Benthowave Instrument Inc.

BENTHOWAVE INSTRUMENT INC. Acoustic Transducer & System 

Flush-Mounting Transducer

Flush-Mounting TransducerFlush-Mounting TransducerFlush-Mounting TransducerFlush-Mounting Transducer

BII-7720  Flush-Mounting Transducer

BII-7720 series transducers mount through a hole or counterbore hole cut in the housing of underwater instruments, apparatus, vehicles or the wall of swimming pools. The flush-mounting design of these transducers minimizes surface discontinuity and allows for smooth water flow over the surfaces, meaning lower induced acoustic noise (hydrodynamic noise, flow noise), less drag/resistance, avoidance of accidental collision and better acoustic performance for the underwater devices in motion such as towed fish/bodies, ROV/AUV/UUV, robots, etc... Low-profile flush installation protrudes only 4.75mm outside the housing with streamlined flange.

BII-7720 transducers emit and receive conical beams, and are designed for use as components in communication/positioning, navigation, fishery, oceanography, Seafloor-mapping, Marine Animals research, etc....

The housing can be mounted on different materials such as woods, plastics, fiber glass, ceramics and metals. Marine sealants shall be used for sealing, bedding and installation. The depth rating is limited by the sealing performance of the cured marine sealants.

If you do not find any transducer suitable to your project, please contact BII for bespoke designs on size, operating frequency, beam width, mounting, etc...

Technical Notes:
The TVR of the transducer is NOT affected with the cable length.

Receiving Sensitivity Loss Over Extension Cable (dB) = 20*log[Ch/(Ch+Cc)];   Ch - Transducer Capacitance; Cc - Extension Cable Capacitance.
Array directivity function = (directivity function of array element) * (directivity function of array pattern).

Towed Bodies, Vessels in Motion, Sonobuoy
Communication/Remote Control/Telemetry/Positioning
TS & Sv Measurement/Assessment
Sonar Navigation, Inspection and Survey
Object Detection/Tracking/Avoidance
Precision Distance Gage, Altimeter, Liquid Level
Surface Continuity for Low Acoustic Perturbation
Aquarium/Pool/Underwater Security, Alarm System
Bioacoustic Research of Marine Animals, Fishery and Plankton
Sound Velocity Profiler
Bathymetric Sounder, Depth Sounder
FM/Chirp Transducer/Sonar/Fishfinder
High Sensitivity
Broadband (Low Q)
Conical Beam
Low Hydrodynamic/Flow Noise
Easy Installation/Mounting/Removing
20kHz to 2MHz, Single or Dual Frequency
Related Products
Power Amplifier Transmitting and Receiving Switching Impedance Matching and Tuning


Mechanical Size:  No Electronics Mechanical Size: Built-in Electronics Flush-Mounting with Counterbore Hole Low-profile Flush Mounting
Flush-Mounting Transducer Flush-Mounting Transducer  Flush-Mounting Transducer  Flush-Mounting Transducer 


TVR: Transmitting Voltage Response (dB µPa/V at 1m); RVR: Receiving Voltage Response (dB V/µPa);  θ: Beamwidth at -3dB;
fs: Resonant Frequency (kHz); Q: Quality Factor, -3dB Bandwidth=fs/Q; ΦD: Flange Diameter; L: Body Length.
BII-7720 Series Single-Frequency Transducers
Transducer fs
TVR RVR θ Q Maximum
RMS Power
Maximum Wall
Thickness (mm)
BII-7723/22 22 130 -170 160° 3 1000W No 41mm Φ59x80 M35x1.5
BII-7723/25 25 130.5 -170 140° 3 1000W No 41mm Φ59x80 M35x1.5
BII-7723/45 45 132 -175 78° 3 600W No 41mm Φ59x51 M35x1.5
BII-7723/50 50 133 -169 70° 3 600W No 41mm Φ59x51 M35x1.5
BII-7723/70 70 139 -174 50° 3 600W No 29mm Φ59x39 M35x1.5
BII-7723/100 100 142 -177 35° 3 600W -17.7dB 29mm Φ59x39 M35x1.5
BII-7723/120 120 149 -190 29° 3 600W -17.7dB 18mm Φ59x28 M35x1.5
BII-7723/150 150 151 -192.5 23° 3 600W -17.7dB 18mm Φ59x28 M35x1.5
BII-7723/200 200 158 -195 17.5° 3 600W -17.7dB 18mm Φ59x28 M35x1.5
BII-7723/300 300 163.6 -193 12° 3 500W -17.7dB 18mm Φ59x28 M35x1.5
BII-7723/420 420 169 -191 8.3° 3 500W -17.7dB 18mm Φ59x28 M35x1.5
BII-7723/600 600 174 -193 5.8° 3 500W -17.7dB 18mm Φ59x28 M35x1.5
BII-7723/1000 1000 174.3 -207.2 3.5° 3 500W -17.7dB 18mm Φ59x28 M35x1.5
BII-7723/2000 2000 184.6 -216.4 1.8° 3 500W -17.7dB 18mm Φ59x28 M35x1.5
BII-7725/120 120 156 -190 17.6° 3 600W -17.7dB 18mm Φ80x28 M56x1.5
BII-7725/150 150 159 -192.5 14° 3 600W -17.7dB 18mm Φ80x28 M56x1.5
BII-7725/200 200 165 -195 11° 3 600W -17.7dB 18mm Φ80x28 M56x1.5
BII-7725/300 300 172 -193 7.0° 3 600W -17.7dB 18mm Φ80x28 M56x1.5
BII-7725/420 420 178 -191 5.0° 3 600W -17.7dB 18mm Φ80x28 M56x1.5
BII-7725/600 600 181 -193 3.9° 3 500W -17.7dB 18mm Φ80x28 M56x1.5
BII-7727/120 120 163 -190 12° 3 600W -17.7dB 18mm Φ100x28 M76x1.5
BII-7727/150 150 166 -192.5 9.6° 3 600W -17.7dB 18mm Φ100x28 M76x1.5
BII-7727/200 200 172 -195 7.3° 3 600W -17.7dB 18mm Φ100x28 M76x1.5
BII-7727/300 300 179 -193 4.8° 3 600W -17.7dB 18mm Φ100x28 M76x1.5
BII-7727/420 420 185 -191 3.5° 3 600W -17.7dB 18mm Φ100x28 M76x1.5
BII-7727/600 600 186 -193 2.8° 3 500W -17.7dB 18mm Φ100x28 M76x1.5
Miscellaneous: BII-7720 Series Transducers
Beam Pattern: Conical Beam
Impedance Matching: BII-6000, Not included. Order separately, append IM to part number for integrating a Impedance Matching Network in the transducer. Customized to optimum load of the power amplifier: 4Ω to 16Ω, 50Ω, 60Ω, 75Ω, 100Ω, etc...
TR Switch: BII-2100 Transmitting & Receiving Switch. Not Included. Order Separately, Append TR to part number for integrating a T/R Switch in the transducer.
Temperature Sensor: 1. Default: No built-in temperature sensor.
2. Built-in temperature sensor. When ordering, append TS to part number for integrating a temperature sensor in the transducer. Click Temperature Characteristics for more information.
Mounting: Flush Mounting: counterbore hole shall be cut.
Low-profile Flush Mounting: through-hole shall be cut.
Fastening Torque: ≤14Nm, a nut is included.
Marine sealants are NOT included.
Click Transducer and Hydrophone Mounting for more detailed information on mounting/installation.
Marine Sealants: BII does NOT provide Marine Sealants with the transducers. Buyer needs to buy Marine Sealants from buyer's local stores. Generally the stores that sell boats and boat repair part/material have marine sealants in stock, or buyer may use search engine to locate the suppliers online.
Maximum Operating Depth: ≤100m, limited by the sealing performance of the cured marine sealants over the mounting hole.
For deeper underwater deployment (maximum 300m), one option is that O-ring grooves are cut on the mounting wall and O-rings are used besides marine sealants or casting sealants.
Cable: 1. Shielded Cable (SC)
2. RG58 Coax (50Ω)  (Voltage Rating ≤ 50Vrms) (RG58)
Connector Options: 1. Wire Leads (WL)
2. BNC male (50Ω)  (Voltage Rating ≤ 50Vrms) (BNC)
    Warning: It is buyer's sole responsibility to make sure that the (female) BNC shield of the signal source is firmly
    grounded for operating safety before hooking up transducer to the signal source.
Operating Temperature: -10°C to +60°C
Storage Temperature: -40°C to +60°C
How to Order: Click How to Order.
Transducer Wiring: Click Transducer Wiring for detailed wiring information.
Transmitting Array: Array & Aperture Design
Cable Information: Nominal Impedance Cable Information: Nominal Impedance
Shielded Cable, Two Conductors 67 Ω RG58 Coax 50 Ω
Shielded Cable, Two Conductors 90 Ω RG174/U Coax 50 Ω
Shielded Cable, Four Conductors 52 Ω  

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