Method for determining the current filling level of a liquid in a container

• US 6,931,925 B2
• Filed: 04/30/2003
• Issued: 08/23/2005
• Est. Priority Date: 04/30/2002
• Status: Expired due to Term

• Current Assignee: Roche Diagnostics Operations Incorporated (Roche Holding AG)
• Original Assignee: Roche Diagnostics Operations Incorporated (Roche Holding AG)
• Inventors: Huemer, Herfried, Ruether, Horst
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): FRANK, RODNEY T
• Application Number:
  US10/426,777
• Publication Number:
  US 20040011127A1
• Time in Patent Office: 846 Days
• Field of Search: 732/99, 733/01, 732/90.R, 732/98
• US Class Current: 73/299
• CPC Class Codes: F04B 51/00 Testing machines, pumps, or pumping installations
• CPC Class Codes: G01F 23/14 by measurement of pressure
• CPC Class Codes: G01F 23/168 with electric indicating or recording
• CPC Class Codes: G01F 25/0092 for metering by volume
• CPC Class Codes: G01F 25/17 using calibrated reservoirs

Abstract

The invention relates to a method for determining the current filling level of a liquid, preferably a calibrating, quality control, or cleaning fluid, or waste water, in a container, for example of an analyzer, where an immersion pipe is dipped into the liquid in the container to be filled or drained. The immersion pipe is connected to a pumping device via a tube system. The pressure p in the tube system is measured and increased, starting from the ambient pressure p₀, until a first discontinuous pressure change occurs at pressure p₁ due to the liquid column in the immersion pipe being forced out of the pipe, and/or the pressure p in the tube system is decreased until the liquid column in the immersion pipe reaches a change in cross-section of the immersion pipe, which change is situated above the maximum filling level of the liquid, such that a second discontinuous pressure change occurs at pressure p₂ due to the liquid column reaching the change in cross-section. The pressure difference between ambient pressure p₀ and the pressure p₁ or p₂ at one of the two pressure discontinuities or the time t₁ or t₂ until one of the two pressure discontinuities is reached, is recorded and used to determine the current filling level of the container.

Claims

1. A method for determining the current filling level of a liquid in a container having an immersion pipe dipped into the liquid in the container, and a tubing system connecting the immersion pipe to a pumping device;

the method comprising;

(a) measuring the ambient gas pressure p₀ in the tubing system at a time t₀;

(b) using the pumping device to increase the gas pressure in the tubing system;

(c) measuring the gas pressure p₁ at a time t₁ when a first discontinuous pressure change occurs due to a liquid column being forced out of an exit end of the immersion pipe;

(d) calculating at least one of the difference in pressure between p₀ and p₁ and the difference in time between t₀ and t₁; and

(e) determining the current filling level of the liquid in the container by the difference in at least one of pressure and time, wherein the current filling level is related to the difference in pressure or time.

2. The method according to claim 1, wherein the liquid in the container is a calibration medium, a quality control medium, a cleaning medium or a waste solution.

3. The method according to claim 1, further comprising determining the current filling level of a liquid in at least one additional container having an immersion pipe connected to the tubing system, wherein the tubing system comprises a valve for each immersion pipe.

4. A method for determining the current filling level of a liquid in a container having an immersion pipe dipped into the liquid in the container, and a tubing system connecting the immersion pipe to a pumping device, wherein the immersion pipe has a change in cross-section located above a maximum filling level of the container;

the method comprising;

(a) measuring the ambient gas pressure p₀ in the tubing system at a time t₀;

(b) using the pumping device to decrease the gas pressure in the tubing system;

(c) measuring the gas pressure p₂ at a time t₂ when a second discontinuous pressure change occurs as a result of the liquid reaching the change in cross-section of the immersion pipe;

(d) calculating at least one of the difference in pressure between p₀ and p₂ and the difference in time between t₀ and t₂; and

(e) determining the current filling level of the liquid in the container by the difference in at least one of pressure and time, wherein the current filling level is related to the difference in pressure or time.

5. The method according to claim 4, wherein the liquid in the container is a calibration medium, a quality control medium, a cleaning medium or a waste solution.

6. The method according to claim 4, further comprising determining the current filling level of a liquid in at least one additional container having an immersion pipe connected to the tubing system, wherein the tubing system comprises a valve for each immersion pipe.

7. A method for determining the current filling level of a liquid in a container having an immersion pipe dipped into the liquid in the container, and a tubing system connecting the immersion pipe to a pumping device, wherein the immersion pipe has a change in cross-section located above a maximum filling level of the container;

the method comprising;

(a) measuring the ambient gas pressure p₀ in the tubing system at a time t₀;

(b) using the pumping device to increase the gas pressure in the tubing system;

(c) measuring the gas pressure p₁ at a time t₁ when a discontinuous pressure change occurs as a result of the liquid column being forced out of an exit end the immersion pipe;

(d) calculating at least one of the difference in pressure between p₀ and p₁ and the difference in time between t₀ and t₁;

(e) using the pumping device to decrease the gas pressure in the tubing system;

(f) measuring the gas pressure p₂ at a time t₂ when a discontinuous pressure change occurs as a result of the liquid reaching in cross-section of the immersion pipe;

(g) calculating at least one of the difference in pressure between p₁ and p₂ and the difference in time between t₁ and t₂; and

(h) determining the current filling level of the liquid in the container by the difference in at least one of pressure and time, wherein the current filling level is related to the difference in pressure or time.

8. The method according to claim 7, wherein the pressure difference measured between the ambient pressure p₀ and the pressure p₁ or p₂ is calibrated with an absolute value of the pressure difference |p₁−

p₂|.

9. The method according to claim 7, wherein the slope of a pressure sensor S is determined using the pressure difference |p₁−

p₂|, the length L of the immersion pipe between the exit end and the change in cross-section, and a hydrostatic pressure p(L) of the liquid column.

10. The method according to claim 7, wherein a pumping rate Δ

v/Δ

t is determined from a ratio V/T, wherein T is the difference between t₁ and t₂, and V is the volume of the immersion pipe between the exit end and the change in cross-section.

11. A method for determining the pumping rate of a pumping device connected through a tube system to an immersion pipe for filling or draining a container with a liquid, the immersion pipe dipping into the liquid in the container;

the method comprising;

(a) measuring the ambient gas pressure p₀ in the tube system;

(b) using the pumping device to increase the gas pressure;

(c) measuring the gas pressure p₁ at a time t₁ when a first discontinuous pressure change occurs due to a liquid column in the immersion pipe being forced out of an exit end of the pipe;

(d) using the pumping device to decrease the gas pressure;

(e) measuring the gas pressure p₂ at a time t₂ when a discontinuous pressure change occurs as a result of the liquid reaching a change in cross-section of the immersion pipe; and

(f) determining a pumping rate Δ

v/Δ

t from a ratio V/T, where V is a known volume of the immersion pipe between the exit end and the change in cross-section, and T is the difference between t₂ and t₁.