title: Phase-sensitive method for background-compensated photoacoustic detection of NO2 using high-power LEDs.
abstract: A photoacoustic (PA) sensor has been developed for the detection of nitrogen dioxide (NO(2)). Ten amplitude-modulated high-power light emitting diodes (LEDs), emitting a total optical power of 9 W at 453 nm, are used to excite the photoacoustic signal in NO(2). The LEDs are attached to the circumference of a cylindrical PA cell. The induced longitudinal acoustics waves are detected using two electromechanical film stacks, located at the ends of the cell. Background signal cancelation is achieved by using phase-sensitive detection of the difference signal of the two pressure transducers. The phase-sensitive approach allows for improved dynamic range and sensitivity. A detection limit of 10 parts per billion by volume was achieved for flowing NO(2) gas sample in an acquisition time of 2.1 s, corresponding to a minimum detectable absorption coefficient of 1.6 × 10(-7) cm(-1) Hz(-1/2). The developed sensor has potential for compact, light-weight, and low-cost measurement of NO(2).
authors: Optics Laboratory, Department of Physics, Tampere University of Technology, PO Box 692, FI-33101 Tampere, Finland. jaakko.saarela@tut.fi
authors: Jaakko
authors: J
authors: Saarela
authors: Tapio
authors: T
authors: Sorvajärvi
authors: Toni
authors: T
authors: Laurila
authors: Juha
authors: J
authors: Toivonen