Low volume sample cell and gas monitoring system using same

• US 20040065835A1
• Filed: 10/03/2003
• Published: 04/08/2004
• Est. Priority Date: 10/08/2002
• Status: Active Grant

• Current Assignee: Philips RS North America LLC (Koninklijke Philips N.V.)
• Original Assignee: RIC INVESTMENTS LLC (Respironics Incorporated)
• Inventors: Rich, David R., Sandor, John L.
• Granted Patent: US 7,294,839 B2
• Time in Patent Office: Days
• US Class Current: 250/343
• CPC Class Codes: G01N 21/05 Flow-through cuvettes G01N21/09 takes precedence; handling fluid samples G01N1/10

Abstract

A sample cell, which is a component of a gas monitoring system, includes a sample cell body and a sample cell core installed therewith. The sample cell is coupled to a sampling tube that communicates with an airway of a patient. Gas from the sampling tube passes through the sample cell such that the flow profile remains substantially undisturbed. Within the sample cell, at least one optical aperture permits radiation to be emitted, pass through the gas in the sample cell core, and detected. In this manner, measurements of the partial pressure or concentration of a gas of interest are determined.

Claims

1. A sample cell comprising:

a sample cell body having a first passage defined therethrough;

a sample cell core having a second passage defined therethrough, wherein the sample cell core is securable to the sample cell body such that the first passage is in fluid communication with the second passage, and wherein the sample cell core includes at least one first optical aperture defined therein to allow light to pass through at least a portion of the second passage; and

a first window disposed over the first optical aperture.

2. The sample cell of claim 1, wherein the sample cell core further includes at least one second optical aperture defined therein, and wherein the second optical aperture is optically aligned with first optical aperture;

and further comprising;

a second window dispose over the second optical aperture.

3. The sample cell of claim 1, wherein the second passage follows a “

Z-shaped”

configuration through the sample cell core.

4. The sample cell of claim 3, wherein a portion of the “

Z-shaped”

configuration is adjacent to the first window.

5. The sample cell of claim 1, further comprising at least one snap-in retainer ring positioned around the first window.

6. The sample cell of claim 1, wherein the first passage defined in the sample cell body includes a chamber adapted to receive the sample cell core, and wherein the sample cell core is mechanically retained within the chamber by the snap-in retainer ring.

7. The sample cell of claim 1, wherein the sample cell core is mechanically keyed to insure alignment of the first and second passages.

8. A gas monitoring system comprising:

(a) a radiation source which emits a plurality of wavelengths of infrared radiation absorbable by a selected gas;

(b) a radiation detector positioned to sense radiation of a plurality of wavelengths emitted from the radiation source, whereby the amount of infrared radiation from the radiation source that impinges upon the radiation detector is proportional to the content of the selected gas passed between the radiation source and radiation detector;

(c) a sample cell having at least one passage defined therethrough and configured as such to not substantially alter a flow profile of gas passing through the passage, and wherein the sample cell includes at least one first optical aperture defined therein to the plurality of wavelengths of infrared radiation from the radiation source to pass through at least a portion of the passage; and

(d) a first window disposed over the first optical aperture,.

9. The gas monitoring system of claim 8, wherein the sample cell includes:

a sample cell body having a first passage defined therethrough; and

a sample cell core having a second passage defined therethrough, wherein the sample cell core is securable to the sample cell body such that the first passage is in fluid communication with the second passage.

10. The gas monitoring system of claim 9, wherein the first passage defined in the sample cell body includes a chamber adapted to receive the sample cell core, and wherein the sample cell core is mechanically retained within the chamber.

11. The gas monitoring system of claim 9, wherein the sample cell core is mechanically keyed to insure alignment of the first and second passages

12. The gas monitoring system of claim 9, wherein the second passage follows a “

Z-shaped”

configuration through the sample cell core.

13. The gas monitoring system of claim 12, wherein a portion of the “

Z-shaped”

configuration is adjacent to the first window.

14. The gas monitoring system of claim 8, further comprising:

at least one second optical aperture defined in the sample cell, wherein the second optical aperture is optically aligned with first optical aperture; and

a second window disposed over the second optical aperture.

15. The gas monitoring system of claim 8, further comprising:

at least one snap-in retainer ring positioned around the first window.

16. A method of infrared gas measurement comprising:

drawing gas through a sample cell including a sample cell body having a first passage defined therethrough and a sample cell core having a second passage defined therethrough, wherein the sample cell core is securable to the sample cell body such that the first passage is in fluid communication with the second passage;

emitting a plurality of wavelengths of infrared radiation from a radiation source through at least one first optical aperture defined in the sample cell core;

sensing of a plurality of wavelengths emitted from the radiation source by a radiation detector upon passing through at least a portion of the second passage; and

determining the content of the selected gas passed between the radiation source and radiation detector by the amount of infrared radiation from the radiation source that impinges upon the radiation detector.

17. A sample cell comprising:

(a) a sample cell body having a passage defined therethrough, wherein the passage includes;

(1) an inlet portion defined along a first axis and adapted to receive a flow of gas,

(2) an outlet portion adapted to communicate a flow of gas from the sample cell body, wherein the outlet portion is defined along the first axis such that the inlet portion and the outlet portion are coaxially aligned, and

(3) a sample chamber portion disposed between the inlet portion and the outlet portion and in fluid communication with the inlet portion and the outlet portion, and wherein the sample chamber portion is defined along a second axis that is substantially perpendicular to the first axis; and

(b) a first window defined in the sample cell body to provide optical access to the sample chamber portion of the passage.

18. The sample cell of claim 17, further comprising a first connecting portion communicating the inlet portion with a first end portion of the sample chamber, and a second connecting portion communicating the outlet portion with a second end portion of the sample chamber.

19. The sample cell of claim 18, wherein the first connecting portion is defined along a third axis that is at a non-90°

angle with respect to the first axis and the second axis, and wherein the second connecting portion is defined along a fourth axis that is at a non-90°

angle with respect to the first axis and the second axis.

20. The sample cell of claim 19, wherein the third axis and the fourth axis are parallel.