Precision depth sensor

Abstract

A system and method for monitoring liquid tanks that includes a submersible sensor within the tank below liquid surface. The system may also include a secondary sensor to determine ambient conditions, and a controller to determine when changes in liquid level are due to ambient events, or potential breach of system. A calibration rod may be used to monitor displacement of liquid in the tank and calibrate system to determine changes in height of liquid level.

I claim: 
     
         1 . A method of determining the qualities of a liquid in a storage tank with an embedded sensor submerged into the liquid, with the embedded sensor along a bottom surface of the storage tank or not more than a few inches above the bottom surface, said method comprising the steps of measuring the initial pressure along a specific point in the bottom of the tank; determining a weight of the fuel based on the initial pressure reading; calibrating the measurement via use of a submersible displacement rod via suspending a rod of a set volume into the fuel; detecting a further pressure; determining a change in the pressure as between the initial pressure and the further pressure readings; setting the pressure differential to determine a pressure to volume ratio; and thereafter monitoring the pressure reading at the sensor. 
     
     
         2 . The method for determining the qualities of a liquid in a storage tank as set forth in  claim 1 , further comprising the step of measuring an ambient condition via a secondary sensor. 
     
     
         3 . A method such as in  claim 2  whereby the embedded sensor determines the properties of a stored liquid, and compares those properties with the expected change of system conditions reported by a simultaneous secondary sensor detecting ambient conditions. 
     
     
         4 . A method as set forth in  claim 1  wherein the embedded sensor rests on the bottom of a fuel storage tank. 
     
     
         5 . A method as set forth in  claim 1  wherein the embedded sensor rests no more than one inch from the bottom of a fuel storage tank. 
     
     
         6 . A method such as in  claim 1  whereby the embedded sensor determines the conductivity or resistance of the liquid. 
     
     
         7 . The method as set forth in  claim 6  wherein the embedded sensor compares conductivity or resistance with the expected change of system conditions reported by a secondary sensor detecting ambient conditions. 
     
     
         8 . The method as set forth in  claim 1  further comprising the step of removing the displacement rod from the fuel, wherein said step of monitoring comprises taking multiple further pressure readings at a set time interval; and comparing the initial, further, and multiple further pressure readings to determine a weight change of the fuel (based on pressure change reading) to detect a leak. 
     
     
         9 . A method according to  claim 1  further comprising determining conditions of a tank of fluid via the embedded sensor within the fuel, and a secondary sensor for determining ambient conditions, and utilizing a temperature compensated volume to determine if differences of fluid level are due to natural ambient conditions. 
     
     
         10 . A system for monitoring the fuel level in a tank, and determining when changes in the fuel are due to leakage, said system comprising:
 a. an embedded sensor submerged either along a bottom surface of the storage tank or not more than two inches above the bottom surface and set below the fuel level within the tank;   b. said embedded sensor comprising a pressure transducer and a power source;   c. a controller determining pressure sensed by said embedded sensor.   
     
     
         11 . The system of  claim 10  further comprising a solid displacement rod moving between a position at least partially outside fuel in tank, and a position at least more partially within fuel of tank. 
     
     
         12 . The system of  claim 10  further comprising a secondary sensor outside the liquid of the tank, said secondary sensor capable of detecting ambient conditions of at least one of temperature, pressure, humidity, and/or dew point. 
     
     
         13 . The system of  claim 12  whereby said secondary sensor is within the tank, said embedded sensor and said secondary sensor connected to a monitoring system. 
     
     
         14 . The system of  claim 12  whereby said secondary sensor is outside the tank, said embedded sensor and said secondary sensor connected to a monitoring system. 
     
     
         15 . The system of  claim 12  wherein said embedded sensor includes an opening to expose the pressure transducer directly to the fuel pressure. 
     
     
         16 . The system of  claim 12  wherein said embedded sensor comprises an analog digital converter coupled to said pressure transducer, said analog digital converter in communication with said controller. 
     
     
         17 . The system of  claim 16  further comprising an interface box housing said secondary sensor. 
     
     
         18 . The system of  claim 16  wherein said embedded sensor and said secondary sensor are coupled via a connector that passes through a vapor-proof bung cap. 
     
     
         19 . The system of  claim 10  wherein said embedded sensor is located within or below a drop tube. 
     
     
         20 . The system of  claim 10  whereby the controller comprises memory to record and store data, and the controller receives simultaneous data from the submerged sensor and data from the secondary sensor.