System diagram

The Simrad SN90 system comprises a Processor Unit (computer) with an operating panel, a transceiver and a transducer. As an option, a hull unit can be used for forward-looking installations.


(A) Display  (the second display is optional)
(B) Processor Unit (computer)
(C) Operating Panel
(D) Transceiver Unit
(E) Hull Unit (optional, commonly used on trawlers)
(F) Transducer

The cable between the wheelhouse units and the SN90 Transceiver Unit in the sonar room must be a high-quality Ethernet cable. It can be purchased locally or ordered from us.

Processor Unit

The Processor Unit comprises a single powerful maritime computer. It is provided as a standard part of the delivery. It serves several functions.

The Processor Unit handles the advanced signal processing required to present the information on the display, and it allows you to control the sonar. It provides the graphic presentation of the sonar views and the images that are created, it holds the menu system, communicates with the transceiver circuitry, and reads information from the peripheral units. The computer is based on a commercial design, but the software and hardware have been specified and assembled specifically to meet the sonar requirements.

Operating Panel

The Operating Panel allows you to access to the most frequently used functions in a fast and efficient manner. It also provides a trackball and the necessary control buttons to operate the menu system.

Transceiver Unit

The Transceiver Unit contains the transmission and reception circuitry for the sonar.

The transceiver transmits acoustic energy through the water. This transmission is commonly referred to as a "ping". After each transmission, the transceiver receives the echoes from the targets in the water and/or the seabed. These echoes are filtered and amplified and then converted into digital format.

The connections for power and communication are made under the cabinet. The transducer cable is connected using a large proprietary plug on the side wall.

The Transceiver Unit has been designed to be mounted on the bulkhead in the sonar room. It is fitted with powerful shock absorbers to withstand the violent motions of a vessel at sea.

Hull unit (option)

The optional hull unit is designed to lower the transducer down below the ship’s hull when the sonar system shall be used. When the sonar is turned off, the transducer is hoisted for protection.

The hull unit is a mechanical construction. It is mounted on the top of the installation trunk. The installation trunk penetrates the ship's hull and allows the transducer to be lowered into the sea.

When placed on a hull unit, the transducer housing can be fitted with two hydrophones. Both hydrophones point aft. The hydrophones are connected to a catch monitoring receiver or transceiver.