Broadband electrostatic acoustic transducer for ultrasonic measurements in liquids.
A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing. The membrane functions as the ground plate of a parallel plate capacitor, the other plate being a dc biased electrode recessed approximately 10 mum from the electrically grounded membrane. An ultrasonic wave incident on the membrane varies the membrane-electrode gap spacing and generates an electrical signal proportional to the wave amplitude. The entire assembly is sealed for immersion in a liquid environment. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 15 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. The use of the ESAT as a broadband ultrasonic transducer in liquids with a predictable frequency response is promising.
Cantrell
J H
JH
NASA Langley Research Center, Hampton, Virginia 23665Department of Physics, University of Tennessee, Knoxville, Tennessee 37916.
Heyman
J S
JS
Yost
W T
WT
Torbett
M A
MA
Breazeale
M A
MA