Integrated tilt sensor
View Patent ↗A tilt sensor having a printed circuit board disposed in a direction normal to a reference plane for measuring a tilt angle with a pair of electrodes formed on a first surface of the printed circuit board. A cover is affixed to the printed circuit board and creates a cavity between the cover and the printed circuit board with a predetermined gap between the cover and the pair of electrodes, the cover acting as a common electrode to the pair of electrodes to create a pair of capacitors. An inert liquid is contained in the cavity, the surface level of the inert fluid varying according to the tilt angle of the reference plane. A signal processing circuit is formed on a second surface of the printed circuit board that produces an output signal corresponding to a difference in capacitance between the two capacitors as a tilt angle detection output.
1. A tilt sensor comprising:
a printed circuit board disposed in a direction generally normal to a reference plane for measuring a tilt angle;
a pair of electrodes formed on a first portion of the printed circuit board;
a cover affixed to the printed circuit board and creating a cavity between the cover and the first surface of the printed circuit board, the cover being adjacent to the pair of electrodes with a gap between the cover and the pair of electrodes, the cover used as a common electrode for the pair of electrodes, the cover and the pair of electrodes defining a pair of capacitors;
an inert liquid contained in the cavity, the surface level of the inert liquid varying according to the tilt angle of the reference plane; and,
a signal processing circuit formed on a second portion of the printed circuit board, the signal processing circuit producing an output signal corresponding to a difference in capacitance between the two capacitors as a tilt angle detection output.
2. The tilt sensor according to claim 1 , wherein the cover is sealed to the printed circuit board to prevent leakage of the inert liquid.
3. The tilt sensor according to claim 1 , wherein the circuit board includes a metal ring and the cover is operatively coupled to the metal ring.
4. The tilt sensor according to claim 3 , wherein the cover is operatively coupled to the metal ring through metal reflow.
5. The tilt sensor to claim 1 , wherein the first portion and the second portion of the circuit board are located on a first side and a second side of the circuit board, respectively.
6. The tilt sensor according to claim 1 , wherein the cover is hermetically sealed to the printed circuit board.
7. The tilt sensor according to claim 1 , wherein the cover is a conductive metal cover.
8. The tilt sensor according to claim 1 , further comprising a second cover affixed to the printed circuit board, the signal processing circuit covered by the second cover.
9. The tilt sensor according to claim 1 , wherein the printed circuit board is metalized.
10. The tilt sensor according to claim 1 , wherein the first surface of the printed circuit board is sealed with glass passivation against the inert liquid.
11. The tilt sensor according to claim 10 , further comprising a seal for each one of the plurality of through holes.
12. The tilt sensor according to claim 1 , wherein the inert liquid fills the cavity up to a predetermined level.
13. The tilt sensor according to claim 1 , wherein the circuit board includes a plurality of through holes.
14. The tilt sensor according to claim 13 , wherein each of the pair of electrodes includes one of the plurality of through holes.
15. The tilt sensor according to claim 14 , wherein signal processing circuit is electrically coupled to the pair of electrodes through the plurality of through holes.
16. The tilt sensor according to claim 13 , wherein the plurality of through holes each comprises a metalized inner surface.
17. The tilt sensor according to claim 16 , wherein signal processing circuit is electrically coupled to the pair of electrodes through the metalized inner surface.
18. The method of claim 17 , further comprising the step of sealing the first surface of the printed circuit board with glass passivation against the inert fluid.
19. A method for assembling a tilt sensor using a circuit board comprising the steps of:
forming a pair of differential electrodes on a first portion of the circuit board;
creating a plurality of through holes in the differential electrodes;
forming a metal ring around the pair of differential electrodes;
forming an electrical circuit on a second portion of the circuit board;
coupling the electrical circuit to the pair of differential electrodes and the metal ring;
attaching a cover to the metal ring to form a cavity;
filling the cavity with a nonconductive liquid; and,
sealing the plurality of through holes.
20. The method of claim 19 , wherein the circuit board includes a first side and a second side, and the first portion is located on the first side and the second portion is located on the second side.
21. The method of claim 19 , further comprising coupling the metal ring to the electrical circuit.
22. The method of claim 21 , further comprising the step of coupling a plurality of contacts to the electrical circuit.
23. The method of claim 22 , further comprising the step of attaching a second cover to the second metal ring, the second cover having a plurality of openings, the plurality of contacts being inserted through the plurality of openings.
24. The method of claim 19 , further comprising the step of plating the plurality of through holes.
25. The method of claim 19 , further comprising the step of forming a second metal ring around the electrical circuit.
26. The method of claim 19 , wherein the step of attaching the cover to the metal ring comprises sealing the cover to the metal ring.
27. The method of claim 26 , wherein the step of sealing the cover to the metal ring comprises hermetically sealing the cover to the metal ring.
28. The method of claim 19 , wherein the step of attaching the cover to the metal ring comprises reflowing metal around the cover.
29. The method of claim 19 , wherein the step of sealing the plurality of through holes comprises soldering the plurality of through holes.
30. A tilt sensor comprising:
a circuit board having a first side and a second side;
a circuit located on the first side; and,
a differential capacitative sensor coupled to the circuit, the differential capacitative sensor comprising:
a pair of electrodes located on the second side;
a metal ring surrounding the pair of electrodes on the second side; and,
a cover affixed to the metal ring and spaced from the pair of electrodes to operate as a common electrode for the pair of electrodes to form a pair of capacitors, the cover having a cavity, wherein the pair of electrodes and the metal ring are electrically coupled to the circuit.
31. The tilt sensor of claim 30 , further comprising an inert fluid contained within the cavity.
32. The tilt sensor of claim 31 , wherein the cavity is sealed to avoid the loss of the inert fluid.
33. The tilt sensor of claim 30 , wherein the cavity is hermetically sealed.
34. The tilt sensor of claim 30 , further comprising a pair of through holes in the circuit board.
35. The tilt sensor of claim 34 , wherein the pair of electrodes and the metal ring are electrically coupled to the circuit through the pair of through holes.
36. The tilt sensor of claim 30 , wherein the pair of electrodes includes an inner surface coated with a conductive material.
37. The tilt sensor of claim 30 , further comprising a second metal ring surrounding the circuit.
38. The tilt sensor of claim 37 , further comprising a second cover attached to the second metal ring.
39. The tilt sensor of claim 30 , wherein the circuit comprises a signal processing circuit producing an output signal corresponding to a difference in capacitance between the pair of capacitors as a tilt angle detection output.