Adjusting The Tvg (Time Variable Gain) Setting - Simrad ES80 Reference Manual

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. (Time Variable Gain) compensates for the loss of acoustic energy due to
TVG
geometric spread and absorption. Use the
Context
The TVG (Time Varible Gain) compensation is designed to counteract the natural
phenomena of geometric spread and absorption loss. In the ES80, the TVG compensation
is made using digital signal processing software. The TVG compensation is expressed
as a logarithmic curve. You can choose from a selection of curves. 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.
Tip
You can select TVG using this function. You can also adjust the TVG setting in the
dialog box. The
Echogram
The ES80 allows you to use different TVG compensation for the echoes from the water
column than from the bottom. By making the bottom echoes individually adjustable,
you can fine tune the presentation from the bottom to investigate the bottom type and
conditions. The
Bottom TVG
adjust the
Bottom TVG
Procedure
1 Click in any echogram view to make it "active".
The setting you choose will only be valid for the currently "active" echogram. The
"active" echogram view is identified with a thicker border.
2 Open the
Active
3 Locate the
TVG
4 Choose your requested setting for TVG (Time Variable Gain).
5 Select
Apply to All
the same type.
Related topics
TVG function, page 414
Echogram: Echogram page, page 424
About sound wave propagation, page 459
406273/C
TVG
function is located on the
TVG
adjustment has no effect on fish close to the bottom. To
, open the
Echogram
menu.
button.
if you wish to use the chosen setting on all the echograms of
button or the
Echogram
Echogram
dialog box.
Operating procedures
dialog box.
page.
113