Ultrasonic sensor and method of use

• US 6,295,873 B1
• Filed: 07/22/1999
• Issued: 10/02/2001
• Est. Priority Date: 07/22/1999
• Status: Expired due to Fees

• Current Assignee: United States Department of Energy
• Original Assignee: United States Department of Energy
• Inventors: Condreva, Kenneth J.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): FAYYAZ, NASHMIYA SAQIB
• Application Number:
  US09/358,549
• Time in Patent Office: 803 Days
• Field of Search: 73/645.3, 73/617.9, 735/97, 732/90.V, 73/614.1, 73/614.5, 73/614.3
• US Class Current: 73/597
• CPC Class Codes: G01N 2291/0258 Structural degradation, e.g. fatigue of composites, ageing of oils
• CPC Class Codes: G01N 29/024 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/38 by time filtering, e.g. using time gates
• CPC Class Codes: G01N 29/40 by amplitude filtering, e.g. by applying a threshold or by gain control
• CPC Class Codes: G01N 29/4427 with stored values, e.g. threshold values

Abstract

An ultrasonic sensor system and method of use for measuring transit time though a liquid sample, using one ultrasonic transducer coupled to a precision time interval counter. The timing circuit captures changes in transit time, representing small changes in the velocity of sound transmitted, over necessarily small time intervals (nanoseconds) and uses the transit time changes to identify the presence of non-conforming constituents in the sample.

Claims

1. A sensor system for measuring the transit time of an ultrasonic wave through a liquid sample, comprising:

(a) a vessel of known dimensions for containing said liquid sample;

(b) an ultrasonic means, having an ultrasonic transducer means operably connected to said vessel in communication with said liquid sample and having an electric pulse generator operably connected to said transducer means, for generating and sending an ultrasonic wave through said liquid sample upon receipt of a trigger pulse;

(c) a system controller means having a trigger signal output for generating said trigger pulse;

(d) a high-resolution, low-power, time interval counter, having a start input gating means and a stop input gating means each operably connected to said controller means and said transducer means;

(e) said start gating means and said stop gating means consisting of at least two voltage comparator means comprising a first voltage comparator means, said first comparator means being preprogrammed with an unvarying first reference voltage of a chosen value, for receiving an electrical pulse signal from said generator, for comparing the voltage of said electrical pulse signal to said first reference voltage, and for providing a start signal to said counter when the voltage of said electrical pulse signal exceeds said first reference voltage, and a second voltage comparator means for receiving a second variable reference voltage from said controller means, said second reference voltage being set by said controller means to a predetermined percentage of a peak amplitude of an echo pulse, said echo pulse derived from said ultrasonic wave after said ultrasonic wave has passed through said liquid sample, for comparing the voltage of said echo pulse to said second reference voltage, and for providing a stop signal to said counter when the voltage of said echo pulse exceeds said second reference voltage; and

(f) a time interval data readout means for providing a time interval between said start signal and said stop signal;

wherein said trigger pulse from said controller means causes said pulse generator to provide said electric pulse signal simultaneously to said start gating means and to said transducer means, which causes said transducer means to produce said ultrasonic wave, said ultrasonic wave being sent through said liquid sample and from said liquid sample to said stop gating means, which causes said stop gating means to produce said stop signal to said counter, and wherein said data readout means provides time measurements between said start signal and said stop signal to said controller means.

2. The sensor system of claim 1, further comprising an amplifying means, operably connected to said stop gating means and inserted between said transducer means and said stop gating means, for amplifying said ultrasonic wave provided by said transducer means after said ultrasonic wave has passed through said liquid sample and for sending an amplified ultrasonic wave to said stop gating means.

3. The sensor system of claim 1, wherein said controller further comprising a means for providing an inhibit signal to said stop gating means simultaneously when providing said trigger signal to said generator, to prevent operation of said stop gating means while said electronic pulse signal is being transmitted and while said ultrasonic wave is being transmitted through said liquid sample.

4. The sensor system of claim 1, wherein said second reference voltage is set to one-half of said peak amplitude of said echo pulse.

5. The sensor system of claim 1, further comprising a means for measuring temperature variations in said liquid sample and a means for providing data representing said temperature variations to said controller means, wherein said time measurements provided to said controller means are mathematically corrected by said data representing said temperature variations.

6. The sensor system of claim 1, wherein said controller means further comprises:

a means for storing at least one predetermined reference transit time for a reference sample, said reference transit time being chosen from a plot of a selected characteristic of the reference sample versus a plurality of transit times;

a means for comparing transit time measurements received from said counter to the reference transit time;

a means for calculating the actual value of a selected characteristic in the sample using the comparison of the transit time measurements to the reference transit time; and

a means for displaying the value of the selected characteristic to a user of the sensor system.

7. The sensor system of claim 1, for identifying the presence of non-conforming constituents in said liquid sample.

8. The sensor system of claim 1, wherein said transducer means is a high-frequency ultrasonic transducer having a frequency range of 10-20 MHz.

9. The sensor system of claim 1, wherein said transducer means is a piezoelectric ultrasonic transducer.