Measuring and testing – Gas analysis – By vibration
Patent
1974-09-16
1976-09-21
Queisser, Richard C.
Measuring and testing
Gas analysis
By vibration
G01N 2902
Patent
active
039811760
ABSTRACT:
An apparatus for determining the composition of a gas by measuring the acoustic impedence and absorption of a gas at two distinct frequencies. The velocity variations due to the presence of a gas in a fixed length column are measured by comparing the phase of the voltage applied to a sending transducer to the phase of the voltage in a receiving transducer. Since the distance between the transducers is fixed, the phase variation is indicative of the velocity of the sound at any particular frequency. The output voltage obtained from a phase comparator is proportional to the phase difference and since the relationship between the concentration of the gas and the output voltage is known, the concentration of the gas is easily ascertained. The influence of temperature changes in the column are eliminated by summing the phase differences measured at the two distinct frequencies. In addition, by a judicious choice of frequencies, the amount of water vapor present in a particular gas may be compensated for.
REFERENCES:
patent: 3429177 (1969-02-01), Webb
patent: 3468157 (1969-09-01), Burk et al.
patent: 3789655 (1974-02-01), Passeri
Stott, Review of Scientific Instr., "Sonic Gas Analyzer for Measurement of CO.sub.2 in Expired Air,", vol. 28 No. 11, pp. 914-915, Nov. 1957.
"National Bureau of Standards Tech. News Bulletin, "Propagation of Sound in Monatomic Gases," vol. 40, No. 9, Sept. 1956, pp. 121-124.
Staffin, Control Engineering, "6 Ways to Measure Phase Angle", Oct., 1965, pp. 78-83.
Kreitman Stephen A.
Queisser Richard C.
The United States of America as represented by the Secretary of
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