Abstract :
The operation of the instrument described is based on the variation of the velocity of sound in a mixture of two gases, with the proportions of the mixture. The velocity of sound is determined at a fixed temperature by measuring the resonance frequency of a double Helmhoitz resonator containing the mixture. The source of the sound is a diaphragm driven electromagnetically from a variable-frequency oscillator; a similar transducer followed by an amplifier and rectifier form the resonance detector. The method of continuous recording of the mixture proportions, is also described. In this, the gas mixture flows through the resonator, and a simple servo-mechanism is used to maintain the condition of resonance and to operate the recorder.
