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Simrad ST90
System units
Hull Unit – description
The hull unit is used to lower the transducer down below the ship’s hull when the ST90 system shall be used. When the ST90 system is turned off, the transducer is hoisted for protection. The hull unit is large and crucial part of the sonar system.

About this manual
The purpose of this publication is to provide the descriptions, procedures and detailed parameter explanations required to allow for safe and efficient use of the ST90 system. The publication also provides you with a thorough understanding of the parameters and adjustments provided by the ST90 system.
Simrad ST90
- Important
  The ST90 is an advanced product. It is used with other advanced products. There is important information that you need to know.
- System description
  The Simrad ST90 is a low-frequency fish-finding sonar with 360-degree coverage and long range. The ST90 system is designed for medium and large sized fishing vessels.
- System diagram
  The system diagram identifies the main components of a basic ST90 system. Only the main connections between the units are shown. Detailed interface capabilities and power cables are not shown.
- System units
  - Display – description
    A display is a required part of the ST90 system. For best readability, the display must be protected from glare and have the correct height and angle.
  - Processor Unit – description
    A dedicated maritime computer is provided. In this publication, the computer can also be referred to as the Processor Unit, and vice versa.
  - Operating panel – description
    The optional Operating Panel contains all necessary control functions for normal operation of the ST90 system.
  - Transceiver Unit – description
    The Transceiver Unit is provided to transmit acoustic energy through water. After each transmission, the transceiver receives the echoes from the seabed and/or the water column. These echoes are filtered, amplified and finally converted into digital format. This transmission and reception sequence is commonly referred to as a ping.
  - Hull Unit – description
    The hull unit is used to lower the transducer down below the ship’s hull when the ST90 system shall be used. When the ST90 system is turned off, the transducer is hoisted for protection. The hull unit is large and crucial part of the sonar system.
  - Transducer – description
    The cylindrical transducer allows the sonar beam to provide a full 360 degrees coverage of the water volume.
- General safety rules
  Safety is important. Observe and follow these safety precautions during all installation and maintenance work.
- Network security
  If a ST90 system is connected to a local area network, data security is important.
- Support information
  If you need technical support for your ST90 system you must contact your local dealer, or one of our support offices. A list of all our offices and dealers is available on our website. You can also contact our main support office in Norway.
Operating procedures
Maintenance procedures
User interface
Menu system
Functions and dialog boxes
Concept descriptions
Technical specifications
The technical specifications summarize the main functional and operational characteristics of the ST90 system. They also provide information related to power requirements, physical properties and environmental conditions.
Datagram formats
The ST90 system can send and receive information to and from several different peripherals. All transmissions take place as datagrams with data sentences. Each datagram has a defined format and length.
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Hull Unit – description

The hull unit is used to lower the transducer down below the ship’s hull when the ST90 system shall be used. When the ST90 system is turned off, the transducer is hoisted for protection. The hull unit is large and crucial part of the sonar system.

CAUTION:

When the transducer is lowered, the depth of water under the vessel must be monitored closely.

If the transducer hits larger objects or bottom, the transducer shaft may be bent, or - in worst case - it can be broken off. A broken transducer shaft will cause water leakage through the top of the shaft. If you suspect that the transducer shaft is seriously damaged do not retract the transducer to its upper position.

To prevent serious damage to the vessel or the vessel stability, you must have a water pump and a warning system in the sonar room.

If you forget to hoist the transducer before the ST90 system is turned off, the transducer is hoisted automatically before the power is disconnected. The transducer is also hoisted automatically if a serious malfunction occurs to the communication between the bridge and the hull unit.

In the event of improper operation, the powerful electric motor on the hull unit may cause serious damage to the equipment and/or injury to personnel. Therefore, before you start manual operation, read carefully through the relevant operating procedures. You must familiarize yourself with the correct handling methods and the relevant safety requirements.

The ST90 system can be provided with one of the following hull units:


Hull Unit	Lowering depth (m)	Transducer cable (m)	Maximum speed (knots)
ST92	1.2	4.6	16
ST92	1.2	7	16
ST93	1.6	4.6	16
ST93	1.6	7	16
ST94	2.1	4.6	11
ST94	2.1	7	11
The same transducer is used on all hull unit types.
If a Hull Unit Controller is supplied with the system, the Motor Control Unit cabinet is used as a junction box.

On some vessels, additional transducer protection is required. One example is vessels working in arctic conditions. It is important for them to prevent ice from damaging the transducer. A gate valve is then added to the hull unit installation. By means of a mechanical construction it shuts off the bottom of the installation trunk when the ST90 system is not used.

For more information, refer to the end-user documentation provided by the manufacturer.