Apparatus for detecting acceleration and method for testing this apparatus

An acceleration sensor to detect a first component along an X-axis and a second component along a Z-axis of an acceleration in an XYZ three-dimensional coordinate system, the sensor comprising:

• a first substrate having a first plane surface which is parallel with an XY-plane of said coordinate system, said first substrate including a working portion to which a force is applied, a fixed portion fixed to a sensor body, and a flexible portion having flexibility formed between said working portion and said fixed portion;
• a second substrate having a second plane surface which is opposite to said first plane surface with a predetermined distance and is fixed to said fixed portion;
• a weight body attached to said working portion to transmit a force produced by an acceleration to said working portion so that said first substrate produces a mechanical deformation;
• eight resistance elements formed on said first plane surface, said elements having a property that a resistance value varies in dependency upon a mechanical deformation produced in said first substrate, wherein four of said resistance elements are arranged along X-axis of said coordinate system and four of said resistance elements are arranged along W-axis which is any axis on the XY-plane;
• a first set of four electrode layers formed on said first plane surface, wherein a first layer is located in a positive field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a second layer is located in a negative field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a third layer is located in a positive field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis, and a fourth layer is located in a negative field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis;
• a second set of four electrode layers formed on said second plane surface, wherein first to fourth layers of the second set are opposite to said first to fourth layers of the first set, respectively;
• detecting means for detecting said first component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the X-axis, and detecting said second component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the W-axis;
• and
• testing means for applying predetermined voltages of said first set of electrodes and said second set of electrodes to exert a coulomb force therebetween, thereby permitting said first substrate to produce a mechanical deformation even in a state where no acceleration is applied.

An acceleration sensor to detect a first component along an X-axis, a second component along a Y-axis and a third component along a Z-axis of an acceleration in an XYZ three-dimensional coordinate system, the sensor comprising:

• a first substrate having a first plane surface which is parallel with an XY-plane of said coordinate system, said first substrate including a working portion to which a force is applied, a fixed portion fixed to a sensor body, and a flexible portion having flexibility formed between said working portion and said fixed portion;
• a second substrate having a second plane surface which is opposite to said first plane surface with a predetermined distance and is fixed to said fixed portion;
• a weight body attached to said working portion to transmit a force produced by an acceleration to said working portion so that said first substrate produces a mechanical deformation;
• twelve resistance elements formed on said first plane surface, said elements having a property that a resistance value varies in dependency upon a mechanical deformation produced in said first substrate, wherein four of said resistance elements are arranged along X-axis of said coordinate system, four of said resistance elements are arranged along Y-axis of said coordinate system and four of said resistance elements are arranged along W-axis which is any axis on the XY-plane;
• a first set of four electrode layers formed on said first plane surface, wherein a first layer is located in a positive field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a second layer is located in a negative field of the X-axis and substantially has a symmetrical shape with respect to the X-axis, a third layer is located in a positive field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis, and a fourth layer is located in a negative field of the Y-axis and substantially has a symmetrical shape with respect to the Y-axis;
• a second set of four electrode layers formed on said second plane surface, wherein first to fourth layers of the second set are opposite to said first to fourth layers of the first' set, respectively;
• detecting means for detecting said first component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the X-axis, detecting said second component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the Y-axis, and detecting said third component of the acceleration applied to said weight body based on the resistance values of the resistance elements arranged along the W-axis;
• and
• testing means for applying predetermined voltages to said first set of electrodes and said second set of electrodes to exert a coulomb force therebetween, thereby permitting said first substrate to produce a mechanical deformation even in a state where no acceleration is applied.