Abstract:
The present disclosure generally relates to a capacitance sensing apparatus equipped with self-calibrating capacity and method of use thereof. The disclosure contemplates the determination using a secondary means of precise fluid levels according to five possible embodiments, and the use of the determined fluid level to recalibrate the capacitance sensing apparatus along its continuous analog level, namely, a variation of the thickness of the insulation of a capacitance sensing apparatus, the variation of the surface geometry of the capacitance sensing apparatus, the use of a dual-probe sensor including a probe with a varied surface geometry, the use of an electromagnetic sensor adjoining the capacitance sensor, and the variation of the electromechanical sensor to serve as a capacitance sensing apparatus. The disclosure also contemplates methods for using the sensing apparatus previously disclosed to measure a fluid level using a self-calibrating capacitance sensing apparatus. Finally, the present disclosure contemplates the use of an improved mathematical method associated with a variability measurement, such as an exponential smoothing method, to determining locally discrete changes in the variability measurement of the capacitance in order to determine a fixed fluid level.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/595,135, filed on Jun. 8, 2005. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    This disclosure relates to a self-calibrating capacitance fluid level sensing apparatus and method of use thereof, and more particularly, to an analog capacitance fluid level sensing apparatus further calibrated at fixed fluid levels with a signal from either a variable thickness in the insulated capacitance probe, a variable geometry of the capacitance probe, an input from an adjoining electromechanical sensor, or an input from a joined electromechanical sensor. 
       BACKGROUND 
       [0003]    Varied technologies exist to measure fluid levels in containers. These technologies include but are not limited to mechanical sensors, electromechanical sensors, radar sensors, visual sensors, weight sensors, laser sensors, ultrasonic sensors, and capacitance sensors. Fluid characteristics such temperature, viscosity, conductivity, chemical abrasiveness, acidity, and the like may vary during the measurement of sensors from one level to a second level. These variations may offset measures from a sensor relying on a fixed characteristic to determine a precise level in a container. For example, if a mechanical sensor determines the level of a fluid by first measuring the weight in a known container geometry and associated the first weight on a fluid level based on calculations of the volumetric density of the fluid, once the fluid temperature increases, the volumetric density may decrease, raising the level above the calculated value. For this reason, analogous measures performed over a long period of time require recalibration to actual measured levels. 
         [0004]    Fluids such as water are known to serve as proper electrical conductors. If a body of water placed between insulated plates is energized at a certain voltage (V) under the strain from the resulting dielectric force field, a conductive fluid is charged (Q). The capacitance (C) of a fluid is a measure of the amount of electricity stored in a fluid volume divided by the potential of the body. The general formula for the determination of capacitance is C=Q/V. The determination of a capacitance (C) when applied to known geometries can be shown to respond to the following equation: C=kA/d, where k is the dielectric constant of the fluid between plates, A is the cross-sectional area of the plates, and d is the distance between the plates. It is understood by one of ordinary skill in the art that correction factors must be applied to the calculation of any capacitance with plates and surfaces of irregular geometries. 
         [0005]    Capacitance sensors consist of either placing two polarized bodies at a fixed voltage (V), often insulated in a conductive fluid, or placing a single insulated body within another body and using the general conductive container of the fluid as a pole of the dielectric force field. As the water level rises in the container, not only does the available capacitive volume increase, the contact surface of the fluid with the polarized bodies increase accordingly. 
         [0006]    Capacitance sensors are used in a wide range of environments, including at extreme temperature or in toxic environment, since they require no moving parts and are resistant to vibration, even absent a gravitational field. For example, cryogenic fuel levels on spacecraft are measured by capacitance sensors. Capacitance sensors are inherently vulnerable to changes in fluid characteristics since the dielectric constant of fluids may vary greatly with temperature, chemical composition, pollutants, segregation, phase changes, and other fluid characteristics. For example, the presence of salt or the formation of blocks of ice in a body of water can dramatically affect its measure of capacitance and ultimately the fluid level determined by a capacitance sensor. Detection based on capacitance is also limited by nonintrusive size sensors with limited surface area and the need to measure at low voltage levels. Capacitance sensors often operate at minimal detection levels and require redundant measures in order to determine a level within a limited margin of error. 
         [0007]    Therefore, there is a need in the art for a capacitance sensor able to self-calibrate along its analog range of measurement at certain fixed fluid levels in order to limit the uncertainties associated with inherent limitations of this type of sensor. 
       SUMMARY 
       [0008]    The present disclosure generally relates to a capacitance sensing apparatus and method of use thereof equipped with self-calibrating capacity. The disclosure contemplates the determination using a secondary means of precise fluid levels according to a plurality of possible embodiments and the use of the determined fluid level to recalibrate the capacitance sensing apparatus along its continuous analog measure. 
         [0009]    In one embodiment of the present disclosure, the thickness of the insulation of a capacitance body is varied along a precise function along its vertical axis. The variations at determined levels creates a change in the variability measurement of the capacitance of the fluid leading to a recalibrating level for the capacitance sensor. In another embodiment of the present disclosure, the surface geometry of the capacitance body is varied along a precise function along its vertical axis. The variations at determined levels also create a change in the variability measurement of the capacitance of the fluid and can be used to recalibrating the level for a capacitance sensor measure. In another embodiment of the present disclosure, a dual-sensor body is used where a third body has a varied surface geometry along a precise function along its vertical axis while a first body has a regular surface geometry. Variations in the capacitance variability measurement between both bodies are used to recalibrate the measure from the first body. In another embodiment of the present disclosure, an electromagnetic sensor is used together with the capacitance sensor to measure predetermined fluid levels. In another embodiment of the present disclosure, the main guide of an electromechanical sensor is modified to allow a guide to serve as a capacitance sensing apparatus recalibrated by the electromechanical sensor. 
         [0010]    The disclosure also contemplates methods for using the sensing apparatus previously disclosed to measure a fluid level using a self-calibrating capacitance sensing apparatus. Finally, the present disclosure also contemplates the use of an improved mathematical method associated with a variability measurement, such as an exponential smoothing method to determine locally discrete changes in the variability measurement of the capacitance in order to determine a fixed fluid level. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]    Certain embodiments are shown in the drawings. However, it is understood that the present disclosure is not limited to the arrangements and instrumentality shown in the attached drawings. 
           [0012]      FIG. 1  is a functional side view of the self-calibrating capacitance fluid level sensing apparatus according to one embodiment of the present disclosure. 
           [0013]      FIG. 2  is a partial functional view of the sensor element of the self-calibrating capacitance fluid level sensing apparatus of  FIG. 1 . 
           [0014]      FIG. 3  is a top sectional view of  FIG. 2  along line  3 - 3 . 
           [0015]      FIG. 4  is a top sectional view of  FIG. 2  along line  4 - 4  according. 
           [0016]      FIG. 5  is a partial functional view of the sensor element of the self-calibrating capacitance fluid level sensing apparatus of  FIG. 1 . 
           [0017]      FIG. 6  is a top sectional view of  FIG. 5  along line  6 - 6 . 
           [0018]      FIG. 7  is a top sectional view of  FIG. 5  along line  7 - 7 . 
           [0019]      FIG. 8  is a functional side view of a dual-probe self-calibrating capacitance fluid level sensing apparatus according to one embodiment of the present disclosure. 
           [0020]      FIG. 9  is a partial functional view of the sensor element of the dual-probe self-calibrating capacitance fluid level sensing apparatus of  FIG. 8  without insulation. 
           [0021]      FIG. 10  is a top sectional view of  FIG. 9  along line  10 - 10 . 
           [0022]      FIG. 11  is a top sectional view of  FIG. 9  along line  11 - 11 . 
           [0023]      FIG. 12  is a top sectional view of  FIG. 9  along line  12 - 12 . 
           [0024]      FIG. 13  is a partial functional view of the sensor element of the dual-probe self-calibrating capacitance fluid level sensing apparatus of  FIG. 8  with insulation. 
           [0025]      FIG. 14  is a top sectional view of  FIG. 13  along the  14 - 14 . 
           [0026]      FIG. 15  is a top sectional view of  FIG. 13  along the  15 - 15 . 
           [0027]      FIG. 16  is a functional side view of the self-calibrating capacitance fluid level sensing apparatus and electromechanical sensing apparatus according to one embodiment of the present disclosure. 
           [0028]      FIG. 17  is a partial side view of the electromechanical sensing apparatus of  FIG. 15 . 
           [0029]      FIG. 18  is a partial side view of the electromechanical sensing apparatus with a capacitance sensing apparatus according to one embodiment of the present disclosure. 
           [0030]      FIG. 19  is a block diagram of the method for measuring a fluid level in a container with a self-calibrating sensing apparatus in accordance with one embodiment of the present disclosure. 
           [0031]      FIG. 20  is a block diagram of the method for measuring a fluid level in a container with a self-calibrating sensing apparatus in accordance with one embodiment of the present disclosure. 
           [0032]      FIG. 21  is a block diagram of the method for measuring a fluid level in a container with a dual probe self-calibrating sensing apparatus in accordance one third embodiment of the present disclosure. 
           [0033]      FIG. 22  is a block diagram of the method for measuring a fluid level in a container with a capacitance and electromechanical self-calibrating sensing apparatus in accordance with one embodiment of the present disclosure. 
           [0034]      FIG. 23  is a block diagram of the determination method for recognition and quantification of irregularities of a self-calibrating capacitance sensing apparatus in accordance with one embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION  
       [0035]    For the purposes of promoting and understanding the principles disclosed herein, reference is now made to the preferred embodiments illustrated in the drawings and specific language is used to describe the same. It is nevertheless understood that no limitation of the scope is thereby intended. Such alterations and further modifications in the illustrated devices and such further applications of the principles disclosed as illustrated herein are contemplated as would normally occur to one skilled in the art to which this disclosure relates. 
         [0036]      FIG. 1  is a functional side view of the self-calibrating capacitance fluid level sensing apparatus according to a first and second embodiment of the present disclosure. The first contemplated embodiment of the sensing apparatus to be placed in a container includes a sensor  100  with a first body  1  made of electrically conductive material, a layer of insulating material  7  as shown in  FIG. 2  of a thickness e 1  or e 2  shown in  FIGS. 3-4 . The insulating material  7  is placed over the first body  1  covering a first surface contact area  15  shown in  FIG. 2 . The sensor  100  also comprises a second body  2  with a second surface contact area  101  made of electrically conductive material placed in opposition to the first body  15 . 
         [0037]    In one embodiment, the second body  2  is a container and the second surface contact area  101  is the inside portion of a stainless steel container, reservoir, or vat without surface insulation. It is understood by one of ordinary skill in the art that in order to create a difference in potential and voltage between the first body  1  and the second body  2 , it is possible to ground the second body and place the first body  1  at the desired voltage in order to prevent the need for use of electrical insulation on the inner surface  101  of the second body  2 . The conductive material of the first body  1  and the second body  2  in a preferred embodiment is made of stainless steel, but it is understood by one of ordinary skill in the art that any conductive material or metal may be used. 
         [0038]    The sensor  100  is located inside a container progressively filled with a fluid  4  in order to change the fluid level from a first position  4  to a second higher position  5 . It is understood by one of ordinary skill in the art that any fluid including a dry powder based or particular based medium with a minimal level of conductivity can be used as a fluid in the scope of this disclosure.  FIG. 2  illustrates an incremental change in fluid level from a first position  4  to a new position  14  quantified shown as ΔH where it is understood by one of ordinary skill in the art that the symbol Δ corresponds to a mathematical differential variation delta of height H in the fluid level. Associated with this incremental change is an incremental change in the contact surface of the fluid  3  with the contact surfaces  7 ,  101  of first body  1  and the second body  2 , respectively. The fluid  3  conductively connects a first fraction of the first surface contact area  7  on the layer of insulating material  6  to a second fraction of the second surface contact area  101 . It is understood by one of ordinary skill in the art that in the disclosed embodiment, the second body  2  acts as the container and is progressively filled with the fluid  4 . It is also understood that the first and second fractions of the first and second surface contact areas  7  as applied by projection to the insulating material  6  and the second surface contact area  101  correspond to the surface in contact with the fluid  3  located below the level  4 . In the case of an increase in the level of fluid  3  by ΔH, each of the first and second fractions of the first surface contact area  7  as applied by projection to the insulating material  6  and the second surface contact area  101  is increased by an incremental surface of height H multiplied by a wet diameter of each surface contact area  6  and  101 . 
         [0039]    Returning to  FIG. 1 , the sensor  100  further includes a means  21  for energizing the first body  1  and the second body  2  at a voltage V. In one embodiment, the first body  1  is connected via a conductor cable  13  to a power source  21  able to apply and modulate a voltage V between two conductors bodies  1 ,  2 . The second body  2  is also connected to the power source  21  by a second conductor cable  11 . It is understood by one of ordinary skill in the art that the induction of voltage between two conductive bodies in association with different connectors can be made by a very wide range of means associated with the generation and transportation of current and ultimately voltage between bodies as known in the art. By way of nonlimiting example, portable power sources such as batteries, magnetically induced currents, piezoelectric currents, current generators, network-transported stabilized currents, static friction generators, wave-based electron excitation, wave based transportation of current like microwave, chemically induced currents, or even induction currents may be used as proper means to energize bodies. It is understood that while these features are described, they are applicable to associated features on other embodiments. 
         [0040]    The sensor  100  further comprises a means  20  for detecting the variability in voltage as the level of fluid  4  or  5  in the container changes by ΔH. The means for detecting a variability of voltage may be an electronics-based circuitry used to precisely measure a voltage, such as a potentiometer. The voltage source  21  and the associated voltage variability measurement means  20  may also include related systems such as current monitoring systems and magnetic field monitoring systems. The sensor  100  may also include a system  22  for the calculation and determination of fixed fluid levels in the container. This system  22  is applicable to all contemplated embodiments found in the present disclosure. 
         [0041]    The sensor  100  is also equipped with a variable thickness e 1  or e 2  of insulating material  6  that varies along the first surface contact area  7  as the level of fluid in the container changes.  FIG. 3  shows a sectional view of part of the first body  1  where the thickness of the insulation is e 1 , and  FIG. 4  shows a sectional view of part of the first body  1  where the thickness of the insulation is e 2 . As a result, forced variations in the voltage  21  detected by the means  20  for detecting the variability of the voltage are observed as the contact area varies from a changing fluid level  4  increases by ΔH. 
         [0042]    To further enable the specification, it is understood by one of ordinary skill in the art that if the first body  1  as described in the prior art has a regular surface geometry and a constant thickness of insulation along its length, the variability in capacitance measured by the means for measuring the variability of the capacitance would change along a first slope. A change to the surface contact area in a section of the first body  1  in contact with the water results in a change in the slope of the variability of the capacitance since the contact surface area A is changed over a section of the first body  1 . If the fluid level rises along a first section  9  of the first body  1 , then a first level of variability and a first slope is measured. Once the fluid level rises along a second section with a different contact surface  8 , the level of variability changes and a second slope is measured. The system  22  recognizes the changes in slopes and determines junction points where the first body changes contact surfaces  8 ,  9 . These junction points correspond with precise heights used to recalibrate the capacitive sensor  100  at these heights in order to reduce any offset resulting from a long analogous measure and slow change in the fluid characteristics. 
         [0043]    In one embodiment, the change in the first body surface  7  evolves along the length of the body according to a step function. A step function is defined as a vertical line along the length of first body  1  where sections of smaller resulting diameters  8  alternate with sections of larger resulting diameters  9 . The step function corresponds to a series of alternating fixed plateaus of two different radii as shown in  FIGS. 3-4 . It is understood by one of ordinary skill in the art that while step functions and plateau regions are disclosed, any variation in the surface sufficient to influence the variability of the capacitance measured by the means  20  for detecting the variability is proper and contemplated, including but not limited to grooves, fins, other functions, and even different frictions and surface finishes. 
         [0044]    The size of the steps in the step function is also to be viewed as a function of the measured variability of the capacitance in a certain system with a certain type of fluid. As a nonlimiting example, if a more conductive fluid is used, such as sea water, the thickness variation between two successive sections (e 1 -e 2 ) may be reduced and the steepness of change between two plateaus in the step function may also be milder. In one embodiment, the first section  9  or the successive high sections as shown in  FIG. 2  are 4 inches long and the second sections  8  are 7/16 inches or ½ inch long. It is understood by one of ordinary skill in the art that the ensuing quantity of step functions depends on the useful length of the first body  1  in the fluid  3 . 
         [0045]    In a preferred embodiment, the insulating material  6  is made of polytetrafluoethylene resins manufactured by DuPont® (Teflon®) or a Teflon®-like coating, but it is understood by one of ordinary skill in the art that the nature and chemical composition of the proper insulating material  6  used depends on the nature and characteristics of the fluid. As a nonlimiting example, if the sensor  100  is used in liquid nitrogen, a very cold fluid, the insulation must maintain its insulating properties, not become brittle, and prevent the formation of surface phase accumulation. The insulator in one preferred embodiment is designed not to accumulate particles or debris upon its surface and to not react with the fluid over long periods of exposure. In all preferred embodiments, the fluid is water or a water-based compound with proper conductive characteristics. The first body may be of cylindrical shape and made of stainless steel, but it is understood by one of ordinary skill in the art that any geometry may be used for the first body  1 . 
         [0046]    The means for detecting the variability in voltage  20  may include the use of a mathematical algorithm optimized to better determine a change in the slope of the measured variability in the capacitance. In a preferred embodiment, the calculation and method for determining if a change in slope comprises the use of exponential smoothing method to determine the changes associated with a fixed fluid level, wherein the fixed level is used to calibrate the fluid level sensing apparatus. The exponential smoothing method consists of a series of means calculation wherein time-sensitive sample data points are taken during changes in the variability in the capacitance and a slope for any new point is calculated and compared with the measured data point to reveal a change in slope. One of ordinary skill in this art recognizes that while a single method for determination and evaluation of the different slopes and their associated junction points is described, all other currently used methods of calculation are contemplated. 
         [0047]    In another embodiment illustrated in  FIG. 5 , the insulation layer  16  remains constant along the first body  1 . The surface  17  of the first body  1  varies in radius along its vertical length along a step function alternating from sections with a smaller radius  8  to sections with a larger radius  9 .  FIG. 1  shows two possible embodiments wherein the resulting change in the surface in contact with the fluid  3  alternates from smaller sections  8  to larger sections  9 .  FIGS. 6 and 7  further illustrate top sectional views of the first body  1  along plane  6 - 6  and plane  7 - 7 . It is understood by one of ordinary skill in the art that while a single type of surface geometry is shown, what is contemplated is an effective variation in the contact surface with the fluid  3  by varying the surface geometry  17  of the first body  1  in order to induce a variability in the measured capacitance of the fluid. What is contemplated is any geometry with change in the surface geometry associated that result in a measurable and quantifiable variability in voltage from the variability capacitance measurement. 
         [0048]    In another possible embodiment as illustrated in  FIG. 8 , a fluid level sensing apparatus for placement in a container includes a sensor  100  with a first body  1 , a first surface contact area  15  made of electrically conductive material, a third body  103  with a third surface contact area  104  made of electrically conductive material, and a second body  2  with a second surface contact area  101  made of electrically conductive material placed in opposition to the first  1  and the third bodies  15 . The container is progressively filled with a fluid  3  in order to change the fluid level  4 . As in the first and second embodiments, the fluid  3  conductively connects a first fraction of the first surface contact area  15  and a third fraction of the third surface contact area  104  with a second fraction of the second surface contact area  101 . The sensor  100  also is equipped with two means  21 ,  36  for energizing the first body  1  and the third body  103  to the second body  2 , a first means  20  for detecting the variability in voltage as the level of fluid in the container changes as the first fraction of the first surface contact area  15  and the second fraction of the second surface contact area  101  changes, and a second means  105  for detecting the variability of voltage  36  as the level of fluid  4  in the container changes as the third fraction of the third surface contact area  104  and the second fraction of the second surface contact area changes  101 . The surface geometry of the first body  1  varies along the first, second and third surface contact areas  15 ,  104 ,  101  as the level of fluid  4  in the container changes to create forced variations in the voltage for both of the first and second means  20 ,  105  for detecting the variability of the voltage. 
         [0049]    In one embodiment, two bodies  1 ,  103  are placed in the fluid  3  in opposition to the second body  2 . This embodiment allows for the parallel measurement of two different variability of capacitance, a standardized measurement  20  based on a body without any variable geometry irregularities, and a measurement  36  based on a body with variable geometry irregularities designed as described in the embodiment of this disclosure and shown in  FIGS. 9-15 , respectively. The embodiment shown in  FIGS. 9-12  illustrates a situation where the probe is not insulated and is grounded while the voltage potential is placed on the second body  2 . In the embodiment shown in  FIGS. 13-15 , the first and third bodies  1 ,  103  are insulated  26  with a fixed thickness of insulation e 1  as shown on  FIGS. 14-15 . The two bodies in one embodiment are shaped in a semicircular or semicylindrical vertical rod configuration placed back-to-back and made of stainless steel. The third body  103  such as that described in the second embodiment is made of a variable surface area of a first step of 4-inch width separated by 7/16- or ½-inch sections forming a regular step function. While two adjacent bodies are shown, it is understood by one of ordinary skill in the art that any two-body geometry is contemplated as long as the external contact areas are varied appropriately in order to change the overall measure of the capacitance of the sensor  100 . 
         [0050]    A layer of insulation  25  is placed between both the first body  1  and the third body  103 . In one embodiment, the insulation is phenolic insulation, but it is understood by one of ordinary skill in the art that while a single type of insulation is disclosed, what is contemplated is an insulation  25  of a type able to effectively insulate two adjacent conductive bodies in a predetermined environment.  FIG. 12  shows a cross-section of the third body  103  illustrating notches  30  created in the surface of the semicylindrical third body  103 . The choice of notches as shown in  FIG. 9  corresponds in some orientation to the step function as previously disclosed in the first and second embodiments. In one embodiment, the notches are of a fixed width and fixed height with a flat bottom portion  29  in order to better calibrate the means for measuring the variability of the capacitance  105 . It is understood by one of ordinary skill in the art that the third embodiment allows for the self-calibration of the sensor  100  by comparing the variability of capacitance from the first means  20  with the variability of capacitance from the second means  105 . It is also understood that in an alternate embodiment, the first body  1 , if placed in opposition to the third body  103 , may lead to self-calibration without the second body  2  by placing the means for applying a voltage difference between both the first body  1  and the third body  103  and appropriately correcting the surface area calculations. 
         [0051]    In certain embodiments, the means for detecting the variability in voltage between the first second body  2  and the third body  103  may include the use of an exponential smoothing method to determine the changes associated with a fixed fluid level, wherein the fixed level is used to recalibrate the fluid level sensing apparatus as disclosed in the first and second embodiments. In another embodiment as shown in  FIG. 14 , an insulating block  27  is placed in a notch in order to better regulate the variability of the capacitance. 
         [0052]    In another embodiment illustrated in  FIG. 16 , a fluid level sensing apparatus for placement in a container comprises a capacitance sensor  41  further comprising a first body  1  with a first surface contact area  15  made of electrically conductive material, a second body  2  with a second surface contact area  101  made of electrically conductive material placed in opposition to the first body  1 , an electromechanical sensor  43  further comprising a guide  40  positioned in a fluid  3  to be measured, a float  42  mechanically connected to the guide  40  for longitudinal movement thereon to rise and fall with the fluid level  4 , a series of reed switches  47  shown in  FIG. 17  placed at fixed intervals along the guide  40 , and a means for establishing a magnetic field  45  across the reed switches  47  mechanically connected with the float  42 . 
         [0053]    It is understood by one of ordinary skill in the art that this embodiment uses a electromechanical sensor  43  to determine the actual level of the fluid level  4  at certain fixed positions determined by the placement of the reed switches  47  within the vertical guide tube  40 . A reed switch  47  is a small, open conductor cable placed in a glass bubble  46  where both magnetized ends of the conductor are normally in an open position. The floater  42  is hollowed and contains air or any fluid of a lighter density than the fluid  3  in order to ensure that the floater  42  remains on the surface  4  of the fluid. As disclosed in  FIGS. 17-18 , a magnet  45  is connected to the floater  42 . In one preferred embodiment, the magnet  45  is located inside the floater  42  and is in contact with the inner section of the floater  42  at its midsection. Once the floater  42  reaches a certain predetermined level, the magnet  45  magnetizes the small conductors, which then close the electrical circuit via two cables  51 ,  52  and send a certain signal to a detector  49  associated with the selected reed switch  47 . Unlike the measure of a variation in capacitance as disclosed in the other embodiments, this embodiment produces a signal directly associated with a fluid level. This embodiment also comprises a container progressively filled with fluid  3  in order to change the fluid level  4 . When the fluid conductively connects a first fraction of the first surface contact area  15  and a second fraction of the second surface contact area  101 , and wherein the change in fluid level changes the float  42  position along the guide  40  to move the means for establishing a magnetic field  45  and close a reed switch  47  associated with a determined fluid level. The capacitance sensor  41  as shown in  FIG. 16  also includes a means for energizing the first body  21  and the second body at a voltage using electrical connectors  11 ,  13 . The means for detecting the variability in voltage  20  as the level of fluid  4  in the container changes as the first fraction of the first surface contact area  15 . The second fraction of the second surface contact area changes  101  with the change in the fluid level  4 , and a means  49  such as a detector or any other means for determining which reed switch  47  is closed and creates a voltage as the level of the fluid in the container changes. The determination of the level based on the means for determining which reed switch  47  is closed is used to correct the determination of the level of fluid based on the means for detecting the variability of the voltage by fixing known step levels.  FIG. 17  shows a electromechanical sensor  43  where the vertical tube  40  is closed by a cap  50  to prevent the fluid  3  from entering the guide  40  as the level of fluid rises. 
         [0054]    In another embodiment, shown as  FIG. 18 , the first body  1  is the circular guide  40  of the electromechanical sensor  43 . The first body  1  is covered with a layer of insulation  26 . This embodiment is equipped with the same level of means of measure and voltage as disclosed in the present embodiment with the only variation that the capacitance sensor  41  is merged into the electromechanical sensor  43 . It is understood by one of ordinary skill in this art that while the first body  1  may be taken as the guide  40 , the geometry of the floater  42  must provide a sufficient passage of water in order to offer proper capacitance measurement. 
         [0055]    Certain embodiments include in one embodiment thereof a circular vertical probe  40  made of stainless steel covered in the fifth embodiment by a layer of insulating Teflon®  26 . In one embodiment, the reed switches  47  are separated vertically by 4 inches and the container of the second contact surface  2  of the container is the inside wall of the container  101 . In yet another embodiment, the fluid is water and the means for establishing a magnetic field is a ring magnet  45  located in the center of the floater  42 . It is also contemplated that other means for establishing a magnetic field be used, such as a localized current, a magnet, or a magnetic element located on the surface of the water. In another embodiment, the floater  42  is made of a hollowed volume made of stainless steel. It is understood by one of ordinary skill in the art that while a stainless steel floater is shown, any type of floater in any noncorrosive material in contact with the fluid  3  is contemplated. 
         [0056]      FIG. 19  discloses a first method for measuring the fluid level in a container with a self-calibrating sensing apparatus in accordance with one embodiment of the present disclosure. The self-calibration is obtained by conducting a first step where the capacitance sensor of the first embodiment is placed in the container where a lower measure point is in contact with a low level of a fluid to be measured and the higher measure point is in contact with a high level of the fluid to be measured  201 , a calibration of the capacitance sensor to the desired output range is then performed so the lower measure point is a first extremity of the output range and the high measure point is a second extremity of the output range  202 . The capacitance sensor and means for detecting the variability of the voltage using a determination method to recognize variations associated with the successive levels in the step function associated with the changes in thickness of the insulation are then calibrated in order to determine precise fluid levels associated with each successive level in the step function  203 . The capacitance sensor first determines a first level of the fluid based on the measured output voltage in an analog fashion  204 , and the capacitance sensor is recalibrated at the successive levels in the step function each time the output voltage based with the precise fluid levels is detected  205 . 
         [0057]    One of ordinary skill in the art recognizes that an analog measure over a range can be recalibrated by the input of a predetermined value at a predetermined time and that such recalibrations are done using two distinct measures of voltage variability. For example, if the lower point corresponds to a fluid level of 2 inches and the high level corresponds to 20½ inches the successive levels in the step function of 4 inch and ½ inch as described in a preferred embodiment of the first embodiment, that imposes variations in slope at 6, 6½, 10½, 11, 15½, 16, and 20½ inches, respectively. As the level of fluid rises, the analog measure gives a fluid level reading based on its extrapolation of the variability of the capacitance over a possible output of 4-20 mA if a standardized probe is used. For example, if the level reaches 5.95 inches, the analog measure may read 5.85 or 6.05 based on the changes in the fluid characteristics. Using the self-calibrating function, if the measure level is above 6.00 inches, it gives a 6-inch reading and waits for the recognized variation associated with the level 6 inches before it proceeds further along its analog reading using the determined level to recalibrate the precise fluid level. If the analog measure is less than 6 inches, the recalibration waits until the recognized variation associated with the level 6 inches is activated, recalibrates the level at 6 inches, and proceeds along its programmed calibrated range with this new fixed value. It is understood by one of ordinary skill in the art that the use of a secondary measure to calibrate a first measurement may be done using a plurality of different algorithms, all of which relate to using the measured voltage of a second sources to rectify a measure from a first source. 
         [0058]    A second method for measuring the fluid level in a container with a self-calibrating sensing apparatus in accordance with one embodiment of the present disclosure is shown in  FIG. 20 . The method comprises the steps of placing the capacitance sensor in the container where a lower measure point is in contact with a low level of a fluid to be measured and the higher measure point is in contact with a high level of the fluid to be measured  210 , calibrating the capacitance sensor to the desired output range so the lower measure point is a first extremity of the output range and the high measure point is a second extremity of the output range  211 , calibrating the capacitance sensor and means for detecting the variability of the voltage using a determination method to recognize variations associated with the successive levels in the step function associated with the changes in irregular geometry in order to determine precise fluid levels for recalibration associated with each successive levels in the step function  212 , determining a first level of the fluid based on the measured output voltage of the capacitance sensor  213 , and recalibrating the first level of fluid associated with the measured output voltage based with the precise fluid levels  214 . 
         [0059]    A third method for measuring the fluid level in a container with a self-calibrating sensing apparatus in accordance with one embodiment of the present disclosure is shown in  FIG. 21 . The method comprises the steps of placing a dual-probe capacitance sensor in the container where a lower measure point of each probe is in contact with a low level of a fluid to be measured and the higher measure point of each probe is in contact with a high level of the fluid to be measured  220 , calibrating each of the two capacitance sensors to the desired output range so the lower measure point is a first extremity of the output range and the high measure point is a second extremity of the output range  221 , calibrating the means for detecting the variability of the voltage in the third body using a determination method to recognize irregularities in voltage associated with the irregularities in the geometry and associating a fixed fluid level with the irregularities in geometry  222 , determining a first level of the fluid based on the measured output voltage of the first capacitance sensor probe of a regular geometry  223 , and correcting the first level of fluid associated with the measured output voltage of the first probe of the capacitance sensor to the fixed fluid level determined by second probe of the capacitance sensor based on the fluid level associated with the selected irregularities  224 . 
         [0060]    A fourth method for measuring the fluid level in a container with a self-calibrating sensing apparatus in accordance with one embodiment of the present disclosure is shown in  FIG. 22 . The method comprises the steps of placing the capacitance sensor and the electromechanical sensor in the container where a lower measure point of each sensor is in contact with a low level of a fluid to be measured and the higher measure point of each sensor is in contact with a high level of the fluid to be measured  231 , calibrating the capacitance sensor to the desired output range so the lower measure point is a first extremity of the output range and the high measure point is a second extremity of the output range  232 , calibrating the electromechanical sensor to the desired output range so a reed switch corresponds to a fixed output voltage located within the output voltage range  233 , determining a first level of the fluid based on the measured output voltage of the capacitance sensor  234 , and correcting the first level of fluid associated with the measured output voltage of the capacitance sensor to the fluid level determined by the electromechanical sensor based on the fluid level associated with the reed switch, once the fluid level of the reed switch is reached  235 . In the fifth embodiment, the first body  1  of the capacitance sensor is the cylindrical sensor probe covered with insulation. 
         [0061]    A fifth method is a determination method for recognition and quantification of irregularities of a self-calibrating capacitance sensing apparatus in accordance with one embodiment of the present disclosure is shown in  FIG. 23 . The determination method comprises the steps of determining a variability in capacitance by measuring and comparing the capacitance over a fixed interval of time  240 , associating the variability of capacitance with a data point  241 , storing the data points and the quantity of data points in two arithmetic sums  242 , determining a new data point to be quantified as a possible irregularity  243 , adding the data point to the arithmetic sums  244 , reviewing the evolution of a derivative function of the arithmetic sums to determine if a change in slope is observed over a fixed number of sum intervals  245 , and comparing the change in the derivative function with a predetermined value to determine if a slope change is observed and if a fixed fluid level is calculated  246 . 
         [0062]    It is understood by one of ordinary skill in the art that the evolution of the derivative function of the arithmetic sums based on a method such as the arithmetic exponential smoothing method relates to the determination without undue experimentation of a proper time interval of acquisition, a proper time interval for each successive data points, a proper variability of each successive data point at the fixed time interval of acquisition, a determination of an equivalent sum associated with the arithmetic sum, an acceptable number of data points in a new predetermined range in order to determine if a change in slope is determined by determining a certain number of data points to add to the sum, and a value of the new determined slope associated with the change in variability. 
         [0063]    Persons of ordinary skill in the art appreciate that although the teachings of the disclosure have been illustrated in connection with certain embodiments and methods, there is no intent to limit the invention to such embodiments and methods. On the contrary, the intention of this disclosure is to cover all modifications and embodiments failing fairly within the scope the teachings of the disclosure.