Amplitude and phase calibration of hydrophones up to 70 MHz using broadband pulse excitation and an optical reference hydrophone

Abstract

A substitution calibration technique for piezoelectric ultrasonic hydrophones is presented that uses an optical multilayer hydrophone as the reference receiver. Broadband nonlinearly distorted focused pulses are first measured with the reference hydrophone and then with the hydrophone to be calibrated. By Fourier transformation of the time wave forms and division of the frequency spectra, the complex-valued frequency response of the hydrophone under test is obtained in a broad frequency range in a very fast and efficient way and with high frequency resolution. The results obtained for a membrane hydrophone and a needle-type hydrophone are compared with those obtained by independent calibration techniques such as primary calibration using optical interferometry and secondary calibration using time-delay spectrometry, and good agreement is found. The calibration data obtained are apt to improve the results of ultrasound exposure measurements using broadband voltage-to-pressure conversion. This is demonstrated for standard pulse parameter determination from exemplar exposure measurements on a commercial diagnostic ultrasound machine. For the membrane hydrophone, the evaluation method commonly used leads to an overestimation of the positive peak pressure by up to 50%, an underestimation of the rarefactional peak pressure by up to 11%, and an overestimation of the pulse intensity integral by up to 28%.

Evaluation of dynamic measurement uncertainty – an open-source software package to bridge theory and practice

“…Dynamic measurements are encountered in a wide range of application areas, covering, for instance, single sensors to complex sensor networks, and measured quantities changing on scales from picoseconds up to several minutes. Examples of dynamic measurements of mechanical quantities can be found in, for instance, (Link et al, 2005) for acceleration, in (Schlegel et al, 2012) and for force, in for torque and in (Gardner, 1981), (Matthews et al, 2014) and (Wilkens and Koch, 2004) for pressure. A more general overview on the current state of dynamic measurements in industrial applications is given in (Schäfer, 2015).…”

Calibration and measurement issues for therapeutic ultrasound

“…See Section 3.6 for discussion of the frequencyweighted pressure. [93][94][95][96]. So far, it seems that deconvolution to determine temporal-average intensity is relatively straightforward because it requires knowledge only of the amplitude response.…”

Primary reciprocity-based method for calibration of hydrophone magnitude and phase sensitivity: Complete tests at frequencies from 1 to 7MHz

“…Regarding sensitivity phase calibration, the literature reports some approaches claiming the merit of being able to disclose the sensitivity phase as well, although the reported methods are mainly of comparison, instead of absolute, i.e., there is a need of a calibrated device to depict the hydrophone phase sensitivity. These approaches rely on time delay spectrometry [10][11][12][13][14][15][16] or optical reference hydrophone [17][18][19][20].…”