Method and Apparatus to Test an Accelerometer

• US 20120036931A1
• Filed: 06/22/2011
• Published: 02/16/2012
• Est. Priority Date: 08/16/2010
• Status: Active Grant

• Current Assignee: Reflection Marine Norge AS
• Original Assignee: WesternGeco LLC
• Inventors: PAULSON, Hans, RÖNNOW, Daniel
• Granted Patent: US 9,010,170 B2
• Time in Patent Office: Days
• US Class Current: 73/514.32
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

A technique includes using an accelerometer to provide an output signal indicative of an acceleration experienced by a movable mass of a sensor of the accelerometer. The technique includes testing the accelerometer, and the testing includes using a closed loop including the sensor to provide the output signal of the accelerometer; injecting a test signal into the loop between an output terminal of the sensor and an output terminal of the accelerometer; and indicating a performance of the accelerometer based on a response of the accelerometer to the injection of the test signal.

Claims

1. A method comprising:

using an accelerometer to provide an output signal indicative of an acceleration experienced by a movable mass of a sensor of the accelerometer at an output terminal of the accelerometer; and

testing the accelerometer, the testing comprising;

using a closed loop comprising the sensor to provide the output signal of the accelerometer;

injecting a test signal into the loop between an output terminal of the sensor and the output terminal of the accelerometer; and

indicating a performance of the accelerometer based on a response of the accelerometer to the injecting.

2. The method of claim 1, wherein the closed loop comprises a feedforward path between the output terminal of the sensor and the output terminal of the accelerometer and a feedback path between the output terminal of the accelerometer and the sensor, and the injecting comprises injecting the test signal into the feedforward path.

3. The method of claim 1, wherein the sensor comprises a capacitive MEMS-based sensor.

4. The method of claim 1, further comprising

using an amplitude detector and a loop controller to generate the output signal of the accelerometer, wherein the injecting comprises injecting the test signal between an output terminal of the amplitude detector and an input terminal of the loop controller.

5. The method of claim 1, wherein the indicating comprises indicating performances of all components in the closed loop.

6. The method of claim 1, wherein the indicating comprises indicating an open loop property of the sensor.

7. The method of claim 1, wherein the act of injecting comprises injecting a signal selected from the following:

a sinusoidal signal, a dual frequency signal, a multitone signal, a noise signal and an impulse signal.

8. The method of claim 1, further comprising:

determining at least one of the following in response to the act of injecting;

a transfer function, a Q value, a total harmonic distortion and an intermodulation distortion.

9. An accelerometer comprising:

a closed loop comprising a sensor comprising a movable mass to sense an acceleration and an output terminal to provide an output signal indicative of the sensed acceleration, wherein the closed loop is adapted to provide a feedback signal to adjust a restoring force applied to the movable mass; and

a tester adapted to inject a test signal into the closed loop between an output terminal of the sensor and the output terminal of the closed loop to cause a signal at the output terminal of the closed loop to indicate a performance of the accelerometer in response thereto.

10. The accelerometer of claim 9, wherein the closed loop comprises a feedforward path between the output terminal of the sensor and the output terminal of the closed loop and a feedback path between the output terminal of the closed loop and the sensor, and the tester is adapted to inject the test signal into the feedforward path.

11. The accelerometer of claim 9, wherein the sensor comprises a capacitive MEMS-based sensor.

12. The accelerometer of claim 9, wherein the accelerometer comprises an amplitude detector and a loop controller to generate the output signal of the accelerometer, and the tester is adapted to inject the test signal between an output terminal of the amplitude detector and an input terminal of the loop controller.

13. The accelerometer of claim 9, wherein the tester is adapted to inject a signal selected from the following:

a sinusoidal signal, a dual frequency signal, a multitone signal, a noise signal and an impulse signal.

14. An apparatus comprising:

a seismic acquisition system comprising at least one accelerometer comprising;

a closed loop comprising a sensor comprising a movable mass to sense an acceleration and an output terminal to provide an output signal indicative of the sensed acceleration, wherein the closed loop is adapted to provide a feedback signal to adjust a restoring force applied to the movable mass; and

a tester adapted to inject a test signal into the closed loop between an output terminal of the sensor and the output terminal of the closed loop to cause a signal at the output terminal of the closed loop to indicate a performance of the accelerometer in response thereto.

15. The apparatus of claim 14, wherein the closed loop comprises a feedforward path between the output terminal of the sensor and the output terminal of the closed loop and a feedback path between the output terminal of the closed loop and the sensor, and the tester is adapted to inject the test signal into the feedforward path.

16. The apparatus of claim 14, wherein the sensor comprises a capacitive MEMS-based sensor.

17. The apparatus of claim 14, wherein the accelerometer comprises an amplitude detector and a loop controller to generate the output signal of the accelerometer, and the tester is adapted to inject the test signal between an output terminal of the amplitude detector and an input terminal of the loop controller.

18. The apparatus of claim 14, wherein the tester is adapted to inject a signal selected from the following:

a sinusoidal signal, a dual frequency signal, a multitone signal, a noise signal and an impulse signal.

19. The apparatus of claim 14, wherein the seismic acquisition system comprises a streamer, a land-based sensor cable or a seabed-based sensor cable.

20. The apparatus of claim 14, wherein the seismic acquisition system comprises a streamer, the system further comprising:

a survey vessel to tow the streamer.

21. The apparatus of claim 14, wherein the seismic acquisition system is a wireless system comprising wireless nodes, and said at least one accelerometer is disposed in one of the wireless nodes.