Apparatus and methods for sensing fluid levels

• US 6,938,476 B2
• Filed: 06/25/2003
• Issued: 09/06/2005
• Est. Priority Date: 06/25/2003
• Status: Expired due to Fees

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Chesk, William G.
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): WILSON, KATINA M
• Application Number:
  US10/603,903
• Publication Number:
  US 20040261524A1
• Time in Patent Office: 804 Days
• Field of Search: 733/04.R, 732/90.R, 733/04.C, 340/620
• US Class Current: 73/290.00R
• CPC Class Codes: G01F 23/24 by measuring variations of resistance of resistors due to contact with conductor fluid
• CPC Class Codes: Y10T 29/49007 Indicating transducer

Abstract

Devices and methods are disclosed for sensing the level of a fluid in a reservoir. The device comprises a generator for generating symmetrical pulses of electric potential, a ground generator in communication with the above generator, means for sensing resistance, and a latch circuit in communication with the above means for sensing resistance. In a method of the invention, a first electric potential is applied to an electrode within the reservoir. The first electric potential has a predetermined value and duration. The resistance of fluid within the reservoir is measured during application of the first electric potential. A second electric potential is applied to the electrode after the measurement for a period of time substantially equivalent to the duration of the first electric potential and of a value substantially equivalent to and opposite to the predetermined value of the first electric potential.

Claims

1. A device for sensing the level of a fluid in a reservoir, said device comprising:

(a) means for applying a first electric potential of predetermined value to said fluid within said reservoir for a predetermined duration,

(b) means for measuring the effect of said fluid on said first electric potential, and

(c) means for applying to said fluid a second electric potential after step (b) for a period of time substantially equivalent to the predetermined duration of step (a) and at a value substantially equivalent to and opposite to the predetermined value of said first electric potential.

2. A device according to claim 1 wherein said means of (a) and (c) comprise a switching circuit.

3. A device according to claim 2 wherein said means of (a) and (c) comprise a ground generator.

4. A device according to claim 1 wherein said means of (b) comprises a sense circuit.

5. A device according to claim 1 wherein said means of (b) comprises an electrode for placing in said reservoir.

6. A device according to claim 1 further comprising a latch circuit.

7. A method for sensing the level of a fluid in a reservoir, said method employing the device of claim 1 and comprising:

(a) applying a first electric potential to an electrode within said reservoir, said first electric potential having a predetermined value and duration,

(b) measuring resistance of said fluid within said reservoir during application of said first electric potential, and

(c) applying a second electric potential to said electrode after said measurement for a period of time substantially equivalent to the duration of said first electric potential and of a value substantially equivalent to and opposite to the predetermined value of said first electric potential.

8. An apparatus for synthesizing an array of biopolymers on the surface of a support, said apparatus comprising:

(a) a plurality of reservoirs for containing reagents for synthesizing said biopolymers,

(b) a droplet dispensing device comprising a plurality of droplet dispensers, each in fluid communication with a respective reservoir,

(c) a plurality of fluid level sensors, one for each of said reservoirs, wherein each of said fluid level sensors is a device according to claim 1, and

(d) a mechanism for moving a substrate with respect to said droplet dispensing device.

9. A fluid dispensing apparatus comprising:

(a) a plurality of reservoirs,

(b) a droplet dispensing device comprising a plurality of droplet dispensers, each in fluid communication with a respective reservoir,

(c) a plurality of fluid level sensors, one for each of said reservoirs, wherein each of said fluid level sensors is a device according to claim 1.

10. A fluid dispensing apparatus comprising:

(a) a plurality of reservoirs,

(b) a droplet dispensing device comprising a plurality of droplet dispensers, each in fluid communication with a respective reservoir,

(c) a plurality of fluid level sensors, one for each of said reservoirs, wherein each of said fluid level sensors is a device according to claim 2.

11. A fluid dispensing apparatus comprising:

(a) a plurality of reservoirs,

(b) a droplet dispensing device comprising a plurality of droplet dispensers, each in fluid communication with a respective reservoir,

(c) a plurality of fluid level sensors, one for each of said reservoirs, wherein each of said fluid level sensors is a device according to claim 3.