Patent KR-20020060005-A (KR)
Title: Opto-acoustic gas analyzer
Inventor: CHOI JUNG GIL
IPC: G01N21/17
Filed: 2001-01-09
Abstract: PURPOSE: A photoacoustic sensor for measuring exhaust gas is provided to reliably measure concentration of exhaust gas especially at low concentration with simple structure. CONSTITUTION: A photoacoustic sensor includes a light emitting part(210) comprising an infrared light source(210a), a chopper(210b) collecting infrared emitted by the infrared light source to convert into pulse and a narrow-band filter(210c) passing only light with specific wave length among infrared passing the chopper ; an optical cell part(220) comprising a sample cell(220a) connected with the narrow-band filter and injected with sample gas to be measured for the light from the narrow-band filter to pass, a standard cell(220d) connected with the narrow-band filter and injected with standard gas not containing gas components constituting the sample gas for the light from the narrow-band filter to pass, a first reference cell(220b) connected with the sample cell injected with first reference gas containing components same with the gas constituting the sample gas with known concentration for the light from the narrow-band filter to pass, a second reference cell(220c) connected with the standard cell and injected with gas containing components same with gas constituting the sample gas with known concentration different from concentration of the first reference gas for the light from the narrow-band filter to pass, a first reflecting mirror(220e) attached on a wall of an end of the first reference cell and re-reflecting light emitted into a body of the first reference cell and a second reflecting mirror attached on a wall of an end of the second reference cell and re-reflecting light emitted into a body of the second reference cell; a detective part(230) comprising a sample cell microphone(230a) attached on the sample cell and detecting photoacoustic sound of the sample gas to convert into alternating current voltage, a first reference cell microphone(230b) attached on the first reference cell to detect photoacoustic sound of the first reference gas to convert into alternating current voltage, a second reference cell microphone(230c) attached on the second reference cell and detecting photoacoustic sound of the second reference gas to convert into alternating current voltage, a standard cell microphone(230d) attached on the standard cell to detect photoacoustic sound of the standard gas to convert into alternating current voltage, a first piezo sensor(230e) attached between the sample cell and the first reference cell and detecting difference between pressure of the sample cell and the first reference cell to convert into alternating current voltage and a second piezo sensor attached between the standard cell and the second reference cell and detecting difference between pressure of the standard cell and the second reference cell to convert into alternating current voltage; and a signal processing part, electrically connected with the chopper and the detective part removing noise contained in alternating current voltage detected by the detective part and amplifying the alternating current voltage to re-convert into direct current voltage.