Kolida SDE-28S, Руководство пользователя

Страница: 18 / 80

Blanking Pulse Length must be one millisecond longer than the Pulse Length except extreme case.
Ⅲ
, Received intensity, it contains TVG curve, start gain, threshold, gate depth and gain.
TVG Curve
, when the sound waves propagate in water, the sound intensity attenuates
exponentially, in order to keep the signal amplitude stable, TVG will control the receiving
amplifier to increase the amplification factor according to the opposite law, which is the time
gain control.
Fig.3-10 TVG curve
Start Gain
, in actual work, due to the weakness of the echo signal, the signal must be amplified
before processing, that is to increase the amplitudes of signal by amplifier circuit. This function
is not only to enlarge the echo signal, clutter also enlarge together, so an appropriate value is
necessary to be set in order to make the instrument can maximum identify the effective echo
signal.
Threshold
, it decides when the timer using for accumulating the echo continuous time stops
working, and to start picking up return signal. When increasing the threshold value, feebler
signal may be picked up, but the signal is more possible unwanted.
Gate Depth
, the purpose of this parameter is to control the rate of change of two adjacent
measurements. In generally speaking, we can think about that the bottom of water change is
continuous, as long as the time interval between the two measurements is relatively short, the
change of the depth will not too big, then the received echo time difference too big as well, so this
can be set a percentage, such as 10%.
Gain
, gain value means the enlargement factor of the return signal. It is useful to increase the
gain when the return signal is feeble, but the noise is enlarged as the gain is increased. So the