Title :
Surface-acoustic-wave (SAW) flow sensor
Author :
Joshi, Shrinivas G.
Author_Institution :
Dept. of Electr. & Comput. Eng., Marquette Univ., Milwaukee, WI, USA
fDate :
3/1/1991 12:00:00 AM
Abstract :
The use of a surface-acoustic-wave (SAW) device to measure the rate of gas flow is described. A SAW oscillator heated to a suitable temperature above ambient is placed in the path of a flowing gas. Convective cooling caused by the gas flow results in a change in the oscillator frequency. A 73-MHz oscillator fabricated on 128 degrees rotated Y-cut lithium niobate substrate and heated to 55 degrees C above ambient shows a frequency variation greater than 142 kHz for flow-rate variation from 0 to 1000 cm/sup 3//min. The output of the sensor can be calibrated to provide a measurement of volume flow rate, pressure differential across channel ports, or mass flow rate. High sensitivity, wide dynamic range, and direct digital output are among the attractive features of this sensor. Theoretical expressions for the sensitivity and response time of the sensor are derived. It is shown that by using ultrasonic Lamb waves, propagating in thin membranes, a flow sensor with faster response than a SAW sensor can be realized.<>
Keywords :
detectors; flow measurement; flowmeters; surface acoustic wave devices; ultrasonic applications; 73 MHz; LiNbO/sub 3/ substrate; SAW flow sensor; SAW oscillator; channel ports; direct digital output; frequency variation; mass flow rate; pressure differential; rate of gas flow; response time; sensitivity; thin membranes; ultrasonic Lamb waves; volume flow rate; wide dynamic range; Cooling; Fluid flow; Fluid flow measurement; Frequency; Lithium niobate; Oscillators; Pressure measurement; Surface acoustic waves; Temperature sensors; Volume measurement;
Journal_Title :
Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on
