Local buffer circuit for sonic waveguides

• US 5,736,855 A
• Filed: 07/10/1995
• Issued: 04/07/1998
• Est. Priority Date: 07/10/1995
• Status: Expired due to Term

• Current Assignee: MTS Systems Corporation (Illinois Tool Works Inc.)
• Original Assignee: MTS Systems Corporation (Illinois Tool Works Inc.)
• Inventors: Sprecher, Arnold Fred Jr., Smith, Stephen Williams
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US08/500,004
• Time in Patent Office: 1,002 Days
• Field of Search: 324/166, 324/207.13, 324/207.22, 324/207.24, 73/290 V, 73/313, 73/314, 73/319, 73/DIG. 5, 333/148, 367/140, 367/908
• US Class Current: 324/207.13
• CPC Class Codes: G01B 17/00 Measuring arrangements characterised by the use of infrasonic, sonic or ultrasonic vibrations
• CPC Class Codes: G01D 5/485 using magnetostrictive devices
• CPC Class Codes: G01F 23/2968 Transducers specially adapted for acoustic level indicators

Abstract

A local buffer circuit for use with a magnetostrictive transducer is disclosed wherein the magnetostrictive transducer includes a pickup coil and the local buffer circuit includes two diodes in parallel with the pickup coil to clip or short the energy produced in the pickup coil generated by an interrogation pulse, and also includes a common emitter amplifier to reduce the electrical impedance of the pickup coil, also in parallel with the pickup coil.

Claims

1. A converter for processing a sonic wave of a magnetostrictive transducer having an exterior surface to an electrical output signal for use by an electronic circuit, the electronic circuit being located outside the exterior surface, the output signal generated by a higher magnitude input pulse, comprising:

means for converting the sonic wave into the electrical output signal, including a pickup coil having at least two leads, said means for converting being located inside the exterior surface;

first means located inside the exterior surface and connected to said leads having solely passive components for modifying the electrical output signal from said coil to avoid saturation of the electronic circuit by ringing caused by the input pulse.

2. The converter of claim 1, wherein said first means clips the peak of the signal.

3. The converter of claim 2, wherein said first means includes:

a first diode connected electrically in parallel to said leads of said pickup coil; and

a second diode oriented oppositely to said first diode and connected electrically in parallel with said first diode;

said first and second diodes sized to clip the signal.

4. The converter of claim 3, wherein there is further included an amplifier having a base and a collector, said base and said collector connected to said two leads of said pickup coil, said amplifier sized to reduce the electrical impedance of said pickup coil and produce the signal.

5. The converter of claim 2, wherein said first means includes:

a first transistor having a collector, said collector connected to one of said leads of said pickup coil and a base, said base connected to the other of said leads of said pickup coil.

6. The converter of claim 5, wherein said first means further includes a second transistor having a base, collector and emitter, said base of said second transistor connected to said collector of said first transistor and said collector of said second transistor connected to said base of said first transistor.

7. The converter of claim 6, wherein said emitter and collector of said second transistor produce the signal.

8. The converter of claim 2, wherein there is further included an amplifier having a base and a collector, said base and said collector connected to said two leads of said pickup coil, said amplifier sized to reduce the electrical impedance of said pickup coil and produce the signal.

9. The converter of claim 8, wherein the exterior surface is part of an enclosure, said enclosure enclosing said pickup coil and said amplifier and having shield means for shielding said pickup coil and said amplifier from the circuit.

10. The converter of claim 1, wherein the exterior surface is part of an enclosure, said enclosure enclosing said pickup coil and said first means and having shield means for shielding said pickup coil and said first means.

11. The converter of claim 1, wherein said windings of said pickup coil are in a range of 400 to 2500 turns.

12. A converter for processing the initial output signal generated by a sonic wave of a magnetostrictive transducer having an outer coveting to produce a modified electrical output signal, comprising:

a pickup coil located within the outer covering and generating the initial electrical output signal from the sonic wave, said pickup coil having at least two leads; and

first means located within the outer covering and connected to said leads of said pickup coil and responsive to the initial electrical output signal for lowering the impedance of said pickup coil, said first means producing the modified electrical output signal.

13. The converter of claim 12, wherein said first means includes an amplifier.

14. The converter of claim 13, wherein said amplifier includes a first transistor having a base and a collector and an emitter, said base and said collector connected to said two leads of said pickup coil, said first transistor sized to reduce the electrical impedance of said pickup coil.

15. The converter of claim 13, wherein said amplifier further includes a second transistor having a base and a collector, said base of said second transistor connected to said collector of said first transistor and said collector of said second transistor connected to said base of said first transistor.

16. The converter of claim 15, wherein said emitter and collector of said first transistor produce the signal.

17. The converter of claim 14, wherein said emitter and collector of said first transistor produce the signal.

18. The converter of claim 13, wherein there is included second means for clipping the peak of the signal.

19. The converter circuit of claim 18, wherein said second means includes:

a first diode electrically connected in parallel to the leads of said pickup coil;

a second diode oriented oppositely to said first diode and electrically connected in parallel with said first diode; and

said first and second diodes sized to clip the signal.

20. The converter of claim 18, wherein said second means includes:

a first transistor having a collector, said collector connected to one of said leads of said pickup coil and a base, said base connected to another of said leads of said pickup coil.

21. The converter of claim 20, wherein said second means further includes a second transistor having a base, collector and emitter, said base of said second transistor connected to said collector of said first transistor and said collector of said second transistor connected to said base of said first transistor.

22. The converter of claim 12, wherein there is included second means for clipping the peak of the signal.

23. The converter of claim 12, wherein said first means includes:

a first transistor having a collector, said collector connected to one of said leads of said pickup coil and a base, said base connected to another of said leads of said pickup coil.

24. The converter of claim 23, wherein said first means further includes a second transistor having a base, collector and emitter, said base of said second transistor connected to said collector of said first transistor and said collector of said second transistor connected to said base of said first transistor.

25. The converter of claim 24, wherein said emitter and collector of said second transistor produce the signal.

26. The converter of claim 12, wherein the outer covering is part of an enclosure, said enclosure enclosing said pickup coil and said first means and having shield means for shielding said pickup coil and said first means.

27. The converter of claim 12, wherein the outer covering is part of an enclosure, said enclosure enclosing said pickup coil and having shield means for shielding said pickup coil.

28. The converter of claim 12, wherein said windings of said pickup coil are in a range of 400 to 2500 turns.

29. A converter for processing a sonic wave of a magnetostrictive transducer to produce an electrical output signal, the magnetostrictive transducer surrounded by an electrical environment, comprising:

a shield means for shielding electronic noise;

a pickup coil within said shield means having a number of windings in the range of 400 to 2500 turns to generate the electrical output signal; and

a buffer circuit mounted in close proximity to said pickup coil within said shield means, said buffer circuit minimizing parasitic reactance between said coil and the electrical environment to avoid adverse noise effect on the electrical output signal.

30. The converter of claim 29, wherein said shield means includes a housing, said housing containing said pickup coil and said buffer circuit.