Abstract:
An apparatus for dynamically measuring a volume of fuel in a fuel tank of unknown geometry includes a fuel level sensor mounted on the fuel tank, a fuel meter for measuring a volume of fuel being consumed, and a rewritable look-up table storing correspondence between volumes of fuel and levels of fuel in the fuel tank. The loop-up table is rewritten as the oil in the tank is consumed. A system website is used for remotely monitoring the fuel tank of a building.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to the field of measuring the amount of fuel in a tank. More particularly, this invention relates to a method and apparatus for measuring and monitoring via a system website the volume of fuel in an irregularly shaped tank. 
     Previously proposed systems have used pressure based level sensors. These systems measure the weight of the oil in the tank and inaccuracies in the measurements are introduced because different grades of oil have different densities. For example, the density of No. 6 oil varies significantly among lots requiring the re-calibration of these systems after each oil delivery. 
     Further, previously proposed systems have handled the conversion from fuel level measurements to fuel volume using a standard look-up table based on the ideal geometry of the tank. 
     A problem with these previously proposed systems is that the actual geometry of the tank varies significantly because its dimensions are not generally held to tight tolerances. Further, many fuel tanks are buried in the ground or installed in places that make it impossible to measure the actual shape of the tank. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an apparatus to dynamically measure a volume of fuel in a fuel tank of unknown geometry. 
     It is another object of the present invention to provide a method for dynamically measuring a volume of fuel in a fuel tank of unknown geometry. 
     It is a still further object of the present invention to provide a system for remotely monitoring a fuel tank of a building. 
     It is a feature of the present invention to provide a rewritable look-up table storing correspondences between volumes of fuel and levels of fuel in the tank. 
     It is another feature of the present invention to provide a system website to connect a user via the Internet to the system for remotely monitoring a fuel tank of a building. 
     It is an advantage of the present invention that the geometry of the tank does not need to be known in advance. 
     These and other objects, advantages, and features of the present invention will become apparent to those skilled in the art upon consideration of the following description of the invention. 
     According to one aspect of the present invention an apparatus for dynamically measuring a volume of fuel in a fuel tank is provided, including a fuel level sensor mounted on the fuel tank, a fuel meter configured to produce an electrical indication when a predetermined volume of fuel passes through the fuel meter, a rewritable memory for storing a look-up table, wherein the look-up table stores correspondences between volumes of fuel in the fuel tank and levels of fuel in the fuel tank, and a controller configured to receive outputs from the fuel level sensor and the fuel meter and for controlling the rewritable memory, wherein when the controller detects the electrical indication from the fuel meter, the controller calculates a current level of fuel from the output from the fuel level sensor and calculates a current volume of fuel by decrementing/incrementing a previous volume of fuel by the predetermined volume of fuel, and the controller rewrites the look-up table with the calculated current volume of fuel corresponding to the current level of fuel. 
     According to another aspect of the present invention a method is provided for dynamically measuring a volume of fuel in a fuel tank having a fuel level sensor mounted thereon, a fuel meter configured to produce an electrical indication when a predetermined volume of fuel passes through the fuel meter, a rewritable memory for storing a look-up table, wherein the look-up table stores correspondences between volumes of fuel and levels of fuel in the fuel tank, and a controller configured to receive outputs from the fuel level sensor and the fuel meter and for controlling the rewritable memory, the method comprising the steps of detecting the electrical indication from the fuel meter, calculating a current level of fuel from the output from the fuel level sensor, calculating a current volume of fuel by decrementing/incrementing a previous volume of fuel by the predetermined volume of fuel, and rewriting the look-up table with the calculated current volume of fuel corresponding to the current level of fuel. 
     According to a still further aspect of the present invention a system for remotely monitoring a fuel tank of a building is provided including a fuel gauge mounted on a fuel tank of a building and provided with a wireless transmitter for transmitting fuel level measurements, and a computer for receiving the fuel level measurements transmitted by the fuel gauge, wherein the computer calculates whether a measured fuel level is below a predetermined level and issues an alarm in response to the calculation. 
     The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to organization and method of operation, together with further objects and advantages thereof, may be best understood by reference to the following description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of the apparatus for measuring a volume of fuel in a fuel tank according to an embodiment of the present invention; 
         FIG. 2  is an example of a look-up table according to an embodiment of the present invention; 
         FIG. 3  is a flowchart showing a method for measuring a volume of fuel in a fuel tank according to an embodiment of the present invention; 
         FIG. 4  is another flowchart showing a method for measuring a volume of fuel in a fuel tank according to an embodiment of the present invention; 
         FIG. 5  is a block diagram of another embodiment of the present invention; and 
         FIG. 6  is a flowchart showing a method for remotely monitoring a building according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail specific embodiments, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of the drawing. 
     Turning now to  FIG. 1 , an embodiment of the apparatus for measuring the volume of fuel in a tank includes a loop-powered ultrasonic level sensor  10  mounted on the top of a fuel tank  20  and connected to a fuel gauge controller board  50 . 
     The loop-powered ultrasonic level sensor  10 , in this embodiment of the present invention, provides a 4-20 mA current signal with 20 mA representing the oil level at 6 inches from the sensor (tank full) and 4 mA representing the oil level at 126 inches from the sensor. This scaling enables the use of the loop-powered ultrasonic level sensor  10  in tanks that are less or equal to 120 inches tall. 
     The loop-powered ultrasonic level sensor  10  could be a COSENSE LL-395 series sensor, for example. Other level sensors producing a 4-20 mA or 0-5V output could be used and other sensors with different scalings could also be used to accommodate larger tanks. 
     The fuel gauge controller board  50  is a microcontroller PCB having as an input the 4-20 mA current signal from the loop-powered ultrasonic level sensor  10 . The controller board  50  includes a signal conditioning and A/D conversion circuit  53 , a microcontroller  51 , a look-up table memory  52 , an LCD display  54 , user input key switches  55 , a computer interface  56 , and a voice record/play IC  57 . 
     The signal conditioning and A/D conversion circuit  53  converts the 4-20 mA current signal input into a digital value representing the oil level in tenths of inches. For example, a digital value of 223 represents 22.3 inches. 
     The look-up table memory  52  stores a look-up table initially loaded with default values, when available, based on the ideal geometry of the tank and supplied by the tank manufacturer or calculated from the tank geometry. 
     The controller board  50  could be designed around a microchip PIC18F452 microcontroller and the computer interface  56  could be a MAXIM MAX232 integrated circuit. Further, the LCD display  54  could be an OPTREX 51553 and the user input key switches  55  could be of the E-SWITCH SERIES 320 type, for example. 
     An in-line fuel meter  30  is installed between a boiler  40  and the fuel tank  20  for measuring the flow of fuel from the tank  20  to the boiler  40 . The in-line fuel meter  30  provides an electrical contact closure indication or “meter tick” to the microcontroller  51  for each tenth of a gallon, for example, of fuel that passes through the fuel meter  30 . The fuel meter  30  could be an ISTEC model 9215 with a dry contact signal output. 
     The user sets up and monitors the system operation directly via the LCD display  54  and the user input key switches  55  of the controller board  50 . 
     The computer interface  56  is provided so that the controller board  50  can be connected to a PC (not shown) to manage the system. 
     The voice record/play IC  57  may be used to play a pre-recorded alarm warning or to play a notification message over a telephone line (not shown) after dialing a pre-programmed alarm dial-out telephone number. 
     Temperature sensors  60  and  70  are connected to the controller board  50  to monitor outdoor and hot water temperatures, respectively. The outdoor and hot water temperatures can be used to improve the operating efficiency of the heating system. 
     Heating degree days can be calculated using the outdoor temperature sensor  60  and compared to the actual fuel usage. When the fuel usage and the degree days do not correlate, a warning can be issued informing the user that the heating system is operating inefficiently and requires maintenance. 
     The apparatus for measuring the volume of fuel in a tank shown in the embodiment of  FIG. 1  is designed to produce an on-site learned look-up table  100  such as the one shown in  FIG. 2 . 
     The on-site learned look-up table  100  providing a translation between the measured fuel level and the fuel volume is produced during the normal operation of the system without a need for shutting down the system and emptying the tank  20 . The fuel meter  30  that measures fuel flow from the tank  20  to the boiler  40  is used to determine the volume differences between incremental levels as the system is using the oil, thereby dynamically producing the on-site learned look-up table  100 . 
     Turing now to  FIGS. 3 and 4 , the method for producing the on-site learned look-up table  100 , shown in  FIG. 2 , will be described. 
     At the request of the user, the microcontroller  51  can be set to operate in a “learn mode”. In the “learn mode” when the fuel level measured by the sensor  10  becomes lower than the previous level by one “level increment or meter tick”, in this embodiment by one tenth of an inch, the microcontroller  51  replaces the value for the current level in the on-site learned look-up table  100  stored in the look-up table memory  52  with the value for the previous level minus the amount consumed between levels as will be described below. As shown in  FIG. 3 , each time a “meter tick” occurs in step S 100  the microcontroller  51  checks whether the system has been set in the “lean mode” in step S 110 . If yes, the microcontroller  51  decrements the gallons value by the amount represented by one “meter tick”, one tenth of a gallon in this embodiment, in step S 120 , then the microcontroller formats the data and displays the gallons value on the LCD display  54  in step S 130  and proceeds to perform the steps shown in  FIG. 4  via step S 140 . 
     As shown in  FIG. 4 , in step S 200 , every four times per second in this embodiment, the microcontroller  51  samples the output signal from the level sensor  10  by triggering an analog to digital (A/D) conversion in step S 210 . The resulting digital value is then filtered to reduce noise, reject bad readings, and smooth the transition from one reading to the next in step S 220  using intelligent digital filtering. Next, the filtered reading is scaled to convert the reading to a level in tens of inches in step S 230  and displayed on the LCD display  54  in step S 240 . 
     In step S 250 , the microcontroller  51  checks whether the system is in the “learn model”. If the system is in the “learn model”, the microcontroller  51  checks whether the current fuel level is lower than the previous level in step S 290  and, if it is, the microcontroller  51  rewrites in step S 300  the current gallons value, as measured by the fuel meter  30  and calculated by the microcontroller  51 , in the look-up table  100 . If the system is not in the “learn mode”, the microcontroller  51  uses the current full level value and looks up the corresponding gallons value in the look-up table  100  in step S 260 , and displays the gallons value in step S 270 . As discussed above, when this process is completed in step S 280  the process is repeated four times a second in this embodiment. 
     In addition to the core fuel volume measurement functions, the fuel gauge controller board  50 , provides a variety of useful data accumulation and reporting functions. 
     For example, each boiler run can be timed and recorded and the data made available in a detailed fuel usage report that is useful in determining whether the boiler is operating properly. 
     Further, by producing a daily fuel usage report that shows fuel used during the daytime and nighttime periods of each day and comparing it with degree-day information, boiler inefficiencies can be identified. 
     Furthermore, a time and amount of fuel delivery report can be created by monitoring a sudden rise in fuel level. 
     In another embodiment of the present invention, shown in  FIG. 5 , the level sensor  10  is a battery powered level sensor including a wireless transmitter  310 . In this embodiment the fuel gauge controller  50  is located in a remote monitoring site  300 , as shown in  FIG. 5 . The fuel gauge controller  50  in this embodiment includes a wireless receiver  320  to receive information from the fuel gauge  10 . 
     In a further embodiment of the present invention the fuel gauge controller  50  communicates wirelessly with the remote monitoring site  300  using the wireless transmitter  310  connected to the computer interface  56  shown in  FIG. 1 . 
     The remote monitoring site  300  includes a computer  330  for monitoring the information transmitted from a building  340  via the wireless transmitter  310 . 
     The computer  330  allows a user  350  to log-in to a system website for monitoring the building  340  using the Internet  360 , for example. The computer  330  is configured to receive information and monitor several buildings. 
     The operation of the system for monitoring the building  340  implemented in the computer  330  located in the remote monitoring site  300  will be described using the flowchart of  FIG. 6 . It should be understood that the flowchart of  FIG. 6  is a simplified flowchart and numerous other measurements and reports can be produced using this system. 
     In step S 400  the fuel level of the tank installed in the building  340  is measured, this measurement is transmitted to the remote monitoring site  300  in step S 410  and stored in a database of a computer  330 . These steps are repeated at regular intervals such as in a daily basis, for example. 
     Numerous calculations and reports can be produced with this system, for example, the system can check whether the measured fuel level is below a predetermined level in step S 430  and set a “low tank level” alarm in step S 440  when this is the case. 
     The user  350  can request a fuel usage report from the system and the system calculates and displays usage levels for a requested time period in step S 450 . 
     The system measures a fuel delivery and compares this measurement to a reported delivery in step S 460 . 
     Heating degree days are compared to the oil consumption of the building in step S 470  and when this comparison is not within predetermined parameters in step S 475 , a “maintenance required” message is displayed to the user  350  in step S 480 . The system will proceed to respond to other requests for information from the user  350  in step S 490 . 
     Thus, it is apparent that in accordance with the present invention, an apparatus that fully satisfies the objectives, aims, and advantages is set forth above. While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, permutations, and variations will become apparent to those skilled in the art in light of the foregoing description. For example, that a wireless level sensor could be used for remote monitoring of the fuel tank. 
     Accordingly, it is intended that the present invention embrace all such alternatives, modifications and variations as fall within the scope of the appended claims.