Abstract
This paper describes a system for measuring the flow velocity and temperature of gases by means of a photothermal effect. We used a differential interferometer for suppressing the influence of external disturbances and detecting small phase variation caused by the photothermal effect. The operating point is set at the maximum inclination point of fringe intensity curve by controlling the position of a photodetector. This system uses two focal spots as measuring points of time-of-flight method. The interferometer signals are analyzed for obtaining propagation velocity of photoacoustic pulse and velocity of photothermal puff. Using jets of a gas mixture of nitrogen and ethylene, we confirmed that this measurement system is useful to measure the flow velocity and temperature.
