Patent ID: 8351040

Claim:
A method of measuring the presence of a gas in an air sample using a cavity ring down system, comprising: when no sample is introduced into the system: measuring an output voltage from a plurality of currents resulting from light introduced into an optical cavity when a light source is ON during a predetermined interval of a rise time of the light wherein the resulting measurement is a reference rise time measurement; measuring an output voltage from a plurality of currents resulting from light introduced into the optical cavity when the light source is OFF during a predetermined interval of a fall time of the light wherein the resulting measurement is a reference fall time measurement; measuring an output voltage from a plurality of currents resulting from light introduced into the optical cavity when a light source is ON during the rise time of the light wherein the resulting measurement is a reference steady state rise time measurement; and measuring an output voltage from a plurality of currents resulting from light introduced into the optical cavity when a light source is OFF during the fall time of the light wherein the resulting measurement is a reference steady state fall time measurement; wherein the reference rise time measurement, the reference fall time measurement, the reference steady state rise time measurement, and the reference steady state fall time measurement are used to calculate the amount of gas in the air sample by a computer.