Capacitive fluid level sensing

Patent metadata

Field	Value
Publication number	US-9604043-B2
Application number	US-201313899917-A
Country	US
Kind code	B2
Filing date	May 22, 2013
Priority date	Nov 7, 2008
Publication date	Mar 28, 2017
Grant date	Mar 28, 2017

Abstract

A capacitive fluid level sensing arrangement for use in a medical device is provided. The arrangement includes at least one pair of conductive plates configured to increase and decrease the amount of electric charge stored in relation to the level of fluid within a fluid maintaining device, such as a reservoir. The conductive plates are electrically connected to a medical device and are configured to measure the charge stored between the plates and thus sense the fluid level. The electric circuit may communicate the measurement to an instrument host arrangement for operating a pump configured to remove fluid from the reservoir and move the fluid to a collector when the level exceeds a preset upper level amount. The instrument host arrangement may stop operating the pump when the fluid level is reduced to a preset lower level amount.

First claim

What is claimed is:

1. A method for performing a surgical procedure, comprising:
exchanging fluid between a handpiece configured to be employed to perform the surgical procedure and a reservoir;
capacitively sensing fluid level within the reservoir; and
depending on fluid level sensed by said capacitively sensing, selectively altering a fluid amount within the reservoir by selectively evacuating fluid from the reservoir to a collector based on sensing at least one of an increase in capacitance, a capacitance exceeding a preset maximum threshold, or a capacitance change rate.

2. The method of claim 1 , wherein the handpiece is a component of an ophthalmic surgical device.

3. The method of claim 2 , wherein the ophthalmic surgical device is a phacoemulsification system.

4. The method of claim 1 , wherein said capacitively sensing includes measuring a voltage between at least one pair of conductive plates.

5. The method of claim 4 , further including:
connecting a cassette including the reservoir to an instrument host including the at least one pair of conductive plates.

6. The method of claim 5 , wherein the at least one pair of conductive plates are positioned on opposite sides of a cavity formed in the instrument host and connecting the cassette includes positioning the reservoir in the cavity.

7. The method of claim 4 , wherein the at least one pair of conductive plates are positioned within the reservoir.

8. The method of claim 7 , further including:
connecting a cassette including the reservoir to an instrument host including an electric circuit; and
electrically connecting the at least one pair of conductive plates to the electric circuit.

9. The method of claim 8 , wherein said electrically connecting includes connecting a first connector to a second connector.

10. The method of claim 7 , wherein each conductive plate has a planar shape.

11. The method of claim 10 , wherein the at least one pair of conductive plates includes a plurality of pairs of conductive plates connected in parallel.

12. The method of claim 11 , wherein said measuring of the voltage between the plurality of pairs of conductive plates is based on the equation:
V o ( p )= V I ( p )*(1− e −t/RC )

where V o (p) is the measured voltage between the pair of conductive plates, V I (p) is the voltage of a square wave provided across the pair of conductive plates, R is resistance of a resistor configured in series with the pair of conductive plates, C is capacitance of the pair of conductive plates, and t is time.

13. The method of claim 1 , wherein selectively altering the fluid amount within the reservoir further includes selectively adding fluid to the reservoir based on capacitively sensing at least one of a decrease in capacitance, a capacitance below a preset minimum threshold, or a capacitance change rate.

14. The method of claim 13 , wherein the fluid is added to the reservoir from the collector.

Assignees

• Abbott Medical Optics Inc

Inventors

• King David A

Classifications

• A61M2205/3317

  Electromagnetic, inductive or dielectric measuring means · CPC title

• A61M2205/3386

  Low level detectors · CPC title

• Y10T137/7306

  Electrical characteristic sensing · CPC title

• A61M2205/3389

  Continuous level detection (A61M2205/3393 takes precedence) · CPC title

• A61M2205/3382

  Upper level detectors · CPC title