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Operating procedures
Defining settings related to user preferences and individual customizing
Defining the middle position of the transducer
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 ST90 system allows you to define a middle position for the transducer.

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
Operating procedures
- Getting started
- Choosing operating mode and key transmit parameters
- Controlling the gain and range settings
- Using the markers and tracking features
- Improving the recognition of fish and schools using receiver filters
- Recording and replaying echo data
- Recording and exporting processed echo data
- Capturing the display presentation in image and video files
- Setting up presentation modes and views
- Defining the visual information in the sonar views
- Defining settings related to user preferences and individual customizing
  - Selecting menu language
    You may prefer to use the ST90 system with the user interface in your own language. The Language function allows you to select the language to be used in the display presentations, menus and dialog boxes.
  - Hiding the menu system
    Unless you need to make frequent changes to the operating parameters, you may want to hide the menu from the display presentation. This gives you more space for echo information.
  - Placing the menu on the left side of the display presentation
    The menu system is by default located on the right side of the display presentation. You can move the menu system to the left side of the presentation.The General page in the Display Options dialog box controls the location of the menu.
  - Selecting the information to appear on the top bar
    The top bar can contain various information. You can choose which information elements to appear at the top of the display presentation.
  - Enabling Coordinated Universal Time (UTC) on the bottom bar
    You can set up the ST90 system to show Coordinated Universal Time (UTC). When disabled, the ST90 system uses local time.
  - Selecting which tooltips to appear in the user interface
    When you move the cursor over the echoes in the display presentation, small "tooltips" are shown to provide additional information. The Tooltip page controls which tooltips that are shown.
  - Adjusting the backlight intensity on the Operating Panel
    The buttons on the Operating Panel have a built-in backlight to improve visibility on a dark bridge.
  - Reducing the light emitted from the display presentation
    When the bridge is dark, the light emitted by the display presentation can affect your night vision. In order to compensate for this, you can reduce the intensity.
  - Increasing the visibility of the information panes
    When you open an information pane, you will see that it is transparent. This transparency allows you to see the echoes behind the pane, but it may also reduce the visibility of the information in it.
  - Changing the colour palette ("skin") used in the display presentations
    Depending on the ambient light, it is possible to change the colours the ST90 system uses in its display presentation. This can help you see the information better. The Palette function allows you to choose which colour theme ("skin") to be used by the ST90 system.
  - Choosing the colours used to present the echoes
    Several different colour scales are predefined and available for the presentation of the echoes. You can easily choose which colours to use. The presentation colours have no effect on the operational performance of the ST90 system.
  - Selecting measurement units
    The ST90 system is prepared to work with several international standards for units of measurements. From the Units page you control which units of measurements are used.
  - Configuring the environmental parameters
    Environmental parameters such as salinity, and sound speed play an important part to present accurate echo data. Use the Environment parameters to define these values. Depending on the current sea and weather conditions, you may need to change these values frequently.
  - Setting up the alarm limits for system protection
    Safe operation of the ST90 system is made possible using multiple sensors that monitor the operation and the performance. Whenever a suspicious event takes place, a relevant message, warning or alarm is provided. Selected alarm limits may be adjusted to fit your operational requirements.
  - Defining the middle position of the transducer
    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 ST90 system allows you to define a middle position for the transducer.
- Saving, retrieving and maintaining user settings
- Defining the user-selected features on the Operating Panel
- Exporting sensor data, marker positions and technical information
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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Defining the middle position of the transducer

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 ST90 system allows you to define a middle position for the transducer.

The physical properties of the hull unit installation are known.

The correct type of hull unit is selected.

The vessel is berthed or at sea.

The middle position is not a fixed length. The physical middle position depends on which type of hull unit you are using with the ST90 system.

Retracting the transducer to a middle position may be useful if you use the ST90 system simultaneously with other sonars. A higher position will permit you to increase the vessel speed. If you operate in very shallow waters, you may also reduce the risk of hitting bottom. However, placing the transducer immediately under the hull may increase the flow noise.

If you have the large hull unit you can define two middle positions.

CAUTION:

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.

Select the middle position carefully. The position is normally selected to place the transducer just under the keel, but low enough to prevent echoes from the trunk. Once the position is selected, make sure that the system protection functionality does not inhibit transmission.

Procedure

Make sure that you have sufficient water depth below the keel before you lower the transducer.
Select Hull Unit on the top bar to open the Hull Unit Control dialog box.
Use the spin box to define the middle position.
On the Setup menu, select Installation.
Observe that the Installation dialog box opens. This dialog box contains a number of pages selected from the menu on the left side.
Lower the transducer to its middle position.
Start normal operation.
Make sure that the ST90 system is fully operational.