Page 22 - HydrophoneHandbook_eReader_Ed2_20151208
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Hydrophone Handbook

         Choosing a Hydrophone

 • HNP and HNC: intended to be used for Doppler modes of
         less than 720 mW/cm2.

 • HNA: intended to be used for pressure amplitudes
         representative of HIFU applications. These devices are
         tested at the focus of a 1.5 MHz source, operated at 50%
         duty cycle in deionized, degassed water at 23 degrees C.
         This provides an exposure intensity of 715 W/cm2
         temporal-average and 1430 W/cm2 pulse-average,
         corresponding to 15 MPa peak compressional and 3.7
         MPa rarefactional pressure.

 • HFO: intended to be used for very high pressure
         applications such as lithotripsy. Successful measurements
         have been made up to 75 MPa (P+) and -11 MPa (P-)
         under controlled environment.

 All these results were obtained in well-degassed water with an
 oxygen concentration less than 4 ppm.
 Users are advised that many models may work at higher
 pressures, but when measuring under such conditions, users
 need to carefully monitor signals on the oscilloscope for
 instability of the hydrophone signal. If any flickering or
 waveform unsteadiness is observed, the driving levels should be
 reduced.

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