A photodetector for the diagnostics of turbulent gas flows and flames by the method of absorption spectroscopy with diode lasers

Abstract

A photodetector device that is intended for absorption measurements at a level of 10^–2–10^–3 under the conditions of large intensity fluctuations of probing radiation, nonstationary broadband illumination of the photodetector, and in the presence of electromagnetic interference is described. Using a differential measurement circuit, an absorption signal is formed in the analog manner and amplified to a level of ~1 V directly near the photodetector. During periodic wavelength scanning, the influence of the broadband illumination and vibrations is compensated at the beginning of each scan. This compensation is preserved during a current scan and renewed in each subsequent scan due to the use of sample-and-hold amplifiers. The device can be used in the diagnostics of turbulent gas flows and flames.