Abstract:
An apparatus and method for measuring the level of a wide range of varied surfaces or materials housed within vessels, and for detecting contact with a solid surface within the vessel is disclosed. A high precision radio frequency admittance measuring system, using capacitance to measure levels of process materials, coupled with detection element to sense contact of the detection element with a solid surface, such as a floating roof. An active element and ground element in coaxial relationship provides means for measuring the level of process materials including water, oil, kerosene, jet fuel, gasoline. Along with detecting the level of a solid surface within the vessel such as a floating roof. One preferred application of the inventive apparatus is to provide vessel or tank overfill protection. The apparatus detection element is capable of sensing level and non-level solid surfaces.

Description:
RELATED APPLICATION  
       [0001]    This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 61/118,548, filed on Nov. 28, 2008, the text and figures of which are incorporated into this application by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]    The present invention generally relates to the measurement of the height of the surface level of varied materials housed within vessels or tanks. More particularly, the disclosed invention relates to an apparatus and system that comprises a radio frequency (“RF”) admittance measuring device using capacitance to precisely measure the level of a process material, coupled with a detection element to detect a threshold level of a solid surface within the vessel or tank, and calibration software, all of which, in combination permit accurate measurement of the level of a wide range of process materials stored within the vessel or tank. 
         [0003]    The software determines, among other system aspects, initial capacitance set points for the measuring device. In a preferred embodiment the apparatus and system is capable of measuring, with a high degree of precision, the level of various process materials housed within a vessel or tank including, without limitation, water, oil, kerosene, jet fuel, gasoline, and other liquids, as well as detecting the level of a solid surface within the vessel or tank, such as a floating roof. 
       BACKGROUND OF THE INVENTION  
       [0004]    In many industrial plants, vessels or tanks store a wide range of process materials. Examples of such process materials housed within vessels or tanks include water, oil, kerosene, jet fuel, gasoline, diesel fuel, and many other liquid and non-liquid chemicals and products. The overall physical design of such storage vessels include, as illustrated in  FIGS. 1A ,  1 B and  1 C, structures with a fixed roof ( FIG. 1A ), an internal floating or moveable roof with a fixed exterior roof ( FIG. 1B ), and an external floating or moveable roof ( FIG. 1C ). 
         [0005]    Most industrial applications of storing materials in vessels require that there is a means to ensure the vessel is not overfilled with the material being stored within the vessel. The primary reasons for not overfilling a vessel are safety concerns, environmental issues, structural limits, and because certain materials can be expensive, financial considerations. More particularly, if the vessel is overfilled, the result could include loss of the excess material being transferred to the vessel, damage to the vessel due to structural loads, and/or contamination of the area around the vessel due to the potential spillage of the excess material. Moreover, if the material being stored within the vessel is corrosive or volatile, such as gasoline, jet fuel, or kerosene, the potential for spillage could result in the need for expensive clean up and remediation around the vessel site should there be any spillage. In addition, as a vessel ages, the structural limits of the vessel may degrade, so the level limits for such older vessels are derated or lowered. Accordingly, overfill protection is a critical need in many, if not most vessel storage applications. 
         [0006]    Various examples of measurement devices and systems have been disclosed and used within material storage vessels. However, each of these known devices and systems have deficiencies which prevent such devices and systems from fully addressing the level measurement problems. By way of example, U.S. Pat. No. 4,811,160, for a Capacitance-Type Material Level Probe issued to Fleckenstein and assigned to Berwind Corporation discloses a capacitance probe for material level sensing, and a method of manufacturing the probe. There is however no disclosure of use of the capacitance probe for high precision measurement of material level within a vessel where the probe is also able to detect contact with a floating solid surface within the vessel. 
         [0007]    Similarly, U.S. Pat. No. 5,554,937 teaches an Apparatus And Method For Sensing Material Level By Capacitance Measurement, and issued to Sanders et al., and is assigned to Penberthy, Inc. The &#39;937 patent specifically discloses a system to measure the level of material in a vessel where the probe is maintained in the vessel such that the vessel and probe are at different potentials thereby creating a capacitance between the probe and vessel wall. As described within the &#39;937 patent, as the material level varies, the capacitance will similarly vary. The &#39;937 patent however provides no disclosure of any means to detect a solid surface within the vessel while also measuring the material level within the vessel. 
         [0008]    Accordingly, there does not appear to be any known prior art devices, systems, methods, patents, or published patent applications that disclose or address the potential advantages of having a highly precise capacitance level probe for use within a material vessel to measure material level within the vessel, that is also coupled with a detection element to detect contact with a floating roof or other solid surface. The inventive apparatus, systems and methods described below disclose solutions to the above noted problems relating to the measurement and monitoring of material with vessels. Such an apparatus, system and method of operation would be highly desirable to system operators that use and monitor vessels with process materials stored in the vessels. Such improved apparatus, systems and methods have not been seen or achieved in the relevant art. 
       SUMMARY OF THE INVENTION  
       [0009]    The above noted problems, which are inadequately or incompletely resolved by the prior art are completely addressed and resolved by the present invention. 
         [0010]    A preferred aspect of the present invention is an apparatus for measuring the level of a material within a vessel and for detecting the level of a solid surface within said vessel, comprising a capacitance probe for measuring the level of the material within the vessel to a high degree of precision, said capacitance probe having an active element and a ground element in close lateral proximity to each other, said capacitance probe further having a proximate end and a distal end; and a detection element incorporated into the distal end of the capacitance probe for detecting the level of a solid surface within the vessel. 
         [0011]    Another preferred aspect of the present invention is a system for measuring the surface level of a material stored within a vessel, comprising a capacitance probe for measuring the level a material within the vessel, said capacitance probe having a proximate end and a distal end; a detection element coupled with the distal end of the capacitance probe for detecting the level of a solid surface within the vessel; and a computer processor to calibrate and monitor the capacitance probe. 
         [0012]    A further preferred embodiment of the present invention is an apparatus for measuring the level of a material within a vessel and for detecting the level of a solid surface within said vessel, comprising a capacitance probe for measuring the level of the material within the vessel, said capacitance probe having an active element and a ground element, wherein the active element and ground element are in a co-axial relationship with each other; and said active element detects the level of a solid surface within the vessel. 
         [0013]    Another further preferred aspect of the present invention is a system for measuring the surface level of a material stored within a vessel, comprising a capacitance probe for measuring the level of the material within the vessel, said capacitance probe having an active element and a ground element, wherein the active element and ground element are in a co-axial relationship with each other; and said active element detects the level of a solid surface within the vessel; and a computer processor to calibrate and monitor the capacitance probe. 
         [0014]    Still another preferred embodiment of the present invention is a method for measuring the level of a material or distinct solid surface within a vessel using a capacitance probe coupled with a detection element, and a computer processor, comprising the steps of (a) calibrating the level of the capacitance probe through the computer processor, (b) monitoring the level of the material within the vessel, and monitoring any contacts of solid surfaces with the detection element, through the computer processor; and (c) providing output data of the material level as measured by the capacitance probe or if a solid surface contacts the detection element. 
         [0015]    In still another preferred embodiment of the present invention is a method for measuring the level of a material or distinct solid surface within a vessel using a capacitance probe coupled with a detection element, and a computer processor, comprising the steps of (a) calibrating the level of the capacitance probe through the computer processor; (b) monitoring the level of the material within the vessel through the computer processor; (c) providing output data of the material level as measured by the capacitance probe; (d) monitoring any contacts of solid surfaces with the detection element through the computer processor; and (e) providing output data if a solid surface contacts the detection element. 
         [0016]    The invention will be best understood by reading the following detailed description of the several disclosed embodiments in conjunction with the attached drawings that are briefly described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0017]    The invention is best understood from the following detailed description when read in connection with the accompanying drawings. It is emphasized that, according to common practice, the various features of the several drawings are not to scale, and the invention is not limited to the precise arrangement as may be shown in the accompanying drawings. On the contrary, the dimensions and locations of the various features are arbitrarily expanded or reduced for clarity, unless specifically noted in the attached claims. 
           [0018]      FIG. 1A : is an open side view illustration of a fixed roof vessel with an embodiment of the present invention within the vessel; 
           [0019]      FIG. 1B : is an open side view illustration of a fixed roof vessel and floating solid surface with an embodiment of the present invention within the vessel; 
           [0020]      FIG. 1C : is an open side view illustration of an open roof vessel having a floating solid surface with an embodiment of the present invention within the vessel; 
           [0021]      FIG. 2 : is an illustration of an embodiment of the present invention capacitance probe and detection element within a vessel connected to a computer processor; 
           [0022]      FIG. 3A : is an end and side view of an illustration of an embodiment of the present invention capacitance probe with a solid disk detection element design; 
           [0023]      FIG. 3B : is an end and side view of an illustration of an embodiment of the present invention capacitance probe with a spoke and rim detection element design; 
           [0024]      FIG. 3C : is an end and side view of an illustration of an embodiment of the present invention capacitance probe showing an internal active element and exterior ground element; 
           [0025]      FIG. 3D : is an end and side view of an illustration of an embodiment of the present invention capacitance probe showing an internal ground element and exterior active element; 
           [0026]      FIG. 4 : is an illustration of an embodiment of the present invention capacitance probe and detection element within a vessel communicating wirelessly to a computer processor; 
           [0027]      FIG. 5A : is an illustration of an embodiment of the present invention capacitance probe and detection element within a vessel, with a cable coiling device connected to the capacitance probe; 
           [0028]      FIG. 5B : is an illustration of an embodiment of the present invention capacitance probe and detection element within a vessel, with a cable coiling device connected to the capacitance probe and communicating wirelessly with the system processor; 
           [0029]      FIG. 6 : is an illustration of an embodiment of the present invention capacitance probe and detection element within a vessel, with a cover over the capacitance probe; 
           [0030]      FIG. 7 : is an illustration of an embodiment of the present invention capacitance probe and detection element within a vessel, with a heating element coupled with the capacitance probe; 
           [0031]      FIG. 8 : is an open side view illustration of an embodiment of the present invention within a fixed roof vessel having a floating solid surface within the vessel, showing contact of the detection element with a floating solid surface; 
           [0032]      FIG. 9A : is an example flowchart of the steps of a preferred embodiment of the present invention method of measuring the level of a material within a vessel and of detecting a solid surface within the vessel; and 
           [0033]      FIG. 9B : is another example flowchart of the steps of a preferred embodiment of the present invention method of measuring the level of a material within a vessel separate from the detecting a solid surface within the vessel. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0034]    The present invention is an apparatus, system and method for measuring the height of the surface level of a material stored in vessel with a high degree of precision, and for detecting the threshold level of a solid surface which may also be within the vessel. A detailed description of various preferred embodiments of the inventive apparatus, systems and methods is provided in this specification. 
         [0035]    The core elements of the inventive apparatus include a capacitance probe for precisely measuring the level of a material stored within the vessel, and a detection element conductively coupled to the capacitance probe to detect a solid surface within the vessel. The design of the capacitance probe having an active element in close proximity with a ground element, including by way of example, co-axially positioned with respect to each other, permits the probe to precisely measure, within a very limited probe measurement range, the level or height of a large group of process materials stored within a vessel. The inventive system further provides for a computer processor communicating with the capacitance probe and detecting element to calibrate the capacitance probe, including its position or level, as well as to monitor signal data from the probe and the detection element. The inventive method includes, in one basic preferred embodiment, the steps of (a) calibrating the level of the capacitance probe, (b) monitoring the level of the material within the vessel through the computer processor and/or monitoring any contacts of solid surfaces with the detection element, and (c) providing output data of the material level as measured by the probe, and/or contacts with a solid surface, to the system operator. 
         [0036]    As shown in  FIGS. 1A ,  1 B, and  1 C, a storage vessel  100  may have an exterior, fixed roof  71  ( FIG. 1A ), an exterior, fixed roof  71  along with a moveable or floating roof  75  ( FIG. 1B ), or have no exterior roof, but only a moveable or floating roof  70  ( FIG. 1C ). Each of these example vessels have different issues to be addressed with respect to measuring the level of a process material  90  that may be stored within the vessel  100 , and with respect to detecting the height of a moveable, interior roof. In order to be able to measure the level or height  91  of material stored within the vessel  100 , along with being able to detect the height of a solid surface, such as a moveable roof  70 ,  75  within the vessel  100 , a preferred embodiment of the inventive apparatus  10  combines a high precision surface measuring capacitance probe with a detecting element. 
         [0037]    In a preferred embodiment, as illustrated in  FIG. 2 , the measuring device  10  has a concentric design capacitance probe  15 , with a center active element  16  and an outer ground wall  17 , coupled with a detecting element  20  connected to the distal end of the capacitance probe  15  active element  16 . More specifically, in a preferred embodiment, the detecting element  20  is an extension of the center active element  16 . The measuring device  10  is electrically connected to and communicating with a processor  30 . Through such communications, the processor  30  is able to calibrate the probe  15  initial signals, including probe  15  level, and is thereafter able to detect material levels as measured by the capacitance probe  15 . Moreover, the processor  30  monitors any signals generated from any contacts between the detecting element  20  and a solid surface within the vessel  100 . The processor  30  may be, in different aspects of the inventive apparatus and system, a digital computer processor, or in a more simplified embodiment, an analog electrical circuit. 
         [0038]      FIG. 3A  illustrates an example embodiment of the measuring device where the detecting active element  20  is in the form of a circular disk  21  with a diameter such that the edge of the disk  21  is wider than the diameter of the ground wall  17  of the capacitance probe  15 . In another preferred embodiment, as shown in  FIG. 3B , the detecting element  20  is in the form of multiple spokes  23  connected at the center to measuring device center element  16 , and at the edge, connected to a rim element  25 . 
         [0039]      FIG. 3C  illustrates a similar embodiment of the measuring device as shown in  FIG. 3A , except that the detecting active element  20  is not in the shape of a disk, and is not wider than the diameter of the ground wall  17 . In this embodiment, the detecting active element  20  merely extends beyond the distal end of the capacitance probe ground wall  17 . 
         [0040]      FIG. 3D  shows an alternative embodiment of the measuring device such that the active element and the ground element are reversed. More specifically, the ground element  17  is the interior element of the capacitance probe  15  and is coaxially surrounded by the active element  16 . In this embodiment, the ground element  17  can be recessed within the exterior surrounding active element  16 . Because the active element  16  surrounds the ground element  17  of the capacitance probe  15  and is the exterior of the capacitance probe, the active element  16  is able to detect contacts with any floating solid surfaces within a vessel. 
         [0041]    The illustrative designs of the capacitance probe  15  shown in  FIGS. 3A ,  3 B,  3 C, and  3 D, having the active element  16  in close lateral proximity with the ground element  17 , provides the means through which the capacitance probe  15  is capable of measuring with a high degree of precision the level or height of a wide range of process materials stored within a vessel. The co-axial designs illustrated in  FIGS. 3A through 3D  allows the capacitance probe  15  to accurately measure the level of a wide range of dielectrics, including within the range of 2 to 80, within approximately 0.75 inch along the capacitance probe  15 . With higher sensitive electronics and variations in the geometric distances between the active element  16  and ground element  17 , further refinement of the precision of level measurements may be readily achieved. 
         [0042]    In another preferred embodiment of the measuring and detecting system, the measuring device  10  may communicate with the processor  30  wirelessly. Such wireless communications require that the measuring device have its own local power supply, which as shown in  FIG. 4  can be a replaceable or rechargeable battery  50 . One consideration with the wireless communication embodiment is the ability to effectively maintain a reliable communications link between the measuring device  10  and the processor  30 . Moreover, having a local power supply  50  integrated with the measuring device  10  may require the use of special insulating materials around the power supply when the measuring device  10  is used with highly volatile stored materials. Accordingly, certain vessel and stored material environments may not be conducive to a wireless implementation. 
         [0043]      FIG. 2  and  FIG. 4  show the measuring device  10  within the vessel  100 . As illustrated in both  FIGS. 2 and 4 , the level of the process material  90  is above the detecting element  20  and above the distal or bottom end of the capacitance probe  15 . With respect to operation of the measuring and detecting system, as the process material  90  within the vessel  100  rises, the material  90  fills the area between the probe center active element  16  and the ground wall  17 . As shown in  FIGS. 3A ,  3 B and  3 C, the area between the center element  16  and the probe ground wall  17  is open. As the process material  90  fills the vessel  100 , and accordingly the material level  91  rises, the process material  90  fills the area between the center element  16  and probe ground wall  17 . With the process material  90  filling part of the area between the center active element  16  and probe ground wall  17 , the measured capacitance of the capacitance probe  15  changes. Similarly for the capacitance probe  15  embodiment shown in FIG.  3 D, the process material  90  would fill the area between the ground element  17  and exterior active element  16  as the material level rises within the vessel, and the measured capacitance will proportionally vary. That is variations in the measured capacitance of the capacitance probe  15  directly correlate with variations in the level  91  of the process material  90 . Because the computer processor  30  may initially calibrate the measuring device  10 , any variations in the measured capacitance are used to provide variations in the level of the process material  90 . 
         [0044]    More particularly, the measuring device  10  measures the capacitance from the capacitance probe  15  and transmits a signal of that capacitance to the processor  30 . The processor  30  then can compare the measured capacitance value to a set trip point  35  that is stored within the processor  30  memory. When the capacitance signal equals or exceeds the user selected trip point  35 , the processor  30  may then transmit a signal to stop filling the vessel  100  with material  90 , or alternatively transmit an alarm signal to a user that the trip point level  35  has been reached within the vessel  100 . 
         [0045]    While  FIGS. 2 and 4  show expanded views of the measuring device  10  within a vessel  100 , to specifically illustrate the filling of the process material  90  within the measuring device  10 , the illustrations shown in  FIGS. 1A ,  1 B and  1 C exemplify particular configurations where the measuring device may be located near the top of the vessel  100 . The placement of the measuring device  10  may also be located at any depth within the vessel  100 . As such the user may position the measuring device at any desired level that is in appropriate relationship to the selected surface level  91  trip point  35 . 
         [0046]    As illustrated in  FIGS. 1B and 1C , the vessel  100  may also include a moveable or floating solid surface positioned within the vessel  100 . The floating surface or floating roof  75  may be located below a fixed roof  71  as shown in  FIG. 1B , or alternatively, the floating roof  70  may be exposed to the open environment as shown in  FIG. 1C . The floating roof  70 ,  75 , is typically fully floating on top of the process material  90 . Accordingly, as the process material  90  level rises, the floating roof  70 ,  75  will likely be the first material or surface to contact the measuring device  10 . The inventive device and system illustrated in  FIGS. 3A and 3B  includes a detecting element  20  connected to the end of the capacitance probe  15  such that when a solid surface, such as a floating roof  70 ,  75  contacts the detecting element  20 , a “contact” signal is transmitted to the processor  30  indicating contact of the solid surface  70 ,  75  with the detecting element  20 . For the  FIG. 3D  embodiment, a floating roof  70 ,  75  would contact the exterior active element  16  and the “contact” signal would be transmitted to the processor  30 . 
         [0047]    As disclosed above, in a preferred embodiment, the detecting element  20  is an extension of the center active element  16  of the measuring device  10 . Accordingly, if the floating solid surface  70 ,  75  within the vessel  100  contacts the detecting element  20 , or the exterior active element  16 , the solid surface  70 ,  75  acts as an electrical ground. The user may desire that if the floating roof  70 ,  75  contacts the measuring device  10 , that such contact should provide a signal to the processor  30  and the user of such contact. More particularly, in a preferred embodiment of the inventive system, if the processor  30  receives such a “contact” signal from the detecting element  20 , active element  16  or measuring device  10 , the processor  30  may transmit a signal to stop filling the vessel  100 , and/or transmit a “contact” alarm to the system operator. 
         [0048]    Because the roof  70 ,  75  is a floating surface, there may exist scenarios where the storage material  90  may have leaked partially or fully above the floating roof  70 ,  75 .  FIG. 8  illustrates an example of a partially submerged roof The design of the inventive measuring and detecting device  10  provides that a signal is sensed by the processor  30 , and transmitted to the user or system operator whether the signal is a trip level signal, due to measuring a high level of the process material  90 , or a contact signal, due to contact of a solid surface with the detecting element  20  or active element  16 . 
         [0049]    In a preferred embodiment of the inventive system, the measuring device  10  need not differentiate between a trip signal generated where the process material  90  (being a conductive process material) first contacts the capacitance probe  15  (e.g., where there is no floating roof  70 ,  75 , or the floating roof  70 ,  75  has submerged below the process material  90 ), and alternatively where the floating roof  70 ,  75  first contacts the measuring device  10  and detecting element  20  or active element  16  (e.g., where there is an internal floating roof  75 , or external floating roof  70  that is above the process material  90 ). The inventive system may, however, in another preferred embodiment, be configured such that the measuring device  10  and/or the processor  30  are able to distinguish between a trip signal generated where the process material  90  contacts the measuring device  10  and reaches the trip level  35 , and where a floating roof,  70 ,  75  first contacts the measuring device  10  and detecting element  20  or active element  16 . 
         [0050]    The detecting element  20  may be designed to be a disk-shaped element as shown in  FIGS. 2 and 3A , such that upon contact of a solid surface with the disk  20 , a contact signal is transmitted to the processor  30 . One preferred embodiment of the inventive apparatus, as shown in  FIG. 2 , has the detecting element disk  20  with a wider diameter than the capacitance probe  15 . In this preferred embodiment, the detecting element  20  is fully operable whether the measuring device  10  is vertically oriented, as shown in  FIG. 2 , or if the device  10  is askew or oriented almost horizontally, as illustrated in  FIG. 8 , due to wind conditions. Similarly the capacitance probe embodiment shown in  FIG. 3D  would effectively operate to sense contacts with solid surfaces even with the measuring device  10  being askew because the active element  16  is the exterior of the capacitance probe  15 . 
         [0051]    As disclosed, in a preferred embodiment of the inventive system, the selected trip level  35  for the process material  90  may be set by the user. Accordingly, the trip level may vary depending upon different factors including consideration of the process material  90 , environmental conditions (e.g., temperature, pressure, weather conditions), fill rate, and/or age of the vessel  100 . As such, it may be advantageous to be able to locate the measuring device  10  at varied heights with the vessel  100 . 
         [0052]    In a further preferred embodiment, as shown in  FIG. 5A , the placement or depth location of the measuring device  10  within the vessel  100  may be varied through use of a coil device  40 . The coil device  40  is positioned in between the processor  30  and the measuring device  10 , to permit retraction or release of the segment of the connecting wire  41  extending between the coil device  40  and the measuring device  10 . In another preferred embodiment, the coil device  40  may also coil the segment of connecting wire  42  between the processor  30  and coil device  40 . For protection purposes, the coil device  40  may be within a housing  43 . 
         [0053]    In one preferred embodiment of the inventive system, one or both of the connecting wires  41  and  42  are shielded coaxial cables, such that the connecting wires  41 ,  42  are inactive extensions of the capacitance probe  15 . For standard vessel applications, the accuracy of the measuring device is easily maintained for total wire lengths within the range of about 1 foot to in excess of about 30 feet. In other embodiments and for larger or deeper vessel applications, the total wire length is primarily determined by the size and capability of the coil device  40  and housing  43 . Accordingly, for longer wire lengths, a larger and more powerful coil device  40  may be required. 
         [0054]    As described above, the communication between the measuring device  10  and the computer processor  30  may, in a preferred embodiment, be wireless. In such an embodiment, the coiling device  40  could be located within the vessel near the top of a vessel wall as shown in  FIG. 5B . If a trip level  35  were to change for varied conditions, for example where the vessel were derated due to age, the height of the measuring device  10  could be lowered through the coiling device  40 . 
         [0055]    As noted above, and as shown in  FIG. 1C , the measuring device may be used within a vessel  100  that is open to the environment and weather, and has an external floating roof  70 . The measuring device  10  in this application is exposed to all weather conditions including wind, rain, snow and freezing rain. In such conditions the detecting element  20  is also exposed to such environmental conditions, which could impair the proper operation of the detecting element  20 . By way of example, if the detecting element  20  became covered with a layer of snow, ice, freezing rain, dirt, or dust, the measuring device  10  could sense a false trip or “contact” signal if the gap between the detecting element  20  and outer ground wall  17  is bridged with electrically conducting moisture, water, ice or snow. This could especially occur for the embodiment with the detecting element  20  being wider in diameter than the capacitance probe. Such false “contact” signals would prevent proper filling operations and should be prevented where possible. 
         [0056]    In a preferred embodiment to address this problem, and as illustrated in  FIG. 6 , a cover or shroud  25  may be located around and above the measuring device  10  to keep snow or freezing rain from collecting on the detecting element  20 . In this design, snow and/or freezing rain is prevented from collecting on the detecting element  20  and bridging the gap between the detecting element  20  and the outer ground wall  17 . In one preferred embodiment, the cover  25  may be designed, as illustrated in  FIG. 6 , such that the lower end of the cover  25  does not extend as far as the bottom of the detecting element  20 . By having the detecting element  20  extend lower than the bottom of the cover  25 , the measuring device  10  and detecting element  20  will properly operate even where the measuring device is not fully vertically oriented. One advantage of the  FIG. 3D  embodiment of the measure device  10  is that the problem of water, ice, freezing rain causing false trips is eliminated because the ground element  17  is surrounded by the active element  16  and not directly exposed to such environmental precipitation. 
         [0057]    An alternative embodiment for use with process materials  90  that are not volatile, a heating element  27  could be incorporated with the measuring device  10 . As shown in  FIG. 7 , the heating element  27  could be used to raise the temperature of the measuring device  10  if the weather or environmental conditions, such as freezing rain or snow, warrant the need to keep the measuring device  10  from becoming covered or layered in ice or snow. 
         [0058]    The method of operation using the inventive apparatus entails several key steps. Those steps include first calibrating the measuring device  10  through the system processor  30 , then monitoring the level of the process material  90  within the vessel  100  and monitoring any detection signals between any solid surfaces  70 ,  75  within the vessel  100 , capacitance probe, and while also providing output data or signals based upon the monitoring of the process material  90  level and any detection signals generated from the measuring device  10 .  FIG. 9A  provides an example flowchart of a preferred embodiment of the inventive method for measuring the level of a process material while also monitoring detection of any solid surfaces within a vessel  100 . 
         [0059]    As shown by the steps in  FIG. 9A , the system first calibrates  400  the probe to initialize the level of the process material  90  within the vessel  100 . Thereafter, in a repetitive or feedback loop process the method undertakes a series of steps. The system monitors  410  the capacitance probe for variations in the measured capacitance data, which equate to variations in the level of the process material  90  and monitors whether a detection signal has been generated by the detecting element  20  or active element  16 . In this embodiment, the system compares  420  whether the measured capacitance data/process material  90  level has “hit” the set trip level  35 , or if a “contact” signal has been generated due to contact of a solid surface  70 ,  75  with the detecting element  20  or active element  16 . If the measured capacitance data shows that the level of the process material  90  has reached  421  the trip level  35 , or if a “contact” signal has been generated, then an alarm signal may be provided  430  to alert the system operator that the process material level has reached the trip level, or that a solid surface has contacted the probe and that no further material should be added to the vessel  100 , or that some of the process material should be removed from the vessel  100 . 
         [0060]    If the measured capacitance data indicates that the process material  90  has not reached  422  the set trip level  35 , or no “contact” signal has been generated, then the system repeats the monitoring step  510 . 
         [0061]    An alternative embodiment of the inventive method of operation provides for separate monitoring of the process material level as distinct from monitoring any contact detections with solid surfaces  70 ,  75 . More specifically, as shown in  FIG. 9B , the alternative embodiment system first calibrates  500  the probe and detecting element to initialize the level of the process material  90  within the vessel  100 , and sets or resets the detecting element  20  or active element  16 . Thereafter, in a repetitive or feedback loop process the method undertakes a series of steps. First, the system monitors  510  the capacitance probe for variations in the measured capacitance data, which equate to variations in the level of the process material  90 . The system processor may provide output data, and system readouts showing the system operator the level of the process material  90  within the vessel  100 . 
         [0062]    The system next may compare  520  the measured capacitance data/process material  90  level with a set trip level  35 . If the measured capacitance data shows that the level of the process material  90  has reached  521  the trip level  35 , then an alarm signal may be provided  530  to alert the system operator that the process material level has reached the trip level, and that no further material should be added to the vessel  100 , or that some of the process material should be removed from the vessel  100 . 
         [0063]    If the measured capacitance data indicates that the process material  90  has not reached  522  the set trip level  35 , the system also monitors  540  the detecting element  20  for any signals showing contact between any solid surfaces  70 ,  75  within the vessel  100  and the detecting element  20 . The system inquiries  550  whether a detection signal has been generated by the detecting element  20 . If a detection signal has been generated  551 , then an alarm signal may be provided  560  to the system operator advising that a solid surface contact with the detecting element  20  has been observed. If no detection signal has been generated  552 , then the system repeats the monitoring steps  510  and  540 . 
         [0064]    While  FIG. 9B  shows an example ordering of the monitoring steps, it should be understood that the monitoring steps  510  and  540 , along with the related inquiry steps  520  and  550 , may be reordered such that the monitoring of the detecting element  20  (or active element  16 ) may be completed before, or in parallel to the monitoring of the capacitance probe. 
         [0065]    The above detailed description teaches certain preferred embodiments of the present inventive measuring and detecting apparatus, and method of measuring and detecting using the disclosed apparatus. As described, the inventive measuring device and system provide high precision measurement of the surface level of a material stored in a vessel, and the ability to reliably detect contacts with a solid surface with the vessel, such as a floating roof. While preferred embodiments of the measuring and detecting apparatus and system, and the method of measuring and detecting have been described and disclosed, it will be recognized by those skilled in the art that various modifications and/or substitutions are possible. All such modifications and substitutions are intended to be within the true scope and spirit of the present invention as disclosed. It is likewise understood that the attached claims are intended to cover all such modifications and/or substitutions.