Drive feedthrough nulling system

• US 6,674,294 B2
• Filed: 08/30/2002
• Issued: 01/06/2004
• Est. Priority Date: 08/02/2000
• Status: Expired due to Fees

• Current Assignee: Charles Stark Draper Laboratory Incorporated
• Original Assignee: Charles Stark Draper Laboratory Incorporated
• Inventors: Ward, Paul
• Primary Examiner(s): Le, N.
• Assistant Examiner(s): Nguyen, Vincent Q.
• Application Number:
  US10/232,278
• Publication Number:
  US 20030011385A1
• Time in Patent Office: 494 Days
• Field of Search: 735/141.6, 735/143.8, 735/040.3, 735/041.2, 735/040.4, 735/041.6, 702/190, 324/687, 324/684, 324/690, 324/658, 324/659, 324/667, 324/668, 324/669, 324/674, 324/679
• US Class Current: 324/684
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

The present invention relates to a system for nulling drive feedthrough error in a sensor having first and second drive electrodes which impart vibratory motion to first and second proof masses in response to first and second opposite phase drive signals, and having first and second capacitances defined between the drive electrodes and their associated proof masses. A mismatch between the first and the second capacitance is measured. Drive feedthrough caused by the measured capacitance mismatch is nulled by adjusting the relative amplitudes of the first and second opposite phase drive signals, whereby the ratio of the amplitudes is proportional to the ratio of the first and second capacitances. A servo loop may adaptively effect the ratio of amplitudes.

Claims

1. A system for nulling feedthrough error in the output of a sensor caused by feedthrough of one or more drive signals into said sensor output, the system comprising:

(a) a source of a drive signal, and a further signal having characteristics different from the drive signal, the drive signal and the further signal being applied to drive the sensor, wherein the further signal can be detected separately from the drive signal;

(b) means for detecting a response of the sensor to said drive signal and said further signal applied thereto; and

(c) means, responsive to components of the further signal in the detected response, for adjusting the drive signal so as to diminish the feedthrough error.

2. A system according to claim 1, wherein said means for adjusting the drive signal is responsive to a controller.

3. A system according to claim 2, wherein said means for adjusting the drive signal includes a feedback servo loop.

4. A system according to claim 1, wherein said sensor includes at least two drive electrodes having associated drive capacitances and being adapted to receive equal and opposite-phase drive signals.

5. A system according to claim 4, wherein said feedthrough error is caused at least in part by a mismatch between said at least two drive capacitances.

6. A system according to claim 5, wherein said further signal provides a measure of said capacitance mismatch.