Device for measuring of acceleration by piezo-electric transducers

• US 5,408,878 A
• Filed: 12/09/1991
• Issued: 04/25/1995
• Est. Priority Date: 04/12/1990
• Status: Expired due to Term

• Current Assignee: PRÜFTECHNIK Dieter Busch AG (Fortive Corp.)
• Original Assignee: PRÜFTECHNIK Dieter Busch AG (Fortive Corp.)
• Inventors: Lysen, Heinrich
• Primary Examiner(s): Williams, Hezron E.
• Assistant Examiner(s): Brock, Michael J.
• Application Number:
  US07/793,439
• Time in Patent Office: 1,233 Days
• Field of Search: 73/517 AV, 73/35 P, 73/493, 73/497, 73/517 R, 310/329
• US Class Current: 73/514.34
• CPC Class Codes: G01P 15/0907 of the compression mode type

Abstract

A device for the measurement of acceleration by piezo-electric transducers. The device comprises a carrier 14 and 16 with a principal axis parallel to the direction of acceleration measurement, a seismic mass 20 and 22 retained to be movable relative to the carrier and piezo-electric elements 12 and 12'"'"' coupled therewith for excitation and co-operating in pairs, wherein the arrangement is such that pyro-electric effects compensate for each other. According to the invention, the carrier has a transverse member 16 which extends transversely to the principal axis and the piezo-electric elements acted on by compression excitation are installed on sides thereof, which are opposite with respect to the direction of the principal axis, between this and the seismic mass 20 and 22. There is thus achieved, apart from the temperature independence, a large insensitivity to base expansion as well as to any accelerations of kind and direction other than linear and parallel to the principal axis.

Claims

1. Device for the measurement of the acceleration of a test piece by means of piezo-electric transducer elements, said device comprising:

a carrier which is rigidly connectible with the test piece and has a principal axis extending in a direction parallel to the direction of the acceleration to be measured, a seismic mass supported for movement relative to the carrier and piezo-electric elements which cooperate in pairs and are coupled for excitation with the carrier and portions of the seismic mass, an electrical connection of the piezo-electric elements with each other and with a signal output, wherein loading of the piezo-electric elements by the acceleration forces of the seismic mass and the polarity of the piezo-electric elements with respect to the seismic mass are so arranged that the pyro-electric effects which are caused by heat flow from the carrier through the piezo-electric elements to the seismic mass compensate for each other, and the piezo-electric effects caused by the acceleration to be measured reinforce each other, characterized in that the carrier comprises a transverse member extending transversely relative to the principal axis and that the piezo-electric elements of each cooperating pair are installed on opposite sides of the transverse member such that each said piezo-electric element is positioned between said transverse member and a corresponding portion of said seismic mass to provide said piezo-electric elements with opposite polarity with respect to said transverse member, said piezo-electric elements being arranged for compression excitation in directions that are substantially parallel to the principal axis.

2. Device according to claim 1, characterised in that the carrier is rigidly connected with a base (28, 30), comprising a contact surface, which is perpendicular to and surrounds the principal axis of the carrier, for placing against the test piece.

3. Device according to claim 1, characterised in that the carrier is T-shaped.

4. Device according to claim 1, wherein the portions of said seismic mass, which are coupled to the two piezo-electric elements of a pair, have substantially the same thermal capacity.

5. Device according to claim 4, wherein the portions of said seismic mass, which are coupled to the two piezo-electric elements of a pair, have the same specific thermal capacity and the same thermal conductivity.

6. Device according to claim 1, wherein the portions of said seismic mass, which are coupled to the two piezo-electric elements of a pair, are connected with each other in a thermally conductive manner.

7. Device according to claim 6 wherein said portions of said seismic mass which are coupled to the two piezo-electric elements of a pair, are connected to the piezo-electric elements and each other in an electrically conductive manner.

8. Device according to claim 1, wherein the portions of said seismic mass, which are coupled to the two piezo-electric elements of a pair, consist of individual parts.

9. Device according to claim 1, characterised in that the piezo-electric elements are disc-shaped.

10. Device according to claim 1, characterised in that the arrangement of the carrier, the piezo-electric elements and the seismic mass has substantially mirror symmetry.

11. Device according to claim 1, wherein the portions of said seismic mass, which are coupled to the two piezo-electric elements of a pair, have the same specific thermal capacity.

12. Device according to claim 1, wherein the portions of said seismic mass, which are coupled to the two piezo-electric elements of a pair, have the same thermal conductivity.

13. Device according to claim 1, wherein the portions of said seismic mass, which are coupled to the two piezo-electric elements of a pair, are connected with each other in an electrically conductive manner.