Inquiry — Custom piezoelectric elements

Flat housing-integrated transducers for compact underwater communication device

Sergej Koch — April 2026

We are developing the successor to our previous-generation underwater acoustic communication device for scuba diving (Buddy-Watcher). The new product targets 10–50 m in-water range, using a soft PZT disc integrated on the inside of the enclosure wall, coupled to water via the housing material and an impedance-matching bonding layer. The previous design used a piezo tube with material equivalent to CTS (former Ferroperm) Pz29 / Pz27; the new design moves to a flat disc geometry at higher frequency.

Target integration concept

Sensor integration concept — Previous design (left): ring ceramic mounted externally, with dedicated pre-sealing. New design (right): flat elements bonded to the inside of the housing with RTV dampening backing and cyanoacrylate bonding. Positions 1, 2 and 3 represent candidate sensor locations; the final array will be one combined TX/RX element plus one or two receive-only elements for direction-sensing.

Specifications at a glance

Parameter	Target / range
Geometry	Flat disc (not ring), bonded inside the housing wall; bidirectional TX/RX
Diameter	8–10 mm preferred, 12 mm maximum
Thickness	< 10 mm (target ~9 mm; the more compact, the better)
Resonance frequency (thickness mode)	200–300 kHz
Material class	Soft PZT (PZT-5H / PZT-5A class). Reference: Pz29 / Pz27 equivalent. Open to your portfolio recommendation.
Mechanical Q (Qm)	< 100 — most important parameter (required for wide bandwidth operation)
Target bandwidth	8–10+ kHz at –6 dB (in water, after potting)
Electromechanical coupling kt	> 0.45
Charge coefficient d₃₃	> 400 pC/N
Electrodes	Silver (Ag) — consistent with previous design
Operating mode	Bidirectional pulsed (same element transmits and receives)
Drive topology	Push-pull via 1:N step-up transformer from 3.7 V Li-Ion; peak drive current 500–800 mA
Duty cycle	Very low — packet bursts of 100–300 ms, occasional 10 s SOS bursts, <1 % cumulative
Integration	Disc bonded to inside of housing wall via cyanoacrylate; acoustic matching layer (recommendation welcomed); RTV silicone backing for damping
Operating temperature	0–40 °C
Lifetime target	≥5 years, ~500 operating hours per year in saltwater environment
Design priorities	(1) wide beam angle for communication, (2) compact form factor

Note on frequency–thickness coupling: Resonance frequency f relates to disc thickness h via f = Nt / h. For soft PZT in the PZT-5A/5H class (Nt ≈ 1900–2050 kHz·mm), 9 mm thickness gives ~210–230 kHz; 7 mm gives ~270–290 kHz. The target band (200–300 kHz) is well covered within the <10 mm thickness constraint.

Volumes

Prototype / sampling	Small series	Production (annual)
20–50 pieces	200–500 pieces	2,000–5,000 pieces / year

Questions

Could you propose suitable standard or custom models from your portfolio? Please provide where available: resonant frequency (fs / fa) — our drive electronics will be tuned to the transducer; capacitance at 1 kHz; impedance curve (or full impedance data); sensitivity (dB re 1 µPa/V or equivalent); maximum operating voltage. Datasheet or test report welcomed. We are open to fully custom specifications.
Can you support us in the acoustic matching-layer design between the element and the housing wall?
Indicative pricing and lead times for prototype, small series, and production quantities?

Sergej Koch
Wilhelm-Haug-Str. 7, 69181 Leimen, Germany
sergej.koch@nq7sk.com · +49 176 41067197
More detailed technical specifications including driver circuit topology, packet structure, and housing drawings available under NDA.