Simrad EY500, Instruction Manual

Page: 133 / 262

Theory of operation
P3403E/A
13
V
$
'
(1852
P
/
QP
)
2
$
(20)
V
$
'
4
U 2
0
@ PHDQ
[
m
U
2
U
1
6
9
GU
]
@
(1852
P
/
QP
)
2
(21)
6
Y
'
V
$
4
U
2
0
(1852
P
/
QP
)
2
@
(
U
2
& U
1
)
(22)
The first equation converts volume backscattering strength to backscattering
area per unit of volume. The corresponding backscattering area per unit of
horizontal area is obtained by integrating over the layer vertically, r
1
to r
2
. The
output parameter from the integrator each averaging interval
F
A
represents the
mean backscattering area per unit of horizontal area and is obtained by
averaging the individual
M F
/
M
A’s over one interval. The quantity s
A
(m
2
/nm
2
) is
related to
F
A
(m
2
/m
2
) as:
The algorithm implemented by the sounder is obtained by combining the four
equations
Calibrating the sounder for the first time with a reference target a small
discrepancy will most likely be observed between the measured S
A
and the
theoretically computed value (refer to section "Installation, System Test and
Calibration"). This discrepancy is due to differences between the true and the
nominal value of physical parameters; transducer gain, attenuation constant,
transmit power etc. Agreement between the echo integrator output and the
theoretically computed value is obtained by finetuning the peak transducer gain
parameter (equation for volume backscattering strength in paragraph 2). This
parameter is set from the menu system in units of dB. Note that different peak
transducer gain parameters are used for computing target strength and volume
backscattering strength.
To find mean S
v
from s
A
(equation 22):