Patent ID: 8098376

Claim:
A method comprising: generating a first waveform at a first modulation frequency using a direct digital synthesis (DDS) algorithm; and dividing the first waveform into a plurality of second waveforms at a plurality of second modulation frequencies using a plurality of frequency dividers, wherein the second modulation frequencies comprise a light source modulation frequency that is used to control the frequency of a light source, a first in-phase modulation frequency and a first quadrature modulation frequency that are used to detect absorption of a first portion of the light source by a sample compound, and a second in-phase modulation frequency and a second quadrature modulation frequency that are used to detect absorption of a second portion of the light source by a reference concentration of the sample compound, and wherein a frequency initially used to modulate the light source is equal to about f, wherein the first modulation frequency is equal to or greater than about 12f, wherein the light source modulation frequency is equal to about f, wherein additional timing waveforms comprise the first in-phase modulation frequency, the first quadrature modulation frequency, the second in-phase modulation frequency, and the second quadrature modulation frequency, wherein the first in-phase modulation frequency is equal to about 2f, wherein the first quadrature modulation frequency is equal to about 2f+90 degrees, wherein the second in-phase modulation frequency is equal to about 3f, and wherein the second quadrature modulation frequency is equal to about 3f+90 degrees.