SAL T3 combines the speed log features with echo sounding – measuring longitudinal relative speed through water as well as two-axis true speed over ground and water depth down to 250 metres.
The SAL T-series is the first type-approved combination of speed log and echo sounder in one housing using only one combined transducer. In combination with an external Rate of Turn Gyro a full docking log functionality is achieved.
Electronics Unit – ELC
The ELC controls the measurements of the system. It contains two independent units, one unit for speed through water and another for depth and speed over ground measuring. Also the depth and the speed over ground systems have full redundancy. Both measuring functions are based on the acoustic correlation principle. The basic concept is the measurement of the time delay between the characteristics of reflected sonic pattern sensed by the receivers. The time delay from transmission till echo reception is used for depth estimation. Echo signal modulation is used for speed estimation. The speed is estimated from the fix distance between sensor elements divided by the estimated time delay from correlation, where two signals are compared by shifting one relative to the other in time, and choosing the time shift where the maximum similarity is found. The data calculated in the ELC is sent as serial IEC61162-1 / NMEA messages for further processing in the LPU.
Transducer – TRU
The combined transducer is mounted in a sea valve arrangement suitable both for single and double bottom designs. The transducer incorporates as standard a 30 metres cable for connection to the ELC. By means of separate crystals, both relative water speed and true speed over ground and water depth are measured. The crystals work both as transmitters and receivers.
Log Processing Unit – LPU
The LPU is mounted on the wheelhouse area and receives the NMEA message from the ELC. The LPU has various options to perform message conversion and calculations and has also variety of inputs for receiving data from other units. Various outputs are available for external users, such as autopilot, radar, AIS, VDR, fin stabilizers, etc.
Serial Digital Indicators – SD4
The SD4 series of indicators gives a flexible solution to the presentation of longitudinal and transverse speeds, distance and depth measurement or docking information.
Echo Sounder Display – ESD2
The ESD gives a comprehensive graphic overview of the echo sounder presentations, as well as provides 24 hours history review.