example, a roll sensing gap (not shown) may be configured including a varying, known width which surrounds the center of rotation of roll of the orientation sensor. Dynamic analysis of the output from such a sensing gap can be used to uniquely identify any particular roll position. In this regard, any combination or configuration of the roll sensing gaps which uniquely identifies roll position of the orientation sensor is useful whether operable in static or dynamic conditions. Another possible modification resides in providing printed circuit boards having sensing gaps of different configurations (not shown) at either end of chamber  106  or, alternatively, identical patterns offset with respect to one another may be provided at either end of chamber  110 . In this way, two roll sensing gaps may be used to uniquely identify the static roll position of orientation sensor  100 .  
         [0036]    Because the orientation sensor disclosed herein may be provided in a variety of different configurations and modified in an unlimited number of different ways, it should be understood that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the invention. For example, electrically conductive patterns may be provided in forms other than as electrically conductive traces on a printed circuit board. In one such alternative, relatively rigid grid wires (not shown) may be used wherein the flowable medium may flow around and between the grid wires. Therefore, the present examples and methods are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope of the appended claims.