Single ended tuning fork inertial sensor and method

• US 5,522,249 A
• Filed: 07/12/1994
• Issued: 06/04/1996
• Est. Priority Date: 03/12/1991
• Status: Expired due to Term

• Current Assignee: BEI Sensors & Systems Company Incorporated (Schneider Electric SE)
• Original Assignee: New SD, Inc.
• Inventors: Macy, David F.
• Primary Examiner(s): Chapman, Jr., John E.
• Application Number:
  US08/273,656
• Time in Patent Office: 693 Days
• Field of Search: 73/1 D, 73/1 DV, 73/505, 310/329, 310/370, 29/25.35, 29/595
• US Class Current: 73/1.37
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719

Abstract

Single ended tuning fork inertial sensor having a housing and a single ended tuning fork of a quartz-like material of a predetermined thickness, the tuning fork has first and second tines lying in a plane and having an axis of symmetry and has a body formed integral with said first and second tines. The body is rigidly secured to the housing. The tines have a rectangular cross section and have a width which is different from the thickness. The body has a stem formed therein which has a width less than that of the body. Drive electrodes are secured to the tines. An oscillatory frequency is supplied to the above drive electrodes to excite the tines in a drive mode and in the presence of an axial angular rate to cause the tines to operate in a pickup mode which is substantially separated in frequency from the drive mode. The electrode patterns are laser trimmed in order to reduce quadrature offset.

Claims

1. In a method for sensing rate by the use of a single ended tuning fork mounted in a housing and having first and second tines lying in a plane and having an axis of symmetry and a body formed integral with the first and second tines and having drive electrodes and pickup electrodes mounted on the tines, the method comprising supplying a drive oscillatory signal to the drive electrodes to drive them in a drive mode, sensing an angular rate signal provided by the pickup electrodes in response to rotation about said axis of symmetry, the improvement comprising symmetrically placing the drive electrodes and the pickup electrodes in electrode patterns on the first and second tines of the fork and trimming the electrode patterns to substantially reduce to zero quadrature offset to minimize the necessity of achieving electrical balance by external electronic circuitry.

2. A method as in claim 1 wherein the trimming is accomplished by laser trimming the electrode patterns.

3. A method, as in claim 1 together with the step of providing symmetrically positioned leads on said fork and connected to said drive and pickup electrodes.