HM-series Membrane Hydrophone

The HM-series membrane hydrophones are the gold standard for pulsed wave imaging applications that require a flat response over a broad bandwidth.

Key Features and Benefits
  • Flat response over a broad bandwidth
  • High Sensitivity
  • Integral preamplifier with sealed design
  • Optional backing and aperture sizes
The HM Series membrane hydrophones are designed for measuring pulsed ultrasound fields. Their extremely flat sensitivity results in the best reproduction of acoustic waveforms. An unbacked version, based on a traditional configuration, can withstand relatively higher power measurements, while a more rugged backed version prevents membrane vibration during scanning motion. Both types are excellent choices as in-house primary or secondary standards.
HMA-0200 HMA-0500 HMB-0200 HMB-0500
Frequency range (±3dB) 0.5 to 45 MHz
Nominal Sensitivity [dB re 1V/μPa] * -260 -248 -256 -244
Nominal Sensitivity [nV/Pa] 100 398 158 631
Max Pressure (p-p) within Linearity Range of Integral Preamp (MPa) ** 53 12 25 7
Output Impedance >50 Ω
Max. Operating Temperature 40 °C

* Provided with traceable calibration 1-20 MHz at 50 KHz intervals. For other calibrations available visit our web site.
** Based on criterion defined by the International Electrotechnical Commission (IEC)
Specifications are subject to change without notice.

What is the difference between an HMA and HMB hydrophone?

The HMB is an HMA back-filled with absorbing material. The backing dampens vibrations of the membrane which may occur during scanning. Free membrane hydrophones are susceptible to this issue, and it is commonly suppressed either by waiting for the vibrations to dampen before taking a measurement, or by using cross-correlation to filter them out. Because both of these solutions require additional time, the HMB is a good option for setups that use motorized scanning. The only other significant performance difference between the HMA and HMB designs is that the HMB is more sensitive. As mentioned in our datasheet, the HMB-0200 is about 4 dB more sensitive than the HMA-0200.

Do I need an amplifier with the membrane hydrophone?

No, the HM hydrophone consists of an integral amplifier.

How does the resistivity of the water affect membrane hydrophone measurements?

When measuring with unbacked membrane hydrophones, it is recommended to use high resistivity water because conducting water becomes a capacitive shunt across the device, which affects low frequency readings. A minimum of 0.2 MΩ -cm is recommended. Use of fresh deionized or distilled water is encouraged since it typically has a high resistivity of 1 MΩ-cm or more. Routine checks of conductivity will ensure accuracy in the measurements.

Related Resources

HM Hydrophones Data Sheet

HM Hydrophones Data Sheet

Get technical specs and information for the AIMS III the latest generation hydrophone scanning system.

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Hydrophone Handbook

Hydrophone Handbook

Learn how to select the best hydrophone for your application.

Read Handbook

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