US 6,619,123 B2 · Micromachined shock sensor

Abstract

A micromachined shock sensor has a substrate with a surface on which are formed an array of acceleration sensing units. Each sensing unit has a mount fixed to the substrate, a cantilever beam extending from the mount, and a proof mass fixed to the cantilever beam and supported above the substrate to permit translation of the proof mass and bending of the cantilever beam in a plane parallel to the substrate surface. Sensing electrodes are formed on the substrate on opposite sides of the proof mass such that displacement of the proof mass in response to acceleration brings the proof mass into contact with one or the other of the electrodes at a sufficient acceleration level, effectively closing a switch and providing an electrical output signal that can be detected. The multiple acceleration sensing units are formed to make contact at different levels of acceleration, allowing the shock sensor to allow measurements over a range of accelerations. A test electrode may be formed adjacent to the proof mass to allow the proof mass to be electrostatically drawn toward and into contact with one of the sensing electrodes to allow testing of the level of acceleration required to make contact in a particular acceleration sensing unit.

Claims29

Dependent claims

A micromachined acceleration sensing unit comprising:

(a) a substrate with a surface;
(b) a mount fixed to the substrate;
(c) a cantilever beam extending from the mount over the substrate surface and free to bend in a plane above the substrate surface;
(d) a proof mass fixed to the cantilever beam and supported by the cantilever beam above the surface of the substrate to permit translation of the proof mass and bending of the cantilever beam in a plane parallel to the substrate surface, the mount, cantilever beam and proof mass being electrically conductive and in electrical contact;
(e) first and second sensing electrodes formed on the substrate on opposite sides of the proof mass and adjacent to the proof mass and having contact elements thereof spaced by a sensing gap from the proof mass such that displacements of the proof mass in response to accelerations brings the proof mass into contact with one or the other of the contact elements of the electrodes at a sufficient acceleration level;
and
(f) a test electrode formed on the substrate adjacent to the proof mass on one side thereof such that application of a voltage between the test electrode and the proof mass draws the proof mass toward the test electrode until at a sufficient voltage the proof mass contacts the sensing electrode that is on the same side of the proof mass as the test electrode.

4 more elements

A micromachined shock sensor comprising:

(a) a substrate having a surface;
(b) an array comprised of a plurality of acceleration sensing units formed on the substrate, each sensing unit comprising:
(1) a mount fixed to the substrate;
(2) a cantilever beam extending from the mount over the substrate surface and free to bend in a plane above the substrate surface;
(3) a proof mass fixed to the cantilever beam and supported by the cantilever beam above the surface of the substrate to permit translation of the proof mass and bending of the cantilever beam in a plane parallel to the substrate surface, the mount, cantilever beam and proof mass being electrically conductive and in electrical contact;
(4) first and second sensing electrodes formed on the substrate on opposite sides of the proof mass and adjacent to the proof mass and having contact elements thereof spaced by a sensing gap from the proof mass such that displacements of the proof mass in response to accelerations brings the proof mass into contact with one or the other of the contact elements of the electrodes at a sufficient acceleration level;
wherein a plurality of the sensing units have cantilever beam dimensions and proof mass dimensions selected to provide contact between the proof mass and the adjacent sensing electrodes at different levels of acceleration;
and
(c) an electrical conductor formed on the substrate electrically connected to all of the first sensing electrodes, and an electrical conductor formed on the substrate electrically connected to all of the second sensing electrodes.

6 more elements

A micromachined shock sensor comprising:

(a) a substrate having a surface;
(b) an array comprised of a plurality of acceleration sensing units formed on the substrate, each sensing unit comprising:
(1) a mount fixed to the substrate;
(2) a cantilever beam extending from the mount over the substrate surface and free to bend in a plane above the substrate surface;
(3) a proof mass fixed to the cantilever beam and supported by the cantilever beam above the surface of the substrate to permit translation of the proof mass and bending of the cantilever beam in a plane parallel to the substrate surface, the mount, cantilever beam and proof mass being electrically conductive and in electrical contact;
(4) at least one sensing electrode formed on the substrate adjacent to the proof mass and having a contact element thereof spaced by a sensing gap from the proof mass such that displacements of the proof mass in response to accelerations brings the proof mass into contact with the contact element of the electrode at a sufficient acceleration level;
(5) a test electrode formed on the substrate adjacent to the proof mass on one side thereof and adjacent to the sensing electrode such that application of a voltage between the test electrode and the proof mass draws the proof mass toward the test electrode until at a sufficient voltage the proof mass contacts the sensing electrode;
wherein a plurality of the sensing units have cantilever beam dimensions and proof mass dimensions selected to provide contact between the proof mass and the adjacent sensing electrode at different levels of acceleration;
and
(c) an electrical conductor formed on the substrate electrically connected to all of the sensing electrodes.

7 more elements

Dependencies are inferred from the claim text.

Micromachined shock sensor

Life of this patent

Micromachined shock sensor

Life of this patent

Abstract

Claims29