Kongsberg Simrad ST90, Reference Manual

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b Place the cursor on the button. Press and hold the left mouse button. Move the
cursor horizontally over the button. Release the mouse button when requested
value is shown.
c Select the middle of the button to open it. If you have a keyboard connected to the
ST90 system, type the requested value.
6 Open the button and select
Apply to all
if you wish to use the chosen setting in all the
views in the current presentation mode.
Related topics
Operating procedures, page 79
Controlling the gain and range settings, page 94
Range function, page 420
Adjusting the TVG (Time Variable Gain) setting
When an acoustic pulse is sent through the water, it will gradually lose its energy. The
greater the distance between the transducer and the target(s), the greater the loss of energy.
TVG
(Time Variable Gain) compensates for the loss of acoustic energy due to geometric
spread and absorption.
Context
The TVG (Time Variable Gain) compensation is designed to counteract the natural
phenomena of geometric spread and absorption loss. In the ST90 system, the TVG
compensation is made using digital signal processing software. The TVG compensation is
expressed as a logarithmic curve. Each curve has a different slope creating a different gain
compensation. Each curve is identified with the equation
X log TVG . The coefficient " X " is
an integer. Typical values for " X " are 10 to 40.
Procedure
1 Click in the view you want to activate.
The setting you choose will only be valid for the active view. The active view is
identified with a thicker border.
2 Open the
Active
menu.
3 Locate the
TVG
button.
4 Select [ + ] or [ - ] to choose the requested setting.
Simrad ST90 Reference Manual