초록 ▼

A linear capacitance displacement transducer (1) comprising first (2) and second (3) fixed capacitor plate and a dielectric structure (5) moveable longitudinally within a space (4) between the first (2) and second (3) capacitor plates, the dielectric structure (5) being operatively coupled to a move

A linear capacitance displacement transducer (1) comprising first (2) and second (3) fixed capacitor plate and a dielectric structure (5) moveable longitudinally within a space (4) between the first (2) and second (3) capacitor plates, the dielectric structure (5) being operatively coupled to a moveable element (8). The capacitor plates and the dielectric material may be cylindrical and disposed coaxially and concentrically. The transducer (1) enables a displacement sensor that is capable of monitoring liquid levels in a syringe type drug reservoir (101) with sufficient sensitivity as to allow detection of erroneous drug delivery. The sensor is inexpensive to manufacture and provides reliable performance through robust design.

대표청구항 ▼

1. A linear capacitance displacement transducer comprising: a first cylindrical capacitor plate;a second cylindrical capacitor plate disposed around the first cylindrical capacitor plate so as to form a space between the first and second cylindrical capacitor plates, the first and second cylindrical

1. A linear capacitance displacement transducer comprising: a first cylindrical capacitor plate;a second cylindrical capacitor plate disposed around the first cylindrical capacitor plate so as to form a space between the first and second cylindrical capacitor plates, the first and second cylindrical capacitor plates being substantially spatially fixed relative to one another; anda third cylinder composed of dielectric material moveable longitudinally within said space such that a proportion of said space filled with the dielectric material can be altered relative to a fixed electric field created, in use, between said first and second cylindrical capacitor plates,wherein said first and second capacitor plates are electrically connected to a circuit board and wherein said first and second capacitor plates are physically connected to said circuit board such that said circuit board acts as a support structure for supporting adjacent ends of said first and second capacitor plates. 2. A linear capacitance displacement transducer according to claim 1, wherein the cylinders are disposed coaxially. 3. A linear capacitance displacement transducer according to claim 1, wherein the cylinders are right circular cylinders. 4. A linear capacitance displacement transducer according to claim 3, wherein the cylinders are disposed concentrically. 5. A linear capacitance displacement transducer according to claim 1, wherein the first and second cylinders are of substantially the same length. 6. A linear capacitance displacement transducer according to claim 1, wherein the second cylinder is longer than the first cylinder. 7. A linear capacitance displacement transducer according to claim 1,wherein the first and second cylinders are electrically isolated. 8. A linear capacitance displacement transducer according to claim 1, wherein the printed circuit board includes a circuit adapted to perform conversion of a capacitance signal to a displacement value. 9. A linear capacitance displacement transducer according to claim 8, wherein the circuit is adapted to further perform analogue to digital conversion of the capacitance signal. 10. A linear capacitance displacement transducer according to claim 1, wherein at least one of the first, second and third cylinders includes a fluted surface. 11. A linear capacitance displacement transducer according to claim 1, wherein the third cylinder is biased into or from the space in the longitudinal direction. 12. A linear capacitance displacement transducer according to claim 1, wherein the first cylinder is hollow or solid. 13. A linear capacitance displacement transducer according to claim 1, further comprising a fourth cylinder disposed around the second cylindrical capacitor plate for electrically shielding the first and second cylindrical capacitor plates. 14. A reservoir for containing a volume of fluid bound in part by a moveable element, in combination with a linear capacitance displacement transducer for measuring the volume of fluid contained in the reservoir, the displacement transducer comprising: a fixed structure including first and second capacitor plates; anda dielectric structure moveable longitudinally within a space between the first and second capacitor plates, wherein the moveable dielectric structure is operatively coupled to the moveable element. 15. A combination according to claim 14, wherein the first capacitor plate is a cylindrical capacitor plate. 16. A combination according to claim 15, wherein the second cylindrical capacitor plate is disposed around the first cylindrical capacitor plate so as to form said space between the first and second cylindrical capacitor plates. 17. A combination according to claim 16, wherein the first and second cylindrical capacitor plates are substantially spatially fixed relative to one another. 18. A combination according to claim 17, wherein the cylinders are disposed coaxially. 19. A combination according to claim 17, wherein the cylinders are right circular cylinders. 20. A combination according to claim 19, wherein the cylinders are disposed concentrically. 21. A combination according to claim 17, wherein the first and second cylinders are of substantially the same length. 22. A combination according to claim 17, wherein the second cylinder is longer than the first cylinder. 23. A combination according to claim 17, wherein the first and second cylinders are electrically isolated. 24. A combination according to claim 23, wherein the first and second cylinders are electrically connected to a printed circuit board. 25. A combination according to claim 24, wherein the printed circuit board includes a circuit adapted to perform conversion of a capacitance signal to a displacement value. 26. A combination according to claim 25, wherein the circuit is adapted to further perform analogue to digital conversion of the capacitance signal. 27. A combination according to claim 17, wherein the first and second cylinders are physically connected to a support structure at adjacent ends thereof. 28. A combination according to claim 27, wherein the support structure is a printed circuit board. 29. A combination according to claim 17, wherein the first cylinder is hollow or solid. 30. A combination according to claim 17, wherein the moveable dielectric structure is a cylinder composed of dielectric material. 31. A combination according to claim 17, wherein at least one of the cylinders includes a fluted surface. 32. A combination according to claim 17, wherein the dielectric structure is biased into or from the space in the longitudinal direction. 33. A combination according to claim 32, wherein the dielectric material is a polymer. 34. A combination according to claim 17, wherein the fixed structure of the linear capacitance displacement transducer is durable and the reservoir and the moveable structure of the linear capacitance displacement transducer are disposable, said moveable element of the reservoir being integrally formed with said moveable structure. 35. A combination according to claim 17, wherein the displacement transducer further includes a cylinder disposed around the second cylindrical capacitor plate for electrically shielding the first and second cylindrical capacitor plates. 36. A combination according to claim 14, wherein the second capacitor plate is a cylindrical capacitor plate. 37. An infusion system for infusion of liquid therapeutic product, including a linear capacitance displacement transducer according to claim 1. 38. An infusion system according to claim 37, further including a pump. 39. An infusion system according to claim 38, wherein the pump comprises a pumping chamber having an inlet valve and an outlet valve, wherein a volume of the pumping chamber is caused to change by operation of an actuator, and wherein the outlet valve has a higher activation pressure than the inlet valve. 40. An infusion system according to claim 38, wherein the pump is disposable. 41. An infusion system for infusion of liquid therapeutic product, including a reservoir in combination with a linear capacitance displacement transducer according to claim 14.