Patent ID: 8098377
Filing Date: 2012-01-17
Classification: G01N,Y02A

Abstract:
1. A method of measuring the presence of a gas in an air sample using a cavity ring down system having an optical cavity, comprising: collecting a first plurality of currents with a detector during a predetermined time period resulting from light introduced into the optical cavity when a light source is ON and while no sample is being introduced into the optical cavity; measuring the first plurality of currents; collecting a second plurality of currents with a detector during a predetermined time period when the light source is turned OFF and while no sample is being introduced into the optical cavity; measuring the second plurality of currents; summing the first plurality of currents to obtain a reference integrated rise time; summing the second plurality of currents to obtain a reference integrated fall time; collecting a third plurality of currents with a detector during a predetermined time period resulting from light introduced into the optical cavity when a light source is turned ON and while the air sample is being introduced into the optical cavity; measuring the third plurality of currents; collecting a fourth plurality of currents with a detector during a predetermined time period when the light source is turned OFF and while the air sample is being introduced into the optical cavity; measuring the fourth plurality of currents; summing the third plurality of currents to obtain a sample integrated rise time; summing the fourth plurality of currents to obtain a sample integrated fall time; using the reference integrated rise time, the reference integrated fall time, the sample integrated rise time and the sample integrated fall time to calculate an amount of absorbing gas present in the air sample.