Ndir gas analyzer based on absorption modulation ratios for known and unknown samples

Claim 2

A nondispersive gas analyzing apparatus comprising: a first means for containing a first gas sample including a reference gas; a second means for containing a second gas sample including an unknown amount of said reference gas; a means for passing radiant energy through said first and said second gas samples for permitting at least partial absorption of said energy by said gas samples; a means for modulating the amount of said energy absorbed by said gas samples at a first and a second frequency; a means responsive to the unabsorbed energy passing through said gas samples for generating a first signal at said first frequency and a second signal at said second frequency; and a means responsive to said first and said second signals for generating a third signal proportional to the density of said reference gas in said second gas sample.

Claim 3

A nondispersive gas analyzing apparatus accordinG to claim 1 wherein said third signal generating means comprises a means for generating a ratio of said first and said second signals.

Claim 4

A nondispersive gas analyzing apparatus according to claim 1 wherein said modulating means comprises means for modulating the density of said first and said second gas samples at said first and said second frequencies, respectively.

Claim 5

A nondispersive gas analyzing apparatus according to claim 2 wherein said first and said second frequencies are not harmonically related.

Claim 6

A nondispersive gas analyzing apparatus according to claim 3 wherein said density modulating means comprises means for periodically varying the volume of said first and said second gas samples.

Claim 7

A nondispersive gas analyzing apparatus according to claim 1 wherein said means for modulating said energy absorbed by said first and said second gas samples comprises means for modulating the length of the path of said radiant energy through said samples.

Claim 8

A nondispersive gas analyzing apparatus as recited in claim 6 wherein said means for modulating the path length of said radiant energy in passing through said gas samples includes a first reflective surface disposed at an angle relative to the incident radiant energy, and a second reflective surface disposed parallel to said first reflective surface, whereby said radiant energy is reflected from said first reflective surface to said second reflective surface, and means for periodically moving one of said reflective surfaces relative to the other.

Claim 9

A nondispersive gas analyzing apparatus as recited in claim 1 comprising chopper means disposed on each side of said first containing means and operative to periodically admit direct radiant energy from said radiant energy source means to enter said first containing means while preventing such direct radiant energy from entering said second containing means.

Claim 10

A nondispersive gas analyzing apparatus as recited in claim 1 wherein said radiant energy source means includes means forming a third containing means for containing a known gas, and means for causing said known gas to fluoresce and thereby provide said radiant energy.

Claim 11

A nondispersive gas analyzing apparatus as recited in claim 1 wherein said radiant energy source means includes means for causing said reference gas in said unknown gas sample to fluoresce, said fluorescence providing radiant energy for passage through said second containing means.

Claim 12

A gas analyzing method comprising the steps of: providing a quantity of a reference gas and quantity of an unknown gas; directing radiant energy serially through said reference gas and said unknown gas in such a manner that said radiant energy is at least partially absorbed in passing therethrough; modulating the absorption of said radiant energy in said reference gas at a first frequency; modulating the absorption of said radiant energy in said unknown gas at a second frequency; detecting the modulated radiant energy and developing an electrical signal commensurate therewith, said electrical signal including signal components related to the constituents of said unknown gas; separating from said electrical signal a pair of signal components comprising said first and said second frequencies; and forming a ratio of said pair of signal components for generating a signal proportional to the density of said reference gas in said unknown gas sample.

Claim 13

A gas analyzing method comprising the steps of: providing a quantity of a reference gas and quantity of an unknown gas; directing radiant energy serially through said reference gas and said unknown gas in such a manner that said radiant energy is at least partially absorbed in passing therethrough; modulating the absorption of said radiant energy in said reference gas at a first frequency; modulating the absorption of said radiant energy in said unknown gas at a second frequency; detecting the modulated radiant energy and developing an electrical signal commensurate therewith, said electrical signal including signal components related to the constituents of said unknown gas; separating from said electrical signal a pair of signal components comprising said first and said second frequencies; and forming a ratio of said pair of signal components for generating a signal proportional to the density of said reference gas in said unknown gas sample.

Claim 14

A gas analyzing method as recited in claim 11 wherein the modulation of the absorption of said radiant energy in said reference gas is effected by varying the density of said reference gas at said first frequency, and the modulation of said radiant energy in said unknown gas is effected by varying the density of said unknown gas at said second frequency.

Claim 15

A gas analyzing method as recited in claim 11 wherein the modulation of the absorption of said radiant energy in said reference gas is effected by periodically varying at said first frequency the length oF the path taken by said radiant energy in passing through said reference gas, and the modulation of said radiant energy in said unknown gas is effected by periodically varying at said second frequency the length of the path taken by said radiant energy in passing through said unknown gas.

Claim 16

In a nondispersive gas analyzing apparatus including a pair of chambers for containing a reference gas sample and an unknown gas sample including an unknown quantity of said reference gas, a source of radiant energy, a means for passing said energy through said samples for absorption by said samples in accordance with their respective energy absorbing characteristics, a means for modulating said energy absorbing characteristics of each of said samples at a first and a second frequency, respectively, and a means responsive to the unabsorbed radiant energy after passage through said samples for generating an electrical signal containing said first and said second frequencies, the improvement comprising, a means responsive to said electrical signal for generating a first signal at said first frequency and a second signal at said second frequency; and a means responsive to said first and said second frequency signals for generating a third signal proportional to the density of said reference gas in said unknown gas sample.

Claim 17

In a nondispersive gas analyzing apparatus including a pair of chambers for containing a reference gas sample and an unknown gas sample including an unknown quantity of said reference gas, a source of radiant energy, a means for passing said energy through said samples for absorption by said samples in accordance with their respective energy absorbing characteristics, a means for modulating said energy absorbing characteristics of each of said samples at a first and a second frequency, respectively, and a means responsive to the unabsorbed radiant energy after passage through said samples for generating an electrical signal containing said first and said second frequencies, the improvement comprising, a means responsive to said electrical signal for generating a first signal at said first frequency and a second signal at said second frequency; and a means responsive to said first and said second frequency signals for generating a third signal proportional to the density of said reference gas in said unknown gas sample.

Claim 18

A nondispersive gas analyzing apparatus according to claim 14 wherein said first and said second signal generating means comprises means for selectively amplifying said first and said second frequency signals and said third signal generating means comprises a means for forming a signal corresponding to the ratio of said first and said second frequency signals.