Multi-frequency photo-acoustic detector

摘要

An apparatus and process for detecting a single specific chemical solid or gas in the presence of other chemical solids or gases or for detecting a number of specific mixed chemical solids or gases. The apparatus and process passes multiple beams of electromagnetic radiation incident on the material in a sample chamber producing acoustic signals at specific frequencies when light of specific wavelengths is absorbed. The electromagnetic radiation is selected to have wavelengths corresponding to optical absorption features of at least one specific chemical in the sample chamber. The acoustic signals are detected by at least one beat tone or combination tone characteristic of and representative of the degree of absorption by a specific chemical or multiple specific chemicals desired to be detected. The apparatus and process are especially useful in leak detection in natural gas systems and for detection of pollutants, explosive gases and the like.