Electric transducer for measuring mechanical quantities

• US 4,772,928 A
• Filed: 04/24/1986
• Issued: 09/20/1988
• Est. Priority Date: 04/27/1985
• Status: Expired due to Fees

• Current Assignee: Messerschmitt-Bolkow-Blohm GmbH
• Original Assignee: Messerschmitt-Bolkow-Blohm GmbH
• Inventors: Dietrich, Klaus, Kroy, Walter
• Primary Examiner(s): James, Andrew J.
• Assistant Examiner(s): Crane, Sara W.
• Application Number:
  US06/855,886
• Time in Patent Office: 880 Days
• Field of Search: 357/25, 357/26, 357/27, 357/22 B, 357/23.1, 73/517 R, 73/518, 73/718, 73/720, 73/726, 73/862.64, 73/862.68
• US Class Current: 257/254
• CPC Class Codes: G01L 1/18 using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
• CPC Class Codes: G01P 15/124 by semiconductor devices comprising at least one PN junction, e.g. transistors
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure

Abstract

An electric transducer for measuring mechanical quantities comprises a movable tongue which is acted upon by the mechanical quantity to be measured and the deflection of which is converted into an electrical signal. The tip of the tongue may be designed as the gate and an electric conduction channel disposed opposite the tip at a small distance therefrom may comprise the source-drain path of a field effect transistor, or vice versa.

Claims

1. An electric transducer for measuring a mechanical quantity comprising:

a substrate comprising a rigid semiconductor yoke in the form of a regular parallelepiped;

a cantilever disposed on a side of the yoke and further disposed so as to face an opposite side of the yoke, the cantilever being both capable of positive and negative motion in a direction substantially perpendicular to the plane of the yoke, the cantilever being electrically conductive;

two partial field effect transistor structures disposed in a plane perpendicular to the plane of the cantilever on upper and lower edges of the side of the yoke opposite the cantilever, said field effect structures each comprising a source-drain path and said cantilever functioning as a common gate for each of said field effect structures;

said cantilever moving in said direction such that when the cantilever moves toward one of said source-drain paths said cantilever moves away from the other of the source-drain paths, signals related to the distance of said cantilever from the resepective source-drain path being generated by each source-drain path.

2. The electric transducer recited in claim 1, further comprising an amplifier etched onto the yoke, the amplifier being coupled to and receiving signals from the two partial field effect transistor structures, the signals being generated by motion of the cantilever, said amplifier amplifying the difference between the signals.

3. The electric transducer recited in claim 1, wherein said field effect transistor structures are disposed on a projection extending toward the cantilever from the side of the yoke opposite the cantilever.

4. The electric transducer of claim 3, wherein the partial field effect transistors comprise two source-drain paths disposed parallel to one another and having a path length perpendicular to the deflection direction of the cantilever.

5. The electric transducer of claim 3, wherein the yoke, cantilever and projection are all disposed on the same substrate.

6. The electric transducer of claim 5, wherein the yoke, cantilever, and projection are all a part of one semiconductor substrate.

7. The electric transducer of claim 5, wherein the cantilever interacts with an external field.

8. The electric transducer of claim 2, wherein the amplifier comprises an integrated circuit means disposed on the yoke means and coupled to the partial field effect transistors.

9. The electric transducer of claim 1, wherein an electrode is placed parallel to the cantilever and generates restoring forces on the cantilever.