Office of Technology Transfer – University of Michigan

Acceleration Sensing Module With a Combined Self-test and Ground Electrode

Technology #1946

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Categories
Researchers
Craig H. Stephan
Managed By
Keith Hughes
Assistant Director, Physical Sciences & Engineering 734-764-9429
Patent Protection
US Patent 5,731,520

Background

Accelerometers are used in a variety of applications to provide an accurate indication of an acceleration force. Because accurate detection of acceleration is often critical, accelerometers typically utilize self-testing mechanisms to check the mechanical integrity and stability of the accelerometer. In the micro-machined type of accelerometers, which are sometimes utilized in vehicle airbag systems, conventional self-testing mechanisms introduce additional circuit elements, thereby adding additional cost and complexity to the manufacture of the accelerometer and to the subsequent diagnostic testing of the accelerometer. Moreover, conventional self-testing mechanisms can cause temperature coefficient problems, and also only test electrical continuity, rather than testing the mechanical integrity of the accelerometer.

Technology

Micro-machined accelerometer, which facilitates the accurate testing of the accelerometer has been developed. The accelerometer includes a substrate and a moveable plate held at a fixed electrical potential, parallel to and above the substrate. The substrate includes, an aperture, a pedestal positioned within the aperture, which are connected to the substrate. The setup allows the moveable plate to rotate relative to the substrate about a flexure axis, in the presence of a force normal to the substrate. The system uses a single electrode to perform both a self-test and a grounding function, which results in a simple design. In addition, charge build-up or leakage onto the insulating substrate may be reduced by the combined self-test and common electrode. Also see UM File 1945 and 1912.

Applications and Advantages

Applications

  • Accelerometer with accurate self-testing mechanism.

Advantages

  • Reduced complexity and potential for charge build-up or leakage onto the substrate, owing to a single electrode performing multiple functions.