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Ultrasonic Pressure Gauge for Static Pressure

IP.com Disclosure Number: IPCOM000075669D
Original Publication Date: 1971-Oct-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Hoechli, UT: AUTHOR [+3]

Abstract

To measure static pressure between 1 and 10/4/kp/cm/2/, with an accuracy of 0,1% in an extremely wide temperature range from a few degrees Kelvin up to about 1000 degrees K parametrically the acoustic path length of two identical solid samples is compared, one of these samples being under stress.

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Ultrasonic Pressure Gauge for Static Pressure

To measure static pressure between 1 and 10/4/kp/cm/2/, with an accuracy of 0,1% in an extremely wide temperature range from a few degrees Kelvin up to about 1000 degrees K parametrically the acoustic path length of two identical solid samples is compared, one of these samples being under stress.

Acoustically, two composite resonators - each consisting of a transducer and a delay line - are coupled in series. Ultrasonic waves are excited by a transducer common to both resonators. It is connected via a resistor to an RF generator. RF is tuned to resonance of the acoustic cell. Application of pressure upon the probe resonator now causes detuning with respect to the reference sample resonator. The resulting variation of the acoustic impedance is detected by a receiving amplifier coupled to the RF connection line. The demodulated RF signal received is fed to a voltage meter. From the measured voltage value the pressure value can be deduced, after suitable calibration.

With losses neglected, the equivalent acoustic impedance of both resonators coupled in series is given by equation (1) above. In this equation the values of 2 are represented by equation (2), and Z' is analogous with all the variables primed. The indices S and T denote sample and transducer, respectively. Xi = density, V = velocity, Theta = omega l/V, omega = frequency, l = sample length.

In case of resonance, e.g. no pressure applied, a loss-free impedance...