Ultrasonic unipolar pulse/echo instrument

• US 5,199,299 A
• Filed: 03/11/1991
• Issued: 04/06/1993
• Est. Priority Date: 03/11/1991
• Status: Expired due to Fees

• Current Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Original Assignee: Iowa State University Research Foundation Incorporated (Iowa State University)
• Inventors: Thompson, Donald O., Hughes, Michael S., Hsu, David K., Wormley, Samuel J.
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Finley, Rose M.
• Application Number:
  US07/667,437
• Time in Patent Office: 757 Days
• Field of Search: 73/609, 73/610, 73/620, 73/629, 73/632, 73/642, 73/612, 73/614, 367/135, 367/137, 367/903, 310/314, 310/316, 310/317, 310/318, 310/319
• US Class Current: 73/610
• CPC Class Codes: B06B 1/0215 for generating pulses, e.g. bursts of oscillations, envelopes
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01S 7/52025 for pulse systems G01S7/52034 takes precedence
• CPC Class Codes: G01S 7/526 Receivers
• CPC Class Codes: Y10S 367/903 Transmit-receive circuitry

Abstract

An ultrasonic unipolar pulse/echo instrument uses active switches and a timing and drive circuitry to control electrical energy to a transducer, the discharging of the transducer, and the opening of an electrical pathway to the receiving circuitry for the returning echoes. The active switches utilize MOSFET devices along with decoupling circuitry to insure the preservation of the unipolar nature of the pulses, insure fast transition times, and maintain broad band width and time resolution. A housing contains the various circuitry and switches and allows connection to a power supply and a movable ultrasonic transducer. The circuitry maintains low impedance input to the transducer during transmitting cycles, and high impedance between the transducer and the receiving circuit during receive cycles to maintain the unipolar pulse shape. A unipolar pulse is valuable for nondestructive evaluation, a prime use for the present instrument.

Claims

1. An ultrasonic pulse/echo transmitting and receiving instrument comprising:

an ultrasonic transducer means for transmitting and receiving ultrasonic mechanical acoustic pulses;

electrical power supply means providing a source of electrical power;

receiving circuit means for isolating and amplifying electrical signals representing return echoes of the acoustic pulses;

timing and drive control circuit means for timing operations of the instrument and driving the transducer means to transmit periodic bursts of the acoustic pulses in a pulse mode;

first switch means operatively connected between the electrical power supply means and the transducer means, controlled by the timing and drive control circuit means to send electrical power in an electrical pathway to the transducer means during a first time period;

second switch means operatively positioned between the transducer means and ground, the second switch means providing a low impedance electrical pathway from the transducer means during a second time period;

third switch means operatively positioned between the transducer means and the receiving circuit means controlled by the timing and drive control circuit means to allow the receiving circuit means to receive the electrical signals representing return echoes of the acoustic pulses in an echo mode of the transducer means during a third time period; and

the timing and drive circuit means including dual one shot triggering means for creating timing pulses in a first portion of the circuitry, and power MOSFET driver means for creating driving signals for the first, second, and third switch means of the instrument.

2. An ultrasonic pulse/echo transmitting and receiving instrument comprising:

an ultrasonic transducer means for transmitting and receiving ultrasonic mechanical acoustic pulses;

electrical power supply means providing a source of electrical power;

receiving circuit means for isolating and amplifying electrical signals representing return echoes of the acoustic pulses;

timing and drive control circuit means for timing operations of the instrument and driving the transducer means to transmit periodic bursts of the acoustic pulses in a pulse mode;

first switch means operatively connected between the electrical power supply means and the transducer means, controlled by the timing and drive control circuit means to send electrical power in an electrical pathway to the transducer means during a first time period, the first switch means including input from and adjustable direct current power supply, input from the timing and drive circuit means, a first MOSFET means between the input from the power supply and an outlet, and second MOSFET means between the input of the timing and drive means and the first MOSFET means, so that the operation of the second MOSFET means from the timing and drive means controls opening and closing of an electrical pathway between the power supply and the transducer means through the first MOSFET means;

second switch means operatively positioned between the transducer means and ground, the second switch means providing a low impedance electrical pathway from the transducer means during a second time period;

third switch means operatively positioned between the transducer means and the receiving circuit means controlled by timing and drive control circuit means to allow the receiving circuit means to receive the electrical signals representing return echoes of the acoustic pulses in an echo mode of the transducer means during a third time period.

3. The instrument of claim 2 wherein first and second diodes and a resistor are connected in series between the first MOSFET means and the input from the power supply.

4. An ultrasonic pulse/echo transmitting and receiving instrument comprising:

an ultrasonic transducer means for transmitting and receiving ultrasonic mechanical acoustic pulses;

electrical power supply means providing a source of electrical power;

receiving circuit means for isolating and amplifying electrical signals representing return echoes of the acoustic pulses;

timing and drive control circuit means for timing operations of the instrument and driving the transducer means to transmit periodic bursts of the acoustic pulses in a pulse mode;

first switch means operatively connected between the electrical power supply means and the transducer means, controlled by the timing and drive control circuit means to send electrical power in an electrical pathway to the transducer means during a first time period;

second switch means operatively positioned between the transducer means and ground, the second switch means providing a low impedance electrical pathway from the transducer means during a second time period; and

third switch means operatively positioned between the transducer means and the receiving circuit means controlled by the timing and drive control circuit means to allow the receiving circuit means to receive the electrical signals representing return echoes of the acoustic pulses in an echo mode of the transducer means during a third time period, the third switch means including an input form the transducer means, an input from the timing and drive means, and an output to the receiving means, and including switching means to open and close an electrical pathway between the input from the transducer means, and the output to the receiving means, and further comprising a MOSFET and a buffer current amplifier in series between the input from the transducer means and the output to the receiving means, wherein the MOSFET has a voltage rating at least as large as the power supply means to protect the buffer current amplifier.

5. A drive for transmitting and receiving unipolar ultrasonic energy for sue in nondestructive evaluation comprising:

a housing to which components of the device can be installed;

first connection means on the housing to connect the device to an ultrasonic transducer means;

second connection means on the housing to connect the device to an electrical power source;

third connection means on the housing to connect the drive to a receiver amplifier means for providing an amplified received signal to an output;

power conversion means connected to the second connection means to provide one or more direct current voltages to the device;

control means for controlling timing and operation of the device according to parameters;

manually adjustable controls connected to the control means for adjusting the parameters related to the control means;

display means for displaying representations of one or more parameters;

first switch means for providing an electrical pathway for excitation voltage to the first connection means, the first switch means being controlled between non-conducting and conducting states by the control means and being conducting during a first time period to charge the transducer means;

second switch means for providing a low impedance electrical pathway to quickly discharge electrical charge from the transducer means, the second switch means being controlled by the control means to be conducting at a time after the first switch means is conducting and then non-conducting; and

third switch means for providing an electrical pathway to the third connection means from the transducer means, the third switch means being controlled by the control means and being in a conducting state when ultrasonic energy is received through the third connection means, at a time substantially after the second switch means is non-conducting after being conducting.

6. The device of claim 5 wherein one of the direct current voltages used for an excitation voltage is a variable voltage generated according to a step function.

7. The device of claim 5 further comprising a housing means.

8. The device of claim 5 wherein the first, second and third switch means, receiving means, control means, and power converting means are contained on printed circuit boards installed in the housing.

9. The device of claim 8 wherein the printed circuit boards are constructed according to ground plane construction, include a ground plane, for fast pulse transition times and enhancement of noise immunity.

10. The device of claim 8 wherein the power conversion means and inputs from the control means are referenced to a separate ground other than the ground plane for eliminating ground loops which can degrade switching time for the first, second, and third switch means.

11. The device of claim 5 wherein first switching means includes the combination of five diodes and a band pass filter to decouple return echoes at first and second MOSFET devices.

12. The device of claim 5 wherein the second switching means includes a resistor and capacitor to decouple low frequency elements of return ultrasonic pulses to ground through a MOSFET gate drive circuitry.

13. The device of claim 5 wherein the third switch means comprises a MOSFET electrically connected to accept ultrasonic energy from said transducer means and a buffer current amplifier of limited input voltage range electrically connected to accept ultrasonic energy from said MOSFET.

14. The device of claim 5 wherein the first, second and third switching means are active switching means.

15. A method for transmitting and receiving unipolar ultrasonic nondestructive pulses comprising:

cyclically triggering excitation voltage to a piezoelectric ultrasonic transducer;

connecting by first active switch means the excitation voltage to the transducer at certain times and providing a low impedance transmission of electrical energy to the transducer to charge the transducer prior to creating a unipolar ultrasonic pulse;

connecting by second active switch means a low impedance pathway to the transducer to discharge the transducer and propagate an ultrasonic mechanical acoustic pulse, and eliminating the low impedance pathway upon return echo of the ultrasonic pulse; and

connecting by third active switch means the transducer to an amplifying and receiving means at a high impedance to communicate a return echo signal to the amplifying and receiving means.

16. The method of claim 15 wherein the excitation voltage is provided by a variable 0 to 1000 volts DC power supply.

17. The method of claim 15 further comprising the step of avoiding parasitic capacitive elements int he first, second, and third active switch means resulting in high impedance paths by decoupling the elements.

18. The method of claim 15 wherein the excitation voltage is created by a step function to produce ultrasonic pulses on the order of 10 nanoseconds or less at a magnitude over a range of 0 to 1000 volts.

19. The method of claim 15 wherein the first, second, and third active switch means utilize MOSFETs.

20. The method of claim 19 wherein further MOSFET devices are used to drive gate junctions of the MOSFETs of the first, second, and third active switch means.

21. The method of claim 15 wherein separate grounds are utilized for the excitation voltage means and for the first, second, and third active switch means, eliminating ground loop currents to increase signal band width.