Airmar UDST820 TriSonic Plastic Thru-Hull Transducer - N2K [UDST820P-N2]

UDST820 TriSonic Plastic Thru-Hull Transducer - N2K

TriSonic Smart Sensor combines a depth sensor, ultrasonic speed sensor, water temperature, and heel and trim data into one sensor. It delivers unmatched reliability and accuracy without the need for paddlewheel maintenance. Its ultrasonic speed solution features no moving parts, eliminating cleaning or wear concerns, making it a high-precision, low-maintenance option for power and sailboats of all sizes. The TriSonic Smart Sensor, along with the CAST™ app, simplifies the calibration of speed-through-water. The Airmar CAST™ App connects directly from iOS and Android™ Smart devices to Airmar's Bluetooth® enabled TriSonic Smart™ sensors and makes configuration simple with intuitive menus and guided calibration. View data from the sensor in digital or graphical format, quickly turn on or off NMEA 2000® PGNs, configure offsets and more.

CAST App for Speed and Depth Calibration:

The CAST app provides a simple and consistent way of calibrating speed and depth. Simple offsets can be applied to compensate for the depth below keel or depth from surface. Calibrations and configuration changes are stored in the Airmar Smart Multisensor and delivered to the NMEA2000® network. CAST provides a consistent and reliable way to calibrate basic and heel-compensated speed-through-water with a step-by-step guided process. For advanced speed-through-water calibration, CAST allows you to manually enter custom speed data for up to four heel angles and up to ten speeds. Before CAST, this feature was only available on the market through expensive PC software.

Embrace Ultrasonic Smart technology and leave paddlewheel maintenance behind, brought to you by the innovators of the Smart™ Sensor.

TriSonic Smart Sensor Combines:

• Ultrasonic speed (no paddlewheel)
• Depth
• Water temperature
• Heel and trim data

Features:

• No paddlewheel or moving parts to maintain or replace.
• Provides NMEA 2000® output of calibrated data to every instrument and MFD on the network.
• Advanced speed filtering and sampling rates for enhanced accuracy at all speeds, with data updating up to 5 times per second.
• Patented Adaptive Signal Processing – adjusts to boat speed, water depth, and water clarity for consistent speed accuracy.
• Suitable for both saltwater and freshwater use.
• Easily retrofits into most existing AIRMAR 2" housings.

Connects wirelessly to Airmar's CAST app, offering user-friendly benefits:

• Simplifies speed calibration through your mobile device.
• Offers basic and advanced speed calibration with the ability to manually enter speeds for multiple heel angles and up to 10 different speeds, a feature previously available only through costly PC software

Specifications:

• Bluetooth Capable: YES Bluetooth BLE
• Cable-Length: 6 m (20') NMEA 2000® cable, 6 m (20')
• Comm Method: NMEA 2000®
• Common Use: Cruising/Racing Sailboats, Leisure/Yachting
• Country of Origin: USA
• Data Rate: Up to 10 times per second
• Depth Range: Minimum Depth .6 m ( 2'), Maximum Depth 100 m (328')
• Display Connector: N2 Micro
• Frequency Band: 235 kHz
• Functions: Depth, Speed, Temperature, Attitude
• Hole Size: 51 mm (2")
• Hull Material: Fiberglass or metal
• Material: Plastic
• Max Depth: 0.6 m (2') to 100 m (330')
• Mounting Style: Low Profile Thru-Hull
• NMEA 2000 LEN: 6
• Power Rating: 100 W
• Power Supply Current: 80 mA - 200 mA, Average 125 mA @12VDC
• Retract Method: Manual
• Retractable housing: Yes
• Retrofits: Fits most Airmar 2" housings
• Speed Range: 0.1 to 35 knots (40 MPH)
• Temperature Accuracy: +0.5°C (+1.0°F)
• Tilted Element: No
• Usable Shaft Length: 57 mm (2.25")
• Voltage: 9 to 16 VDC
• Water Temperature: -4° to 40°C (24.8° to 104°F)
• Weight: 1.4 kg (3 lb.)
• Wireless Range: Up to 30' depending on mount location

⚠️ Professional Installation Recommended
Thru-hull transducer installation requires drilling through the hull below the waterline. Airmar strongly recommends this work be performed by a qualified marine technician or boatyard professional. Improper installation may result in water ingress, hull damage, or sensor malfunction. Always consult the full Airmar UDST820 Installation Guide before proceeding.

Installation & Compatibility Checklist (Airmar-Approved)

1. Pre-Drill Planning

• Review the full Airmar UDST820 Installation Guide (available at airmar.com) before starting.
• Select a mounting location on the hull that is fully submerged at all speeds, away from propellers, strakes, and turbulence-generating hull features.
• For sailboats, avoid mounting near the keel or areas prone to heeling-induced air entrainment.
• Ensure the chosen location provides a minimum depth of 0.6 m (2') of water below the sensor face at rest.
• Verify adequate interior access for installation, cable routing, and future servicing.

2. Housing Retrofit Check

• The UDST820 element retrofits into most existing Airmar 2" thru-hull housings — verify your existing housing model is compatible before ordering a replacement housing.
• If replacing a non-Airmar or incompatible housing, plan for a full housing replacement and schedule a haul-out accordingly.
• Inspect the existing housing (if reusing) for cracks, corrosion, worn threads, or seal degradation; replace if any defects are found.

3. Hole Size Verification

• Required hole size: 51 mm (2") — confirm with a calibrated template or hole gauge before drilling.
• Use a hole saw specifically rated for marine composite or metal applications.
• Apply marine-grade sealant (e.g., 3M 4200 or equivalent recommended by Airmar) to the flange and fasteners per the installation guide.
• Do not overdrill; verify pilot hole alignment before committing to the final cut.

4. Hull Material Compatibility

• Compatible hull materials: Fiberglass or metal (per Airmar specification).
• Not recommended for wood, ferro-cement, or composite hulls without consulting Airmar technical support first.
• For metal hulls (aluminum or steel), use an appropriate isolation kit and anti-galvanic sealant to prevent electrolytic corrosion between the plastic housing and metal hull.
• For cored fiberglass hulls, fill the core in the drilling area with epoxy prior to installation to prevent water intrusion into the core material.

5. NMEA 2000® Network Connection

• The UDST820 connects via the included 6 m (20') NMEA 2000® Micro cable.
• Confirm your N2K network backbone is powered (9–16 VDC) and properly terminated at both ends with 120-ohm terminator plugs.
• NMEA 2000 Load Equivalency Number (LEN) for this sensor: 6 — verify your network backbone and power tap can support this load alongside existing devices.
• Snap the Micro connector into an available T-connector on the backbone; do not splice or extend with non-NMEA 2000 cable.
• After connection, confirm the sensor appears on the network via your MFD's device list.

6. Calibration with the Airmar CAST™ App

• Download the free Airmar CAST™ app (iOS and Android) prior to first use.
• Enable Bluetooth on your mobile device and position it within 30 feet of the sensor (Bluetooth BLE range).
• Open CAST, select the UDST820, and follow the guided setup to configure PGN outputs, set depth offset (below keel or from surface), and apply speed-through-water calibration.
• For basic calibration: perform at a known steady speed on calm water and apply the CAST speed offset.
• For advanced calibration: manually enter speed values for up to 4 heel angles and up to 10 speed points for maximum accuracy on sailboats.
• Confirm calibrated data is appearing correctly on all MFDs and instruments on the N2K network before departing the dock.

7. Post-Installation Checks

• With the vessel still in the slip, inspect the thru-hull fitting and all sealant areas for any signs of weeping or seepage.
• Confirm the retractable housing retracts and locks properly.
• Conduct an initial sea trial at low speed to verify depth, speed, and temperature readings; compare to known references where possible.
• Log calibration settings in the CAST app and retain a copy of the installation guide onboard for future reference.