LOW COST APPARATUS FOR DETECTION OF NITROGEN-CONTAINING GAS COMPOUNDS

• US 20090128819A1
• Filed: 04/25/2006
• Published: 05/21/2009
• Est. Priority Date: 04/26/2005
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: VAN KESTEREN, HANS WILLEM, WILLARD, NICOLAAS PETRUS, VINK, TEUNIS JOHANNES
• Application Number:
  US11/912,695
• Publication Number:
  US 20090128819A1
• Time in Patent Office: Days
• US Class Current: 356/437
• CPC Class Codes: A61B 5/083 Measuring rate of metabolism by using breath test, e.g. measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/0833 Measuring rate of oxygen consumption
• CPC Class Codes: A61B 5/0836 Measuring rate of CO2 production
• CPC Class Codes: A61B 5/411 Detecting or monitoring allergy or intolerance reactions to an allergenic agent or substance
• CPC Class Codes: G01N 2021/1704 in gases
• CPC Class Codes: G01N 2021/1708 with piezotransducers
• CPC Class Codes: G01N 21/1702 with opto-acoustic detection, e.g. for gases or analysing solids
• CPC Class Codes: G01N 2201/0612 Laser diodes
• CPC Class Codes: G01N 2201/0625 Modulated LED
• CPC Class Codes: G01N 2201/0691 Modulated (not pulsed supply)
• CPC Class Codes: G01N 2291/0427 Flexural waves, plate waves, e.g. Lamb waves, tuning fork, cantilever
• CPC Class Codes: G01N 29/2425 optoacoustic fluid cells therefor
• CPC Class Codes: G01N 33/0037 NOx
• CPC Class Codes: G01N 33/4975 other than oxygen, carbon dioxide or alcohol, e.g. organic vapours
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters

Abstract

Nitrogen-containing compounds are detected by chemically converting (210) them to nitrogen dioxide, and detecting (10) the amount of nitrogen dioxide. A semiconductor laser or light emitting diode (132) provides a modulated light (131) in the blue-violet-green wavelength range and a narrow bandwidth photo-acoustic sensor (10) detects the standing waves produced by the absorption of the light by the nitrogen dioxide. The photo-acoustic sensor (10) uses a resonant cavity (161, 182a-b) with a resonant frequency that corresponds to the modulation frequency of the light (131). For detecting nitric oxide, a surface chemical oxidation unit (210) is preferably used to convert the nitric oxide to nitrogen dioxide, using, for example potassium permanganate (KMnO4) filter, or a platinum (Pt) catalyst unit (260).

Claims

1. A detector for detecting one or more nitrogen-containing compounds in a gas mixture comprising:

a converter that is configured to convert at least one nitrogen-containing compound in the gas mixture into nitrogen dioxide, and

a photo-acoustic sensor, operably coupled to the converter, that is configured to detect the nitrogen dioxide provided by the converter, and includes;

an acoustic pickup unit that exhibits a structural resonance at a resonant frequency, and

a light source that is configured to emit light at a wavelength corresponding to an absorption of nitrogen dioxide in a visible wavelength range, and with a modulation frequency corresponding to the resonant frequency.

2. The detector of claim 1, wherein the light source includes at least one of:

a semiconductor laser and a light emitting diode.

3. The detector of claim 1, wherein

the acoustic pickup unit includes

a piezoelectric sensing unit that includes

a resonant tuning-fork and

one or more cylindrical acoustic

4. The detector of claim 3, wherein the tuning-fork is configured to include a cylindrical cavity that has a radius that is substantially equal to a radius of the one or more cylindrical acoustic resonators.

5. The detector of claim 1, further including a scrubber that is configured to remove one or more nitrogen-containing compounds from an input that is used to generate the gas mixture.

6. The detector of claim 1, further including a pressure sensor that is configured to determine an amount of pressure associated with the gas mixture.

7. The detector of claim 1, wherein the sensor is configured to detect at least one other gas in the gas mixture, and the light source is further configured to emit light at a wavelength corresponding to an absorption of the at least one other gas in a visible wavelength range.

8. The detector of claim 1, wherein the modulation frequency is substantially equal to one of:

the resonant frequency, a multiple of the resonant frequency, and a sub-multiple of the resonant frequency.

9. A method of detecting one or more nitrogen-containing compounds in a gas mixture, the method comprising:

converting at least one nitrogen-containing compound in the gas mixture into nitrogen dioxide, and

detecting the nitrogen dioxide by

exposing the gas mixture to light at a wavelength corresponding to an absorption of nitrogen dioxide in a visible wavelength range within a resonant cavity,

modulating the light at a modulation frequency corresponding to a resonant frequency of the resonant cavity, and

detecting vibrations that are produced within the resonant cavity due to the absorption.

10. The method of claim 9, further including

scrubbing an input that is used to generate the gas mixture, to remove nitrogen-containing compounds in the input.

11. The method of claims 9, wherein converting the at least one nitrogen-containing compound includes at least one of:

oxidation,

catalytic conversion, and

ozone generation.