Z-AXIS PHYSICAL PROXIMITY SWITCH
Sensors and systems are described herein for out-of-plane sensing. In particular, the sensors and systems relate to vibratory inertial sensors implementing time-domain sensing techniques with linear combinations of multiple signals. In out-of-plane sensing, these multiple signals may be produced from a single sense mass oscillation. Time intervals produced from linear combinations of these multiple signals can be used to measure inertial parameters, such as acceleration, and other values of interest.
1 . An out-of-plane sensor, comprising:
a sense mass coupled to an in-plane support structure; the sense mass configured to oscillate out-of-plane with respect to the in-plane support structure;
a time domain switch coupled to the sense mass, comprising:
a first electrode at a first radial distance of the sense mass and producing a first signal; and
a second electrode at a second radial distance of the sense mass and producing a second signal; and
a processor in signal communication with the time domain switch and configured to detect time intervals from a linear combination of the first signal and the second signal.
2 . The out-of-plane sensor of claim 1 , wherein the sense mass oscillates out-of-plane in rotation about an axis in a plane of the in-plane support structure.
3 . The out-of-plane sensor of claim 2 , wherein:
the first radial distance is larger than the second radial distance;
the first electrode has a first area; and
the second electrode has a second area, wherein the first area is larger than the second area.
4 . The out-of-plane sensor of claim 3 , wherein the linear combination of the first signal and the second signal is a differential in capacitance.
5 . The out-of-plane sensor of claim 4 , wherein the time intervals are based in part on times at which the differential in capacitance is equal to zero.
6 . The out-of-plane sensor of claim 5 , further comprising determining an acceleration of the in-plane support structure based on the time intervals.
7 . The out-of-plane sensor of claim 1 , wherein the first electrode is vertically offset upward from the sense mass.
8 . The out-of-plane sensor of claim 7 , wherein the second electrode is vertically offset downward from the sense mass.
9 . The out-of-plane sensor of claim 8 , wherein a portion of the sense mass and the second electrode are etched to the same height.
10 . The out-of-plane sensor of claim 8 , wherein the sense mass oscillates by raising and lowering linearly along an axis perpendicular to the in-plane support structure.
11 . The out-of-plane sensor of claim 10 , wherein the first radial distance is larger than the second radial distance, and wherein the area of the first electrode is equal to the area of the second electrode.
12 . The out-of-plane sensor of claim 11 , wherein the time intervals are a first set of time intervals based on zero-crossings of a time derivative the first signal, and a second set of time intervals based on zero-crossings of a time derivative of the second signal.
13 . The out-of-plane sensor of claim 12 , wherein the time intervals of the first set and the second set do not include points of zero velocity.
14 . The out-of-plane sensor of claim 13 , further comprising determining an acceleration of the in-plane support structure based on the time intervals.
15 . A system for out-of-plane sensing, comprising:
a sense mass coupled to an in-plane support structure, the sense mass configured to oscillate out-of-plane with respect to the in-plane support structure;
a time domain switch coupled to the sense mass, comprising:
a first electrode at a first radial distance of the sense mass and producing a first signal; and
a second electrode at a second radial distance of the sense mass and producing a second signal; and
a processor in signal communication with the time domain switch and configured to detect time intervals from a linear combination of the first signal and the second signal.
16 . The system of claim 15 , wherein the sense mass oscillates out-of-plane in rotation about an axis in a plane of the in-plane support structure.
17 . The system of claim 16 , wherein:
the first radial distance is larger than the second radial distance;
the first electrode has a first area; and
the second electrode has a second area, wherein the first area is larger than the second area.
18 . The system of claim 17 , wherein the linear combination of the first signal and the second signal is a differential in capacitance.
19 . The system of claim 18 , wherein the time intervals are based in part on times at which the differential in capacitance is equal to zero.
20 . The system of claim 19 , further comprising determining an acceleration of the in-plane support structure based on the time intervals.
21 . The out-of-plane sensor of claim 15 , wherein first electrode is vertically offset upward from the sense mass.
22 . The out-of-plane sensor of claim 20 , wherein the second electrode is vertically offset downward from the sense mass.
23 . The out-of-plane sensor of claim 22 , wherein a portion of the sense mass and the second electrode are etched to the same height.
24 . The system of claim 23 , wherein the sense mass oscillates by raising and lowering linearly along an axis perpendicular to the in-plane support structure.
25 . The system of claim 24 , wherein the first radial distance is larger than the second radial distance, and wherein the area of the first electrode is equal to the area of the second electrode.
26 . The system of claim 25 , wherein the time intervals are a first set of time intervals based on zero-crossings of a time derivative of the first signal, and a second set of time intervals based on zero-crossings of a time derivative of the second signal.
27 . The system of claim 26 , wherein the time intervals of the first set and the second set do not include points of zero velocity.
28 . The system of claim 26 , further comprising determining an acceleration of the in-plane support structure based on the time intervals.