On many motorboats, a traditional log with a paddle wheel measures the speed through the water. If the small wheel no longer rotates freely – for example, due to fouling or dirt – the reading becomes unreliable. That is why Airmar has opted for ultrasonic technology in its new TriSonic. The sensor is designed for boats with an NMEA-2000 network, on which depth, temperature and speed data are to be displayed centrally on a multifunction display.
No cleaning of the impeller
Anyone familiar with a traditional log is usually aware of the downside: the paddle wheel must be able to turn freely. Mussels, seaweed or dirt can distort the reading or stop it altogether. The TriSonic has no moving parts. According to Airmar, the signal processing adjusts the measurement to take account of speed, water depth and water quality.
The sensor measures speed through the water from 0.1 to 35 knots. It also provides depth readings from 0.6 to 100 metres, water temperature and attitude data for heel and trim. The readings are transmitted via NMEA 2000 to plotters and other instruments in the vehicle electrical system. The sensor thus complements systems such as those found, for example, in modern chartplotters in the cockpit be used.
Calibration via smartphone
The TriSonic connects via Bluetooth to the Airmar CAST app for iOS and Android. In the app, you can set depth offsets, for example to display depth below the keel or from the water’s surface. The log can also be calibrated using the app.
For further customisation, according to Airmar product page You can store up to four heel angles and ten speed values. This is useful for sailing yachts, as the yacht’s attitude and the flow around the hull can affect speed measurements. The settings are stored in the sensor and are then available throughout the NMEA 2000 network.
The TriSonic is a retractable plastic through-hull transducer for GRP and metal hulls. It requires a 51-millimetre borehole and is designed to fit into most existing Airmar inch-sized housings. Whilst this may make replacement easier, it does not replace the need to check the installation position, hull material and existing sleeve.
Technical Specifications
| Characteristic | Information |
| Measurements | Speed, depth, water temperature, heel, trim |
| Speed range | 0.1 to 35 kn |
| Depth range | 0.6 to 100 m |
| Network | NMEA 2000 |
| Furnishings | Bluetooth via Airmar CAST |
| Installation opening | 51 mm |
| Design type | Retractable plastic break-through sensor |
Of interest for retrofitting
The TriSonic really comes into its own where regular maintenance of a paddlewheel log is difficult, for example in areas with heavy vegetation. The ultrasonic transducer combines four measurement functions in a retractable through-hull transducer and transmits the data directly to the NMEA-2000 network. Whilst this does not necessarily reduce the number of individual sensors on the hull in every system, it can make retrofitting a clearer process.
For yacht owners who are already connecting their instruments or transferring data to a Smartboat system for remote monitoring When it comes to integration, the TriSonic is an attractive retrofit option, particularly due to its low-maintenance speed measurement.
Book recommendation
Theory and Practice of Vehicle Electrical Systems explains the electrical equipment on a yacht, from batteries and charging systems through to installation and troubleshooting. The book also covers log, depth sounder and chart plotter. For yacht owners who wish to integrate a new sensor into the NMEA-2000 network or who want to better understand the on-board electrical system when carrying out retrofitting work, it provides the basics for planning, selecting materials and ensuring safe implementation.
What experience have you had with paddlewheel logs and fouling, and would an ultrasonic transducer be a viable alternative for your yacht?
Michael Rinck
Redakteur Test & Technik
