Absolute calibration technique for broadband ultrasonic transducers

US5325339A · kind A · utility

Assignee

• The United States of America as represented by the Administrator of the National Aeronautics and Space Administration · US

Inventors

• William T. Yost · Newport News, US
• John H. Cantrell · Williamsburg, US

Key dates

• Filing date: Aug 31, 1993
• Grant date: Jun 28, 1994
• Expiry date: Aug 31, 2013

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N29/30
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Calibrating an ultrasonic transducer can be performed with a reduced number of calculations and testing. A wide-band pulser is connected to an ultrasonic transducer under test to generate ultrasonic waves in a liquid. A single frequency is transmitted to the electrostatic acoustic transducer (ESAT) and the voltage change produced is monitored. Then a broadband ultrasonic pulse is generated by the ultrasonic transducer and received by the ESAT. The output of the ESAT is amplified and input to a digitized oscilloscope for Fast Fourier Transform. The resulting plot is normalized with the monitored signal from the single frequency pulse. The plot is then corrected for characteristics of the membrane and diffraction effects. The transfer function of the final plot is determined. The transfer function gives the final sensitivity of the ultrasonic transducer as a function of frequency. The advantage of the system is the speed of calibrating the transducer by a reduced number of measurements and removal of the membrane and diffraction effects.