Method for accurately measuring fluid in a vessel

Abstract

A system and method for accurately measuring fluid level in a vessel is provided. Generally, the system contains an elongated portion being a coaxial tube having a hollow center, an arm being coaxial in shape, and a sensor containing a transmitter capable of creating and transmitting an excitation electromagnetic pulse for traversing the elongated portion and the arm, and a receiver for receiving reflected pulses, wherein a proximate end of the elongated portion joins a distal end of the arm in a manner to create a waveguide for an electromagnetic pulse provided by the sensor.

1 . A method for accurately measuring fluid level in a vessel over a period of time with a sensor comprising a transmitter configured to transmit an excitation electromagnetic pulse traversing a transmission line, and an aliasing sampling receiver for converting high speed reflected waveforms into a slower speed equal time waveform for processing, the method comprising the steps of:
 scanning a length of the transmission line that is placed partially or fully in fluid to determine a current fluid level along the transmission line;   identifying a first detection point within the slower speed equal time waveform output, where the first detection point in the equal time waveform indicates a first position in the pulse reflection waveform representing the current fluid level;   tracking the fluid level within a scan window of the aliasing sampling receiver; and   adjusting the aliasing sampling receiver scan window to track the first detection point within the equal time representation of the high speed reflected waveforms.   
     
     
         2 . The method of  claim 1 , further comprising the step of identifying a second detection point on the slower speed equal time waveform, where the second detection point in the pulse reflection waveform indicates a second position in the pulse reflection waveform. 
     
     
         3 . The method of  claim 2 , wherein the second detection point is an end portion of the transmission line. 
     
     
         4 . The method of  claim 1 , wherein the step of scanning a length of the transmission line further comprises the steps of:
 transmitting a first excitation electromagnetic pulse;   recording a first sample of a reflection of the first excitation electromagnetic pulse at a first time interval after transmitting the first excitation electromagnetic pulse;   transmitting a second excitation electromagnetic pulse;   recording a second sample of a reflection of the second excitation electromagnetic pulse at a second time interval after transmitting the second excitation electromagnetic pulse, wherein the second time interval is greater than the first time interval;   transmitting a third excitation electromagnetic pulse;   recording a third sample of a reflection of the third excitation electromagnetic pulse at a third time interval after transmitting the third excitation electromagnetic pulse, wherein the third time interval is greater than the second time interval; and   combining the first sample, the second sample, and the third sample within the slower speed equal time waveform.   
     
     
         5 . The method of  claim 4 , wherein the step of identifying the first detection point within the slower speed equal time waveform output further comprises the step of detecting a discontinuity within the slower speed equal time waveform, wherein the discontinuity is formed at a boundary between media. 
     
     
         6 . The method of  claim 5 , wherein the aliasing sampling receiver scan window comprises a range of time starting at the first time interval and the time ending at the third time interval. 
     
     
         7 . The method of  claim 6 , wherein the step of adjusting the aliasing sampling receiver scan window comprises at least one of the group consisting of increasing the first time interval, decreasing the first time interval, increasing the third time interval, and decreasing the third time interval. 
     
     
         8 . The method of  claim 1 , wherein the excitation electromagnetic pulse comprises a unit step function. 
     
     
         9 . The method of  claim 1 , wherein the step of scanning a length of the transmission line further comprises the steps of:
 transmitting an excitation electromagnetic pulse;   recording a first sample of a reflection of the excitation electromagnetic pulse at a first time interval after transmitting the excitation electromagnetic pulse;   recording a second sample of the reflection of the excitation electromagnetic pulse at a second time interval after transmitting the excitation electromagnetic pulse, wherein the second time interval is greater than the first time interval; and   combining the first sample, and the second sample to form a portion of the slower speed equal time waveform.   
     
     
         10 . The method of  claim 9 , wherein the step of identifying the first detection point within the slower speed equal time waveform output further comprises the step of detecting a discontinuity within the slower speed equal time waveform, wherein the discontinuity is formed at a boundary between media. 
     
     
         11 . The method of  claim 10 , wherein the aliasing sampling receiver scan window comprises a range of time starting at the first time interval and the time ending at the second time interval. 
     
     
         12 . The method of  claim 11 , wherein the step of adjusting the aliasing sampling receiver scan window comprises at least one of the group consisting of increasing the first time interval, decreasing the first time interval, increasing the second time interval, and decreasing the second time interval. 
     
     
         13 . A method of accurately measuring the level of a fluid in a vessel with an apparatus comprising a transmission line and a sensor, wherein the transmission line comprises a partially hollow coaxial waveguide, and the sensor comprises a transmitter, power supply circuitry, and an aliasing sampling receiver for converting high speed reflected waveforms into a slower speed equal time waveform for processing, the method comprising the steps of:
 at least partially submerging the coaxial waveguide in the fluid within the vessel to a current fluid level within the coaxial waveguide;   creating an excitation electromagnetic pulse by the sensor;   transmitting the excitation electromagnetic pulse through the transmission line;   receiving a reflection waveform of the excitation electromagnetic pulse;   sampling the reflection waveform of the excitation electromagnetic pulse; and   accumulating the sampled reflection waveform into the slower speed equal time waveform.   
     
     
         14 . The method of  claim 13 , wherein the power supply circuitry is configured to prevent high energy signals from propagating into the vessel. 
     
     
         15 . The method of  claim 13 , further comprising the steps of:
 initiating the transmitter to send the excitation electromagnetic pulse;   synchronizing the receiver to the transmit pulse; and   recording time elapsed between transmitting the excitation electromagnetic pulse and sampling the reflection waveform of the excitation electromagnetic pulse.   
     
     
         16 . The method of  claim 15 , further comprising the step of deriving a propagation velocity of the excitation magnetic pulse through the fluid. 
     
     
         17 . The method of  claim 16 , wherein deriving a propagation velocity further comprises the steps of:
 identifying a first transition in the slower speed equal time waveform, wherein the first transition corresponds to a first boundary of the fluid;   identifying a second transition in the slower speed equal time waveform, wherein the second transition corresponds to a second boundary of the fluid;   identifying a first sample corresponding to the first transition, wherein the first sample comprises a first sample time;   identifying a second sample corresponding to the second transition, wherein the second sample comprises a second sample time; and   calculating the time elapsed between the first sample time and the second sample time.   
     
     
         18 . The method of  claim 16 , further comprising the step of measuring a temperature of the fluid. 
     
     
         19 . The method of  claim 18 , wherein the step of measuring a temperature of the fluid further comprises:
 deriving the dielectric constant of the fluid from the propagation velocity of the excitation magnetic pulse through the fluid; and   comparing the derived dielectric constant of the fluid to a table of fluids having known dielectric constant values to determine a temperature of the fluid.   
     
     
         20 . The method of  claim 13 , further comprising the step of determining the current fluid level via use of time of flight of the excitation electromagnetic pulse to the end of the coaxial waveguide. 
     
     
         21 . The method of  claim 20 , wherein the step of determining the current fluid level via use of time of flight further comprises the steps of:
 receiving a reflection of the excitation pulse from the end of the coaxial waveguide;   measuring a lapse of time between transmitting the excitation electromagnetic pulse and receiving the reflection;   determining the dielectric constant of the fluid in the vessel; and   measuring a distance along the transmission line between the sensor and the end of the transmission line.   
     
     
         22 . The method of  claim 13 , wherein the coaxial waveguide comprises a center conductor and an outer tube, wherein the outer tube is formed of metal. 
     
     
         23 . The method of  claim 22 , further comprising the step of electrically connecting the outer tube to the vessel. 
     
     
         24 . The method of  claim 13 , further comprising the steps of:
 determining the temperature of the fluid;   measuring a perceived length of the coaxial waveguide immersed in the fluid; and   calculating the dielectric constant of the fluid from a ratio of the perceived length and a measured length of the coaxial waveguide having the fluid therein.   
     
     
         25 . The method of  claim 13 , further comprising the steps of:
 determining a current fluid level of the fluid; and   maintaining the current fluid level within a scan window, wherein timing of the scan window is adjusted to keep the current level of the fluid within the window.   
     
     
         26 . The method of  claim 13 , wherein the excitation electromagnetic pulse comprises a unit step function. 
     
     
         27 . A method for scanning, tracking and analyzing data from a transmission line used to monitor fluid in a vessel by a sensor comprising a clock, a processor, a transmitter, and a receiver, the sensor being in electrical communication with the transmission line, the method comprising the steps of:
 providing a clock signal comprising clock pulses;   transmitting, by the transmitter, a first transmit pulse and a second transmit pulse into the transmission line, the first transmit pulse comprising a first amplitude;   receiving, by the receiver, a first reflection pulse resulting from the first transmit pulse, the reflection pulse comprising a second amplitude;   receiving, by the receiver, a second reflection pulse resulting from the second transmit pulse;   synchronizing the receiver to the transmission of the transmit pulse, whereas said synchronizing comprises measuring the number of lapsed clock pulses between said transmitting and said receiving;   filtering, by the processor, the first reflection pulse and the second reflection pulse;   sampling, by the processor, the first reflection pulse and the second reflection pulse; and   accumulating a first sample from the first reflection pulse and a second sample from the second reflection pulse into a slower speed equal time waveform.   
     
     
         28 . The method of  claim 27 , further comprising the step of gating the receiver, wherein gating comprises delaying, by a first number of clock pulses, initiation of said receiving, and terminating, after a second number of clock pulses, said receiving, the time elapsed between the first number of clock pulses and the second number of clock pulses comprising a gate window. 
     
     
         29 . The method of  claim 28 , further comprising the steps of:
 tracking an event of interest within the gate window; and   adjusting the gate window to maintain the event of interest within the gate window.   
     
     
         30 . The method of  claim 27 , further comprising the steps of:
 monitoring, by the receiver, the magnitude of second amplitude; and   adjusting, by the transmitter, the first amplitude in response to the monitored magnitude of the second amplitude.