Liquid measuring system and methods

• US 5,765,433 A
• Filed: 03/10/1995
• Issued: 06/16/1998
• Est. Priority Date: 03/10/1995
• Status: Expired due to Fees

• Current Assignee: National Environmental Service Company
• Original Assignee: Arizona Instrument Corporation
• Inventors: Johnson, Glen A.
• Primary Examiner(s): Will, Thomas B.
• Application Number:
  US08/401,874
• Time in Patent Office: 1,194 Days
• Field of Search: 73/290 V, 367/908, 367/108, 340/621
• US Class Current: 73/290.00V
• CPC Class Codes: G01F 17/00 Methods or apparatus for determining the capacity of containers or cavities, or the volume of solid bodies measuring linear dimensions to determine volume G01B
• CPC Class Codes: G01F 23/2962 Measuring transit time of reflected waves
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01S 15/88 Sonar systems specially adapted for specific applications seismic or acoustic prospecting or detecting G01V1/00
• CPC Class Codes: G01S 7/527 Extracting wanted echo signals Doppler systems G01S15/50

Abstract

Ultrasonic apparatus determines the fluid depth, volume, and temperature in a storage tank. A system description for monitoring an underground storage tank containing gasoline is described. The system determines the water'"'"'s and gasoline'"'"'s depth, volume, and temperature. The apparatus consists of a remote console, ultrasonic probe, and interconnecting cable. The remote console contains a display to report tank information and a computer to operate the probe. The probe consists of an ultrasonic transducer above the bottom of the probe facing upwards to transmit and receive ultrasonic signals, vertically spaced reflectors and a temperature sensor to measure fluid temperature.

Claims

1. A system for determining the amount of liquid in a tank, comprising:

an ultrasonic probe device extending in said tank, said ultrasonic probe including a plurality of reflectors spaced apart thereon and an ultrasonic transducer;

a controller coupled to said transducer and operable to cause said transducer to periodically transmit ultrasonic signals in said liquid and operable to receive signals produced by said transducer in response to echo signals received from the surface of said liquid and certain ones of said reflectors;

said controller being operable in a first mode wherein said controller computes the volume of liquid in said tank from the echo times of reflections received from two of said reflectors and from the surface of said liquid, said controller being further operable in said first mode to calculate an average sonic velocity; and

said controller being operable in a second mode to compute the volume of said liquid in said tank from the echo time of reflections received from said surface and from said average sonic velocity.

2. A system in accordance with claim 1, wherein:

said controller when in said first mode computes a sonic velocity from echo delay times of said echo signals received from said two reflectors, and utilizes said sonic velocity to determine the height of said surface above one of said two reflectors.

3. A system in accordance with claim 2, wherein:

said controller when in said first mode determines the depth of liquid in said tank from said height of said surface above one of said two reflectors and the height of said one of said two reflectors.

4. A system in accordance with claim 3, wherein:

said controller when in said first mode determines the volume of liquid in said tank from said depth and from volumetric characteristics of said tank.

5. A system in accordance with claim 3, wherein:

said controller when in said first mode periodically calculates an average volume from a plurality of said liquid depths.

6. A system in accordance with claim 3, wherein:

said controller calculates said average sonic velocity from said depth and from an echo delay time of said echo signals received from said surface.

7. A system in accordance with claim 6, wherein:

said controller switches between said first and second modes under predetermined conditions.

8. A system for triggering on ultrasonic echoes to determine volumetric changes of liquid in a tank, said system comprising:

an ultrasonic probe, said probe comprising a plurality of spaced apart reflectors and an ultrasonic transducer disposed below said reflectors;

a controller for periodically causing said transducer to emit ultrasonic signals in said liquid and to process signal waveforms generated by said transducer in response to echo ultrasonic signals received from the surface of said liquid and from a submerged one of said reflectors, said controller operating to determine a portion of said signal waveforms generated by said transducer as a reference trigger point; and

each said reference trigger point being determined by measuring peak amplitudes of peaks in each said waveform, determining differences between said peaks, and selecting said portion of said waveform having the largest of said differences as said reference trigger point, said reference trigger point being utilized to trigger on subsequent ones of said echo ultrasonic signals to determine said volumetric changes.

9. A system for determining the amount of liquid in a tank, comprising:

an ultrasonic probe suspended in said liquid, said probe carrying a plurality of reflectors spaced apart thereon and carrying an ultrasonic transducer;

a controller coupled to said transducer to periodically cause said transducer to emit ultrasonic signals in said liquid and operable to process echo signals generated by said transducer in response to ultrasonic echo signals reflected from the surface of said liquid and from submerged ones of said reflectors;

said controller being operable to profile echo signals for each of said submerged reflectors and from said surface to determine reference points whereby repetitive accurate time measurements may be determined for said echo signals;

said controller being operable in a first mode to compute the depth of liquid in said tank from echo signal times of two of said submerged reflectors and from the echo signal time for said surface, and further operable to calculate an average sonic velocity for said liquid from said depth and said echo signal time for said surface, said controller being operable to compute the volume of liquid in said tank from said depth and from volumetric characteristics of said tank; and

said controller being operable in a second mode to determine the volume of liquid in said tank from said echo signal time for said surface and from said average sonic velocity.

10. A system in accordance with claim 9, wherein:

said controller is operable to determine temperature dependent volumetric changes of said liquid.