Flow-responsive detector unit and its applications to infrared gas analyzers

Claim 2

Apparatus according to claim 1, in which the sensor is a thermistor bead.

Claim 3

Apparatus according to claim 1, in which the first gas chamber is irradiated and contains the entire gas sample to be analyzed.

Claim 4

Apparatus according to claim 1, in which both gas chambers are irradiated by separate pulsed beams of infrared energy, and in which the first gas chamber contains the entire gas sample that is to be analyzed and the second gas chamber contains a reference gas that does not include the component of interest.

Claim 5

Apparatus according to claim 5 that also includes a separate filter cell in the path of each infrared energy beam between the source and the gas chambers, each filter cell containing a gas absorbing infrared energy in a first region of the spectrum overlapping a second region absorbed by the component of interest, thereby to counteract interference from background gas in the sample absorbing radiation in said first region.

Claim 6

Apparatus according to claim 1, in which both gas chambers are irradiated by separate pulsed beams of infrared energy and, together with the gas flow chamber, contain the entire gas sample to be analyzed, and in which a filter cell is disposed in the path of the infrared energy beam between the source and the second gas chamber, the cell containing a gas that absorbs infrared energy in the same region of the spectrum absorbed by the component of interest.

Claim 7

Apparatus according to claim 7 that also includes a conduit connecting the two gas chambers for initially flushing those chambers with the sample gas and means for shutting off gas flow through the conduit during analysis of the gas sample.

Claim 8

Apparatus according to claim 7, in which a second filter cell is disposed in the path of the infrared energy beam between the source and the first gas chamber, said second cell containing a gas absorbing infrared radiation in a first region of the spectrum overlapping a second region absorbed by the component of interest, thereby to counteract interference from background gas in the sample absorbing radiation in said first region.

Claim 9

Apparatus according to claim 1, in which both gas chambers are irradiated by separate pulsed beams of infrared energy, and in which means are provided for continuously flowing the gas sample sequentially through one of the gas chambers and the flow chamber and the other gas chamber, and in which a filter cell is disposed in the path of the infrared energy beam between the source and one of the gas chambers, the cell containing a gas that absorbs infrared energy in the same region of the spectrum absorbed by the component of interest, whereby irradiation of both gas chambers will modulate the gas flow through the flow chamber at a frequency twice that of the pulsed beam of infrared energy, the electrical circuit including means for tuning the circuit to the modulation frequency.

Claim 10

Apparatus according to claim 10, in which the passages connect the flow chamber to the gas chambers adjacent the ends of the latter.

Claim 11

Apparatus according to claim 10 that also includes a second filter cell disposed in the path of the infrared energy beam between the source and the first gas chamber, said second cell containing a gas absorbing infrared radiation in a first region of the spectrum overlapping a second region absorbed by the component of interest, thereby to counteract interference from background gas in the sample absorbing radiation in said first region.

Claim 12

Apparatus according to claim 1, in which only the first gas chamber is irradiated by a pulsed beam of infrared energy, and that also includes dispersion means disposed in the path of said beam between the source and the first gas chamber for splitting the beam into various component wave lengths, and directing means for causing said component wave lengths successively to traverse the first gas chamber for measuring the infrared absorption at different wave lengths by the gas in that chamber.

Claim 13

Apparatus according to claim 13, in which the dispersion means include an optical prism.

Claim 14

Apparatus according to claim 13, in which the dispersion means include an optical prism and the directing means include means for rotating the prism.

Claim 15

In an infrared gas analyzer of the type in which the component of interest in a gas sample is selectively detected and measured by its absorption of a pulsed beam of infrared energy emitted by a source of such energy, the improvement comprising: first and second gas chambers both of which are adapted to be irradiated by a pulsed beam of infrared energy and to contain the gas sample to be analyzed, a filter cell containing a gas that absorbs infrared energy in the same region of the spectrum absorbed by the component of interest disposed in the path of the radiation beam between the source and one of the gas chambers, first and second gas flow chambers, a separate passage connecting each gas chamber to the first flow chamber and connecting the second gas chamber to the second flow chamber, the passages providing relatively high velocity gas flow in the flow chambers as gas flows from one of the gas chambers in response to the alternate expansion and contraction of gas in at least one of those chambers when subjected to said pulsed infrared energy means for continuously flowing the gas sample sequentially through the first gas chamber and the first flow chamber and the second gas chamber and finally through the second flow chamber, an electrically heated resistance sensor responsive to cooling by gas flow and having a rate of change or resistance that varies inversely with temperature mounted in each of the flow chambers in the path of the high velocity gas flow to enhance the cooling effect of such gas flow by the entrainment of cool gas in the flow chamber, and electrical circuit means for measuring the change in resistance of the sensors when subjected to such gas flow.

Claim 16

Apparatus according to claim 16, in which the passages connect the first flow chamber to the gas chambers adjacent one end of each gas chamber and in which the second flow chamber is connected to the other end of the downstream gas chamber.

Claim 17

Apparatus according to claim 16 that also includes a second filter cell disposed in the path of the infrared energy beam between the source and the other gas chamber, said second cell containing a gas absorbing infrared radiation in a first region of the spectrum overlapping a second region absorbed by the component oF interest, thereby to counteract interference from background gas in the sample absorbing radiation in said first region.