Hydrophone ZET 351

ZET 351 — robust compact spherical hydrophone for absolute measurement of sounds propagating in operating environment.

  • reversible hydrophone without integrated amplifier;
  • the instrument can be used both as sound receiver and sound generator;
  • suitable for detection of low-power signals in medium frequency range;
  • research of long-distance propagation of acoustic signals.


(price on request)


of hydrophone ZET 351

Technical specifications 
Name of the item ZET 351
Configuration of the product submersible
Nominal sensitivity (by voltage) 160 µV/Pa
Sensitivity level (relative to 1V/µPa) -196 dB
Frequency range 3…25 000 Hz
Electrical capacity (with the integrated cable) min. 33 nF
Package material stainless stell
Dimensions (length × diameter) 150 × ⌀56 mm
Weight (without the cable), max. 400 gr
Standard length of the cable 10 m
Max. length of the cable 250 m
Type of the cable coaxial cable with PVC housing, central conductor, the cable is resistive to environments containing sulphuric acid
Cable plug BNC
Operational environment of measurements performance water, air, oil and petrochemicals, conventional gas
Operational environment temperature 0…+60 °С
Ambient air temperature −60…+80 °С


of hydrophone ZET 351

measurement of:

  • sounds propagating in water;
  • ultrasonic sounds in liquid media;
  • noise in moist and polluted environments;
  • noise in liquid and gaseous media (both in laboratory and industrial environments).

application scenarios

  • as a reference transducer for calibration purposes;
  • as a sound generator;

Installation requirements

for hydrophone ZET 351

The hydrophones should be installed in the relevat mounting  seats of pipes, underwater equipment or walls of pools/ vessels. It is crucial to reduce the gap between the mounting surface and the transducer (which means, that only the sensing element of the transducer should be protruding from the inner wall of the pipe). This mounting technique allows to secure free flow of liquids as well as to reduce acoustic nosie (both hydrodynamic and flow noise).

When installing the hydrophone to the relevant mounting seat, use a wrench and a hex drive of the sensing element. It is not allowed to use any other parts of hydrophone during its installation.

In order to secure hermeticity at the installation place of the hydrophone, use the components included into  delivery scope: end gasket (rubber O-ring). It is not recommended to use other types of sealants (e.g., foam tape, flax fiber), since they are not able to provide the required hermeticity level.

Hydrophone ZET 351 - Layout of the mounting seat
Layout of the mounting seat

Hydrophone ZET 351 - installation instructions
Example of hydrophone ZET 351 installation

Connection scheme

for hydrophone ZET 351

Hydrophone ZET 351 is connected to FFT Spectrum analyzers via charge amplifiers ZET 420 (if the hydrophone is used for sound emission) and ZET 440 (if the hydrophone is used for measurements performance).

Hydrophone ZET 351 - using the hydrophone for measurements performance - connection scheme

Hydrophone ZET 351 - using the hydrophone for sounds emission - connection scheme

In order to connect hydrophone ZET 351 to FFT Spectrum anayzers via charge amplifer ZET 440, it is necessary to configure several parameters so that to secure proper operation of the system.

In the “Configuration” tab of charge amplifier ZET 440 set “×10” as the amplification ratio value.

Then go to the parameters of FFT Spectrum analyzer channel, which is used for connection with charge amplifier ZET 440. In the “Measurement channel” tab of the channel properties set the sensitivity value of the connected hydrophone in compliance with the data sheet of the product.

Charge amplifier ZET 440 - setting the amplification ratio

Establishing connection to the FFT Spectrum analyzer

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