Apparatus for measuring no{11 {11 concentrations

Claim 2

APPARATUS FOR ANALYZING A GASEOUS SAMPLE FLOW TO MEAURE THE CONCENTRATION OF A CONSTITUENT OF THE FLOW WHICH REACTS IN A CHEMILUMINESCENT MANNER WITH OZONE, SAID APPARATUS COMPRISING: A SAMPLE CHAMBER; PHOTODETECTOR MEANS FOR DETECTING LIGHT IN SAID CHAMBER AND GENERATING A SIGNAL WHICH IS RESPONSIVE THERETO; MEANS FOR PROVIDING A CONTINUOUS FLOW OF THE GASEOUS SAMPLE INTO THE CHAMBER; MEANS FOR PROVIDING A CONTINUOUS FLOW OF A REACTION GAS INCLUDING OXYGEN; MEANS, INCLUDING AN ELECTRICALLY ENERGIZABLE OZONATOR, FOR COUPLING THE FLOW OF REACTION GAS TO SAID CHAMBER FOR REACTION WITH THE SAMPLE GAS FLOW, SAID OZONATOR BEING OPERATIVE, WHEN ENERGIZED, TO CONVERT AT LEAST A PORTION OF THE OXYGEN IN SAID REACTION GAS FLOW TO OZONE; MEANS FOR PERIODICALLY ENERGIZING SAID OZONATOR; AND MEANS FOR MEASURING THE COMPONENT OF THE PHOTODETECTOR SIGNAL WHICH VARIES PERIODICALLY WITH THE SAME FREQUENCY AS TTHE PERIODIC ENERGIZATION OF SAID OZONATOR, THE MEAS-

Claim 3

Apparatus as set forth in claim 1 wherein said photodetector means comprises a photomultiplier.

Claim 4

Apparatus as set forth in claim 1 wherein said ozonator is of the silent discharge type.

Claim 5

Apparatus as set forth in claim 1 wherein said reaction gas is dry air.

Claim 6

Apparatus as set forth in claim 1 wherein the frequency of energization of said ozonator is about 0.5 cycles per second.

Claim 7

Apparatus as set forth in claim 1 wherein said ozonator is energized by a step-up transformer driven from a.c. mains through a triac and wherein conduction through said triac is controlled by a timer.

Claim 8

Apparatus as set forth in claim 6 wherein said timer is a free-running electronic oscillator.

Claim 9

Apparatus as set forth in claim 1 wherein said measuring means comprises a synchronous detector.

Claim 10

Apparatus as set forth in claim 8 wherein said synchronous detector is provided with a timing signal which is delayed with respect to the periodic energization of said ozonator.

Claim 11

Apparatus for analyzing a gaseous sample to measure the concentration of NOx compounds, said apparatus comprising: a sample chambEr; a photomultiplier for detecting light produced in said chamber and generating a signal which is responsive thereto; means for providing a continuous flow at a predetermined rate of the gaseous sample into the chamber; means for providing a continuous flow of air at a predetermined rate; means including an electrically energizable ozonator for converting at least a portion of the oxygen in the air flow to ozone, the flow from said ozonator being coupled into said reaction chamber; timing means for periodically energizing said ozonator; and detector means controlled by said timing means for measuring the component of the photodetector signal which varies periodically with the same frequency as the periodic energization of said ozonator, the measurement so obtained being indicative of the concentration of NOx compounds in the gaseous sample.

Claim 12

Apparatus for analyzing a gaseous sample to measure the concentration of NOx compounds, said apparatus comprising: a sample chambEr; a photomultiplier for detecting light produced in said chamber and generating a signal which is responsive thereto; means for providing a continuous flow at a predetermined rate of the gaseous sample into the chamber; means for providing a continuous flow of air at a predetermined rate; means including an electrically energizable ozonator for converting at least a portion of the oxygen in the air flow to ozone, the flow from said ozonator being coupled into said reaction chamber; timing means for periodically energizing said ozonator; and detector means controlled by said timing means for measuring the component of the photodetector signal which varies periodically with the same frequency as the periodic energization of said ozonator, the measurement so obtained being indicative of the concentration of NOx compounds in the gaseous sample.

Claim 13

Apparatus as set forth in claim 10 wherein said timing means includes a free-running electronic oscillator.

Claim 14

Apparatus as set forth in claim 11 wherein said detector means comprises a synchronous detector and wherein the signal obtained from said oscillator is delayed to provide a reference signal for said synchronous detector.