Fluidic oscillator, incorporating piezoelectric transducer to sense molecular weight of gas mixture, is used to continuously monitor ratio of a mixture of two gases in a flowing system. Device is lightweight, compact, reliable, easy to install, and also produces a simple output signal for controller. Frequency of oscillation is measured and signal converted to ac output

Gorland, S. H.

Leroy, M. J., Jr.

English

NASA Technical Reports Server

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May 1972	 B72-10229 
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NASA TECH BRIEF 
Lewis Research Center	
_4V 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to-the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Continuous Monitor for Gas Ratios in a Mixture 
The problem: 
To devise a unit which will continuously monitor the 
ratio of a mixture of two gases in a flowing system. The 
device must be lightweight, compact, reliable, easy to 
install, and also produce a simple output signal for a 
controller. Ordinarily, a gas sample must be taken and 
an analysis made using a mass spectrometer, but this 
is costly, time consuming, and does not produce a con-
tinuous record. 
The solution: 
• Use a fluidic oscillator incorporating a piezo-electric 
transducer to sense molecular weight of the gas mixture. 
The frequency of oscillation is measured by the trans-
ducer and the signal can be converted to an AC output. 
How it's done: 
A fluidic oscillator operates on the principle that a 
pressure pulse propagates through the feedback loop at 
acoustic velocity. For steady state conditions, the 
acoustic velocity is inversely proportional to the square 
root of the molecular weight of the gas mixture. The fre-
quency output is very stable and the fluidic oscillator 
can be calibrated for any range of temperatures and 
pressures. For changes of ± 15% in molecular weight of 
the mixture, a linear relationship between molecular 
weight and frequency can be used for proportional ad-
justments by a controller.
Notes: 
1. A related application is described in NASA Tech 
Brief 67-10063, "Fluidic Oscillator Used as Humidity 
Sensor." 
2. The following documentation may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Single document price $6.00 
(or microfiche $0.95) 
Reference: NASA TM-X-1939 (N70-17724), 
Sensing Molecular Weights of Gases with a 
Fluidic Oscillator 
Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B72-10229 
Patent status: 
No patent action is contemplated by NASA. 
Source: Sol H. Gorland and
Milton J. Leroy, Jr.
Lewis Research Center 
(LEW-11095) 
(	 ---
JUl. 1313 
KSC ucs. 
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Continuous monitor for gas ratios in a mixture

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