Magnetostrictive transmitter with improved piezoelectric sensor

1. A magnetostrictive level sensing instrument for sensing level of a process material comprising:

an elongate tube having a near end and a distal end;

a magnet selectively positionable proximate the tube responsive to level of the process material;

a magnetostrictive wire in the tube having first and second ends, the second end being operatively secured at the tube distal end;

a pair of shear mode crystals mounted proximate the tube near end, the crystals sandwiching the magnetostrictive wire proximate the first end;

a sensing circuit operatively connected to the magnetostrictive wire and the pair of crystals for generating an electrical pulse on the magnetostrictive wire whereby a magnetic field produced by the magnet interacts with the electrical pulse to produce a torsional wave on the magnetostrictive wire sensed by the pair of crystals; and

a support tray mounting the crystals proximate the tube near end and the tray clamps the magnetostrictive wire between the crystals, wherein the support tray comprises a two piece plastic tray and each piece supports one of the crystals.

2. The magnetostrictive level sensing instrument of claim 1 wherein the two tray pieces are secured together with threaded fasteners to clamp the magnetostrictive wire between the crystals.

3. A magnetostrictive level sensing instrument for sensing level of a process material comprising:

an elongate tube having a near end and a distal end;

a magnet selectively positionable proximate the tube responsive to level of the process material;

a magnetostrictive wire in the tube having first and second ends, the second end being operatively secured at the tube distal end;

a pair of shear mode crystals mounted proximate the tube near end, the crystals sandwiching the magnetostrictive wire proximate the first end; and

a sensing circuit operatively connected to the magnetostrictive wire and the pair of crystals for generating an electrical pulse on the magnetostrictive wire whereby a magnetic field produced by the magnet interacts with the electrical pulse to produce a torsional wave on the magnetostrictive wire sensed by the pair of crystals,

further comprising a conductive adhesive filling between the pair of crystals.

4. The method of assembling a position sensor for a magnetostrictive sensing instrument comprising:

providing an elongate tube having a near end and a distal end;

inserting a magnetostrictive wire having first and second ends into the tube and securing the second end at the tube distal end;

tensioning the magnetostrictive wire by applying a force proximate the first end;

mounting a support tray at the tube second end, the support tray supporting a pair of crystals sandwiching the magnetostrictive wire;

clamping the crystals to the magnetostrictive wire to maintain the wire under tension; and

removing excess magnetostrictive wire between the support tray and the first end.

5. The method of claim 4 further comprising polarizing the crystals in the shear mode.

6. The method of claim 4 further comprising securing the a magnetostrictive wire second end to the tube distal end using a compression spring.

7. The method of claim 4 wherein the support tray comprises a two piece plastic tray and each of the crystals is placed in one of the tray pieces.

8. The method of claim 4 further comprising filling a gap between the pair of crystals with a conductive adhesive.