Plural gas non-dispersive infrared analyzer

Claim 2

A non-dispersive infrared analyzer for indicating individual concentrations of plural component gases in a sample gas mixture, comprising means providing a beam of infrared radiation; means for directing said beam sequentially along separate paths, said paths being equal in number to the number of component gases to be analyzed in said sample gas mixture; a plurality of filter cells, each of which is filled with a known concentration of one of said component gases, one of said filter cells being positioned in each of said separate beam paths so as to be illuminated by radiation from said source and each to absorb therefrom radiation at wavelengths dependent upon the composition of gas in said illuminated cell and to transmit radiation at other wavelengths; a sample cell filled with the gas mixture to be analyzed; means for directing into said sample cell radiation transmitted by said filter cells in said separate paths; a plurality of radiation detectors positioned to detect radiation transmitted by said sample cell, said detectors being equal in number to the number of said separate paths; a plurality of optical filters, one each preceding one each of said detectors, said filters each transmitting different bands of wavelengths of radiation, each said band corresponding to the wavelengths absorbable by the gas in each of said filter cells, said filters each rejecting substantially all radiation having wavelengths outside the transmission band associated with each said filter; and demoduLating means for each of said radiation detectors, each said demodulating means operating synchronously with said beam directing means and providing signals for comparing detector output when said beam passes through the one of said filter cells containing gas absorptive of the wavelengths transmitted by said optical filter associated with said detector with output of said detector when said beam passes through a different one of said filter cells.

Claim 3

An analyzer as claimed in claim 1 with additionally, means in one of said separate beam paths for attenuating the radiation contained in said beam.

Claim 4

An analyzer as claimed in claim 1 wherein said beam directing means comprises a rotating mirror.

Claim 5

A non-dispersive infrared analyzer for measuring the concentration of two different analyte gases in a sample mixture of gases comprising means providing a beam of infrared radiation; means for directing said beam alternately along two separate paths; a first filter cell containing a first analyte gas in known concentration positioned in one of said separate beam paths to absorb radiation from said beam in a spectrum characteristic of said first analyte gas; a second filter cell containing a second analyte gas in known concentration positioned in the other of said separate beam paths to absorb radiation from said beam in a spectrum characteristic of said second analyte gas; a sample cell filled with gas to be analyzed; means directing both said beams passing through said first and second filter cells into said sample cell; first and second radiation detectors positioned to detect radiation transmitted through said sample cell from said beams directed therein; first and second optical filters preceding said first and second detectors, said first optical filter transmitting only radiation within a band of wavelengths of radiation absorbable by said first analyte gas and rejecting substantially all radiation of other wavelengths, said second optical filter transmitting only radiation within a band of wavelengths of radiation absorbable by said second analyte gas and rejecting substantially all radiation of other wavelengths; and first and second demodulating means respectively receiving the outputs of said first and second detectors, said demodulating means being synchronized with said beam directing means to provide for each of said detectors signals for comparing the absorption of radiation by analyte gas contained by said sample cell with the absorption of radiation by that analyte gas contained in one of said filter cells.

Claim 6

A non-dispersive infrared analyzer for measuring the concentration of two different analyte gases in a sample mixture of gases comprising means providing a beam of infrared radiation; means for directing said beam alternately along two separate paths; a first filter cell containing a first analyte gas in known concentration positioned in one of said separate beam paths to absorb radiation from said beam in a spectrum characteristic of said first analyte gas; a second filter cell containing a second analyte gas in known concentration positioned in the other of said separate beam paths to absorb radiation from said beam in a spectrum characteristic of said second analyte gas; a sample cell filled with gas to be analyzed; means directing both said beams passing through said first and second filter cells into said sample cell; first and second radiation detectors positioned to detect radiation transmitted through said sample cell from said beams directed therein; first and second optical filters preceding said first and second detectors, said first optical filter transmitting only radiation within a band of wavelengths of radiation absorbable by said first analyte gas and rejecting substantially all radiation of other wavelengths, said second optical filter transmitting only radiation within a band of wavelengths of radiation absorbable by said second analyte gas and rejecting substantially all radiation of other wavelengths; and first and second demodulating means respectively receiving the outputs of said first and second detectors, said demodulating means being synchronized with said beam directing means to provide for each of said detectors signals for comparing the absorption of radiation by analyte gas contained by said sample cell with the absorption of radiation by that analyte gas contained in one of said filter cells.

Claim 7

An analyzer as claimed in claim 4 wherein said beam directing means comprises a rotating mirror.

Claim 8

An analyzer as claimed in claim 4, with additionally, means in at least one of said separate beam paths for adjustably attenuating the radiation contained in the beam following said one path.

Claim 9

A non-dispersive infrared analyzer for measuring the concentration of two different analyte gases in a sample mixture of gases, comprising: means producing a beam of infrared radiation; a rotating mirror, said mirror being located with respect to said beam so that in one position of mirror rotation said beam is directed along a first path and in another position of mirror rotation said beam is directed along a second path; a first filter cell positioned in said first path, said first filter cell being filled with a known concentration of a first analyte gas and absorbing radiation in a spectrum characteristic of said first analyte gas while transmitting other radiation; a second filter cell positioned in said second path, said second filter cell being filled with a known concentration of a second analyte gas and absorbing radiation in a spectrum characteristic of said second analyte gas while transmitting other radiation; a sample gas cell filled with gas to be analyzed; a first fixed mirror positioned in said first path for directing radiation transmitted by saId first filter cell into said sample cell; a second fixed mirror positioned in said second path for directing radiation transmitted by said second filter cell into said sample cell; first and second radiation detectors positioned to detect radiation transmitted by said sample cell; first and second optical filters preceding said first and second radiation detectors, said first optical filter transmitting a band of radiation within the spectrum of radiation absorbable by said first analyte gas and rejecting other radiation, said second optical filter transmitting a band of radiation within the spectrum of radiation absorbable by said second analyte gas and rejecting other radiation; and first and second demodulating means, said first demodulating means receiving the output of said first radiation detector and providing signals for comparing said first detector output occurring when said beam is directed along said first path with said first detector output occurring when said beam is directed along said second path, said second demodulating means receiving the output of said second radiation detector and providing signals for comparing said second detector output occurring when said beam is directed along said second path with said second detector output occurring when said beam is directed along said first path.

Claim 10

A non-dispersive infrared analyzer for measuring the concentration of two different analyte gases in a sample mixture of gases, comprising: means producing a beam of infrared radiation; a rotating mirror, said mirror being located with respect to said beam so that in one position of mirror rotation said beam is directed along a first path and in another position of mirror rotation said beam is directed along a second path; a first filter cell positioned in said first path, said first filter cell being filled with a known concentration of a first analyte gas and absorbing radiation in a spectrum characteristic of said first analyte gas while transmitting other radiation; a second filter cell positioned in said second path, said second filter cell being filled with a known concentration of a second analyte gas and absorbing radiation in a spectrum characteristic of said second analyte gas while transmitting other radiation; a sample gas cell filled with gas to be analyzed; a first fixed mirror positioned in said first path for directing radiation transmitted by saId first filter cell into said sample cell; a second fixed mirror positioned in said second path for directing radiation transmitted by said second filter cell into said sample cell; first and second radiation detectors positioned to detect radiation transmitted by said sample cell; first and second optical filters preceding said first and second radiation detectors, said first optical filter transmitting a band of radiation within the spectrum of radiation absorbable by said first analyte gas and rejecting other radiation, said second optical filter transmitting a band of radiation within the spectrum of radiation absorbable by said second analyte gas and rejecting other radiation; and first and second demodulating means, said first demodulating means receiving the output of said first radiation detector and providing signals for comparing said first detector output occurring when said beam is directed along said first path with said first detector output occurring when said beam is directed along said second path, said second demodulating means receiving the output of said second radiation detector and providing signals for comparing said second detector output occurring when said beam is directed along said second path with said second detector output occurring when said beam is directed along said first path.

Claim 11

An analyzer as claimed in claim 7, with additionally, means positioned along said first path for attenuating an adjustable amount of radiation in the beam following said first path.

Claim 12

An analyzer as claimed in claim 8, with additionally, means positioned along said second path for attenuating by an adjustable amount a limited band of radiation in the beam following said second path.

Claim 13

An analyzer as claimed in claim 7 wherein said rotating mirror comprises a circular sector of reflecting material, the axis of rotation of said mirror intersecting said first path at an acute angle, the rotation of said mirror periodically interrupting said first path to reflect said beam of radiation along said second path.

Claim 14

An analyzer as claimed in claim 10 wherein said means producing said beam, said first filter cell and said first fixed mirror are positioned along a first axis, and said sample cell, said second filter cell and said second fixed mirror are positioned along a second axis, said first and second axes being parallel and equally spaced from the center of rotation of said rotating mirror.

Claim 15

An analyzer as claimed in claim 11 wherein said first and second mirrors are plane mirrors respectively positioned at 45* to said first and second axes, and the axis of rotation of said rotating mirror intersects said first and second axes at 45*.

Claim 16

An analyzer as claimed in claim 12 wherein said sector of said rotating mirror is a plane mirror both surfaces of which are reflective.