Real time measurements of fluid volume and flow rate using two pressure transducers

Patent metadata

Field	Value
Publication number	US-9482563-B2
Application number	US-201113884099-A
Country	US
Kind code	B2
Filing date	Nov 9, 2011
Priority date	Nov 12, 2010
Publication date	Nov 1, 2016
Grant date	Nov 1, 2016

Abstract

To provide accurate determinations of volumetric flow rate and thus of total liquid volume transported over a given time period, two pressure transducers are disposed a predetermined distance apart along a conduit. Precise pressure measurement readings are generated from which volumetric flow rate can be derived with accuracy. Integration of the volumetric flow rate over time yields an improved measure of the total liquid volume that has flowed through the conduit during the respective temporal interval. The two pressure transducers are disposed along the conduit a predetermined distance apart with no obstruction or restriction in the conduit between the transducers. A controller can be used to determine the volumetric flow rate using the Hagen-Poiseuille Equation.

First claim

What is claimed is:

1. A fluid-bearing circuit for conveying a fluid from a reservoir to a sample container in an in vitro analyzer comprising:
a fluid-bearing conduit;
two pressure sensors disposed a predetermined distance apart along the conduit, each for measuring pressure within the conduit proximate the respective pressure sensor and for generating a pressure signal indicative thereof;
a probe having a probe tip;
a first valve disposed within the conduit for selectively controlling fluid flow through the conduit;
a pump disposed in association with the conduit for selectively pumping fluid in at least one direction within the conduit; and
a controller in communication with the two pressure sensors, the first valve, and the pump,
wherein the conduit is of substantially uniform cross-section and is unobstructed between the two pressure sensors,
the conduit defines a fluid path and includes a proximal portion and a distal portion,
the proximal portion of the fluid path extends from the probe to the first valve,
the distal portion of the fluid path extends from the first valve to a reservoir and includes a first segment and a second segment,
the first valve is disposed between the proximal portion and the distal portion for selectively controlling fluid flow therebetween,
the pump is disposed between the first segment and the second segment of the distal portion,
the controller receives the respective pressure signal from each of the two pressure sensors,
the controller selectively controls the first valve to thereby control the fluid flow through the conduit,
the controller selectively controls the pump to thereby selectively pump the fluid in at least one direction within the conduit, and
the controller is configured to calculate the difference in the measured pressures and, from the difference, to calculate the volumetric flow rate of the fluid through the fluid-bearing conduit between the two pressure sensors.

2. The fluid-bearing circuit of claim 1 , wherein the two pressure sensors are disposed in the proximal portion.

3. The fluid-bearing circuit of claim 2 , further comprising a second valve disposed within the second segment of the distal portion and wherein the distal portion is in fluidic communication with a fluid reservoir.

4. The fluid-bearing circuit of claim 3 , wherein the controller is operative to selectively open the fluid path through the first valve and the second valve and for selectively operating the pump to convey fluid from the reservoir, through the second valve, the pump, and the first valve, past the two pressure sensors, and through an open end of the proximal portion to the probe.

5. The fluid-bearing circuit of claim 4 , wherein the probe tip comprises a removable probe tip.

6. The fluid-bearing circuit of claim 3 , wherein the pump is a syringe pump and the conduit is in fluidic communication with a syringe pump piston chamber, and wherein the second valve is opened while the first valve is closed to enable the aspiration of liquid from the reservoir by the withdrawal of the syringe pump piston.

7. The fluid-bearing circuit of claim 3 , wherein the pump is a syringe pump and the conduit is in fluidic communication with a syringe pump piston chamber, and wherein the first valve is opened while the second valve is closed to enable the dispensation of liquid from the syringe pump piston chamber by the insertion of the syringe pump piston.

8. The fluid-bearing circuit of claim 1 , wherein the two pressure sensors are disposed in the second segment of the distal portion.

9. The fluid-bearing circuit of claim 1 , wherein the controller is configured to calculate the volumetric flow rate through the conduit proximate the pressure sensors on the basis of a known relationship between a calculated difference in the measured pressures between the two pressure sensors, the distance along the fluid-bearing conduit separating the two pressure sensors, a predetermined dynamic viscosity of the fluid flowing through the fluid-bearing conduit, and a predetermined radius or diameter of the fluid-bearing conduit intermediate the two pressure sensors.

10. The fluid-bearing circuit of claim 9 , wherein the known relationship is the Hagen-Poiseuille Equation.

11. The fluid-bearing circuit of claim 1 , further comprising translating apparatus associated with the end of the fluid-bearing conduit for translating an end of the fluid-bearing conduit at least in a horizontal or vertical direction, the translating apparatus being in communication with and under the control of the controller.

12. The fluid-bearing circuit of claim 11 , wherein the translating apparatus is for moving the end with respect to at least one of a fluid reservoir and a cuvette.

13. The fluid-bearing circuit of claim 1 , wherein the controller is for selectively opening the first valve and controlling the pump to move the fluid:
in a first direction within the fluid-bearing conduit in order to aspirate the fluid through an end of the fluid-bearing conduit and past the two pressure sensors; and
in an opposite, second direction within the fluid-bearing conduit, past the two pressure sensors, to dispense the fluid through the end.

14. The fluid-bearing circuit of claim 1 , wherein the fluid-bearing conduit has a circular cross-section.

15. The fluid-bearing circuit of claim 1 , further comprising a memory in association with the controller, wherein the controller is further for recording pressure measurements from each of the two pressure sensors at regular temporal intervals.

16. The fluid-bearing circuit of claim 15 , wherein the controller is further for determining the value of volumetric flow rate at each of plural temporal intervals from the respective recorded pressure measurements and for determining a fluid volume that moved between the two pressure sensors during a time period by mathematically integrating volumetric flow rate values over the time period.

17. The fluid-bearing circuit of claim 16 , wherein the controller is further for comparing the determined fluid volume to a predetermined threshold value to determine whether a desired fluid volume moved within the conduit proximate the pressure sensors and, if not, to identify an error condition.

Assignees

• Calderin Domingo
• Hsieh Pei-Ying
• Siemens Healthcare Diagnostics Inc

Inventors

• Calderin Domingo
• Hsieh Pei-Ying

Classifications

• G01F1/34 Primary

  by measuring pressure or differential pressure · CPC title