Technical data

314
Smart Sensors
If you are looking for a solution to show you precision depth in water as shallow as 2 feet and
temperature changes as minute as 2/100
ths
of a degree, then the Furuno Smart Sensor is the answer.
What is a Smart Sensor?
Furuno Smart Sensors are transducers specifically
designed to give an accurate numerical value for
depth instead of drawing an image on the
screen. Smart Sensors are available in
a variety of housing styles and can be
transom or thru-hull mounted on the
vessel. Processing of the return echoes
is accomplished by circuitry within the
transducer housing and then output as
NMEA0183 or NMEA2000 information
- electronic text that can be interpreted
and displayed by a variety of Furuno elec-
tronics such as GPS, chart plotters, NavNet 3D,
FI50 Series Instruments, or our popular RD30 NMEA data
repeater. Molded, waterproof 7-pin or 10-pin connectors
connect directly to these and many other Furuno products.
B122 7" Bronze Thru-Hull
P17 Plastic Thru-Hull
B17 Bronze Thru-Hull
All Smart Sensors operate at 235 kHz, so they will never interfere
with your fish finder's performance.
NMEA0183
Models
Functions Housing Style
235DT-PSE Depth and Temperature (+/ - 1 degree ) P17 Plastic Thru-Hull
235DST-PSE Depth, Speed and Temperature (+/ - 1 degree ) P17 Plastic Thru-Hull
235DT-MSE Depth and Temperature (+/ - 1 degree ) B17 Bronze Thru-Hull
235DST-MSE Depth, Speed and Temperature (+/ - 1 degree ) B17 Bronze Thru-Hull
235DHT-MSE Depth and Precision Temperature (+/- 0.02 degree) B17 Bronze Thru Hull
235DHT-LMSE Depth and Precision Temperature (+/- 0.02 degree)
B122 7
"
Bronze Thru Hull
235DST-PWE Depth, Speed and Temperature (+/- 1 degree) P66 Plastic Transom Mount
NMEA2000
Models
Functions Housing Style
DST-800PSF Depth, Speed and Temperature (+/ - 1 degree ) P17 Plastic Thru-Hull
DST-800PWF Depth, Speed and Temperature (+/ - 1 degree ) P17 Plastic Thru-Hull
DT-800PSF Depth and Temperature (+/ - 1 degree ) P66 Plastic Transom Mount
DST-800MSF Depth, Speed and Temperature (+/ - 1 degree ) B17 Bronze Thru-Hull
DT-800MSF Depth and Temperature (+/ - 1 degree ) B17 Bronze Thru Hull
235-MSLF Depth and Temperature (+/ - 1 degree )
B122 7
"
Bronze Thru Hull
235-IHF Depth only P79 Plastic In Hull
Sidelobes
The image to the right illustrates a typical beam pattern. It is a graphic
representation of the pattern the acoustic energy takes as it radiates
from the transducer. The center cone represents the energy within
the -3db down points, what is referred to as the Mainlobe, and is the
focus of the transducers energy. In this image we can see that not all of
the energy is concentrated within the Mainlobe. Some of the acoustic
energy spills out to the sides in what are referred to as Sidelobes, areas
outside of the main beam in which a small level of energy is radiated.
Since this energy is capable of producing return echoes from objects it
encounters, it is possible to receive weak returns from the Sidelobes in
shallow water.
Target masking is a phenomenon where acoustic energy from the
transducer encounters a ledge which is only partially within the beam.
This produces an echo which is sent back to the transducer sooner
than the echo returned by either the sea bottom or fish targets. The
result is that these fish targets will not be discernible on the fish finder
screen. This phenomenon can occur with trenches as well as when
traveling over sloping ground.
It is also possible to pick up a second echo from the sea bed, which will
show as an echo on the screen at a greater depth than that of the ledge.
When two or more echo sounders are operating in close proximity and
at the same frequency, it is possible for each to receive false returns
from the others transducer. In such cases the operator will see noise
and clutter, false returns, multiple bottoms or other video anomalies
on the screen. This is most common in and around marinas or har-
bors where there may be multiple fish finders operating at the same
frequencies. Furuno fish finders have interference rejection circuitry
which should be used in such instances, but use it sparingly to avoid
eliminating small targets. Many boaters have found that adding a
Furuno Smart Sensor, operating at 235kHz, will ensure a reliable nu-
meric value for depth when their 50/200kHz fish finder suffers from
interference.
Target Masking
Interference