Selective gas detector

• US 4,647,777 A
• Filed: 05/31/1985
• Issued: 03/03/1987
• Est. Priority Date: 05/31/1985
• Status: Expired due to Fees

• Current Assignee: Ametek Incorporated
• Original Assignee: Ametrek Incorporated
• Inventors: Meyer, Emilio
• Primary Examiner(s): Howell, Janice A.
• Assistant Examiner(s): Hannaher, Constantine
• Application Number:
  US06/740,186
• Time in Patent Office: 641 Days
• Field of Search: 250/338 GA, 250/353, 250/349, 250/344, 250/343, 250/339, 250/340, 250/347, 250/345, 356/435, 356/437
• US Class Current: 250/339.11
• CPC Class Codes: G01N 2021/3522 balancing by two filters on two detectors
• CPC Class Codes: G01N 2021/536 Measurement device mounted at stack
• CPC Class Codes: G01N 21/3504 for analysing gases, e.g. multi-gas analysis

Abstract

A selective infra-red detector is used to determine the amount of a selected gas present in a gas sample. A beam of infra-red energy is passed through a gas sample and into the selective infra-red detector. An outer annular portion of the beam is reflected from a paraboloidal mirror onto a first focal point, while an inner annular portion of the beam passes through a chamber containing a fluid which will absorb the spectral wavelengths of the selected gas and is reflected by a spherical mirror onto a second focal point. Separate infra-red energy detectors are positioned near the first and second focal points to measure the infra-red energy. The difference or ratio between the infra-red energy measured by each infra-red energy detector is a measure of the amount of selected gas present in the gas sample.

Claims

1. A selective gas detecting device for providing an indication of the presence of a selected gas in a gas sample comprising:

a housing having an inlet opening for receiving a beam of infra-red energy;

means comprising a parabolic mirror to reflect a first portion of said beam of infra-red energy to a first focal point;

means comprising a spherical mirror to reflect a second portion of said beam of infra-red energy to a second focal point;

means to absorb selected spectral wavelengths of said second portion f said beam; and

first and second energy detectors positioned respectively proximate said first and second focal points to be exposed to infra-red energy and to provide signals which are indicative of the presence of a selected gas in the gas sample.

2. The selective gas detector of claim 1 further including means for moving at least one of said paraboloidal and spherical mirrors to change the position of the first or second focal point, respectively.

3. A selective gas detecting device comprising:

a housing having a cylindrical bore therein with an inlet opening for receiving a beam of infra-red energy;

a first mirror carrier mounted for axial movement in said housing;

a paraboloidal mirror mounted in said first mirror carrier and positioned to reflect a first portion of said beam of infra-red energy to a first focal point;

a second mirror carrier including a chamber mounted for axial movement in said housing;

a spherical mirror mounted in said chamber of second mirror carrier and positioned to reflect a second portion of said beam of infra-red energy to a second focal point;

first and second energy detectors mounted in said housing and positioned between said first and second mirror carriers and proximate said first and second focal points respectively; and

absorbing means positioned in the chamber of said second mirror carrier to absorb selected spectral wavelengths of said second portion of said beam of infra-red energy.